This weekend I intend to go out and get that Stromberg Carlson X-21 M4B television that is to be my restoration project next year.

It's a bit of a drive, but not TOO FAR, but I am having to borrow my mom's car to move it, ( laid face down in the back on foam and covered with blankets ) as there is no way to fit it in my Yaris. :(

I can find little about this specific model “M4B” but it IS seen in this reference, http://www.earlytelevision.org/pdf/rider-67.pdf
And I know that the inner core of it, X-21 was used in many other sets, so it should not be that hard to deal with.

From what I saw, the cabinet had some exposure damage, and will need some work as well, no telling what the chassis is like after being in storage, just gotta wait ant see! :)

But the very first thing I will do when I get it home is get the 21AUP4A on my BK Precision 490B, and see how well it is going to wake up!

I can find little about this specific model “M4B” but it IS seen in this reference, http://www.earlytelevision.org/pdf/rider-67.pdf
And I know that the inner core of it, X-21 was used in many other sets, so it should not be that hard to deal with.


Since you're not in a hurry keep your eyes open for a copy of Riders Television 16. There is a PDF available but I hear they were scanned in black and white instead of greyscale. Those higher volumes should be between dirt cheap and free if you can locate one.

i have it!

https://imgur.com/DzWYsx1
https://imgur.com/LeBQKOI
https://imgur.com/2VzMtmN
https://imgur.com/IEPS7PV
https://imgur.com/u2OLLyq
https://imgur.com/MWX0FI7
https://imgur.com/VwqCuEK
https://imgur.com/2gGWpb3
https://imgur.com/hRrG3Br
https://imgur.com/vlKvF3t

it got pretty beat up in storage :(

I have it on the CRT tester now, in wake up mode

it's a keeper! :banana::D

it went from 0 emissions to...
https://imgur.com/w949ztm
in just 3 hours,
will keep it on the tester for a few days!

something tells me that this cap has been replaced before!
https://imgur.com/YXDFt0l

:D

something tells me that this cap has been replaced before!
https://imgur.com/YXDFt0l

:D

Paper label us usually the giveaway!

bottom view

yop!

this has been worked on before!
https://imgur.com/6TDSerm
https://imgur.com/uFMrgvK

CRT removed.
https://imgur.com/sluDuPp
https://imgur.com/O1CIaSV

losing some DAG already :(

CRT removed.
https://imgur.com/sluDuPp
https://imgur.com/O1CIaSV

losing some DAG already :(

Just knock the loose stuff off, mask the areas that shouldn't have dag and spray some Slip Plate on it. That will fix the bald spots long term.

The chassis is in better shape than I thought it would be, having spent unknown years in what appears to be a barn or something, it IS still quite dirty topside, I may try to clean it off before setting it aside for the cooler time of year to start on it.

The cabinet will no doubt prove harder than the electronics itself, having taken most of the beating over the years, the wood under the chassis has to be replaced, its ruined, and I will most likely pant the entire thing after removing the rotted bits and filling it in with filler, its mostly all on one lower side.

One thing that may be a PITA once I get this thing working and cleaned up and ready to go back together, 2 of the 3 little control knobs on the front are missing, not gonna be easy to find 2 to match the one left or 3 that fit that look well on the set. :/

The chassis is in better shape than I thought it would be, having spent unknown years in what appears to be a barn or something, it IS still quite dirty topside, I may try to clean it off before setting it aside for the cooler time of year to start on it.


You guys are really cooking down there. My son is southeast of Austin and reported 99 over the weekend. With the humidity I think I would wilt doing anything outside during the daytime. :sigh:

...

You guys are really cooking down there. My son is southeast of Austin and reported 99 over the weekend. With the humidity I think I would wilt doing anything outside during the daytime. :sigh:


yes, we be roasting here :(

https://forecast.weather.gov/MapClick.php?lat=30.55737350000004&lon=-97.66795299999995#.XzGXuH57lQI

Well you all could come to Wisconsin to cool off in the severe thunderstorms we've been getting the last couple of days... The dime sized rain drops are refreshing till the thunder scares you inside. I make it sound so appealing don't I? :D

Well you all could come to Wisconsin to cool off in the severe thunderstorms we've been getting the last couple of days... The dime sized rain drops are refreshing till the thunder scares you inside. I make it sound so appealing don't I? :D

Oh, we also get pretty bad thunderstorms here too, lots of huge rain, wind, hail... Hail hail fire and snow, call the angel, we will go... :o
Wait a sec, lets NOT go there! :)
Anyway, thunderstorms, tornadoes, etc...
Which leads to another strange tale, my parents place has ( still does ) a primitive intercom system in it, all transistorized, with the electronics being in the main unit, and the remotes being nothing but a speaker, switches and pots.

One night there was a rather bad thunderstorm, as I was trying to sleep, ( or as I was almost asleep), there was a deafeningly loud KOBOOM and bright flash outside the widow, ( my window and my parents faced front), it was soon found out that struck the oak tree out front.
It felt like I jumped 3 feet above my bed when it hit...

It was quickly seen that not only was the tree hit, but the bolt had forked, and blasted through the roof and hit some metal molding that ran between the wood boards above the awning over the entryway and found it's way to a light fixture, all the edges were burned.
Afterward, it was found that the intercom control unit had been burned out and had to be replaced, but after it was, the 2 forward facing remote units still did not work right, this made no sense, for there was no semiconductors in them, so how could they be affected?
After they too were replaced and the entire system working again, it was soon discovered what happened to the remote units, the strike had somehow disrupted the permanent magnets in the speakers leaving them too weak to be of use anymore.
Something to this day that still boggles the mind. :o

Shortly after that happened, my parents had lightning rods added to the house, and there was never a problem with strikes again.

Lol.

Back when I lived in Florida the family home had been through something similar before we bought it. Supposedly it had taken a lightning strike and the ground floor AC was taken out (it's junction box and a number of outlets were rather sooted up). We had this late 70s Nutone intercom system that was dead (don't know if it was the lightning or what) but the early digital LED clock still worked (albeit it wouldn't allow setting time). I was a teen then and just getting the hang of tube stuff but not familiar with SS so I left the intercom be.

what I find amusing is, this thing has 23 tubes, and the RCA 630TS / FADA has 30. :o

Just knock the loose stuff off, mask the areas that shouldn't have dag and spray some Slip Plate on it. That will fix the bald spots long term.


would something like film tape work also?
like i am using here?
https://imgur.com/xOxAbso

would something like film tape work also?
like i am using here?
https://imgur.com/xOxAbso

Unless the glue in the tape is conductive, NO it's not a substitute. Slip Plate is fairly affordable and is essentially aquadag spray paint. If you want to continue restoring sets this $18 can will respray many CRTs for future projects. https://www.amazon.com/Slip-Plate-Plate%C2%AE-Aerosol-12-oz/dp/B005ESITFQ I got 3 roundy CRTs and 2-5 black and white tubes out of my last can....I'd have gotten more out but the mixing ball was a glass marble and it eventually chipped up and the chips clogged the spray valve...I ended up carefully venting the remainder of the can into a bottle where it dried on me before I could use it all...I need to order another can one of these days.

Many sets especially those with doorknob HV caps don't need all their dag....But the dag has to be grounded, and every bit of dag has to be electrically connected to every other bit or arcing will occur between day islands. This arcing creates electrical interference, HV ripple and if strong and sustained can locally heat the CRT glass and cause implosion in some extreme cases.

In a pinch Blaster graphite spray lube from the hardware store can work but it's resistance is a bit too high for the application....it's basically watered down slip Plate.

Is it me, or does it seem that the GE 21AUP4A in the Stromberg Carlson x-21 was made rather thin compared to other tubes of its size? :O

hauled the SC chassis upstairs to take a look at it, and noticed as i mentioned before, it has been worked on before at least once if not more.

I also saw this right away.

https://imgur.com/Ob83Mxm

burned resistor

it SHOULD BE100 ohms...
https://imgur.com/xAm1uzk

it checked at 187 ohms.
the cap with it is way bad too, should be 5mfd checks at 210 pf.


that being on the HOT cathode, I have doubts this TV was working very well at all like this when it was put in storage.

I will no doubt find many other crappy caps all over the set, and it's too risky to power up in this state as of now.

As i showed before, C1 in this set has been replaced before, but that does not mean that it is still good :(

most likely is, but who knows

https://imgur.com/fCAigeF

right now, i have it isolated from everything else and am powering up on a variac to 300 v for a while.
the cap is rated at 450v

While the rest of the country tends to think of the northeast as being always cold , every so often even here the heat vents of Hell open up and we roast pretty much like the rest of ya . Only difference is on average we get maybe 20 or so days of this each Summer , VS the southern states that roast pretty much all Summer long .

I live in northeastern Ohio, 30 miles east of Cleveland, which often gets very hot weather this time of year. This summer has been very hot and humid here so far, with temperatures in the 80s and lower 90s; fortunately, I live in an apartment building with central air, so the heat doesn't bother me as long as I don't go outside during the day for any length of time. If I have things to do outside my apartment (taking out trash, etc.) I always wait until at least seven or eight o'clock or so, when the heat is not nearly as bad.

I like summertime, as it is my favorite time of year (I was born in the middle of the summer of 1956, which has a lot to do with it), but gee whiz, this beastly hot weather we've been seeing here this summer is too much. I guess I should enjoy it while I can, though, because it won't be long before it gets colder than the proverbial iceberg and the snow starts. This region can and does get some bad snowstorms (how can I ever forget the Blizzard of 1978, in which the entire Cleveland area and other parts of the country were snowed in for days or weeks), but not nearly as bad as Buffalo and Syracuse, New York, so I guess I should count my blessings.

Oh well, that's life in the Great Lakes region of this country, like it or not. I've been here all my life and am used to it by now. Goodness knows I don't like it, but that's the way our weather is in the winter.

FAILED!
https://imgur.com/nCuesm2
after 10-15 min the cap was 115f-120f not going to trust it! :thumbsdn:

FAILED!
https://imgur.com/nCuesm2
after 10-15 min the cap was 115f-120f not going to trust it! :thumbsdn:


I hope you get that SC TV working again. Those were good sets. My aunt, now deceased, had a Stromberg-Carlson TV in a white console cabinet with doors and Chinese style door pulls (the thing weighed the proverbial ton, as do all consoles; in fact, the picture of your own SC console reminded me of it), which was, I believe, the first TV she and her husband had. I don't know how long that SC TV lasted for them (I think it may have gone until the mid-1960s), but when it finally died it was replaced by a metal-cased RCA Victor 17-inch portable.


The RCA portable lasted some time (don't recall how long) and was replaced by a Westinghouse instant-on (!) color console. By then (after she divorced her husband), my aunt had moved to a Cleveland suburb that was in a very strong signal area, so her new Westinghouse color TV could receive all six Cleveland TV stations in color (the picture looked great, as I recall), without an antenna (the first "antenna" she used on that set was a piece of wire). Eventually, however, she got a Spico all-channel rabbit-ear TV antenna which she wouldn't have needed in that area, as strong as the TV signals from the local stations were. She eventually moved to an eastern Cleveland suburb, but kept the Westinghouse TV and its rabbit-ear antenna.

The rest is history.

I'm a bit disappointed the cap is bad, but not surprised, seeing as the set was kept in a damp environment for such a long time that the cabinet is warped, and will most likely be harder to fix than the electronics.
No telling when in the past that cap was replaced, but it should not be uncomfortably warm to the touch after being powered up for just such a short time, oh well, just one more electrolytic capacitor to replace, IE all of them...

OK... this is a bit confusing
the 21aup4a has an aluminized screen and an ion trap?:saywhat:

I thought ones with aluminized screens did not need traps.

or is this just an odd tube?

https://frank.pocnet.net/sheets/093/2/21AUP4B.pdf

snip/ paste from another froum
>The Ion trap was used to prevent “ion burn” to the screen.. It is impossible to remove every molecule of gas from the tube. The electron beam strikes molecules of gas, knocking off an electron thus creating an ion. These ions would travel to the screen and damage it causing “ion burn” which showed up as a dark patch in the middle of the screen. Eventually aluminized tubes solved this problem completely. But before aluminized tubes were invented the combination of a “bent gun” and an ion trap protected the screen. The bent gun was actually pointed at an angle so the electrons would have struck the neck of the tube somewhere. But the magnetic ion trap was used to bend the electron beam so that it would hit the screen. Those nasty ions, being heavier than electrons were deflected by the magnet of the ion trap, differently than the electrons so they did not hit the screen. In an aluminized tube, a thin coating of aluminum is deposited over the rear surface of the screen. The Aluminum also covers the whole inside surface of the tube. It does at least 4 important things. <P>(1) It protects the screen from ions, thus eliminating the need for the bent gun and ion trap.<BR>(2) It reflects the light emanating the rear surface of the phosphor screen to the front thus almost doubling the brightness.<BR>(3) It prevents scattering of the light inside the tube thus improving contrast.<BR>(4) It acts as one plate of a high voltage capacitor. The other plate is the conductive outside paint or “aquadag”. This capacitor filters the high voltage. Which is derived from the horizontal oscillator and has 15 kHz ripple.

thus my confusion with this tube

If it was rebuilt it's possible the rebuilder only had the older bent guns on hand and used what they had... I've heard of this several times before.

I doubt it had a trap from new but some of the early aluminized types did either due to logistics or cases where the standard type of a tube was non-aluminized but the A postfix version was aluminized.

And it starts! :)

I have just ordered a mess of electrolytic capacitors for this set.
This sort of adds more fuel to the discussion that popped up in another thread about replace vs reform, I pretty much knew that C1 would fail, but I was gonna try it anyway, because the original had 3 sections in it, and the replacement cap had 4, one that was unused left unhooked, and when I hooked a tester up to it, ( I tried 2 different ones. ) it mesured over 3 times what it should have been...
So as I mentioned, I was not surprised when I put power to it and it got uncomfortably warm to the touch after only 15-20 min, not to start the replace vs reform thing going again, but for me at least, after that, there was no way I was going to trust that cap.

.....(4) It acts as one plate of a high voltage capacitor. The other plate is the conductive outside paint or “aquadag”. This capacitor filters the high voltage. Which is derived from the horizontal oscillator and has 15 kHz ripple.

I beg to differ. the capacitor that filters the HV is composed of the aquadag coating on the outside of the CRT, the aquadag coating inside of the CRT and the glass between the two aquadags acting as the dielectric. The aluminized coating on the back of the screen is not part of this capacitor.

I doubt it had a trap from new but some of the early aluminized types did either due to logistics or cases where the standard type of a tube was non-aluminized but the A postfix version was aluminized.

Indeed, it appears that the first configuration of the tube was not aluminized, only the A and B were. The later versions provided a brighter picture, but the gun design was not changed.

https://frank.pocnet.net/sheets/127/2/21AUP4.pdf

jr

worked on the SC a bit tonight :)
replaced the multi can caps, and a few papers.
https://i.imgur.com/HrEK6JY.jpg

admired the really ugly solder work of the person who replaced the cap before me.
:thumbsdn::nono:

then did something rather bold and Shango like, did a slow power up just to see what would happen, YES, I still have a bunch of papers to replace, but I wanted to see anyway.

after a slow bring up... no smoke , no fire, had the teltale hiss in the speaker.

flipped the phono/TV switch into TV mode to see if HV would come on,.,,, nothing... no surprise, it has been sitting forever.
did some checking ,, found NO power at the cap of the HOT, hmmm am i missing a voltage?
did some checks, they seem to be all there, what's going on here :o

check fuse for HV, Ok... voltage at damper OK, out of damper, OK... this is NOT looking good! :(

power is getting to the FBT, but not the HOT plate cap? :(

pulled out the FBT.. resistance check OK... huh? :o
https://i.imgur.com/bd06HX6.jpg

power comes in from damper to FBT on red wire, out to HOT on the yellow...
wait a sec, it is there and OK when measured at the lug of the FBT but gone at the HOT?

this is something I have not seen before :o the wire IS connected, but degraded and not carrying power :o
it's all green and krusty...
a first for me :p

The SAMMs for this set is getting extremely frustrating with its lack of info/ omissions.
Example, the LV power source seems to be just 2 voltages, 290v and 95v, there is a voltage divider off the 290v line noted as “voltage source R” this goes to the 95v line, it has r128 r129 (4.7k) and c5 (10uf)
however they are flagged as “not used” in some sets, I have looked, and looked AND LOOKED... their location is not shown anywhere in the pics in this SAMMs folder, I have no idea where they would be if they are in this set, furthermore... if it DOES NOT have that voltage divider (r128-129 c5) then where the hell does the 95v come from?
Been looking for hours and can't work it out, the SAMMs must be incomplete, :(

:scratch2::tears:
If you wish to share in this agonizing frustration, you can grab the SAMMs from my FTP and see for yourself!

Yes, people still use ftp :o

address = suzaku.us
name = videokarma
pass = rcavictor100

it's alive! sort of!!
https://imgur.com/76iHGNt

I saw what I wanted to see.

I have a lot of caps to replace!

things done so far...
replaced the 2 multican electrolytic caps C1 & C2

https://imgur.com/9cm9vHf
C1
replaced a few paper caps in the area.
will silicone the caps down next to the x-former once the other caps are replaced.

https://imgur.com/H0w6Qs0
C2

Replaced the faulty wire from the FBT to the HOT place cap.

there is obvious Vert sweep problems, and the Horz is off freq.

will try to work on it a bit each week a bit .

This SAMMs is really starting to annoy me,, where the HELL does the 95v come from?

it does not make any sense...

does anyone have the riders version for this? perhaps they did not lay it out so stupidly...

Looks like they are pulling it from the cathode of the 12BY7 video output tube. They are using that tube as a voltage divider in other words.

I'm look as Riders vol 16. Not sure how it looks in Sams.

Looks like they are pulling it from the cathode of the 12BY7 video output tube. They are using that tube as a voltage divider in other words.

I'm look as Riders vol 16. Not sure how it looks in Sams.
the Sams is very very confusing

https://imgur.com/YseSmi3
those dots mean voltage mesured from 95v line.

https://imgur.com/Ev1QkEu


r56 is 1/2 watt, (or so it says ) here om sams, that is a lot of power to be pulling through that resistor for that line esp when the alt version Volt source R, which is not in this set, is seems, uses 2 watt resistors :/

nothing here seems to make any sense...
there should be a alt high power source for the 95v but not sure what it it.

i spent the night replacing a lot of paper caps, 90% were quite bad, after which i was able to get a full screen raster, but still could not tune in anything...

then I remembered :yikes:

the horrid problems with contacts the drum tuners have, so i opened it and looked...
https://imgur.com/ZhqjAHK
:eek::yuck:
black as night.

so i scrubbed off chan 3 with an eraser, and.
https://imgur.com/Heff2BR

:yippy:

great progress for such a short time!
I still got caps to replace, and I'm sure that there are bad resistors in there too.
but it's going OK so far.

https://imgur.com/fEsFhYK

here it is today

tuner is still giving problems.
works sometimes then stops

this is with direct video input

still have vert lin problems
will prob have to pull all tubes and scrub pins and sockets.
and replace even the caps that were replaced before, and not assume that they are OK even though they are not paper ( film type ) who knows how long they were in there...
https://i.imgur.com/HrEK6JY.jpg
you can see one of the old replaced caps in the top left. although, it could also be resistors causing the problem.

vert linearity looking much better.
https://imgur.com/gcteUfS

found bad resistors.

https://imgur.com/5c1EP28
r58 r59
way WAY off, they had been replaced before, but are still no good.
had 1/2 watt ones in there, put in 1 watts

https://imgur.com/jduVGCo
REALLY BAD :o

will prob find other very bad resistors too :/

All tubes have green krud on the pins like my FADA did, so I'm guessing the sockets are dirty too, rather than trying to clean the RF/ IF tubes, I will just replace them, they are old enough, example, when I removed the 4th IF, this was not easy because the tube shield was rusted on, ALL of them are rusty :( , the tube under was an original stromberg carlson tube ( 6cb6 ) though I could not find any trace of that number on the tube, I don't know if it came off, or if was never on or what :o

I'm still debating on taking apart the tuner to try t clean it, the SAMS clearly shows a pic with the drum removed , showing the contacts, but I'm not sure how it comes out, if it comes out w/o much trouble, then it would make easy access to the contacts for cleaning.

I always took out 3-4 of the individual strips and that was enough to gain access to the stationary contacts. No need to remove the whole drum.

Yes, I see that now, I just found a site that shows that they can be removed for cleaning.
https://www.rfcafe.com/references/popular-electronics/taming-tv-tuner-popular-electronics-march-1967.htm

This is my first time ever trying to clean this type of tuner, have seen mostly rotary switch type before.
Though the contacts ARE dirty and black in this tuner, I'm still not sure what is going on with the front end, by video injection, I have proven that all after video detector diode is OK and stable but tuner input is intermittent, which may or may not be due to contacts or dirty tube pins, (new clean tubes on the way) , or, it could also be out of tol resistors in the tuner/IF/AFC area.
Not really sure at this point, will have to see how it behaves with known good clean tubes in and cleaned sockets.
How it is behaving is a bit unusual something I have not seen before anyway, when the front end works, it works rather well, stable and solid for quite some time, but when it acts up, the screen goes to a blank raster, but only if it's being fed a signal on a given channel (rf mod into 3) , if I change away from chan 3, or shut off the rf modulator, the screen goes to snow, and back to raster when turned back on.
AGC problem? Noise cancel error? Flaky video detector? Or just a weird symptom contact problems perhaps?

Looks like they are pulling it from the cathode of the 12BY7 video output tube. They are using that tube as a voltage divider in other words.

I'm look as Riders vol 16. Not sure how it looks in Sams.


this may be what I have been looking for!
https://imgur.com/1NfY1AN

not on the 12BY7 video output tube, but on the 12AU7 sync phase inv,
it has the 1w 3.9k resistors on the plate and cathode, and is most likely the source of the 95v in this version of the set, which I have been looking and looking for, so I could replace those resistors to stabilize the 95v line. :o

Look at the revised circuit in the SAMS which you show in your last post. In the revised circuit the 12AU7 isn't even connected to the 95V line. R96 goes to ground, not the 95V bus in the revised circuit. The voltage dropping function is typically handled by the audio output tube.

Look at the revised circuit in the SAMS which you show in your last post. In the revised circuit the 12AU7 isn't even connected to the 95V line. R96 goes to ground, not the 95V bus in the revised circuit. The voltage dropping function is typically handled by the audio output tube.

that's what i dislike about this SAMS. you do not know what is really in this set until you track it down.
i did a quick look, and the cathode is indeed tied to the 95v line and not ground in this set.
https://imgur.com/mVtjfmc

that being the white wire...
r96 checked as 4.7k in circuit, i got to replace both! :(

Look at the revised circuit in the SAMS which you show in your last post. In the revised circuit the 12AU7 isn't even connected to the 95V line. R96 goes to ground, not the 95V bus in the revised circuit. The voltage dropping function is typically handled by the audio output tube.

the voltage divider you mention on the audio output is on another version of the set, tied to a 110v line, and can be seen in sams 0258-13n.pdf , the one for this set is, 0314_11n.pdf


I'm really not sure why they chose to create the 95v in such an odd way in this version :o

I'm defiantly going have to go go over this set for bad resistors, I tried again to bring in a signal in the tuner and it was still unstable, worked sometimes, and then blanking out to raster again, but only when there is RF input, 95v line is also unstable at this point, dropping to 82v when there is a pic locked in, and when it seems IF section collapses, it goes up to 109v, then when I remove the RF input, and the snow comes back to the screen, it goes back up to 95v.

And no sound at all from RF input.

But oddly enough, with direct AV input, the 95v is stable, and the picture is fine for a long time, I have had it on for 40 min or more.

https://www.youtube.com/watch?v=L7ypgEFao8s

the speaker was also moisture damaged so it also hardly works.

I'm sure I will find a lot of bad resistors :(

I think i may have found the problem.... and it's not good... :thumbsdn::no::tears:

https://i.imgur.com/lIhTLGp.jpg ( ignore my finger in the pic again :O )

after looking around for bad resistors , and finding just a few.
I poked around some caps...
there are many of these 3 leggers in the IF section.

they SHOULD be 4000pf, but the 3 i checked were at 5.0 5.1 5.2 and leaky at low voltage. they are rated at 400, I don't have the means to test them at 400 :(
seems to me that this will throw the IF all out of wack.

now I am debating, replace them and most likely face IF alignment? or stick with AV input?

Apparently, this TV is getting weirder and weirder, for it seems that the 95v line is not sourced from just v15 12AU7 or v8 12BY7 , but both... to me this just seems very problematic, and just asking for trouble to happen sooner or later, and have no idea why the hell they would do it like this, because it just seems like they are begging for things to fluctuate and oscillate, which is basically what I am seeing when I try to use RF input.

with v15 removed, 95v line drops to 82v , and with v8 removed, 95v line drops to 60v, with both removed, it's 13v.

Symptoms
direct a/v input,
95v line stable, picture is stable, no jitter or sync problems horz or vert.

RF input, tuned,
95v line unstable, fluctuating, 95v with video on screen or snow, over 100+ when IF fails to blank raster with rf input, horz & vert freq fluctuating, and horz & vert waviness seen in video on screen ( not seen at all with direct input )

Suspect bad caps in IF section may be causing problem, should be 4000pf but most testing over 5k (tried more than 1 tester, same result)
however, the original dual caps can't be found, nor can new 4000pf, but 3900pf seem to be all over the place, so I will guess they will be the ones to try, esp since 810-FG24C0G2W392JNT6 are much higher tol and more stable than what was in there in the first place.

It's actually not that uncommon a power supply design. Every design needs multiple voltages. Typically the main B+ for the tuner, horizontal and audio output stages, Boosted B+ for the vertical output and a lower B+ for the IF.

You have a few choices for the lower B+, power resistor voltage divider, separate secondary power transformer winding, rectifier and filter or do what this design did. Use tubes as voltage dividers. I really don't think the fluctuation is any big deal. It's going to vary as the tubes draw more or less current in response to the incoming signal.

Tube circuits are designed with a wide tolerance. I wouldn't be concerning if readings differ +/- 20% from what the service info shows.

Those caps are ceramic and very reliable. I'd be surprised if they are bad. 3,900 is more than close enough. They are just RF bypass caps.

If you want to hurt your brain some more try to wrap it around the Motorola VT-71s voltage divider. They basically had 2 voltage rails and the lower was basically many different stages (the majority of the set) in series/parallel all collectively acting as a B+ voltage divider. It did its job well though.

I'm still a bit stumped by the odd behavior of rf input vs direct video feed, and the way when there IS video via rf in, its very unstable and wavy on the screen and 95v is all over the place.

Granted, all the IF tubes are original and I have new ( tested good ) ones on the way, also the AGC KEYING, and tuner tubes, I also intend to replace cathode and plate resistors on both source tubes for the 95v line, not done it yet. Right now, there is only 1 filter electrolytic capacitor on the line , as original design, 40uf, I may add another 5uf in there.

What would be really helpful is to use a 1077 B&K TV Analyst (or equivalent) and inject an IF signal directly after the tuner. Note the stability of the picture and the 95V bus reading. That would tell you whether the problem is in the tuner or in the IF section of the set. A problem in the AGC can also cause a TV to shut down as you have described.

BAnderson is right. These ceramic caps rarely fail. They are typically used for bypass and therefore their value is not critical. No IF alignment should be required after you replace them.

I intend to re-do the AGC KEYING area as well, especially C54, the .001 1kv that carries horz pulse to the AGC circuit from the fbt, even though it looks like it was replaced before, I do not trust it, this set spent countless years in a damp dirty barn, it had rust, cobwebs and roach castings in it, so far, 95% of every cap paper/ electrolytic, even some film ones replaced before, have been bad, but luckily it seems that only 10 to 15% of resistors are bad, mostly 1watt and above.

To give an example, at first, some of the pots were so rusty, that they would not turn before being sprayed down with deoxit before I could get them to turn :o

I have the 3900pf npo 5% caps ordered, should be here tomorrow, prob won't hurt much just to replace the bypass caps, & the “new” tubes mentioned are already on the way.
Will just have to see how it behaves.

Replaced a few more marginal parts last night, caps / resistors, found that the dual pot R9 for AGC/NOISE CANCEL is in sad shape, even after taking it apart and cleaning, replacing it is proving very hard, because, where as dual concentric 500K audio taper pots seem to be very easy to find all over the place, linear taper ones are about as easy to find as a goldfish in a desert at high noon.
Dare I use audio taper?

Most tubes ordered will be arriving today, so I will be able to try will known good (tested ) RF/IF tubes soon.

Audio tapers are logarithmic. They will work, but the adjustment will not be uniform like a linear taper. The adjustment range of the audio taper will be "bunched" at one end.

I think it's Mark Oppat who has the parts to recreate most vintage radio potentiometers.

If you're feeling adventurous you could try finding a new dual audio taper pot mechanically identical to individual linear pots from the same maker and swap the resistance elements between the three.

There is yet another option,
https://i.imgur.com/VwqCuEK.jpg

You can see just how ugly that pot looked before I tried to clean it. :(
There is no reason both adjustments MUST be on the same shaft, the HOR LIN , option is not installed in this set, so, if I can't get the original pot to behave, and find a suitable dual concentric replacement that's linear, I can just split it and put it in 2 locations.

Another thing I have noticed while poking around under this thing, the yolk has been replaced before, splices in all 4 wires underside.

IF tubes replaced, new bypass caps, and new AGC tube,

https://i.imgur.com/Zipl6L3.jpg

now much more stable with RF input, but still has a tenancy to oscillate on the 95v line, gonna add one more electrolytic cap.

sound was still weak, after replacing the old caps in the sound area, did find a bad 86 ohm resistor on the plate of the audio output,( checked at 105 ohm ) that did help a bit, but still not very loud, it may just be the crappy speaker.

I WILL have to change the AGC pot, It's unstable.

To clarify, what I mean by oscillation is, some weird harmonics in the 95v line, that tend to show with RF input as unstable picture and sync, it can be fine for some time and then just go nuts, and I can get it to stop by briefly shutting off the RF modulator and turning it back on.

As mentioned before, the source for 95v is a bit odd in this set, v8 & v15 with one filter c2b.
https://i.imgur.com/YseSmi3.jpg

C2 b 40uf the only filter on the 95v line, is on the front of chassis, focus socket is at the back, (95v is being used,)
v8 1/2 the source of 95v is on the left side, v15 the other half is on the right.
I'm hoping that adding another filter cap at the focus socket may help things run more stable.

For the most part, when tuned in and NOT oscillating, it has a pretty good picture for it's age.

Well, video via RF input is now pretty stable and OK, but I have not been able to get sound to work, still very quiet.

It is NOT the tubes, and I have been through the whole area and replaced every resistor that was less than 10% what should be, but it still is very weak sounding, tried tweaking the sound IF, that was no help.

https://i.imgur.com/c1mGoQR.png

been all over it , voltages are OK, but poor sound.
i suspect the cap hidden in L24 may be causing a problem.

a new coil can be gotten but at this point I feel it's not worth the trouble, esp since there is a easy way to feed audio into this set via an RCA input and would only take re-wiring a switch.
https://www.youtube.com/watch?v=6puItmZnQsk

this is with RF input and direct audio, ( faulty audio IF bypassed ) and a decent speaker! sounds great!

keep in mind, I have not put on the centering magnets yet, so the final screen adjustments are not done.

I am assuming this has to be a mistake...

https://i.imgur.com/sdXG704.png

VTVM to point D, common to chassis, input 4.5mhz at point C, adjust input till 1.5 volts is read, keep there for the remainder... BUT UM...

https://i.imgur.com/c1mGoQR.png

POINT D HAS A - VOLTAGE ON IT!
and is tied to a negative side of an electrolytic cap.
so, should that be, adjust generator output until -1.5 volts is seen at point D?

THEN adjust for max defection?
confusing...

Looks like a mistake to me. I would say if you connect the VTVM reversed of what they say, that should give you a positive reading. If you look at the diode conduction, it seems like the voltage at point C [EDI T - oops, point D] must be negative compared to chassis.

Then tune A11, A12, A13 for maximum while reducing the input level to keep the reading near 1.5 volts.

I may be succumbing to another geriatric grand mal brain fart:eek: since this has been over 50 years ago. But the few times I've replaced that small electrolytic in a ratio detector, the cap was always 'upside down' with the positive end to ground.

...If you look at the diode conduction, it seems like the voltage at point C must be negative compared to chassis.

Um.. don't you mean point D? Going by direction of conduction >, the diode is gonna put an excess of electrons (negative voltage) on pt. D

Compare to diode direction if pt. D were positive.

Again, I may be all wet, so all bets are off.

Sorry for the typo, yes, point D should be negative. I don't even see point C (the input) on that clip of the schematic.

Sorry for the typo, yes, point D should be negative. I don't even see point C (the input) on that clip of the schematic.

point C is tied to the far side of that 5pf cap, (c58) and goes directly to the video detector diode, before any peaking coils.
https://i.imgur.com/goeH862.jpg

I am seeing barely perceptible contrast smear on bright objects on the screen, (to the left/right ) this is seen with both RF and direct video input, not sure if this is a sign of a real problem or not, or if this is just the standard for a set this old.

looking better

replaced a peaking coil
https://youtu.be/rDpXewiOVNM

RF audio now working after new L24 coil ratio det.
Speakers that were with the set are shot, not sure what I can replace them wit, I just may use a big ext one.

:thmbsp:

Where in the world did you find the peaking coil (L24)?

Where in the world did you find the peaking coil (L24)?

Talon had it.

https://talonelectronics.com/shop/item.aspx?itemid=7720

they have a lot of hard to get parts.

It's blatantly obvious the the original yolk had a … problem and needed to be replaced, it seems to have failed rater violently, it's no wonder it did not take the CRT with it.
https://i.imgur.com/zzpbKHC.jpg
it says in the Sams to use the back of the original yolk with the centering magnets on the new yolk, which seems to be what was done, but it was so damaged, I do not think I can ever get it back on again.
The damn thing is melted to death!

I may be able to bodge some of the rings from my projector tubes on to it, don't know how well it will work , or somehow use the plastic from the projector assy with these old rusty rings, somehow...

who knows.

Your problem with the centering rings is very common. The plastic used could not withstand the repeated heat-cool cycles. There have been many posts about making a new yoke back end to accommodate the centering rings.

*yoke

All the plastic on the yokes do that over time, nothing violent about it. Bob Andersen has a couple videos showing how to rebuild them. One he did out of some PVC and as I recall the other from a yogurt container.

https://i.imgur.com/5c1EP28.jpg

I DO know that something very drastic happened to it sometime before I got it, because, i can tell that T4, T5 ,C94, C6, C7, ,C78, R58,R59 R106 had all been replaced before :o

It might be a case of a technician "shotgunning" a repair when they couldn't determine the exact cause of the problem.

*yoke

All the plastic on the yokes do that over time, nothing violent about it. Bob Andersen has a couple videos showing how to rebuild them. One he did out of some PVC and as I recall the other from a yogurt container.

You might be thinking of someone else.. I built mine from scratch using styrene stock sheet and plastic solvent.

Photos here: https://www.flickr.com/photos/70039806@N00/albums/72157663009940550

HA!

i knew that those old dead projector tubes would be useful for something someday!
https://imgur.com/Io3iUj0
https://imgur.com/wMz82D9
:banana:

The worst spot on the enclosure is gonna be hard to fix :(

https://imgur.com/FnsKri9

https://imgur.com/tLCYEop

before
https://imgur.com/LdbQKDD
after

https://imgur.com/iHz7AMA

waiting for filler to dry si it can be sanded
it will never be perfect again, there was too much rot. but after paint, it will be decent, i hope.

why they left it in such a damp place for so long, i will never understand..

https://imgur.com/mznzZpn
https://imgur.com/VD4NM7L

just ripped out what was LEFT of the base for the chassis bottom in the case, it was too far gone, gonna have to replace it with something. :(

holy cow!
I may have found another RCA color roundy!
https://i.imgur.com/WvpxRTp.jpg
no info on it yet
not even sure WHAT it is yet,,, waiting to find out...

holy cow!
I may have found another RCA color roundy!
https://i.imgur.com/WvpxRTp.jpg
no info on it yet
not even sure WHAT it is yet,,, waiting to find out...

It looks like a Philco made RCA clone. If it is it's probably a mid 64 (based on it having UHF) to 66 set. IIRC it was ~1967 that philco restarted engineering their own color chassis and changed up the control panel significantly. It's probably some mash up of CTC15/16 design and if a clone may have small design and construction tweaks.

https://imgur.com/BTljJ8t
new bottom is made, mostly of spare pieces of wood I had.

I still need to cut air holes in it.

https://imgur.com/H8TanEw
outside painted, covered up the major water damage.

BTW,, I'm told the mystery color roundy is a GE, but no MO# yet.

https://i.imgur.com/qAdVuvd.jpg
FADA and stromberg carlson x-21 "m4b" side by side.

almost complete, just minor cosmetic stuff to do now,

just had a burnout on my SC-x21, did not take long to find what happened.

the Vert size pot started to arc out on the center lead to the chassis.

https://i.imgur.com/mUX12ih.jpg

there is about 500v there and very little spacing there, and once it stared to arc and carbon, there was nothing to stop it.

It is powered from the HV boost so it really messed things up
I have it cleaned up and doped and waiting to dry

while i had it out, I too the chance to address the buzz-o-matic sound.

The burn was worse than first thought, had to take the POT apart and scrape out the carbon burn.
https://i.imgur.com/SrGOwaf.jpg

Seems that they did not use a high enough voltage rated POT and it arced to the metal frame, also the voltage on the center pin seems to be a bit higher than shown in the SAMs.

https://i.imgur.com/YidsRwG.jpg

cut metal away from center pin area to keep it from happening again.

https://i.imgur.com/Uu0v6oY.jpg

repair done

this seems odd, cause the linearity pot which has MUCH less voltage on it, seems to be built with better isolation and higher voltage capacity. :scratch2:

Anyway, once it was dry, put it back in and ran it OK for 90 min.