Hi everyone,

So I have been working on the rca ctc 36 that I bought off ebay a few weeks ago. Things were going good, after recapping I put the chassis back in and got an image with some color issues and horizontal hold issues. I pulled the chassis, replaced 3 resistors, and cleaned the controls, but since then when I reinstalled the chassis and tried again, all I get on screen is the 3 color horizontal lines you get when you are in service mode. My first thought was perhaps there were tin whiskers in the controls on the back. They had been dirty before and had some bad spots that made the screen go to the horizontal lines when I adjusted them, but I measured all of them and they all were working right. The switch for service mode also is working fine. Next I thought maybe I messed up replacing the 3 resistors, but they all seem fine. The circuit measures out ok and nothing seems out of place. I'm not sure what to look for next. I can't think of anything else I may have done that could have caused this issue. Any suggestions are much appreciated, I always hate going backwards in progress through human error.

Here are some photos of the chassis as a whole and the board where I replaced the 3 resistors. The shot of the back is a bit out of focus but I can tell I have not caused any shorts.

http://i290.photobucket.com/albums/ll246/eviljoebob/IMG_2408.jpg (http://s290.photobucket.com/user/eviljoebob/media/IMG_2408.jpg.html)

http://i290.photobucket.com/albums/ll246/eviljoebob/IMG_2409.jpg (http://s290.photobucket.com/user/eviljoebob/media/IMG_2409.jpg.html)

http://i290.photobucket.com/albums/ll246/eviljoebob/IMG_2410.jpg (http://s290.photobucket.com/user/eviljoebob/media/IMG_2410.jpg.html)

http://i290.photobucket.com/albums/ll246/eviljoebob/IMG_2411.jpg (http://s290.photobucket.com/user/eviljoebob/media/IMG_2411.jpg.html)

Loss of vertical sweep - check the 'GF7 voltages, look for any broken wires - the wires on the wirewrap terminals break easily. Check that the yoke wires are okay, not pulled from the plug or the yoke.

Possibilities:

Vert Osc quit
XXGF7 tube quit
B+ bad to 'GF7
broken wires - terminals or yoke
bad ground to vertical area (eyelet solder grounds on board in Vertical osc/output area)
open resistor in the 'GF7 area
.....and yes I've seen service switches fail, but check okay in circuit.

Thanks for the suggestions as to where to look. My schedule is pretty busy the next few days but hopefully I will have made some progress by the end of the weekend.

I had some time to do some probing, here is what I have found so far. I triple checked the yoke, convergence, and wire mounts on the pcb and could not for the life of me find any broken wires. Next I started checking the voltages on the 12jq6 vertical output tube (this sucker gets hot enough to cook food off of!). I have attached a portion of the schematic below, but here are what the voltages are supposed to be for the tube

1- do not measure
2- not given
3- 135v
4 and 5 - 40 ma
6- -60v
7- -5v
8- -5v
9- 10v

I checked 3 and it was spot on at -135v, but when I checked pins 6 through 9 they were all around 47v! Clearly something is wrong there. I attached a pdf of the schematic, so you can follow along there. I checked the 280v source and that was correct. I checked R111 and it wasn't open, neither was 116. i noticed on the waveform picture off of r116 they say the wave is 40v peak to peak, so maybe something around the tube is not pulling the voltages down to what they are supposed to be? I noticed the vertical linearity control was near the circuit, but rotating it didn't seem to make any difference. I don't know if it should influence the voltage or not. I know the service switch is in the circuit, but putting it in service mode did change the voltage like it seems it should. I will keep probing around for any obvious things like open resistors, but any advice would be appreciated. I know there are a few diodes near the vertical output, I don't know if they were bad would cause something like this or not. Thanks for the advice guys!

Can you scope to see if the oscillator is running? That would be the 40V P-P signal. If it isn't there, your problem is with either the oscillator or the service switch - they can be funny that way - ohm out okay, but be leaky enough to kill the oscillator signal to the grid. Make sure it is pushed in all the way, and keep cleaners from it for now - the phenolic absorbs the cleaner and becomes conductive - several megohms, but enough to mess with the oscillator getting to the grid of the output tube.

My guess is the oscillator output isn't getting to the grid of the output tube, and you either have a leaky service switch (it was a "Quick Turnover" [QT] part for RCA) or an open resistor going to the grid from the oscillator.

You did check the grounds/resolder the eyelet grounds on the board already, yes?

Neat seeing my Dad's handwriting on the Sams. :D My whole library is like that - dad denoted all repairs on the Sams. He had a full library, and other shops would call to see if he had the Sams. Dad would ask what their problem was, look at the Sams, and if there was any notation, tell the other shop to check that first. If no notation, he'd tell them to come get the Sams - he ran a loaner service to the other shops. Seemed counterproductive to help the competition, but Dad was always swamped with backlog, so he couldn't have taken on any additional repairs...so he leveraged the Sams to get parts, service seminar invites, and the occasional parts chassis.

Service switch can be removed & jumped out to test.
After doing Find M Keep M's checks the most likely
thing if its NOT self induced is the caps in the vert
feedback. The ones going from the plate of the output
back to the grid of the V osc. Also the gang controls
they used were NOT very good, especially the H. hold.
We stocked them. So clean the crap out of them & the switch.

These sets even when not old often needed a lot of work.
But yours looks clean & not over heated. They are
quite capable of an exelent pix if done right.

BTW if you need a manual & cant get a free one PM me.

73 Zeno:smoke:

Thanks for the tips guys. I checked the ground posts but will reflow them to be sure. I don't yet have an oscilloscope but I am browsing around on rbay for a decent one. I still am looking around for an error I may have made since before I was getting a bit of an image, but I will keep looking and get back. Additionally, I don't know how the service switches typically fail, but I do get sound when in normal mode which is cut off in service mode. Also, I noticed the horizontal hold is pretty scratchy, so maybe cleaning that will help. I'll get back with results. It looks like with these controls I can bend back the tabs that hold them in place and remove the cardboard cover to clean inside.

One more thing to check, as Zeno tickled my memory - the tube socket for the Vert tube - check the solder joints closely, and the condition of the socket. The micalex sockets would get hot, dry out and get funky. They had two types - a light tan that would darken to a chocolate brown, and a red one that would get crumbly - the socket pins would then fail at the solder joints. The deflection tubes - HOT, Vert and Damper were all prone, as were some of the 5GH8 sockets, particularly ones at the top of the board.

http://www.americanradiohistory.com/hd2/IDX-Consumer/Archive-Radio-Electronics-IDX/IDX/70s/1976/Radio-Electronics-1976-08-OCR-Page-0103.pdf

Just one vertical/service switch issue with the CTC-36..

Alright, I really cleaned out the 3 pot block that had the horizontal control and that seemed to fix things up. I probably should have looked there first, but the control had been working earlier (albeit scratchy) and when it wasn't working the entire control was shorted out. I'm thinking the control may have had tin whiskers, so if it fails again I will either pull the control and try to remove those or replace the control. Now I just need to work on the lack of good horizontal hold, something that seems to be a typical problem on all old sets I work on. I already replaced a few resistors directly off the control but I will expand out to try to find the few that are causing the poor hold.

This is about as close as I can get. It actually is rolling a lot more than this, but that is because I have no clue where the vertical should be set with the poor horizontal hold.

http://i290.photobucket.com/albums/ll246/eviljoebob/IMG_2414.jpg (http://s290.photobucket.com/user/eviljoebob/media/IMG_2414.jpg.html)

Additionally, thanks for all the help and links you guys have found. Findm keep m, thanks for the cool story about the notes on the sams, I always like finding notes like that and hearing the stories behind them. I have an rca tt5 service manual with a bunch of notes in it, I would love to have known the history behind those.

Two things to check - your AGC control setting, and all 100K ohm or above resistors around the sync separator and horiz osc. tubes. We kept a drawer full of 100K, 120K, 180K and 220K resistors for those RCAs and the ones with the 13GF7 Vertical tubes. They would go up in resistance by about 20-30% and cause problems. Also, if the set has the original Horizontal AFC diodes, replace them - any silicon diodes should suffice. The AFC diode is a black block about the size of a starburst candy, with three leads. They go bad all the time, and cause no/weak sync. The one in your set is a replacement, but not an RCA numbered device - probably an aftermarket one or from another set.

Also, don't be afraid to move 5GH8 tubes around a bit to achieve a good pix. Remember the maxim/corollary to Murphy's law:

For any TV utilizing n 5GH8 tubes, n+1 will be bad.

They were an Achilles heel for those portables.

I was able to do some work and replaced some resistors in the horizontal hold circuit and changed some caps. It improved horizontal hold, but only marginally. Basically the image has a very, very small window of hold, then turns left or right. Also, when I was able to get the image to hold, it was off-center. I am not quite sure what would cause an issue like this. One thing I thought might potentially be causing this problem is, when I measured the resistance of the horizontal hold pot, it seemed to jump around a bit in the middle instead of going from 0 to 50k. Perhaps this is why I have such a small window of hold? Any other thoughts? Thanks for the advice!

http://i290.photobucket.com/albums/ll246/eviljoebob/IMG_2416.jpg (http://s290.photobucket.com/user/eviljoebob/media/IMG_2416.jpg.html)

I was able to do some work and replaced some resistors in the horizontal hold circuit and changed some caps. It improved horizontal hold, but only marginally. Basically the image has a very, very small window of hold, then turns left or right. Also, when I was able to get the image to hold, it was off-center. I am not quite sure what would cause an issue like this. One thing I thought might potentially be causing this problem is, when I measured the resistance of the horizontal hold pot, it seemed to jump around a bit in the middle instead of going from 0 to 50k. Perhaps this is why I have such a small window of hold? Any other thoughts? Thanks for the advice!

http://i290.photobucket.com/albums/ll246/eviljoebob/IMG_2416.jpg (http://s290.photobucket.com/user/eviljoebob/media/IMG_2416.jpg.html)

What I'd most be focusing on regarding the horizontal symptoms is the sync separator and the horizontal AFC. If the vertical sync is as solid as it should be focus on the AFC...Otherwise go after the AFC. My gut says AFC; it will affect H centering too. If the AFC diodes are stock, try changing them. Check voltages on the H AFC tube too.

First I notice the AFC diodes are tacked in from the top.
So probably someone started looking & gave up.
I would start with 2 NOS 5GH8's one in sync & one
in hoz osc. Also go through every resistor from AFC
on. Be sure the diodes didnt get unsoldered when
they got tacked in.

Controls are a problem. You may have to mouse that.
Someone used to make a kit to build them with shafts,
elements & housings. Maybe someone here has one.
One from a scrap chassis probably no better & NOS
probably all gone but worth a try.

73 Zeno:smoke:

Controls are a problem. You may have to mouse that.
Someone used to make a kit to build them with shafts,
elements & housings. Maybe someone here has one.
One from a scrap chassis probably no better & NOS
probably all gone but worth a try.

73 Zeno:smoke:

Ah, the CTS Striptrol kit - I have a small kit, with a few housings and elements. Sams shows two multisection pots - the horiz hold is in the 126346 part number one. Talonix shows two in stock: http://www.talonix.com/shop/item.aspx?itemid=15929

Ah, the CTS Striptrol kit - I have a small kit, with a few housings and elements. Sams shows two multisection pots - the horiz hold is in the 126346 part number one. Talonix shows two in stock: http://www.talonix.com/shop/item.aspx?itemid=15929

I had actually just ordered one of the pots from talonix today! I have put new 5gh8 tubes in, checked most of the resistors in the afc circuit, and put in a new dual diode to see if that helped. Image was the same, so I am feeling pretty confident that the issue is in the crummy pot. Part should arrive monday, so i'll post an update probably monday night.

part actually arrived earlier than expected. Was able to replace the horizontal hold today. Unfortunately this did not solve the problem. I will do some voltage measurements next.

ok, I measured the voltages of the horizontal afc/osc tube and there are some issues there. Here are the voltages I got compared to what the sams says they should be.
pin # sams what I measured
1 225v 224v
2 -.2v 3.5v
3 80v 38v
4 and 5 are filiment
6 140v 19v
7. 2.5v 4.3v
8 .1v .16v
9 60v -50v

So clearly something is wrong in the horizontal hold circuit. I linked the relevant part of the schematic earlier in the thread to those interested, I qill start double checking components and making sure I didn't put a wrong value component in.

Anyone have ideas here. I'm pretty sure the issue is with the 5gh8 horiz afc/osc tube. The voltages come of the 260v line and seem fine, but when looking at the schematic, I measure the other side of the 3.3 meg resistor the voltage is pulled down to -50v. I checked the two coils in the area and they measured fine. I have replaced the resistors and caps so I am not sure what would cause the voltage to be so low. Any ideas? I posted the relevant part of the schematic, but more of it is uploaded elsewhere in this thread.

Here are the voltages again
pin # sams what I measured
1 225v 224v
2 -.2v 3.5v
3 80v 38v
4 and 5 are filiment
6 140v 19v
7. 2.5v 4.3v
8 .1v .16v
9 60v -50v

I see one thing wrong is that + 60 volts on pin 9 grid. It should be -50 volts or so more negitive. Plus 60 volts on the grid would red plate the triode and most likely crack the glass. Sams blows it yet again with dumb errors. You should try to find the factory service manual or pdf for any set that you want to restore or just repair.All the best,Tom

One other thing that jumps out is the +3.5 volts on pin 2 control grid of the pentode,it is turned on hard. Ckeck for leaky C83,carbon track between pin 2,3 on board or in the socket or solder brige in same place. All the best,Tom