I have three complete RCA "new vista" 21" color TVs, none work and all three had bad CRTs when I got them. I need to get ONE of these working so I can enjoy some classic cartoons and movies for the holidays.

After that Zenith 21" went to a new home, the living room is empty and
I miss clearing RCA's multiple hurdles, which are a given! So, which will it be?

The latest arrival is a plain walnut-screw legs CTC 20C from upstate NY. So far it has a gassed CRT (Sylvania re-gunned) and flyback that won't ring test but looks clean:sigh:, along with several fried resistors and frozen power switch/volume control. Pretty hopeless, or is it?

Almost a year ago, I ventured 2 hours south to Delaware for a beautiful Danish walnut Karlstat GG721W using a CTC16XL chassis. The Colorama CRT label gave false hope - the green gun had no emission because its heater element was GONE. However it had a replacement fly:D. I cant wait to put this chassis on the jig to see what other gremlins exist. This may be the "easy" one.

Long ago, a locally-placed CL ad for a free tv was pointed out to me by Kamakiri himself. I arrived to find a complete Lynnhaven CTC12 213G612MU in Mahogany with a Colorama CRT replaced 1967 but a typically skanky flyback. The CRT has a H-K short in blue gun - just needed the isolation trans inserted and now its my jig tube. Thanks to another Tim at VK:thmbsp:, I have an NOS FLY 273. The other work needed is typical of RCA's 4-board flat chassis, but likely more than wrong with it than the 16x.

Whatever your wife chooses.
:D

Whatever your wife chooses.
:D

Depends on your cabinet and chassis preferences the cabinet face masks on the 16 and 20 almost certainly swap so you could mix and match.

Sounds like the 16 chassis is best but all should be fixable. The 20 chassis has the 6GH8 law of guaranteed bad tubes going against it...A lot of stuff can cause a fly not to ring from rectifier filaments loading it to shorted caps... I'd assume %75 chance the fly is okay till deeper digging is done.

Personally, I'd hit the CTC-20 first! :) I have always wanted to play with one of those! 6GH8As from hell!!
You don't know for sure right now that the FBT is bad, it may be, then you are in a really bad spot, cause it seems to be ultra unobtanium, :(
I would just replace any fried parts, and see if it can get HV without smoking anything, if it can, you are in luck, if not, move on, you only risk a few resistors and perhaps a HOT.

The fun is to compare these three versions of RCA color. I suspect the CTC12 will be the spouse's preference though. It is sort of Early American like the cherry hutch, etc.

I have only seen one CTC20 before. It does have (7) 6GH8s, four of them tested bad. Yes, I wanted to do it first and I did replace bad resistors but no HV and the VA-48 tells me the HOT is bad though it measure 600 ohms.. If I'm lucky, an NOS fly-back may be available.

My opinion is to not waste your time on the CTC20. Those toilets had a lousy picture and terrible color when they were new (I was there).

The 12 and 16 will both give you a superior picture, as good as you'll ever see on any vacuum tube TV.

John

....the VA-48 tells me the HOT is bad though it measure 600 ohms..

The resistance between the plate cap of the horiz out and the HV rectifier is the first quick test when checking the fly, but if it passes that test, there's still the possibility of a shorted turn. An ohmeter treats coils like resistors and a single shorted turn renders a coil useless and won't be discernible with an ohmeter. The VA48 will ferret out those with shorted turns.

John

The fun is to compare these three versions of RCA color. I suspect the CTC12 will be the spouse's preference though. It is sort of Early American like the cherry hutch, etc.

I have only seen one CTC20 before. It does have (7) 6GH8s, four of them tested bad. Yes, I wanted to do it first and I did replace bad resistors but no HV and the VA-48 tells me the HOT is bad though it measure 600 ohms.. If I'm lucky, an NOS fly-back may be available.

which resistors were bad? ( via Sams #s? )

The resistance between the plate cap of the horiz out and the HV rectifier is the first quick test when checking the fly, but if it passes that test, there's still the possibility of a shorted turn. An ohmeter treats coils like resistors and a single shorted turn renders a coil useless and won't be discernible with an ohmeter. The VA48 will ferret out those with shorted turns.

John


I'm not gonna fall into that trap again!

my FADA HOT had the primary of much less than the 180 ohms than all the schematics said it should have, by almost 1/2, but it's still working fine, VERY confused by that one :o

I'm not gonna fall into that trap again!

my FADA HOT had the primary of much less than the 180 ohms than all the schematics said it should have, by almost 1/2, but it's still working fine, VERY confused by that one :o

We all know it's not uncommon to have a bad value in a schematic, but it's very uncommon to have more than one schematic make the same exact error.

My best guess is that FADA made a running change to the fly after the schematic was printed or that other companies redrew the original factory schematic in their own notation and transferred the incorrect reading at the same time. I know that early SAMS credits the original manufacturer in helping. I wonder if early SAMS were simply redrawn and later ones were drawn with a working example.

Speaking of running changes, I have an Andrea I was screwing around with earlier this year and it has a tube and associated circuitry that the SAMS doesn't show.

John

The CTC-20 was a low-end special. We sold a few, and they were dogs right out of the box. First run had weak vert sync, and the factory issued a field mod requiring changing two resistors in the sync separator circuit. The chassis was a mashup of the CTC-19 (designed for the new 19" rectangular tube), back-engineered to drive a 21" round tube. It's as if the factory was overstocked with round tubes and needed a quick way to use 'em up. And it was the perennial 6GH8 hog (as was the '19 and all its later derivitives).

The fun is to compare these three versions of RCA color. I suspect the CTC12 will be the spouse's preference though. It is sort of Early American like the cherry hutch, etc.

I have only seen one CTC20 before. It does have (7) 6GH8s, four of them tested bad. Yes, I wanted to do it first and I did replace bad resistors but no HV and the VA-48 tells me the HOT is bad though it measure 600 ohms.. If I'm lucky, an NOS fly-back may be available.
The last CTC20 I repaired and sold had a bad flyback and the CRT had a H-K short on one of the guns. The RCA distributor didn't have a flyback in stock and had to order it. That was when the set was seven years old!
I used an isolator and replaced the flyback and sold it reasonable.

We all know it's not uncommon to have a bad value in a schematic, but it's very uncommon to have more than one schematic make the same exact error.

My best guess is that FADA made a running change to the fly after the schematic was printed or that other companies redrew the original factory schematic in their own notation and transferred the incorrect reading at the same time. I know that early SAMS credits the original manufacturer in helping. I wonder if early SAMS were simply redrawn and later ones were drawn with a working example.

Speaking of running changes, I have an Andrea I was screwing around with earlier this year and it has a tube and associated circuitry that the SAMS doesn't show.

John
https://i.imgur.com/x1izfje.jpg

I never DID work it out.
EVERYTHING matched...
every capacitor, resistor, tube and voltage, EVEN the part # was the same on the FADA part list, and it shows 180 ohms pin 1-2 and 240 2-3
I did get 240, but not the 180. was very confused, the same is shown on EVERY fada clone and rca 630ts and one like it.
no idea why my FBT is weird.
and just to be safe, I got a new replacement RAM FBT that was listed as a replacement for this FADA, in case this one blows, but so far,,. :D

0: CTC20-I checked the fly again after unplugging 2AV2 and 6JE6 disconnecting the hor yoke, damper and boost terminals. The VA-48 ring test showed in the good zone on 1-2 settings. I think Moyer's has a flyback but trouble shooting is not done.

Oddly, while powered up with good HOT voltages (G1 drive and G2 screen) and making no HV this morning, the two 470 ohm resistors in the vert yoke bypass started smoking. That smell now takes me back only 10 years, when we still heated with coal -LOL.

I was already trying to make sense of the initially toasted resistors; 680 ohm/15 watt , 560 ohm 7 watt , 1000 ohm 6BK4 grid.

Ill post some pictures with schematic, etc

The CTC-20 was a low-end special. We sold a few, and they were dogs right out of the box. First run had weak vert sync, and the factory issued a field mod requiring changing two resistors in the sync separator circuit. The chassis was a mashup of the CTC-19 (designed for the new 19" rectangular tube), back-engineered to drive a 21" round tube. It's as if the factory was overstocked with round tubes and needed a quick way to use 'em up. And it was the perennial 6GH8 hog (as was the '19 and all its later derivitives).

Very interesting that RCA did what Philco and Magnavox did. Reverse engineer the new rectangular chassis for a surplus of round tubes.

Very interesting that RCA did what Philco and Magnavox did. Reverse engineer the new rectangular chassis for a surplus of round tubes.
Actually it was the cabinets that they had a surplus of. I worked on one that had a real fancy cabinet like the prior year CTC16X.
Curtis-Mathis had a cheapie knockoff of the CTC20, but used a 6KM6 horiz out instead. :thumbsdn:

R202 & R203, RCA is famous for burning those up in color sets, esp if there is leaky caps.

But the 2 470 ohm resistors in the vert yoke section really makes no sense, :o
the vert output transformer CAN'T put out that much power to be doing that, something must be really wrong :o
shorted yoke? horz- vert? You don't even need vert at this point, horz seems to be powered direct from +385v (3) , you could yank the vert output, (v9), disconnect the vert drive wires from the yoke, leaving the horz only, pop the top off the HV cage, and first see if you can draw a healthy arc off the top of the FBT, also at this point, if you measure any voltage at the vert yoke connect points, you know there is a problem.
And... if you CAN get a good healthy arc from the FBT and are feeling bold, unhook the CRT anode and close the cage and see if you can get any DC, stick it in a mason jar or something!
Yes, I have been watching a lot of shango66 videos!

Shango_66 gets right to the issue with great commentary. So far as I can tell, this TV was "run to fail" and later found when someone moved at last from a home that was also new in '66, and forever seemed new to the first ones to live there.

First the volume control froze, with the shaft worn out from a tool used to operate it. The escutcheon was all scratched up from this awful practice. Good thing the tuner knob and channel cup was OK, that tool would have annihilated a tuner shaft. The cord was arced on the plug/recept as well. Tubes as often the case after 50 years, were from all over, Radio Shack - Raytheon (Japanese) - GE - Sylvania - RCA (new logo) GE "engineering test samples" , an Amperex 6GH8A made in France O.o, but that "new" Colorbrite CRT had me going until I hooked up some tester-source DC to it and saw the purple genie of death in the guns.

After the CRT lost vacuum, even that did not stop someone from using it for sound. HV was hitting a brick wall, likely overloading the B+ via those resistors. No wax stalactites under the fly is very odd and I cant figure that out, being common for RCA. The HOT cap wire was scorched from the heat yet the 6LQ6 tested good:scratch2:.

I will get back at it this evening, and post some pictures of the schematic copy with bad parts circled. I have another yoke and will try that with the vertical wires disconnected. I have not measured 6LQ6 cathode current, that remains to give a clue. I will jig up the CTC16XL next. CTC12 is last and best hope for watching Rudlolf so Im going for speed, just like old days in a shop where you did easy stuff first to get it back in the customers home and get paid. Not always in that order:sigh:

Those "tough dog" customer sets similar to this CTC20 you had to take several breaks and clear your head to get at what the issue really is. When you nailed it finally, after a week of shake-down tactics, owner and everyone was interested in the play by play even the road guy.

I appreciate the help, thinking these were old hat for me. I must have forgot some basics of RCA sweep circuits.

I am really starting to wonder what the RCA engineers were smoking when they made the CTC-20...
From what I have seen, almost all leading up to it has had the FBT power taken from a shared point on the vert output transformer, and thus, if the yoke was not plugged in, HV was shut off as a safety feature. ( this is a guess by observation ).
But there seems to be no such thing in the 20, what were the thinking? :O

The mystery burned resistor in the cathode circuit of the regulator tube 6BK4 is R141 - 1000 ohm half watt. I replaced it with a 1 watt film resistor and like the 680 ohm 15 watt, does not run hot now. Not sure how R141 got burned in half. The tube is a good 6EL4A.

Well, if the dummies were running it with a bum CRT, who knows what kind of feedback it created, R141 is the path for the shunt regulator to try and clamp down the HV, if that let go, who knows what may have happened, especially if the HV rect let go, and flooded AC all over the place, it could have even got into the LV power supply, if they were really not watching things.

Here is the first of three RCA 21" color. The model is GH but the tag was half missing. The Sams lists possible models as GH608, GH618, GH626 or GH630, ending with a W for walnut finish. I have many extra knobs, least of the problems.

201869

Well, if the dummies were running it with a bum CRT, who knows what kind of feedback it created, R141 is the path for the shunt regulator to try and clamp down the HV, if that let go, who knows what may have happened, especially if the HV rect let go, and flooded AC all over the place, it could have even got into the LV power supply, if they were really not watching things.
The 2.7 ohm resistor in the HV cup was a half watt and looked original, schematic and Sams picture shows it as 1 watt. It drifted to 4.2 ohms so the 3A3C was not bad as would have seemed. I replaced it with a 1 watt:scratch2:

Here is the first of three RCA 21" color. The model is GH but the tag was half missing. The Sams lists possible models as GH608, GH618, GH626 or GH630, ending with a W for walnut finish. I have many extra knobs, least of the problems.

201869

That's a nice CTC20. Makes me miss my old one....If you get sick of it and it shows up at an ETF meet you could sell it to me fairly easily.

that looks almost exactly like my CTC-16XL :O

That's a nice CTC20. Makes me miss my old one....If you get sick of it and it shows up at an ETF meet you could sell it to me fairly easily.

The one I saw in VoTech made an impression on me too, with the last-gen tube 2-PWB chassis no less. Two variations that look just like CTC16 AND CTC16x sets make a '20 necessary to round out any RCA collection.

If you have any tube-color (non-WID) by Motorola, its an even trade:thmbsp:

Until I take my last swing at it tonight, an update. The Fly is good and I got HV last night. The cathode current on 6LQ6 is 126ma. yet it was 195 initially. HV is low, 22 kV and control is at max. Boost at 1040v is right on.

The grid voltage on HV reg tube 6BK4 is affected by two 1.5 Meg 1-watt carbons, R139 & R140. These tested 1.44 and 1.55 meg respectively but the schematic note on both the RCA and Sams notes these as a "matched pair". This is a regulator problem because the only voltage out of whack is 6BK4-G1 which goes from 365 to 375 over the HV control range. Weak/worn 6LQ6's can cause low HV,, yet voltages on it are spot-on, even G3 which is not grounded but instead feeds some h-blanking network :scratch2::scratch2: Oh well whatever it takes to make it work, right?
201876

The CTC20 apparently needed its own yoke, instead of the CTC12 yoke and convergence parts Im using on the jig for all those 15s and 16s I worked on for others. Even the jig is showing a full raster, all colors present and a blue H-K short in its gun seems to have healed itself:D. The HV cage and shields go back on so I can flip the chassis on its side to put signal and test using Sencore VA-48.

As much as we note RCA's shortcomings on design, shops all made good money because so many were sold and looked pretty darn good so everyone wanted them fixed at some point. Even RCA factory service had a shop to service all those C-M inspired service agreements.

I am really starting to wonder what the RCA engineers were smoking when they made the CTC-20...
From what I have seen, almost all leading up to it has had the FBT power taken from a shared point on the vert output transformer, and thus, if the yoke was not plugged in, HV was shut off as a safety feature. ( this is a guess by observation ).
But there seems to be no such thing in the 20, what were the thinking? :O
True for the rectangular sets using a yoke plug. None of the 21" round sets used an interlock in the B+ as those did, all were connected with the familiar Red and Blu for Horz and for vertical, Yellow and Yellow with a Black-stripe all individual leads.

Sams did not show (dotted line) that the CTC20C has the Yel/Blk lead grounded! I lit the 6DW4 damper tube up when mis-wired the yoke leads initially:yikes:

True for the rectangular sets using a yoke plug. None of the 21" round sets used an interlock in the B+ as those did, all were connected with the familiar Red and Blu for Horz and for vertical, Yellow and Yellow with a Black-stripe all individual leads.

Sams did not show (dotted line) that the CTC20C has the Yel/Blk lead grounded! I lit the 6DW4 damper tube up when mis-wired the yoke leads initially:yikes:

Out of curiosity I have looked at almost all RCA CTC schematics, (sams), and noticed that almost all but the 20, power the horz from the vert output transformer, ( GRN tap ) , often from the far side of the centering pot, at first I thought this was a bit strange, cause it would feed vert pulses into the damper circuit and so on, then I realized they are using this as some sort of safety feature, and that most likely any pulses would get filtered out by the coils the have before the damper anyway, but what they are doing is, vertical centering (10 ohms) + vertical yoke winding (23 oms ish ) allows horz to energize, but remove it, and HV/ HORZ cuts out, to prevent screen burn.

Until I take my last swing at it tonight, an update. The Fly is good and I got HV last night. The cathode current on 6LQ6 is 126ma. yet it was 195 initially. HV is low, 22 kV and control is at max. Boost at 1040v is right on.

The grid voltage on HV reg tube 6BK4 is affected by two 1.5 Meg 1-watt carbons, R139 & R140. These tested 1.44 and 1.55 meg respectively but the schematic note on both the RCA and Sams notes these as a "matched pair". This is a regulator problem because the only voltage out of whack is 6BK4-G1 which goes from 365 to 375 over the HV control range. Weak/worn 6LQ6's can cause low HV,, yet voltages on it are spot-on, even G3 which is not grounded but instead feeds some h-blanking network :scratch2::scratch2: Oh well whatever it takes to make it work, right?
201876

The CTC20 apparently needed its own yoke, instead of the CTC12 yoke and convergence parts Im using on the jig for all those 15s and 16s I worked on for others. Even the jig is showing a full raster, all colors present and a blue H-K short in its gun seems to have healed itself:D. The HV cage and shields go back on so I can flip the chassis on its side to put signal and test using Sencore VA-48.

As much as we note RCA's shortcomings on design, shops all made good money because so many were sold and looked pretty darn good so everyone wanted them fixed at some point. Even RCA factory service had a shop to service all those C-M inspired service agreements.

Odd I thought they were all interchangeable.
But if you look closely at the Sams info, is says for the CTC-20, 70 degree, Horz 12mh Vert 38mh, same data for the 16/xl
but the 15 is Horz 12.4mh Vert 40mh, so I guess one from a 16 should work, but not a 15? I have no data about the CTC-12 :(

Im pretty sure yokes for 15 and 12 are the same. There are identical on the RCA schematics.

If you don't already have it, RCA vol. 1 Color TV service Manual (Tab Books #496)
https://picclick.com/Vintage-Tab-Books-Rca-Color-Tv-Service-Manual-203177180696.html
is a very important text if you want to understand all about these. .

Carl Babcoke never included a foreword like other Authors in this series BUT he must have really been listening in the service seminars RCA must have had. The troubleshooting steps for the ever-common issue of red-plate/No HV so common to RCA New Vista color TVs.

After the development of Color television it seems like some of the later models became victims of Corporate greed. I remember several chassis runs that had on going problems. They were good money makers for service, but didn't seem to hold up well to Zenith.

It's been fascinating to read the play-by-play on the CTC-20... the lovely Early American 1967 Zenith "Harvard" now alive and sitting in our living room was it's predecessor at Dave's!

After the development of Color television it seems like some of the later models became victims of Corporate greed. I remember several chassis runs that had on going problems. They were good money makers for service, but didn't seem to hold up well to Zenith.
I think the late 60s saw Zenith dealers proliferate for that reason, even here just 5 miles from Lancaster's New Holland Avenue CRT and orthicon plant.

I think the late 60s saw Zenith dealers proliferate for that reason, even here just 5 miles from Lancaster's New Holland Avenue CRT and orthicon plant.

Zeniths were more reliable, that's a fact. RCAs outperformed Zenith, that's a fact.

My recollection is that in our town, Zenith shops outnumbered RCA shops 8-1. We were only one of three that sold and serviced RCA. I remember the older shops just didn't like printed circuits and far preferred the hand wiring of the Zenith chassis. I suspect that was a big reason why there were more Zenith shops.

John

Why were TVs so hungry for 6GH8s? For that matter, why did every pentode/triode combo out there suck? I can't think of one that didn't have dome stupid issiue or another...

Why were TVs so hungry for 6GH8s? For that matter, why did every pentode/triode combo out there suck? I can't think of one that didn't have dome stupid issiue or another...

I think the manufacturers were trying to reduce tube count and except for GE compactrons, number of different tubes. The CTC16 had only two 6GH8A and it was more for convenience, combining 3.58 mhz osc and reactance, killer and killer and bandpass, a two in one tube.

Then...some wizard figured half a hard-driving 6GU7 could be replaced by half a 6GH8A and that led to higher demands on the pentode section. Maybe the relative success of the 5GH8/6GH8 in smaller screen sets led to mis-application in 25" models. :smoke:

Then as you say, 6BL8s in Motorola and Philco, 6KT8 in Zenith, 6GH8 in Magnavox, RCA etc. Seemed to fill tube caddys I collected over the years. I often read the 6U8 and 6EA8 were tougher of the triode-pentodes but the substitution is never guaranteed.

The resistance between the plate cap of the horiz out and the HV rectifier is the first quick test when checking the fly, but if it passes that test, there's still the possibility of a shorted turn. An ohmeter treats coils like resistors and a single shorted turn renders a coil useless and won't be discernible with an ohmeter. The VA48 will ferret out those with shorted turns.

John

Spot on. The only way to be 99% sure the FBT is good or bad is
is to totally remove it & ring it. If it dont resonate its NFG. Shorted
turns were the most common fail on FBT's & yokes.

73 Zeno:smoke:
LFOD !

Why were TVs so hungry for 6GH8s? For that matter, why did every pentode/triode combo out there suck? I can't think of one that didn't have dome stupid issiue or another...

We used to buy 6GH8's by the gross every few months. The tubes just
seemed to suck BUT a lot of the problems were tube sockets.
Sets with 5GH8's were the 14" & 19" plastic cabinet sets. Same problem
with those BUT in the late chassii they got much better. Those sets ran
real hot & cooked up all the low level tubes. Add to that the low focus
CRT's & you have a real POS TV in a few years. That being said a good
one could throw a fantastic pix if you damn near retubed it gave
the CRT a clean & balance.
To add to the fustration if you "swap" GH8's the symptoms often changed.
You may start with no color, test the tubes then put them back
& get different symptoms. This drove the home tube tester types to drink.

enuf fer now
73 Zeno:smoke:
LFOD !

We used to buy 6GH8's by the gross every few months. The tubes just
seemed to suck BUT a lot of the problems were tube sockets.
Sets with 5GH8's were the 14" & 19" plastic cabinet sets. Same problem
with those BUT in the late chassii they got much better. Those sets ran
real hot & cooked up all the low level tubes. Add to that the low focus
CRT's & you have a real POS TV in a few years. That being said a good
one could throw a fantastic pix if you damn near retubed it gave
the CRT a clean & balance.
To add to the fustration if you "swap" GH8's the symptoms often changed.
You may start with no color, test the tubes then put them back
& get different symptoms. This drove the home tube tester types to drink.

enuf fer now
73 Zeno:smoke:
LFOD !
The RCA distributor sold a box of 100 Raytheon Japanese tubes for $98.00.
In the later model sets, the color osc tube was made by a different supplier. The only one, the other ones were RCA made.
I have an RCA CTC51K that has OEM 6GH8's that are Japanese. The horiz output as well.

...
To add to the fustration if you "swap" GH8's the symptoms often changed.
You may start with no color, test the tubes then put them back
& get different symptoms. This drove the home tube tester types to drink.
...
73 Zeno:smoke:
LFOD !

I know it's mean to say it, but this made me laugh.

I remember an acquaintance got his 15" RCA (CTC22) serviced and gave me 5 (?) 5GH8s in the boxes new RCAs came in. I thought it was odd that 5 of a same type were in one set! But at 10 yrs old, he figured the set was still worth it.

I know it's mean to say it, but this made me laugh.

I found that hilarious myself.
I don't think it's mean...if they were not smart enough to realize that a tube is bad by substituting it with another of the same type in a different circuit and watching symptoms switch circuits then that's on them.
I literally used that to verify an intermittent that had fought me for years. My hybrid Zenith had a bad red video output transistor that was intermittent and REFUSED to malfunction while metered. Switching the identical red and blue channel transistors and watching the intermittent move to the other color was how I finally found it.

The 6GH8A madness continues...while sweep problem is all but gone, but what remains appears to be weak sync AND video, likely AGC.

So far it's crummy-looking video but chroma-locked color bars are good to see, the AGC control has no effect using the Sencore VA-48 at both antenna & tuner link going to first IF amp.

Unlike the 4-board color chassis like CTC-21/25/28..., the 2-pcb CTC19/20/24/31 video is taken off before a 6GH8 pentode section amplifies chroma/sync and AGC.

This is the last place to look before I move on to the CTC16X. I'm getting bored for now and need a change, that's why I line up triage of at least two similar sets.

Time for a change. The CTC20 began exhibiting a vertical issue along with its funky shaky video with color. Voltages on the 6GH8s are close enough that I suspect the video detector is possibly bad. This could really lead down along road to get this set right before daring to assemble it.

201904

I unplugged everything and put the CTC16X chassis up, plugging in all the tubes and powering up from 70-100 volts over an hour.

The difference in CTC16 and 20 chassis is remarkable.

Time for a change. The CTC20 began exhibiting a vertical issue along with its funky shaky video with color. Voltages on the 6GH8s are close enough that I suspect the video detector is possibly bad. This could really lead down along road to get this set right before daring to assemble it.

201904

I unplugged everything and put the CTC16X chassis up, plugging in all the tubes and powering up from 70-100 volts over an hour.

The difference in CTC16 and 20 chassis is remarkable.

:O
That setup looks like something out of the movie Brazil!

:O
That setup looks like something out of the movie Brazil!
I remember that movie, the elevator buttons were quite amusing and confusing.

That CRT is my test jig. Precisely what us gluttons for RCA punishment make from a decent CRT and 3/4" plywood or a junk cabinet. I painted mine black.

But I did that only after failing to get one of those RCA 21FJP22 https://www.radiomuseum.org/r/rca_11a1015_color_test_jig.html (blue hammertone finish). I placed a $100 bid on one at a clean-out sale 7 yrs ago for a shop, but it must have sold for more:sigh:

Before I get into it tonight, I should confirm that a silicon signal diode will sub for a germanium diode in a video detector or sound detector application.

I'm pretty sure that diode is causing the effect seen here, not unlike the CTC20's issue.
201908

I never used to see these fail but HW Sams will point it out like a tube, LV, boost or focus rectifier.

I remember that movie, the elevator buttons were quite amusing and confusing.

That CRT is my test jig. Precisely what us gluttons for RCA punishment make from a decent CRT and 3/4" plywood or a junk cabinet. I painted mine black.

But I did that only after failing to get one of those RCA 21FJP22 https://www.radiomuseum.org/r/rca_11a1015_color_test_jig.html (blue hammertone finish). I placed a $100 bid on one at a clean-out sale 7 yrs ago for a shop, but it must have sold for more:sigh:
The later 19" rectangular jigs will work on roundy with the right adapters.
http://videokarma.org/attachment.php?attachmentid=201909&d=1607467591
I have one but on sets like my Packard Bell roundys where the CRT mounting bracket makes it into its own test jig I take the path of least resistance.
http://videokarma.org/attachment.php?attachmentid=201844&d=1606442909

I remember that movie, the elevator buttons were quite amusing and confusing.

That CRT is my test jig. Precisely what us gluttons for RCA punishment make from a decent CRT and 3/4" plywood or a junk cabinet. I painted mine black.

But I did that only after failing to get one of those RCA 21FJP22 https://www.radiomuseum.org/r/rca_11a1015_color_test_jig.html (blue hammertone finish). I placed a $100 bid on one at a clean-out sale 7 yrs ago for a shop, but it must have sold for more:sigh:

I meant the way TVs and monitors we all open and deconstructed in the movie, often with a magnifying lens in front of them they were really vintage sets, i saw that right away .

I meant the way TVs and monitors we all open and deconstructed in the movie, often with a magnifying lens in front of them they were really vintage sets, i saw that right away .

I know that movie only from cable, which I last had 32 years ago while in BSET school in suburban D.C. This was also when I had the 78 Magnavox Touch-Tune T995 (3rd run) I invested a new Maggy-Chrome 25VCX CRT in, the household was Monty Python fans already, it was repeated by HBO or something weekly, "Brazil" appealed to any random drop-in guests. I need to watch it again to gain the new perspective on the deconstruction.

The later 19" rectangular jigs will work on roundy with the right adapters.
http://videokarma.org/attachment.php?attachmentid=201909&d=1607467591
I have one but on sets like my Packard Bell roundys where the CRT mounting bracket makes it into its own test jig I take the path of least resistance.
http://videokarma.org/attachment.php?attachmentid=201844&d=1606442909

I know a Check-A Color by Sylvania seemed to be the go-to jig at some places, not sure if it was backward compatible on a 21" yoke, etc without pincushion.

Only my first employer at a GE-Mag dealer had a 21" jig, which I have a picture of him standing under. Its framed on my bench:D. The last round CRT he pulled a chassis on was a '65 Magnavox U450, no more GE 21" CW-CX-FY-CA-CB21 sets were on the service roster by 1979:sigh: We Just saw KC-KD-KE-KEII and later awful portacolor-inspired C1-L2 hybrids until SS models MA-MB gave some hope for GE, which my transistor/module-wary boss referred to another shop.

I know that movie only from cable, which I last had 32 years ago while in BSET school in suburban D.C. This was also when I had the 78 Magnavox Touch-Tune T995 (3rd run) I invested a new Maggy-Chrome 25VCX CRT in, the household was Monty Python fans already, it was repeated by HBO or something weekly, "Brazil" appealed to any random drop-in guests. I need to watch it again to gain the new perspective on the deconstruction.

MY favorite bit from the movie!
https://www.youtube.com/watch?v=0B61_5sRoBI

201910

201911

Who would have ever thought that people like us would be keeping these sets going after all of these years?

Nice...

MY favorite bit from the movie!
https://www.youtube.com/watch?v=0B61_5sRoBI

:lmao: A/C repairmen - hahahah - forgot the 27B/6 form!!!

Who would have ever thought that people like us would be keeping these sets going after all of these years?

Nice...

A lot of that equipment was only designed to last 10 years or so.
I understand that manufacturers were only required to furnish service parts for 7 years, one most products. :scratch2:

A lot of that equipment was only designed to last 10 years or so.
I understand that manufacturers were only required to furnish service parts for 7 years, one most products. :scratch2:

I'm still amazed I fired up two of RCA 21's original fly's without much issue. Of course I cleaned off the sticky slime first using spray-9.

I just wish I had known 40+ years ago, what I could have saved....we were SO sure even way back then all parts for a 10+ TV were unobtanium.

The jobber in our area sold OEM RCA parts along with Sylvania tubes (like Moyer's still does), yet they always shoo'ed me away saying old parts were on back order, I don't stock that...etc.

16x update: Germanium diodes video and sound detectors tested good, that is 0.3volts fwd drop and no reverse current.

The HV is behaving, providing proper focus yet strangely low cathode current of 128 ma.(normal is 195 per std info). H-drive amplitude possibly affected by sync issue?

The CTC16x locks in very barely horizontally, using crosshatch or color bars it appears the first video is weak going to the 6KA8 so the scope is needed. You just know its not a tube, either

16x update: Germanium diodes video and sound detectors tested good, that is 0.3volts fwd drop and no reverse current.

The HV is behaving, providing proper focus yet strangely low cathode current of 128 ma.(normal is 195 per std info). H-drive amplitude possibly affected by sync issue?

The CTC16x locks in very barely horizontally, using crosshatch or color bars it appears the first video is weak going to the 6KA8 so the scope is needed. You just know its not a tube, either

I had to replace the 40uf cap (C1c) in mine, before AGC/SYNC would behave.

I had to replace the 40uf cap (C1c) in mine, before AGC/SYNC would behave.

I will try replacing that one on the AGC control, then check ESR on all the 'lytics in-circuit to be thorough.

I understand that multi-section lytics can present odd issues such as high impedance in the common ground, resulting in coupling of ripple between stages:thumbsdn:. My CTC11 worked OK on its originals until 2008, when it got the bends and I shut it down.
My other CTC11 had all its caps replaced, seldom used but works reliably.

To bridge all the 'lytics while observing pic, I used a 40mf @ 450v but that did not accomplish much. The alternative is to replace all 3 cans' caps*, which needs done regardless.

*I was thinking I could skip that step to see what set gets the "full monty" :sigh:first!

16x update: Germanium diodes video and sound detectors tested good, that is 0.3volts fwd drop and no reverse current.

The HV is behaving, providing proper focus yet strangely low cathode current of 128 ma.(normal is 195 per std info). H-drive amplitude possibly affected by sync issue?

The CTC16x locks in very barely horizontally, using crosshatch or color bars it appears the first video is weak going to the 6KA8 so the scope is needed. You just know its not a tube, either


Once had a blanker issue on a CTC-25 clone cause low h output current....

Once had a blanker issue on a CTC-25 clone cause low h output current....

It was a temporary issue, 6LQ6 cathode current is now dipped at 175 ma., which is still low but after an hour of narrowing the noise inverter issue, the fly is fairly warm which is concerning as always. RCA figured to "box-in" the fly to keep dust and airborne slime off the HV rect, etc. The downside is well known and Im considering a reversible modification to address that.

The Tuner-IF-1st/2nd video are cleared of causing the current issue of poor V-H lock, video appears to change every 16 seconds and I verified it by scoping the input to the 6KA8 AGC/Noise inverter. A series of sync pulses float slowly to the left on the scope, with a bunch of odd spikes appearing for an interval. All tubes have been swapped, with no changes noted.

The only clue left is 28 volts of DC voltage on the plate (keyed AGC side) of the 6KA8 where schemo shows 0.2v of DC, which gets the keyer pulse from the fly, the other voltages are within 10% of RCA schematic I'm using. I went after a few electrolytics including the 2mf on 6LF8 screen bypass and 40 mf on the AGC control, still no improvement.

I highly suspect the 560K and 22M resistors around the 6KA8 and in particular, ANY capacitor coupling on the flyback pulse leg.

"Video appears to change every 16 seconds"

This is an indication of AC line rate hum somewhere. 16 seconds is the beat period between AC power and NTSC 59.94 Hz field rate. It will show up with a full-standard NTSC source, but not with old test gear that locked the vertical to the AC line.

Bad power supply filtering? Maybe a heater-cathode short?

"Video appears to change every 16 seconds"

This is an indication of AC line rate hum somewhere. 16 seconds is the beat period between AC power and NTSC 59.94 Hz field rate. It will show up with a full-standard NTSC source, but not with old test gear that locked the vertical to the AC line.

Bad power supply filtering? Maybe a heater-cathode short?

I am in process of changing the electrolytics a few at a time, though none are heating up, they may be past reforming again. Im using the VA-48 for video, possibly explaining that periodic differentiation-style spikes going to the 6KA8 grid. It cannot even show a good air signal via the ch 6 broadcast MOD I'm using.

The H-K short must be somewhere possibly back-feeding video, from output 12BY7? I also need to throw my iso-trans/non-brightener on the CRT, it (had) tested good except with a H-K short in blue gun:scratch2: Gray scale is easy to set, but with an H-K short (considering B+ is on heater winding) THAT would present an obvious clue!

After replacing a few more electrolytic caps and the AFC diodes, no real improvement. I figure it's (the bad part) not affecting the vertical like the horiz anyway.
201953
Then I decided to scope H-osc sync coming from the horizontal AFC diodes, it looks like the trouble may be what is coming out of the AFC network :scratch2: into pin 2 of 6CG7 H-osc, also where a series RC network 12k resistor and .15mf goes to ground.

I assume this network is meant to "filter" the wave shown below.
201954

Some more caps replaced and still the same issue. The 47pf feeding AFC diodes from 6KA8 plate was a suspect along with seven others identified in the "RCA color tv service manual" to which I am referring any schematic notes to. I have an 820pf and 27pf yet to try.

Vertical lock is OK but horizontal is affected by the phantom stuff riding on what should be a cleaned up, semi-sine shaped horz sync pulse. It is no wonder the video pulls and loses lock-in, sometime locking with a blanking bar on the left side.

After replacing a few more electrolytic caps and the AFC diodes, no real improvement. I figure it's (the bad part) not affecting the vertical like the horiz anyway.
201953
Then I decided to scope H-osc sync coming from the horizontal AFC diodes, it looks like the trouble may be what is coming out of the AFC network :scratch2: into pin 2 of 6CG7 H-osc, also where a series RC network 12k resistor and .15mf goes to ground.

I assume this network is meant to "filter" the wave shown below.
201954

W/O knowing what v scale you were set to, no way to know what P-P voltage that is, :O
The Sams says 30v on the other side of R111, so without knowing what the scope was set to, I'm assuming it's abnormally high, and the clipping at the top does no look so healthy as well.
Never having had such problems on mine, I never had to poke around there, so I;m not sure what it SHOULD look like, but I'm guessing the flat tops is abnormal.:thumbsdn:
I guess I have been lucky with my 16xl and it has behaved in that aspect, or is it that you are unlucky?:D

Vertical lock is OK but horizontal is affected by the phantom stuff riding on what should be a cleaned up, semi-sine shaped horz sync pulse. .

Maybe I missed it, but have you tried another source besides the VA48? I have two and both had issues with failing bypass electros in the power supply and on the generator boards.

John

Maybe I missed it, but have you tried another source besides the VA48? I have two and both had issues with failing bypass electros in the power supply and on the generator boards.

John

My scope at input (6KA8 pin 6) shows a very noisy video with AC riding it. I assume the noise inverter is meant to clip video, leaving clean sync pulses.

EDIT: Relatively good 6 V p-p video going into 6LF8 pin 2 and then odd stuff at the plate pin 9 at much higher amplitude. The screen grid bypass cap was replaced early on, as it causes these issues in older chassis using a 6AW8.

I will put the VA 48 on a '70 Zenith 16" color and see what its does. It was fine when I was working on a Zenith last month. I have three more orange and maroon drops to try then I give up for now.

EDIT : The Zenith shows a normal picture with fill range of output, and the RCA 16x looks equally un-synced with an air signal .

This is going nowhere:sigh:, so I change chassis and go back 3 years to a simpler RCA design with a few less "features" in its circuits:scratch2:.

[QUOTE=DavGoodlin;3229725 ...I assume the noise inverter is meant to clip video, leaving clean sync pulses...[/QUOTE]

The noise inverter is expected to clip noise pulses that go in the direction of sync but are momentarily bigger than sync, like impulse noise from motors. It does not clip video, which is opposite polarity of noise pulses.

This is going nowhere:sigh:, so I change chassis and go back 3 years to a simpler RCA design with a few less "features" in its circuits:scratch2:.

Whatever the problem is, it isn't the design. I worked on many many hundreds of 16s when they were still in daily use (although getting older), and they were always rock solid on any quality of signal.

John

Whatever the problem is, it isn't the design. I worked on many many hundreds of 16s when they were still in daily use (although getting older), and they were always rock solid on any quality of signal.

John
Agreed, these look super when something wacky isn't going on. I just need a break but I appreciate the help everyone.

“Relatively good 6 V p-p video going into 6LF8 pin 2 and then odd stuff at the plate pin 9 at much higher amplitude.”

This does makes sense, as Sams shows the input to the 2nd video amp ( pin 2 v4 ) to be 5v ptp, and shows no wave for output of the 1st, pin 9, as that point still has the bias on there, I'd expect it to be garbage if you hook up there, but the fact that pin 2 is clean, means that it must be OK by default, one could also hook to the far side of color link cap (c22) and see what you have there.

But by default, if as you say the signal at pin 2 v4 is nominal, then 1st video should be fine, and path 21 is screwy if the signal is crap down there or something :o

The video circuits, if the waveforms are simpatico, can be used to compare what the 16x looked like. I replaced 14 caps and 4 resistors with nothing worse but no better.

I hope anyone trying to get one of these sets restored learns something from the trial and error. Im using the RCA factory schematic, which shows a waveform going into the 6LF8 pin 2.


I can pull out Sams 818 to double check my voltages on the 16X but at this point, we need to go back in time.

The CTC12B set I have was built in the 34th week of 1962. Edit: Model 213G216MU "Lynnhaven" in walnut.

You have me curious enough to see what that wave looks likes on my GE CTC-15 & ½ , not enough to pull apart my 16 and look, but I wanna see what that wave looks like.

Also. This may be a dumb question, but you have replaced X9 in that 16xl , cause I know the damn things have the stupid Selenium phase detectors, and when they work, they work, but when they mess up, it's pure HELL!

The GE has silicone.

You have me curious enough to see what that wave looks likes on my GE CTC-15 & ½ , not enough to pull apart my 16 and look, but I wanna see what that wave looks like.

Also. This may be a dumb question, but you have replaced X9 in that 16xl , cause I know the damn things have the stupid Selenium phase detectors, and when they work, they work, but when they mess up, it's pure HELL!

The GE has silicone.

I have replaced the horz AFC diodes, both video and sound detectors tested OK on my fluke. I wasn't looking on the convergence board for a problem yet, but some issue is lurking there like that Zenith I worked on.

The GE CA chassis has a similar video circuit to the '15, usually trouble-free.

I have replaced the horz AFC diodes, both video and sound detectors tested OK on my fluke. I wasn't looking on the convergence board for a problem yet, but some issue is lurking there like that Zenith I worked on.

The GE CA chassis has a similar video circuit to the '15, usually trouble-free.

the difference in the CTC 15/16/XL in that part of the circuit is almost non existent all use 6ka6 and almost the same circuits for generating sync.

and my GE is a hodge podge of the 15and 16/XL

what mine looked like
https://i.imgur.com/w05ehHg.jpg
and it was like that all the way to the AFC input I did think your flat tops looked odd, I would think, that if you found what was causing that, would fix most of the problems IMOH.

I think I'm starting to understand a bit more about what GE did with this thing and why RCA has a Shark Fin wave and GE has more of a sinewave in the horz AFC , RCA has the lower diode of the phase detector grounded, and GE added filtering, WHY GE chose to change RCA's design, who knows :scratch2: but that is neither here nor there when it comes to the problem with your set, :no:
having never had too look that deeply into that part of my 16, i never really got that into it.

A double post

As to your Horz AFC diodes, I wonder if RCA's patents would be infringed, yet the GE is mainly an RCA clone. The 6BH11 and another few tubes were GE's finishing touch. The only CA I saw was in HS, where we had one with a dead red gun so :sigh: nobody wanted it, as we thought a bad CRT meant death to any TV 40 years ago. Who knew they were so interchangeable and you would still find good CRT's in otherwise abandoned TVs.

The sync is indeed messy on this 16x and that garbage riding signal can be traced all the way back to 1st video stage. I am spending too much time going in circles, literally circling back to the same places to find where the phantom junk originates.

When I get back on the 16x, electrolytic caps will all be replaced, like SOP on any vintage set. But Im not sure that is the cause because bridging all the PS caps with an 80 uf / 450 v did not produce any improvement. Then again, this still could be THE whole problem.:smoke:

The sync is indeed messy on this 16x and that garbage riding signal can be traced all the way back to 1st video stage. I am spending too much time going in circles, literally circling back to the same places to find where the phantom junk originates.



It's been 40 years since I've seen a 16 much less worked on one, but one of the things we used to do with an issue like yours is to disable the sweep and see if the noise went away. The nice thing about a power transformer TV like the 16 is that it gives you the opportunity to remove any tube not associated with the circuit that seems to be suffering from spurious noise.

John

EDIT: LOL, I actually *remember* the last CTC16 I ever handled! It was somewhere about 1977 or so and I swapped it (with a new picture tube) for some minor body work on my 1973 Gran Torino. Johnny's Auto Body on West Main St. in Waterbury CT!!

.

As you may recall, it took me months to get mine working, mostly trying to get color working, and sorting out the mess that the person/persons who worked on it before I got it.
Almost EVERY resistor on the color/video pcb had been replaced with carbon film, almost all being correct values, I think that only 3-4 were wrong, 10% of the caps were replaced, color takeoff coil and bandpass also replaced before I got it, and the most disturbing sign was that the cover for the IF section was gone.
For almost ½ year, nothing I could do could get color via the tuner, but I got barberpoleing if video was fed into 1st amp, but no color lock, this was found to be because of a partially open color osc coil, fixed and BOOM color, took a while to sort that out, but still no color from tuner.
Then had the idea to go back 1 stage, unhook the video detector diode and feed video in there, NO COLOR, ding! The 4.5mhz trap was way of, some putz had tweaked it, I adjusted it while feeding in video at that point, and was able to get color via the tuner after that.

My set works pretty well now, but there are a few minor stuff.
It's obvious the IF has been messed with and can use alignment, which I don't have the setup to do, it works but not as good as it should, so I have direct input option.

Vertical blanking does not work well as it should, retrace is seen sometimes, most likely related to C31, still original part.

Shadowing in relation to light and dark objects on screen, IE, bright stationary credits on darker background, symptom seen often in these sets, also most likely due to old caps in video output.

As I deem these minor, and can do nothing about the IF, I leave it as is.

But like someone alluded to, restoring a vintage color set is like fighting a trench war with one arm and leg tied behind your back.

Slow , steady , methodical!
As suggested above, disable what is not needed and see what happens.

It's been 40 years since I've seen a 16 much less worked on one, but one of the things we used to do with an issue like yours is to disable the sweep and see if the noise went away. The nice thing about a power transformer TV like the 16 is that it gives you the opportunity to remove any tube not associated with the circuit that seems to be suffering from spurious noise.

John

EDIT: LOL, I actually *remember* the last CTC16 I ever handled! It was somewhere about 1977 or so and I swapped it (with a new picture tube) for some minor body work on my 1973 Gran Torino. Johnny's Auto Body on West Main St. in Waterbury CT!!

.

Thanks! If I still have AC getting in where it should not even after doing 100% of electrolytic caps, there are tubes I can pull like the damper, HOT and osc, HV regulator even.

............
But like someone alluded to, restoring a vintage color set is like fighting a trench war with one arm and leg tied behind your back.

Slow , steady , methodical!
As suggested above, disable what is not needed and see what happens.
After reading the VA-48 manual, its a better way to check alignment than doing the factory thing: marker and sweep gen with need for clamping AGC, etc.

You will probably tinker some more with that set over time, it looks like you have great equipment, that did not exist in the 60s.

For about 7 years now and thanks to the internet leading me to awesome folks like this forum has, I have tripled my number of projects and just now I start to recall the persistence needed. I feel fortunate to be the first one in other than tube-swappers, to see these sets as they came from the factory. To be sure, I have been able to repair super-dogs that showed evidence of long bench hours..

Each time I populate these with tubes and fire them up, my intent is to reassemble the TV again and if not 100% ready for home or sale (?), trade it to another collector. That's what we do to keep each other sharp:D:smoke:

Out to the barn I walked, thru 8 inches of snow this morning to get some tubes from about 6 caddies, and sorted vegetable flats. Caddies are all full of boxed tubes but often used/tested are found in boxes. But I did get a new 6EA8 for the tuner, several 6BK4s. I try to pick RCA tubes if possible with dates close to 62-35, date chassis is stamped.

I just fired up my CTC12 starting at 70 then up to 95 volts AC, got some RF on the 6DQ5 cap evidenced buy my neon stick, no hot stuff or smoke and good sound.:thmbsp: pics up soon :yes:

And now for something completely different. :scratch2:

looking up your scope i find...

https://www.youtube.com/watch?v=aMli33ornEU
Weird!

I usta do this on the shop scope to impress the Boss (no audio of course). Used the Z input on the back of the scope for luma.

https://www.youtube.com/watch?v=hqKssQYLWaA

I usta do this on the shop scope to impress the Boss (no audio of course). Used the Z input on the back of the scope for luma.

https://www.youtube.com/watch?v=hqKssQYLWaAVery cool thanks for posting this. I worked at two companies in the 80s that were Defense Contractors and they had a zero-tolerance for any outside radios, players, walkman, etc. I had an uber-expensive HP spectrum analyzer and the receivers we made used headphones, that is all you needed plus an antenna to get FM. Several of us were able to listen to the Iran-Contra hearings on WAMU from DC, then we talked about it in the lunch room. The DCAS guys were the G-men who came in to audit procedures, etc. These guys were in to audit while I was listening to WWDC-101.1 and pretending to work on a receiver, still could not help but laugh up my sleeve at the whole affair, my headphones were plugged into the spectrum analyzer the whole time.:D

My Tek-516 is huge and the RCA WO-91 is just a bit tricky to measure voltage, but the Hitachi scope is fast and portable. Is this what you do at work if "TV sets" are not permitted?
I bought it from the son of a repairman from RI. He lives above my storage garage and one day showed all this stuff of his Dad's he was trying to sell on Ebay. I made a fair offer and got the scope, a Lafayette signal generator and some RC sub boxes.

O_o

Stop making me feel like such like one of the “Young Ones” here, in the 80s, I was still in the middle of my school years, watching as much MTV as I could on a 19 inch BW tube set that I got someplace, recording rock and all sorts of stuff on my voice of music 722 reel to reel deck, including The doctor demento show, annoying my parents by blasting the home with sound from my Sansui 1000 which was more powerful than anything they had at the time!

The generation 20 years later has easily picked up what we sometimes learned ONLY the hard way by having to make a living fixing other peoples TVs. Watching some of DRH4683's videos on U-toob I cant believe he's 20 years younger. I was positive this would fade by the late 80s and what I see on this forum, ARF and FB give eternal optimism.

Being fortunate to grow up with a tank-like Motorola BW ('63 like my avatar), a '46 Philco transitone AM in bakelite (my Dad's at age 12) then a 71 Zenith color TV at age 8, the smell of hot dust on tubes was irresistible. For the next 5 years, I had real modest stuff in my room and was not allowed a TV until age 13 when the old Motorola BW came back dead (just the line thermistor) from its travels. I also got a working '63 Zenith BW (16K20?) that my uncle left on their porch for summer ballgames.

I toasted my Fisher 610 receiver chassis' iron over the summer leaving it on overnight listening to any myriad of stations that thing pulled in with ease. I saved $27 from painting jobs and bought a GE C-4315 AM-FM clock radio just in time for 8th grade. The FM reception was poor, so I opened it up and ran an external antenna out and added external speakers. I later got the guts of a Motorola Stereophonic with 4x6BQ5 outputs and the rest is HiFi history.

MTV went on cable the same year I graduated HS and left for the big city of Allentown, moved into an apartment complex which was in a terrestrial dead-zone, cut off from the PHL and NYC, TV and FM. We had a series of Zenith, RCA, Magnavox and Admiral sets there hooked to cable with FM simulcast of MTV, HBO and some others. The Dynaco amp and speakers became our very own "pro-feel" system at least power and sound quality rivaled a new Sony then.

201966
As you can see some rust where mice peed on the CTC12B chassis but only destroyed the damper tube socket, the filament keeps going out. All 4 PC boards were spared the :thmbsp:. This set was full of nesting material when I got it.

This looks very promising as long as there are no gremlins like the other two chassis. The 12's HV is robust at 25 kV (dark screen) and adjusts easily and so is audio. I can’t get a picture unless I reduce then advance the contrast control and see a momentary flash of a raster. The service switch gave me a fuzzy but solid line that I could verify R-G-B screen controls operated. I pull out my handy “Pomona” CRT adaptor so I could easily measure crt gun voltages, and they looked within 10% of schematic K=335v, G1=190v, G2=615v

It was then, right at bedtime that I noticed a little black wire was missing from the 4.7meg 2w resistor in the HV cage to the CRT socket for the focus anode. It must have been pulled out of the CRT socket, leaving the pin when I initially got the set and immediately cleaned it out 5 years ago.

The CRT socket has two rivets so I can access to solder on some Belden wire rated for 20 kV that of similar size and black insulation like original. I can replace the wire to 6DQ5 cap as well. If this works out, I will do all the electrolytics, they being even older than me:sigh:

Very cool thanks for posting this. I worked at two companies in the 80s that were Defense Contractors and they had a zero-tolerance for any outside radios, players, walkman, etc. I had an uber-expensive HP spectrum analyzer and the receivers we made used headphones, that is all you needed plus an antenna to get FM. Several of us were able to listen to the Iran-Contra hearings on WAMU from DC, then we talked about it in the lunch room. The DCAS guys were the G-men who came in to audit procedures, etc. These guys were in to audit while I was listening to WWDC-101.1 and pretending to work on a receiver, still could not help but laugh up my sleeve at the whole affair, my headphones were plugged into the spectrum analyzer the whole time.:D

My Tek-516 is huge and the RCA WO-91 is just a bit tricky to measure voltage, but the Hitachi scope is fast and portable. Is this what you do at work if "TV sets" are not permitted?
I bought it from the son of a repairman from RI. He lives above my storage garage and one day showed all this stuff of his Dad's he was trying to sell on Ebay. I made a fair offer and got the scope, a Lafayette signal generator and some RC sub boxes.

A friend of mine works at a defense contractor it's easier for him to listen to 8-tracks than any other format. Since most machines especially the one he uses can't record. CDs, MP3s cellphone media playback fuggedaboutit.

It was then, right at bedtime that I noticed a little black wire was missing from the 4.7meg 2w resistor in the HV cage to the CRT socket for the focus anode. It must have been pulled out of the CRT socket, leaving the pin when I initially got the set and immediately cleaned it out 5 years ago.



Wow, that triggered a memory. Back when I was 15 or so, I had an early RCA (15, 16?) that had no picture. It had good HV, all the voltages on the CRT socket were there, and I even put our old RCA scope on it and verified video to the CRT socket (my older brother was schooling me on scopes and things). I told my dad that I thought the picture tube was bad. He laughed and told me to change the 2AV2. I then noticed the tube had white residue inside it - hard to see when it had a lovely amber coating of cigarette tar on the outside. The 2AV2 fixed it. Never forgot that lesson.

John

Wow, that triggered a memory. Back when I was 15 or so, I had an early RCA (15, 16?) that had no picture. It had good HV, all the voltages on the CRT socket were there, and I even put our old RCA scope on it and verified video to the CRT socket (my older brother was schooling me on scopes and things). I told my dad that I thought the picture tube was bad. He laughed and told me to change the 2AV2. I then noticed the tube had white residue inside it - hard to see when it had a lovely amber coating of cigarette tar on the outside. The 2AV2 fixed it. Never forgot that lesson.

John

the 2AV2 is used in the CTC-16XL not the others like the 15 or 16. :no:

:smoke:The contrast control was open, allowing the 12BY7 cathode to rise to 40 volts DC, cutting it off. Part #112840 I could easily order another from Moyer's, but found a 368 ohm with same shaft in my "stash" that even had the tap when the original did not. Ill end up placing an order for something before this is over.

Now I have a raster, can get chroma lock with hum bar and poor vertical sync. The next step is a full recap, CTC12 chassis has a similar problem to the other two and I just need to bite the bullet and recap.


I was also working on this set Saturday night during the Zoom with ETF with my video on.
Steve, Mr. Mike and everyone else made it the most interesting thing "on" that night!

the 2AV2 is used in the CTC-16XL not the others like the 15 or 16. :no:

1V2, 2AV2... pretty much the same tube. Your Nitpick award is in the mail.

But I **did** forget that the 15 was the lone departure of a long line or RCA color TVs that didn't use some sort of tube focus rectifier. :cry:

We used to carry at least six 2AV2s on the truck all the time, but I can't recall changing more than a small handful of the SS rectifier in the 15 series.

John

1V2, 2AV2... pretty much the same tube. Your Nitpick award is in the mail.

But I **did** forget that the 15 was the lone departure of a long line or RCA color TVs that didn't use some sort of tube focus rectifier. :cry:

We used to carry at least six 2AV2s on the truck all the time, but I can't recall changing more than a small handful of the SS rectifier in the 15 series.

John

The 1V2 has an absolute max heater volt rating of 1.45v and a min of 1.05.

The heater voltage for the 2av2 is, 1.8v +/- 0.27v
and the spec clearly states “ under no circumstances should heater voltage be less than 1.53v or more than 2.07v

And yes, where the may be almost the same tubes, the heater voltages make them unsuitable to be interchangeable, or at least I would never do so, thus the reason I mentioned it.

:thmbsp:The 1V2 has an absolute max heater volt rating of 1.45v and a min of 1.05.

The heater voltage for the 2av2 is, 1.8v +/- 0.27v
and the spec clearly states “ under no circumstances should heater voltage be less than 1.53v or more than 2.07v

And yes, where the may be almost the same tubes, the heater voltages make them unsuitable to be interchangeable, or at least I would never do so, thus the reason I mentioned it.
I worked on a CTC16E, that had a 1V2. The filament dropping resistor changed value and couldn't get proper focusing.
I jumpered out the resistor and installed a 2AV2. Problem solved.

:thmbsp:
I worked on a CTC16E, that had a 1V2. The filament dropping resistor changed value and couldn't get proper focusing.
I jumpered out the resistor and installed a 2AV2. Problem solved.

Or just forgo the differences with them all as I did with my 16XL , and get a plug in SS tube, ECG511 / R-2AV2, less draw on on the FBT helps, even if it's tiny as the heater current.
However, it's been proven that the SS substitute for the HV rectifier will not work, and overheat and burn up, it happened to me, and to shango066 ( as seen in one of his videos ) on a CTC-16.
Not sure why it smokes, but it seems only the good old glass type works.

And yes, where the may be almost the same tubes, the heater voltages make them unsuitable to be interchangeable, or at least I would never do so, thus the reason I mentioned it.

You missed the context of the story, which was how a bad focus rectifier tube could eliminate the raster (a fairly non-intuitive cause/effect which is why I related the story from 45 years ago). I put a question mark after CTC 15 or 16 because I wasn't sure which chassis it was, and indeed it wasn't important to the story. I wasn't offering any specific technical advice to someone asking about focus rectifiers, or suggested the 1V2 or 2AV2 would sub for each other. Again, within the context of the story, it's sort of picking nits.

John

However, it's been proven that the SS substitute for the HV rectifier will not work, and overheat and burn up, it happened to me, and to shango066 ( as seen in one of his videos ) on a CTC-16.
Not sure why it smokes, but it seems only the good old glass type works.

Strange. I used to use the EDI 3A3 sub towards the end of the tube era and they worked fine (I think it was EDI, it had a brown and black box). I used both the 3A3 and 3AT2. They were nice because the 3A3 subbed the 1V rectifier tubes in B&W TVs as well as offer X-Ray protection, or so they claimed.

When we changed my dad's original sulfide CRT in his CTC11 with a HiLite rare earth tube, it would eat up 3A3s every couple of months (blooming). We put in an EDI 3A3 and lasted a day and failed. We returned it for exchange and the replacement lasted another 5-6 years or so until the replacement picture tube got weak and it was retired for a '77 XL100.

I cannot say with any degree of certainty that I used on in a CTC16 specifically though.


John

Always like the idea of less flyback load:D, also glad not to be using the SS version of a 3A3, yet that filament load could have a measurable effect on 6JE6 cathode current.
Very Good point. Its not enough that I use the 128v High Line tap on the power transformer when we run 121-124 v here thanks to a new pole transformer:sigh:- not an option on CTC11 and older chassis tho.

Both shango066 and I tried the NTE508 / SK3756 version and they both fried, mine in 90 seconds, his in about an hour, who knows, perhaps a real EDI 3A3 sub would have worked, but they be hard to find.:tears:

This does however bring up a question that I have tossing with for a while, should the FBT in my 16LX ever fail beyond repair, I do have a replacement for it, but it's not a FBT for an XL, but an NOS one for a CTC-16, which is vertically identical, save for the heater windings/ voltages, since I have a SS focus tube, that won't matter, it will be unhooked, but the HV rect, add a 2.4 ohm res and use a 3A3? Or hook direct and keep using a 3CA3?

Of course, this is all moot, if the FBT in there now never dies!

Both shango066 and I tried the NTE508 / SK3756 version and they both fried, mine in 90 seconds, his in about an hour, who knows, perhaps a real EDI 3A3 sub would have worked, but they be hard to find.:tears:


That makes me wonder if the ECG and SKs weren't sourced from the same company not named EDI. Other than the one bad SS EDI in my dad's TV, I sold a few dozen (not a big sample I agree) and can't remember any problems. I also sold a few dampers as I recall with no callbacks.

I may still have one somewhere in storage. If I run across it, I'll take a pic of it or you can have it for experimentation.

In retrospect though, I wonder how a shorted SS rectifier would affect the fly. If a 3A3 goes bad, they only go inert. Maybe a SS rectifier isn't a great idea.

John

Of course, this is all moot, if the FBT in there now never dies!

God willing..

Most of the RCA flybacks we changed back in the 60s and 70s were in the summer. We'd get a run on them whenever we had a stretch of hot humid weather. Today, most of us have AC which would mitigate that factor at least. Plus, most of us don't run our vintage TVs 50 hours a week either.

Seeing that a good portion of the RCA flybacks that failed did so by burning a trail from the 3A3 cup to the core, I would carefully clean any vintage fly boot with alcohol to remove any remnants of dirt or ciggie smoke left over from the old days that might show the arcing gremlins the way.

John

This is his video where it happened.
https://www.youtube.com/watch?v=anXLhlAefG0&t=4s

I kept saying to myself, “it's gonna burn up, it's gonna burn up!”
and sure enough.. as soon as I saw his screen dim, and shrink I knew exactly what was happening, cause it did it in mine.

This is his video where it happened.
https://www.youtube.com/watch?v=anXLhlAefG0&t=4s

I kept saying to myself, “it's gonna burn up, it's gonna burn up!”
and sure enough.. as soon as I saw his screen dim, and shrink I knew exactly what was happening, cause it did it in mine.

OK, I watched it. His voice makes me want to poke ice picks in my ears...:yes:

That SS stick rectifier he pulled out looks exactly like the EDIs I used to use. I was skipping along the video so I didn't hear if he said what kind of rectifier it was.

I don't think this would be an issue with using stick rectifiers with the 16 necessarily, but just a substandard device that would fail in any color TV. That rect will probably still be able to replace a 1X3 series since the B&W requires less HV and current than the 21" color tube.

During the Christmas break, I'm going to see if I can find an EDI 3A3. If I can find it, I'll send it to you for experimentation if you want to screw with it.

John