Dumont RA-110 from ETF

[Kamakiri]

First power up. Not perfect, but it focuses in and has great sound. Inadequate width, not very bright, and the picture's not lined up, but it's something

Video: https://www.youtube.com/watch?v=Hk2S...ature=youtu.be

[Kamakiri]

Weird how it's just rolled up on the left...

https://www.youtube.com/watch?v=OELi...ature=youtu.be

[wiseguy]

did you replace all of the paper caps yet?
there are a few in the Horiz Sweep area that when bad/leaking will cause this, and also a weak damper tube 5v4 would cause this, if the Horiz drive is turned up too high will cause this also
I would start first making sure all the caps in the Horiz osc/output/flyback are new, there is a resistor r122 and r120 that will change value, check those
But the Capacitors c101,102,103,106,105,107 is very important

[Kamakiri]

All of the paper caps have been done. This set was totally restored when I got it, except for the one filter cap mentioned above. Even the disc caps are new...picture tube was just shot.

I agree, all signs kind of point to the damper circuit especially with the dim raster, but the 5V4 is new, just got it in from ebay (it was the only tube I didn't have). Tested strong before putting it in the set.

I've obviously got multiple issues here....it's got extreme foldover in the horizontal right in the middle of the screen and lacks width. Width control does nothing to improve it, so I'm inclined to think that I've got a bad horizontal output transformer. Gonna have to pull the chassis and ohm that out.

The horizontal drive was maxed out, but even bringing it all the way back to halfway caused no change, and with width also causing no change, that also points me to the horiz output transformer. Sound right?

[wiseguy]

I have a known good Flyback and Yoke from the 12Qp4 version of that set, but the 19" version has a beefier Flyback part numbers are different.
one of those chassis I had one of those Riveted Wirewound Resistors was bad, but I can't remember which exact one
of Course you know to be careful when measuring Pulsed Voltages around the Sweep area so you don't Damage your Meter

[Kamakiri]

Well, one of those is for the focus coil, and the set does focus, so I can assume that's good. Other is a bleed resistor. Probably will end up having to check them anyway.

Unfortunately the only voltage test adapter I have is for a 7 pin miniature, so that's going to limit me in testing chassis voltages, and I'm sure as hell not doing it from underneath

Maybe it's time to finally buy an octal one. Never really needed one up till now.

[Kamakiri]

Having never seen horizontal roll up before, I went to the shelf and grabbed my trusty GE Tele-Clues binder. Well son of a gun.

[Kamakiri]

Tossed the 5V4 on the tester, and it was perfect, so I got to thinking of what ELSE might cause the damper tube to be out of circuit. Peered underneath, and why HELLO Mr. Capacitor!!! Apparently something came loose from the previous tech that did the work! Yay!

Problem solved, right? Nope.

Clip leaded the cap across what I figured was a very obvious connection as seen in the pic. Powered it up and heard a SNAP. Shut it down. Grr.

The one end of the cap is definitely at pin 3 of the octal socket that goes to the HV chassis. It's a .1 uF. Have to do some tracing to figure out what the devil is going on.....

[Kamakiri]

Definitely have the right attachment point according to the Sams. But, found a half dozen OTHER loose solder joints, some barely touching. I swear I gave the whole chassis the once over too, before installing it.

Welp, I have something to do tonight

[holmesuser01]

I really like seeing yet another DuMont coming back to life. I love the way they were built.

[wiseguy]

C105 and 106 have a 1000 volt rating in the Damper circuit, the one is your pic looks way underrated, the snap you heard could have been one of those

[Kamakiri]

That's actually C103. But as far as the SNAP goes, my God....

I stopped counting at 12 badly soldered connections. And I KNOW I checked them before powering up, but maybe not well enough. This wasn't my recap job, so I'm also in the habit of giving each cap a good tug at each end before moving on to the next.

The cap connected to the focus pot was TOTALLY disconnected. What a mess, everything was falling apart. I'm just scratching my head as to HOW. I don't end up buying a recapped set very often, so I guess as long as it's fixed, that's what matters.

Well, we'll give her another go and see what happens....

[Kamakiri]

Powered up. Lost audio, raster, and the tuning eye. Fuses are both good, all tube filaments are lighting, including the picture tube. Dammit.

I'll admit that I'm at a loss as to where to even start from here.

[earlyfilm]

1) Get a bright light and look for a solder bridge or burned through insulation during the resoldering.

2) Measure B+.

3) If no luck, download the Sams on ETF and check socket resistance measurements.

Jas.

[Kamakiri]

Kind of what I had in mind. I was hoping to find a common component for an easy fix, but I should know by now that never happens

My assumption that the snap I heard was coming from the loose end of the cap that should have been going to the focus pot with voltage finding its way to chassis ground, though it wasn't grounded out.

Time to start from scratch.