RA-103D, some pointers on where to look after recap

[CJVx]

Hi, recently recapped this Dumont RA-103D, gorgeous Rumson model. Recapping was uneventful, replaced all values of electrolytics, cans and paper caps with like for like values.

The seller actually plugged this thing in and sent me a video of when he did on his listing. I’ll attach a screenshot. The image showed a hort vertical with full horizontal across the screen, not sure if there was any snow.

I brought it home, turned it on since it didn’t blow up for the seller to confirm it was still in the same condition. I had a similar image with short vertical, full horizontal but this time I had vertical bars in the center of the image. No photo of this.

Now after the recap, I have more vertical and can stretch it with the controls I’d need be, but I do hear audible noise corresponding with the vertical controls, sort of louder than I’ve heard on other sets. The vertical bars are still there, screenshot is anttached. Also I do not believe there is any rf or video. The brightness and focus controls do their thing, but no change to the image with the contrast control. Adjusting the

Any thoughts on this are appreciated! Thanks.

PS, I did test all of the tubes and found all of the 6SN7’s were weak, so those were replaced. The only tube I was not able to test or sub with a known good was the 5V4 horiz. damper. When the rf tubes and video tubes are removed, I get the same image on the screen as described after the recap.

Will be seeing with the audio situation is later today when I attach the speaker. Have not done that yet.

[CJVx]

Before and after recap images

[bandersen]

Verticals bars are going to be from an issue in the horizontal deflection. Have you tried adjusting the horizontal drive?

The continuous tuner shaft is made from ceramic and prone to cracking. Could also be dirty contacts inside tuner.

[Electronic M]

Wiggle the video IF tubes from highest to lowest and see if you get any crackling (or if you have a B&K analyst you can inject IF into it). If you can get noise to pass from the first video IF to screen then the problem is likely in the tuner... These sets are often unusably dirty on the variable coils.

[CJVx]

Ok guys, thanks for the advice. I had no luck wiggling the video tubes, but I did confirm the tuner was working. I got FM reception and sound from the TV broadcast. This, of course, lead to further investigation.

I did start poking around and found an open R36, B+ Power resistor divider. I was able to use two power resistors to replicate it and now I have video as the picture shows. But currently I am still suffering from this weird horiz/vert issue. Both lock, the vertical bars move around with the horizontal drive control, but no combination of horizontal drive or other controls will eliminate the bars.

[Electronic M]

Have you checked the GIGANTIC dogbone ceramic power resistor in the HV cage? Those sometimes corrode open and cause issues in the horizontal similar to what you are experiencing.

[CJVx]

Originally Posted by Electronic M

Have you checked the GIGANTIC dogbone ceramic power resistor in the HV cage? Those sometimes corrode open and cause issues in the horizontal similar to what you are experiencing.

Well you nailed it with that resistor. It was open. It was wired up for 6.2K ohms, so I replaced it with a similar value. Now the picture is a really dark, and shrunken down some, but looks a lot more linear and I was able to adjust the bars out with the horizontal drive control. Strange thing is that the picture will go away when I turn the brightness control up, and slowly come back on at its dim state as I lower the brightness control slowly. The voltages on either side of the resistor seem to be where the riders’ manual said they should. But I feel like the audio even got weaker. I’ll be back on it later tonight.

[CJVx]

And I’m getting somewhere. There’s positive voltage on the second bias cap, it blew quietly. Going to search for a leaky mica or ceramic cap that could be causing this.

[CJVx]

All right, replaced the blown capacitor, as well as the 250 on resistor in the bias supply…replaced a leaky mica C98 (Sams) and the picture is starting to come together. Still have some work to do but it’s the best it has looked so far.

[CJVx]

Hey guys, to close the loop on this. Ultimately after replacing all of the paper and filter electrolytics, I still had some leaky moulded caps, open power resistors and resistors in the vertical circuit that drifted roughly 2x higher. With all of this sorted, I was able to get a decent and stable image! Thanks for the guidance and suggestions.