This weekend, I began on what's sure to be a long resto on the CTC-4B chassis I hauled home from Indy. Why long? This set was apparently in operation in the same household from the time it was purchased until at least 1976, as evidenced by the repair tags left by RCA techs over the years. There are some ugly looking hack repairs, which will need undoing if it's ever gonna work again. CRT it had was a factory rebuilt 21AXP22, date code says 6543- which seems kinda odd. I would have thought they would've replaced it with a 21CYP22, but apparently the factory rebuilt metal tubes for a long time after they were 'out of service'.

First thing I did to the chassis was wipe most of the dust off, and test the tubes it had. All of them are good, so I won't have to worry about them. First thing I noticed was the power input jack was destroyed, so it will need to be replaced. Looked like the cord had melted to it, but the power trans ohms out fine (crossed fingers for the PTX). Next, I turned my attention to the HV cage. Looked good at first, but a second look revealed a burn under the horiz centering pot and a blown capacitor. Some past tech had wired the (replacement?) caps in totally wrong, which lead to the pot smoking. It will need to be replaced with a new one. Other than that, the horiz output transformer looks brand new so I hope the pot is the only trouble I have with the HV section.

Next, I pulled a few of the can caps and started restuffing them. They will have all new caps installed inside the old cans, then I'll reinstall the cardboard covers so it looks factory. After the rest of the power supply caps are replaced, I'm going to go ahead with a cursory run of the chassis to see what's alive at this point. I'll bring it up slow with the variac, and if nothing blows I'll probably recap the horizontal section so I can tell if HV is good to go.

More after next weekend! :thmbsp:

More pics.

Some guys get to have all the fun!

This'll keep you off the streets for a while! Keep us up on progress. Do you know the CRT condition? Can lend you the tester if you need it (after Thanksgiving).

Yes, fun... that is, if you like long nights slaving over a hot soldering iron as I do! :D

It is always possible that you have a leak somwhere at the glass/metal union, however the work that John Folsom and I have done with leak testing suggests that the more likely point of leakage is the weld that joins the front and rear sections of the crt. In that case it is not likely that frit glass would be of much use in sealing the leak. Frit glass is used to seal the leaks on the glass/metal or glass/glass joints.

There is also the possibility that your 21AX has a leak on one of the leads at the gun end, but a weld leak is more likely. By the time they started making 21AX crt's, the technique of bonding glass to metal cone crt components, was very well perfected. It is likely that there was a small weld leak in the tube before RCA rebuilt it. RCA probably saw silver getters on the dud, and figured the dud was air tight, and so they went ahead and rebuilt it. The leak is so small that even today your getters are still silver, but it only takes a very tiny leak to let enough air into a crt to destroy it. After RCA rebuilt your tube it likely worked fine for quite a while until enough air got in to prevent it from working.

John Folsom and I are in the process of getting our used helium leak detector up and running which will allow us to pinpoint where the vacuum leaks are. Then we will need to proceed with a process to repair weld leaks. Progress has been slow, so don't hold your breath. Hopefully some day we will be able to repair the leakers and have them rebuilt.

That's great news!

What's the deal with welding the funnel, is it a heat issue or the type of metal? And you're right, from what I can see there's still a getter there. I take it the leaks are too small to be found by traditional means (like dye inspection)?

Yes, fun... that is, if you like long nights slaving over a hot soldering iron as I do! :D

Wayne: unfortunately, the CRT has a little air in it. I borrowed Mark's CR-70, and though the filaments light up without burning, the gun gets a blue/purple glow when HV is applied (I powered it with my CTC-9 chassis for a test). This means it will likely need to be sent off to RACS for the frit treatment, which means big bucks. In the meantime, I put a 21FJP22 in it. That might have to come back out though, because I noticed the HV button fouls the CRT support (possible arcing issue). A 21CYP22 would make a better fit, so I'll probably swap it out later on.

Here's what the 21AXP22 looks like.

Yep, sad to look at the thing and know it doesn't work. I have 2 like it, one which may have taken many years to develop a low level of air, and the other (in Bob's posession for now) that Scotty tried to rebuild, but showed air within a few days.

I am using the "rubber" shield from the 21AX to shield the HV button on the 21FB - can you slip that between your tube and your mounting hardware? Doesn't look elegant, but works, and can still be re-used if I get a good 21AX.

That's great news!

What's the deal with welding the funnel, is it a heat issue or the type of metal? And you're right, from what I can see there's still a getter there. I take it the leaks are too small to be found by traditional means (like dye inspection)?

Making a vacuum tight weld is a very tricky and difficult thing to master. On the 21ax it is not so much the heat issue or the material, but making sure that the weld has no porosity. Proper welding takes very accurate temperature control so the heating and cooling of the molten metal is free from porosity. I had a very skilled welder try fixing a 21ax that we leak tested with John Yurkon, and it still leaked after we rewelded it. Originally we thought the material was Kovar, but after we tested it we found no Cobalt, so we now believe it is more likely some sort of nickel stainless. At some point we will probably need to have the metal analyzed so we can obtain the proper filler rod material for the welding processs.



BTW, Waynem your 21ax is in safe keeping :-) I will drag it to ETF next year for you to take home with you.

Interesting.

Can't detect the bad weld via x-ray inspecting either? We use x-ray and dye penetrant inspections in the military all the time to look at welds, check critical aluminum parts for stress cracks, ect.

Interesting.

Can't detect the bad weld via x-ray inspecting either? We use x-ray and dye penetrant inspections in the military all the time to look at welds, check critical aluminum parts for stress cracks, ect.

It would show up the obvious big leaks, but not the nasty slow leaks. Air molecules are pretty small.

John

...Some past tech had wired the (replacement?) caps in totally wrong, which led to the pot smoking.

Perhaps your cause and effect are inverted...
:D

Nice flyback, still looks raw and uncooked!.

Perhaps your cause and effect are inverted...
:D

That could very well be! :D


Red Raster: Yes, either it's a replacement or these things are easy on FB transformers. It looks brand new, only mark that I can see is some slightly melted wax on one side and it's from rectifier tube heat.

New updates, from this weekend of deer hunting/CTC-4 rebuilding! :D

Didn't bag any deer, though. :tears:


First I went about reinstalling the first round of restuffed power supply caps, which went well. So far all of the cardboard can covers have come off with little or no heat applied, so that's good. At this point I have both caps from the doubler portion done, and one of the others which is in the audio output section. Only 2 more multi-section caps to go, and the power supply is done. (3rd pic is the restuft caps. :thmbsp:

I also cleaned the front of the chassis up, and the results are stunning! Under all the old cad plating there was nice shiny metal waiting to come out, so I went ahead and did the entire front where the controls are. First pic is the nasty state of the chassis before cleaning, second is a shot of the front after a good de-gunking.

Bonus: the tuner appears to be in working order, no stuck shafts or anything. Even the cords are in good shape, so it looks like a little lube and Deoxit will be all the tuner needs to come back to original glory.

Items for next week: finish the restuffing, do more work cleaning up the chassis, and probably test fire on the variac to see what's still alive!

Nice, tidy work on those caps. What did you use on the chassis?

Phil

First I tried to wipe the crud off with solvent and a rag, which didn't get me anywhere. Then I grabbed a piece of 0000 steel wool, which removed the crap and polished the surface at the same time. You have to be gentle with it though, or it will leave scratches.

Time for another update!



This weekend began much like the last, lots of hunting and not a single sign of any deer whatsoever. In fact, the only deer we ever saw was an already dead one in the back of a fellow hunter's truckbed. All that freezing for nothing, I guess. :thumbsdn:



Fast forward a few hours, and I went on down to the basement to get more work done to the chassis. I finished restuffing the last power supply capacitors, so they all have brand new caps living inside the original paper tubes now. I made sure to use plenty of adhesive, to keep them from bouncing around and possibly shorting. As soon as the glue had set enough to reposition the chassis, I flipped it up, double checked all my work by bouncing it off the schematic, and cautiously applied power for the first time through a heavy 20 ohm resistor in case the PTX was bad (variac is currently OOC).

Nothing happened at first- was the PTX actually bad? No, both fuses were blown. I replaced them with their rated values and tried again. Success this time! :banana: I got B+ (380) and B++ (285), within 20 VDC of the values given in schematic. -20 VDC also looked good, if a few volts high. All tube filaments lit up, so that tells me the PTX is 100% good to go.

Just for kicks, I scoped the horizontal oscillator to see if anything besides the power supply was alive at this point. I was pleasently surprised to find a perfect waveform at the grid terminal of the HOT! Picture of the waveform is below.

All in all, not a bad day!

I was not content to stop at having a waveform, as the next day dawned. Something about finding life in a 56 year old chassis gets me going, call me crazy. So after finding the horizontal oscillator working, I decided to pump as many new caps as I could find into critical circuits to see what else I could get. I ended up doing everything on the 2 PCB's, everything in the vertical oscillator, everything in the horizontal oscillator, and a few other random caps just to exhaust my supply. I'm now totally out of .047's, .022's, .01's, and the 'lytic bin took a good hit as well. :D

Turns out the vertical section is just fine as well, though the 6AQ5 running the show tests barely into the green scale on the tube tester. I'll have to get a fresh one before attempting to run a CRT. As you can see in the first 2 pics, I did a whole lot of recapping. Took me the better part of the day to get to this point, my back is killing me. I'm way ahead of the power curve as a result though, I figure there's only about 2 more days of recapping to the matrix section (3rd pic), and the chassis will be 100% free of PIO's.

Tidbit: every single paper cap in this chassis was made by Dumont...strange? :scratch2:
Most were MicaMold labeled made by Dumont, a few were were Aerovox and 'MicoMould'. I left the ElMenco micas in place, as every one I tested was within tolerance. I'll probably get to those at a later date, when I'm not so tired of capacitors.

The one bad part I found so far was a video peaking coil that had split it's case all the way around. The wires inside were eaten by corrosion, so it's toast. If I can't get another one, I'll have to wind one with the help of my brother.

Last day of work to the CTC-4 for this weekend. I decided that after the success of getting both oscillators up and running, I should go for broke and see if I couldn't get some HV flowing.

I wired some 10-meg power resistors from the HV tower to ground as a load, and let 'er rip.....


Nothing. Not only did I not have any HV, but the previously observed waveform at the HOT grid was mysteriously gone. :scratch2:

I couldn't find anything at all wrong with the horizontal oscillator, then I pulled the HOT and damper out. Come to find, the HOT had a short which shunted the grid to ground, which explained the loss of a drive signal. I don't have any spare 6CB5's around, so I subbed in a 6CD6 for testing (not same ratings, I know!). Still nothing. Tested the 6AU4 damper next, and it had 0 emission. I was beginning to think the HV transformer was bad at this point, since both tubes that run it had gone bad...dramatically, as it turns out.

In the pic, you can see what's left of the 6CB5 HOT. It burned a hole right through the plate on both sides! Cathode was done for too, and the grids were melted. :yikes:

But my fears were proved wrong about the HV transformer. I put a new 6AU4 in along with the 6CD6, and while the 6CD6 did not like being put in the position of having it's ratings exceeded, it did drive the HV transformer for long enough to let me know HV was working. I saw the normal blue glow from the 3A3 rectifier as HV came up strong, and the power resistors got nice and toasty after a short run. I'd call this a very productive weekend, all in all.

So to 'recap' recent events (pardon the pun!):

I now have a redone power supply, 2 good oscillators, good HV, and all that remains is the matrix recapping before I can take this thing on it's maiden voyage with a real picture tube! Nothing but excitement on my end! :music:

I hate to tell you, but you also let the vacuum out of that 6CB5 :D

Really, great progress! Keep us informed.

miniman82-

Do you have a color TV test jig? If you do, and you need the details of how to hook up your CTC-4 chassis to it, let me know.

Chris,

I have the Sylvania check-a-color with a butt ton of adapters, but nothing for 70* picture tubes or early RCA chassis. I suppose I should cannibalize the NOS brightener I got off Ebay and make my own harness, but I just figured I bring a spare 21CYP22 with me next time I head home for tetsting purposes. Do you have wiring diagrams on how to hook up the check-a-color?

I hate to tell you, but you also let the vacuum out of that 6CB5 :D
That's whutcha call a sacrificial anode (and cathode too):
http://videokarma.org/attachment.php?attachmentid=168735&d=1290924895

:D
Bill(oc)

0000 steel wool, which removed the crap and polished the surface at the same time.
I have given up steel wool for fear of spreading tiny metal hairs all over. The plastic sanding pads used for refinishing are a pretty good substitute.

Phil Nelson

I haven't had a problem yet, I just blow off the chassis with compressed air and that gets the whiskers out.

I haven't had a problem yet, I just blow off the chassis with compressed air and that gets the whiskers out.

I'd be worried about tiny metal whiskers getting inside wafer tube sockets and such. So I'd avoid steel wool. I even hate to have to drill holes in metal chassises for fear of the chips getting into somewhere.

I'm not superstitious, it'll be fine. :p

Chris,

I have the Sylvania check-a-color with a butt ton of adapters, but nothing for 70* picture tubes or early RCA chassis. I suppose I should cannibalize the NOS brightener I got off Ebay and make my own harness, but I just figured I bring a spare 21CYP22 with me next time I head home for tetsting purposes. Do you have wiring diagrams on how to hook up the check-a-color?
Yes, I do have the setup guide for my jig, also a Sylvania (CK3000). The guide only covers CTC-7 and later RCA roundies, but I figured out how to make a yoke adapter for the CTC-4 and CTC-5 using another adapter I had a duplicate of. I will pull out my information and send you a message, or post it here, in the next couple of days or so.

OK, thanks for that!

Meantime, Allied Electronics dropped off an early Christmas present today for the '4. Plenty of new caps, the new horizontal centering pot (2-watt wire wound), various 'lytics and so forth. :D

Still on the way is a pair of 6CB5A's, a pair of 6AU4GTA's, a 6AQ5 and a 3A3 rectifier. Those are coming from Antique Electronics Supply, should be here Friday or Saturday. :banana:

I've seen that 6AQ5 cause lots of odd problems in convergence issues if it is gassy.

Your set will be a real sweetie when you get done.

I don't think it's gassy or anything, just reads weak on the tube tester.

The fix is in now anyway, new tubes from AES have arrived! :banana:

NOS RCA 6AQ5, GE 3A3, Dumont/GE 6AU4 dampers, and a nice pair of Amperex 6CB5A's with black plates. Should make for a stout high voltage section. :yes:

Just found out after some resistance checks that the screen/grid control pots are bad, with some intermittent places on the carbon track. Been looking around on the net for replacements, but all I'm finding are crappy quality ones that probably wouldn't last long considering they have boost voltage running through them. Anyone got a good lead on a quality replacement? I'm looking for 5 1-meg linear pots total, preferably with plastic shafts.

You could try contacting Mark Oppat, http://www.oldradioparts.net/controls.html .

Phil

Sent him an email, thanks for the tip!

Just found out after some resistance checks that the screen/grid control pots are bad, with some intermittent places on the carbon track. Been looking around on the net for replacements, but all I'm finding are crappy quality ones that probably wouldn't last long considering they have boost voltage running through them. Anyone got a good lead on a quality replacement? I'm looking for 5 1-meg linear pots total, preferably with plastic shafts.

What's the RCA part numbers? How do they mount? bushing with nut or tabs that twist? I have a stash of (gasp!) GE parts and hundreds of other pots - some NOS Westinghouse stuff from JCPenny's/Penncrest replacement stock.

Trying to help,

What's the RCA part numbers? How do they mount? bushing with nut or tabs that twist? I have a stash of (gasp!) GE parts and hundreds of other pots - some NOS Westinghouse stuff from JCPenny's/Penncrest replacement stock.


They are twist-lock, with a tab on either side of the plastic shaft. RCA part number on the back is 972137-1, but I'm not really concerned about brand. I just want something that's not going to break 2 months from now, like most of the Chinese stuff is likely to do.

Crisis averted for now, I was able to take each one apart and clean them with contact spray. No idea if it will last, but they seem to be working for now.

OK, latest work has revealed the following:

I thought the horizontal osc was working just fine, but when supplied with a signal with my NTSC gen it refused to lock at the correct frequency. I figured I had some more bad caps, so I made a trip to Chesters. After replacing the rest of the old micas, the problem persisted. I then read out the voltages in the circuit, and every single one was 60 high!

I then had a look at the power supply, where I confirmed that B+ was indeed 60 high (440 vs 385). I'm guessing that selenium rectifiers were grossly ineffecient, because there's no way 5 extra input volts equals an increase that large. Short of always running it on a variac or bucking transformer, I guess I'm looking at dropping it with resistors.

So the question becomes do I get a huge high power wirewound, or insert 2 smaller ones right before the rectifiers?

You need to get bypass the selenium stacks with silicon diodes. Leave the selenium stacks in place for looks, but leave them disconnected.

I don't understand why you would have High B+ using the selenium stacks because they normally will be inefficient and produce lower voltages than the silicon diodes.

AFter installation of the silicon diodes I use some 20 watt wirewounds to reduce the B+ to the correct specified voltage in my sets. I use a 20 watt power rheostat to determin the correct value of fixed resistor use.

The seleniums have long since been replaced by a pair of obligatory RCA 'tophat' diodes, sorry if that wasn't clear. I'm trying to correct B+ as a result, since it's now 60 volts higher than it should be. I've understand dropping resistors in the 150-200 ohm range should do the trick, I'll find exactly what value tomorrow or the next day.

OK here is what to do.

First, measure the current on the B+ line you want to place the dropping resistor into.

Now using Ohm's law solve for R. R=E/I ..... Plug in the current (I) in AMPS and the voltage you want to drop (E) in volts (60) and the solve for R (the resistance needed).

So lets assume 500ma is the measured current, the equation would look like this:

R=60volts /.5 Amps so R=120 ohms

Then to figure out how many watts the resistor needs to be use P=IE Where P the power in watts = the current (I) in AMPS times the voltage drop across the resistor E (which in this case is 60 volts)

Lets assume the following for the Power equation

P (watts) = IE so P= .5 Amps * 60 volts Therefore P=30 watts

No guesswork needed if you know the current flowing and the voltage drop needed.

The value of the resistance will not likely be a standard value, so get one of those tubular ceramic types with the adjustable slider band so you can adjust to the needed value.

Good Luck!

The value of the resistance will not likely be a standard value, so get one of those tubular ceramic types with the adjustable slider band so you can adjust to the needed value.


It is a great idea to use one of these! The calculation will get you very close, but there is a "second order" effect... As you drop the voltage applied to the circuit, the current drawn by the circuit will drop as well, and perhaps not in a linear fashion. Likely slightly more than the calculated resistance will be required to produce the desired voltage drop. Always nice to be able to make a slight adjustment! :yes:
jr

The value of the resistance will not likely be a standard value, so get one of those tubular ceramic types with the adjustable slider band so you can adjust to the needed value.


Exactly what I did, final value ended up being 75 ohms. My brother ended up having a 30-watt Ohmite resistor, I mounted it on a piece of angle aluminum and fixed that onto the removable plate that bolts to the HV cage. B+ is now a perfect 385, while the other line is slightly high at 292 ish. I think that will be just fine.

Important update: I have something on screen! :banana::banana::banana:

I ended up having to slightly rewire the power supply because of the B+ resistor I installed. At first I had some lines crossed, and that was causing a strange hump (like the negative going half of a sine wave) to appear in the vertical scanning waveform. It also screwed with the sync circuits, causing a no lock situation for both vert and horizontal. After fixing the B+ supply, the voltages fell perfectly in line and the scanning waveforms looked perfect as well as having perfect sync. I had been injecting a signal into the video amp tube, because I wasn't sure of the condition of the tuner. Now that I have things in order though, I hooked the tuner back up and it works just fine. :thmbsp:

Color is even trying to work, but it's not quite there. I think I'll probably end up having to do a full on chroma alignment, even though it pains me to think about it. Last time (on the CTC-7), it took like a weeks worth of fiddling to get things to fall into place. :sigh:

Here's a pic of what I have thus far:

As you can see on the above screenshot, covergence is still horrible and there are bad purity issues. Right now the raster buttons on the NTSC gen have little effect, so I'm thinking it's now time to delve into the demods and figure out why I can't get the chroma part of the chassis to do anything. Once I get that sorted, I should be able do the screen tweaks necessary to get a nice picture up on the tube.

I hope you don't really mean a full chroma bandpass align first. First thing is to make sure the oscillator locks and then that the tint control is centered. And really, before that, why not work on getting the purity at least approximately right, so you can see if the tint looks OK.

Well, first I have to see if I can get the driver tubes to do the right thing. Otherwise anything in the chroma circuit is pretty useless. I can see right now that the local oscilator does in fact lock, because there are bars that will float by vertically then lock in. It's only visible as a slight change in brightness right now, but it's there. I scoped the burst amp tube a bit ago, and it looks like the burst is gated correctly and getting through to the rest of that section, so at least I have that much going for me. I think for now the right thing to do will be to see if I can somehow get the purity magnets mounted (something like what you had to do to your 5), and sort that out.

Before any of that though, while I was scoping the burst gate (amp, whatever) I smelled ozone coming from the HV cage and heard leakage. Pretty sure I'll have to pause and replace the filament windings for the rectifier tubes before going any farther, so I'm off to scrounge some 40 kv wiring.

Oh, I almost forgot: I was perusing Ebay the other day, and found myself an RCA WP-25A Isotap isolation transformer for the pauperly sum of $25. Should make a nice addition to my vintage arsenal of electronic tools. :p

Today, I was working on the set and the smell of ozone was in the air. I suspected the old HV wiring in the cage was to blame, so I set about replacing it. I have a slew of newer chassis in the garage thanks to Doug, so I grabbed a spare Sylvania chassis and robbed the wiring from it. The old CTC-4 stuff was cracked in a few places, so I have no doubt there was leakage occurring. It was only single jacket stuff anyway, the new stuff is more modern double jacket.

First I replced the filament winding for the 3A3 rectifier, holding it in place with shrink tubing around the flyback core.

Then I tried to replace the wire on the focus rectifier, but it was no use due to the molded cap. I didn't have a spare small size top cap, so I had to carefully remove the one on the tube and solder a bigger one on to it. This involves carefully grabbing the cap with pliers and slightly twisting it, so the old glue will break free of the glass. Then it's simple to desolder the cap, and replace it. I took the replacement one from a dead HO tube, and used epoxy to glue the metal cap onto the top. Then I used a normal size connector, some more replacement wire, and sealed the connection on the flyback with non-acetate RTV. I doubt there will be any leakage from there now. :thmbsp:

Also, for some reason there was a 22K resistor in series with the anode cap lead. I couldn't find it anywhere in the schematic, so it was removed. There seems to be more range in the focus control now, so that's good.

Back to the rectifier. Having already replaced the filament wiring, I now soldered that to the socket. That brought me to the wiring under the socket, which connects to the HV capacitor and HV tower on the side of the cage.

I never really liked the way the HV capacitor was connected under the rectifier cup, with an 'X' shaped solder lug. It screwed into the capacitor, then the rectifier cup and HV tower connection soldered to that. This made wire breakage an issue, since to remove the cage means leaving the tower flapping in the breeze.

So I made a short wire with round terminals on each end: one screws into the cap, the other end goes to the top of the rectifier cup.

This does 3 things for me:

1. I can pull the rectifier cup and the cap doesn't fall out now, because there's still a screw and a lug holding it in.

2. It also allows me to remove only the cap if I choose, since I can put a phillips screwdriver down the center of the tube socket (no need to pull the cup if I just want the cap out).

3. the HV wiring is now modular. The HV tower can be disconnected from the rectifier cup, so the tower and shunt reg cap all come off in one piece. Very neat now, and I no longer have to pull the cover of the cage to get the cage off the chassis. I simply remove 1 screw from the rectifier cup, and the whole cage comes out in one piece.

The pics below show what it looks like now. :smoke:

And now, for the grand finale!


After a few tweaks to the demod driver transformer, we now have color bars!

:banana: :banana: :banana:


Purity and convergence are still a mess, but this proves that 99% of the parts in the chassis are doing what they are supposed to do. That makes me very happy indeed, since this thing was a basket case of prior hacks when I first picked it up. Twice rebuilt picture tube, melted insulation, frazzled video peaking coil, bad solder joints, and more incorrect connections than I can count on both hands...

Along the way, I also found that whoever replaced the flyback had mistakenly swapped terminals U2 and U3, which supply pulses to the blanker and burst keyer tubes. Not sure how much difference it makes since the voltage difference in the actual pulses is small (50 volts), but I fixed it anyway for the sake of correctness.

Congratulations - but your dancing bananas are purer than your color bars :D

That set is looking nice already. Keep up the good work.

COOOOOOOL ... just plain COOOOOL

Did more work the other day, and discovered that I would never get correct purity without the correction magnets- this CRT has a large area of impurity in the lower left hand side. So I installed the magnet assembly around the CRT, and tweaked it best as I could. Result is below, how's it look now Wayne? :D

Did more work the other day, and discovered that I would never get correct purity without the correction magnets- this CRT has a large area of impurity in the lower left hand side. So I installed the magnet assembly around the CRT, and tweaked it best as I could. Result is below, how's it look now Wayne? :D

hey hey - much nicer :thmbsp: :tresbon:

Nice :thmbsp:

That looks really nice! Mine has a very small purity problem in the lower right corner, and I think it might be due to the tube needing to be degaussed, but I'll try the magnet again. The rest of the screen is just right.
BTW, I notice that your 4 also doesn't fill the screen all the time at the left side. Interesting; mine does the same thing. If I increase the line volts to 120 I can get a full pic. These things have notoriously poor voltage regulation, so maybe that's one of the problems. Don't want to screw around with the width circuit again yet.
Kevin :thmbsp:

Mine has a very small purity problem in the lower right corner, and I think it might be due to the tube needing to be degaussed, but I'll try the magnet again.

I tried degaussing this one too, but the spot persists. It's pretty close to optimal, but there's still a tiny little area I can see where it's not right. It's a shame, because the tube checks as new on the tester. None of my other sets even needed the purity magnets, the screens are just perfect.

BTW, I notice that your 4 also doesn't fill the screen all the time at the left side. Interesting; mine does the same thing. If I increase the line volts to 120 I can get a full pic. These things have notoriously poor voltage regulation, so maybe that's one of the problems. Don't want to screw around with the width circuit again yet.


I haven't yet messed with the width controls on this set, because the replacement centering pot's shaft is too short for the knob to fit on it. I think once I graft an extension on it and adjust horizontal width, the screen will look normal.

Can you post a pic of the total CRT back magnetics? Does this set have the little hairpin-shaped purity poles on a tube mounting ring (around the CRT bell) like the CTC-7 mount I put in my -5 to accomodate the 21FJP22? Those hairpins do make a difference in uniformity of the purity.

If this chassis has the multiple magnets around the edge of the face, I'd suggest removing them when using a glass tube. They were necessary for the metal-bell tube, which strongly distorts the fields very near the edge, but their effect is probably too strong right at the edge of the glass tube and falls off too rapidly towards the center.

No, it has a band with round magnets on it. I need to do the same thing you did on your 5, but I don't have a spare set of hardware to modify. My main issue is what to do with the yoke; it doesn't mount to the CRT neck, it's held by the large metal piece which also supports the CRT. Perhaps there's a way to use a later yoke with the pull up ring?

No, it has a band with round magnets on it. I need to do the same thing you did on your 5, but I don't have a spare set of hardware to modify. My main issue is what to do with the yoke; it doesn't mount to the CRT neck, it's held by the large metal piece which also supports the CRT. Perhaps there's a way to use a later yoke with the pull up ring?

Looks like you have the edge magnets screwed out towards minimum strength - I'd guess that's the best position. If the ones on the bottom aren't screwed out all the way, you might try that. Also, if you have a small refrigerator magnet, you could try moving it around the bell about halfway back to see what effect you get.

I'd try getting the purity with added magnets before changing the hardware. I had no choice on the -5 when I went to the glass tube.

Yes, most of them are at min strength. The only ones I had to actually use were the ones at the bottom left side of the tube, and you're right, thye are a strong effect at first but it quickly diminishes at the center. I'll try an additional magnet farther back, sounds like a good idea.

I noticed that the crosshatch pattern looks funky, anyone ever see something like this? It looks mostly fine, until the solid horizontal line passes through the vertical one right in the center. It's like the horizontal line causes some ringing in the video amp or something, see the squiggly vertical line? It also looks funny on the left side, something that was pointed out by a member on ARF. At first I didn't think anything of it, but there's clearly an issue there. See how the horizontal lines continue off screen, while the vertical line of brightness that stops near the edge?

I checked my other sets, and they don't do this. Think maybe it's because of all the inductors in this chassis? It does have 10 times the number of peaking coils than any other chassis I've worked on, but I'm inclined to believe it should still be able to display a simple cross without an issue. Thoughts?

Second shot is just more brightness than the first.

looks like sync separator problem - white video causing the sync to be clipped at a different level. I also notice it occurs at the top, where the horizontal sync has been disturbed by vertical sync Do you have a multi-square crosshatch? Does the wiggle follow every horizontal white line?

Also might try turning the noise threshold control to see if it affects this.

I was thinking sync as well, but it's so darn stable! I can twist the horizontal control multiple times, and it stays locked. Vertical is pretty solid too, is it possible to have stable sync while still having an issue? Yes, it happens with the multiple chrosshatch too- at the intersection of every horizontal line, the vertical gets a little squiggle to it. Noise inverter and AGC have no effect on it.

Well, now I'm just fishing, but have you checked component values in the horizontal oscillator/control section? Even if it's getting an input jolt it shouldn't get, I think it maybe should respond with a more damped response instead of a decaying oscillation.
The following three components are the main control loop filter:
C160 .01
R165 3900
C159 0.47

+ other R's and C's in the vicinity

All the caps and resistors in the horizontal section are either new or within tolerence. I thought I was having a problem with the originals before, but it ended up being a power supply wiring glitch that was my fault. The power supply is fine now, and I strongly doubt issues with the oscilator.

Thanks, Wayne! :D


In the end, you were right. When I initially set this thing up, it still had a miswired power supply with 60hz noise. That means I tuned the horizontal sine coil with that same noise in it, but I failed to recheck it after I corrected the problem. Looked at it with the scope the other day, and sure enough the first hump of the waveform was was lower than the second one! I watched the screen as I tweaked for equal humps, and sure enough that coil being detuned will cause the ringing I was seeing. Now I have nice straight lines on the screen, just like I should. :banana:

I wasn't thinking of the sine coil, but it makes sense because it could affect the pulse shape going to the phase detector. Glad you found it!

No matter, you got me looking into the horizontal section and that's what sparked my pot-frazzled memory. :smoke:


OK, so at this point I did a very rough setup with the bar gen and reconnected the tuner. Still have some issues with a dirty AGC and color killer pot, those will be next on the clean/deoxit schedule. Here's the result, as seen via the Crapcast DVR! :thmbsp:

Getting very close to a good picture now, all I have to do is another round of purity/convergece,
and nail the color alignment. What was that about keeping me off the streets for a while? :D

Did work on red purity, and was able to just about cure that patch on the bottom of the screen and left hand side. Looks pretty good now, aside from a few little issues with red convergence in the bottom right corner. Can't really see it from normal viewing distance. I think I'm gonna call this a winnah for now, I'd like to enjoy it for a while before I send it off for refinishing. that will be the next problem, since all the people who work on wood around here are booked till the return of Christ. Any leads on someone who's free to do that kind of work?

I know a great refinisher here, but you probably don't want to ship the cabinet to Seattle.

Looks like you're making real progress. I'm glad you mentioned the horizontal squiggle. I have seen that before (don't recall exactly when). If I see it another time, I'll know what to look for.

Phil Nelson

No, I'm definitely not up for shipping it across the country. I'll just have to keep bothering the refinishers around here till they help me I guess, I just can't believe more people aren't getting into woodworking. With the economy in the tank, you would think people would flock to a trade that's always telling me they have no spare time to help...

Maybe they just want nothing to do with an old TV cabinet.

Thanks for the nice Sams CTC-4 Photofacts, Brian! Now I can align the matrix correctly.

OK, overdue update!

Long story short I was able to get acceptable matrix alignment after a long time messing with it, but the 21FJP22 CRT I borrowed from Mark has some purity issues that the CTC-4 magnets cannot correct. What it needs is more correction closer to the center of the screen, and the -4 edge purity ones run out of steam after a couple inches or so. I think I could get it near perfect if I had a spare CTC-9 purity ring assembly, but I don't have one. I'll either save it for another set, or give it back to Mark so he can put it into one of his. It has perfect emission.


Which leads me to the next big thing- Tom Schulz over on ARF was very generous indeed by GIVING me a 21AXP22A for free! Neither of us was sure if it even worked, but I just put it in and it has a raster!!! :banana: :banana: :banana:


Much more to come in a short while, the tube obviously needs to be set up. But from what I can tell right now all the guns respond to the screen controls, and I can see a plain image on the face. Here's hoping for the best!

It's confirmed, the tube is good! :thmbsp:


Now off to do a full setup...

Here is my theory about the cabbinet refinishers. When they hear the words "vintage TV" they think of plastic that is made to look like wood or in the case of more experienced refinishers those annoying "photo phinishes", and decide to try and avoid working on something that ,in their minds, is either not wood or very anoying very crappy wood in disguise.

I maybe wrong, but that is what I think.
You could prove this by haveing someone you know call about having some nice piece of furniture restored...

Tom C.

I don't think that it, though. Like I said, all the ones I called around here were too busy with other projects to help me. The type of work most around here do is custom cabinetry, where they go to a home and build things right into the house. Very involved work, and very costly.

Example, here's a picture from a guy's site that I called:


http://www.edswoodwork.com/img/media/media-1a-900.jpg



I guess that's why I can kind of understand when I come along with a relatively cheap job- it's simply not worth them putting down their $10,000 job to do a $300 TV case. What I need to do is get in touch with someone who works out of their garage, someone who has the time to take this task on. I still may end up doing it myself, I just don't know what to do about the worn spot fingers have made near the tuning dial.

Back to the electronic resto...


One of the tube sockets (V109, 3rd IF/1st sync amp) has been giving me fits since the beginning, so I finally gave in and repinned it. The wore out contacts had been causing goofy sync since day one. It's actually not as hard as I thought it would be, just tedious. Below you can see how bad they really were compared to a new pin, and what the socket now looks like.

Looking better now, but man, convergence is a real PITA on this set! You can't change the settings to get exactly the result you want, it's always a little bit off in one part of the screen or another. If the center is smack on, the sides are horrible and vice versa. I know I shouldn't expect perfection on a set this old, but I've been able to get all my other ones very close.

Anyone have tips on how to converge the CTC-4? All I have to go on right now is what's in the RCA service manual, and a Sams folder. Those are great and all, but actual experience trumps the textbook every time if you ask me.

If the center is smack on, the sides are horrible and vice versa.

I may be telling you stuff you already tried, but here goes:

If it's like the CTC-5, you have to forget making it right in either the center or the edges, but first get the 3 colors to make parallel lines on the crosshatch using the dynamics. Then you can do a static adjustment, then retouch the dynamic, then final retouch on the static. Later sets had clamping diodes so the center would stand still when the dynamics were adjusted.

Can you see the pole pieces in the neck? If not, experiment with the forward/back position of the convergence yoke to get maximum effect. Towards the end, a very slight turn of the convergence yoke CW or CCW may also affect the coupling between the 3 guns and give you the final tweak.

I agree with what Wayne had to say. To this I will add that there are two versions of the wiring for the convergence circuit. One of them works a bit better than the other, I don't remember which one is the better one. I would presume it is the version used on the ctc4A. I will have to find out when I get my ctc4 up and running in about 4 to 6 weeks after the cabinet is finished. Chassis is 90% done but I will not waste my time converging the picture on my 21AX crt test jig.

BAck in the early 70's is the last time I had the chance to converge a 4 that I owned when I was in my 20's. But I do recall that I was never happy with the convergence. No matter how hard I worked at it, it was always off somewhere. I learned to just accept it. I can tell you that it will never be as good as the convergence that I got on my ctc5 Wingate.

But Wayne is correct. Use a cross hatch with the static convergence out about 1/8" in the center. Then do your best to create lines that are as close to parallel and equidistant as you can get them using the dynamic controls. Then pull the 3 images together using the static magnets on the convergence yoke. Pull red and green together first, then drop the blue vertically and finally use the blue lateral to move it left and right. It will always be a comprimise and will never be perfect. I try to get a good average across the entire screen. I do not strive for perfection in the center, because that will only cause the edges to be GROSSLY out of convergence. A little bit off in the center usually allows for much more acceptable convergence in the outer areas. I never use dots, I always use cross hatches because you can see the direction of the displacement better as you are in the process of making the adjustments.

AS I recall the phasing coils will have a sweet spot where it will cause maximum deflection of the amplitude controls. Once you find the sweet spot, you won't have to adjust the phasing coils very far in either direction from the sweet spot. I also recall on my old 4 some of the controlls had little to no effect.

That is about all I can offer. Less than perfect convergence is just something a person learns to live with. And I don't know why convergence on a 4 should be problematic. After all, the convergence on my 21ct55 is dead nuts on, after it's warmed up. You would think that it would be as good or better on a 4, being that it's a generation later.

Good luck..

My guess is that the CTC-5 circuit is better at producing symmetrical waveforms, and the CTC-4 has less-perfect parabolas therefore making differences either left to right or between edge and halfway to center.

How does the horizontal linearity look? It occurs to me that poor linearity could affect convergence of left vs. right also.

Thanks Wayne and Bob!

The linearity is fine horizontally, but vertical could use work. I'm not too concerned about it though, because every single roundie I've owned had a slightly stretched vertical near the top and I've just come to accept it. It's like the scanning lines get farther apart near the top, but the voltages in the vert circuit always check out fine.

Anyhow, I'll give what you guys say a try when I get off work today. Here's what it looks like after this morning's effort.

It's hard to tell, but the top horizontal line looks to be slanted up towards the right. Even allowing for the misconvergence. You may want to look at a circle pattern and see if there are still some linearity issues, or if the yoke may be turned slightly.

The yoke is just tilted a little bit, that's all.

That is wierd, because red and green are supposed to move at plus or minus 120 degrees, and this pattern shows red displaced straight down on the far left. Red is displaced a normal way (down-left) at left center. But it appears that if you fix the left center, the far left will be displaced inward. Red in the lower-center-right has a direct inward displacement. I'm now thinking this could be deflection yoke design or winding tolerance. Purity looks good, so the yoke is not in the wrong position.

It makes me wonder if the yoke from a good CTC-5 can be subbed electrically, just to see what happens electro-optically.

Good luck!

Well, the only thing I can think of is the wiring mods done at the time the flyback was replaced by RCA. If the polarity was not reversed to work with the positive going pulse coming from the replacement fly (original has a negative going pulse), then it might cause the convergence to operate incorrectly. I guess the next step should be verifying all the convergence stuff, which may take some time.

I would double-check the values of all the parts in the convergence circuits, especially if any of the controls are not responding the way the RCA service procedure describes them. I don't remember having problems with the one CTC-4 I have done, and on my CTC-5, the convergence was mediocre and not every control worked right. I found out two or three of the caps that had been replaced were the incorrect values, maybe .015 instead of .15 or similar. I fixed that problem and convergence came in pretty nicely.

Went back and redid all the dynamic setup stuff IAW the Sams booklet, and noticed that I had misread a few of the instructions. I hadn't properly adjusted the horizontal phase slugs to work with the amplitude controls. That's why I wasn't previously able to get the lines to bend the way I wanted. It's still not perfect, but very acceptable for everyday viewing. There's a slight red shadow in the bottom left of the scene, but it's livable. Next I'll have to retackle the matrix alignment because there's too much blue in the picture, and the killer circuit could use a little help as well- it's very touchy. Overall, it's starting to look much better!

Found that the color killer was wonkey because of incorrect chroma amplitude, a tweak to the color take off and bandpass transformers fixed that. Then all it took was a few minor tweaks to the 3.58 CW transformer (which adjusts the phase of the local oscilator going to each demod), and along with a touch up of convergence and CRT drives it's good enough to call done!

Now I'll move it into the living room, and start enjoying it. :thmbsp:

that set should be enjoyed.looks very good and it will last another 50 plus years.great set and happy that an vker got it.i saw the auction and it is worth every cent you paid!

?

Maybe you're confused, this is the CTC-4 I picked up in Indianapolis.

Speaking of 4's, you should come over Nick, I'd like to show you something that I'm sure doesn't happen often......

that set should be enjoyed.looks very good and it will last another 50 plus years.great set and happy that an vker got it.i saw the auction and it is worth every cent you paid!

Hey RON! Where where you this year?? The convention just wasn't the same....lol

sorry.thought it was the set at the etf.well this one looks great.didnt make it this year.was out in Tennessee. glad you all had a good time.next year,i m there!

Speaking of 4's, you should come over Nick, I'd like to show you something that I'm sure doesn't happen often......



You mean like a CTC-4 that works on all original caps? :D

Mine didn't, that thing was used for a solid 20 years before I got it! I often wonder how the flyback could look as good as it does if it was used that much- I know it was replaced at least once, but I don't know if the tag left on the chassis was the only one, know what I mean?