RCA ctc36 short issue?

[pendulum]

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.

[pendulum]

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!

[Findm-Keepm]

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. 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.

[zeno]

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

[pendulum]

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.

[Findm-Keepm]

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.

[Findm-Keepm]

http://www.americanradiohistory.com/...-Page-0103.pdf

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