Still Having RCA 8TS30 Issues

[Chris K]

Hi all,

Still having problems with this TV. I can't get horizontal lock when I feed a signal into it. I think the best thing to do is list what I've eliminated as possible causes. I am using the 5" CRT for testing and I have left the focus coil in place. It doesn't affect the image focus. All electrolytics and film caps have been replaced along with a couple of 270pf micas in the IF. Here's the list of what I've checked off as probably not causing the issue.

1.Signal Source. I've tried 2 signal generators, a live broadcast feed and I have fed an IF signal into the video IF in 2 places using the B&K 1077. No change in the absence of horizontal lock.
2. Tuner. As I said, I bypassed the tuner by injecting a signal directly into the IF.
3. 5" CRT. Not the cause. Same symptoms on 2 different 10BP4 CRTs.
4. Horizontal and vertical control pots. This is a concentric shaft pair. Each has been cleaned and each ohms out within specification. Just for good measure, I swapped out the control with one from a parts chassis that was cleaned and ohmed. No change in the symptoms.
5. Tubes. Every tube in the TV has been tested, replaced with NOS tubes, swapped out tubes from stock and other working TVs etc. All socket pins cleaned. No change.
6. Control pots on rear of chassis. All extensively cleaned (Horizontal and vertical position, focus, vertical linearity, height, horizontal drive) and tested for resistance. All within specs. Focus, horizontal drive pots swapped out with clean and evaluated pots from parts chassis. No change.
7. Sync Discriminator Transformer T-108. Ohmed and swapped with transformer from parts chassis. No change.
Contrast pot. Cleaned and resistance tested. Replaced with parts chassis pot. Replaced with new 10K pot rigged up separately. No change in symptoms.

So, I'm running out of ideas! I checked the signal from the horizontal oscillator at point A on T-108 and it is clean as a whistle...15.75K and a smooth sine wave. On pin 2 of the Horizontal Sync Discriminator 6AL5, it's a jumping mess of a signal that occasionally looks like an accurate waveform but it scrambles with the picture.

I've been concentrating the troubleshooting in the sync and horizontal circuits and any resistor >10% out of spec has been replaced. I even did some Shango troubleshooting by whacking a few things with the back of a screwdriver with no luck.

I know I've caused some frustration with some being a rookie who doesn't know enough about how these things work and sometimes has taken the experts through pages of messages only to find out the problem isn't in the TV but the signal generator or a bad tube. I apologize for that. I think I'm learning at least to eliminate the dumb stuff first before posting a situation that has me stumped. I'm also getting better at accurately following through with some of the suggestions that are given.

The deflection circuitry on most of these early RCAs is pretty much the same if not identical. My hope is there are some members experienced in these early RCA chassis to provide some insight.

Thanks everyone.

Chris