Dumont RA-110 from ETF

[jr_tech]

Originally Posted by Kamakiri

One of the wires that was connected goes to pin 8 of the 5U4s, the others I can't see where they go, but I assume that those two complete that particular circuit. From what I can find, the relay should show 5000 ohms across the coil, I have 3800.

If this relay were dead, and with those strands of wire connected, could this have caused the set to work before, and not now?

Makes sense, if the relay or driver circuit were bad, the connection might have been bridged on purpose to provide B+ to the set.

jr

[Kamakiri]

Yep, that was it

Had the chassis on the bench, so on my lunch break I jumpered the connection, and used the variac to power it up.

It's sure an improvement from where I was when I had a picture last, but it's still not right. Contrast control does nothing, and neither does width. I can get it wider, but then I have to max out the horizontal drive and the whole picture darkens up in the center. Focuses fine. Not very bright, but I did notice that the picture is getting better just with tweaking and use, as everything is beginning to "wake up".

Getting there, getting there . Think it's time to re-test tubes before I go further. One candohm was working but was out of spec, so I'll place that on my next Mouser order.

[earlyfilm]

Originally Posted by Kamakiri

. . . . width. I can get it wider, but then I have to max out the horizontal drive and the whole picture darkens up in the center. . . . .

After tubes, the first thing I'd check would be the cathode resister on the horizontal output tube.

If your other checks do not find the problem. . . .

I notice that the Sam's that you are using lumps the 12 inch RA-103 with the 19 inch RA-110 chassis. I see that Rider keeps them separate.

I have no idea what Du Mont changed (other than the yoke) for the bigger CRT, but there is a slight chance that the person who recapped your set used the more readily available Sam's instead of either Du Mont or Rider diagrams and accidentally created an image size problem.

Jas.