The Family DuMont

[CaryLee]

Originally Posted by earlyfilm

Cary, I believe you said this is your first TV, correct?

I also understand that you have neither substitute tubes, nor a tube checker, correct?

Next step is to dim your lights and verify that the plates on the 5U4 rectifier, the 6BG6 Horizontal Output, and the 6W4 Damper are not getting pink as this indicates something is badly wrong.

If any plates are glowing, turn the set off immediately.

Since you have not replaced any resistors, I assume that a resistance check will not be productive at the moment.

I cannot call the Sam's part numbers as the only schematic of the RA-112 is the Riders one at ETF which uses the factory numbers.

http://www.earlytelevision.org/tv_sc..._diagrams.html

However, I'm going to suggest that you measure all the resistance reading listed in Sam's from tube sockets, with the set unplugged. This will give practice for the next step and it might spot a pre-existing problem.

Make a Xerox of the two pages of Sam's and write down the resistance, at each point and color marking the ones that are off by more than 20%.

If no tube plates were getting too hot, your next step is to check the voltages that are shown in Sam's voltage chart.

Follow the same procedure of writing them down, again marking those 20% off in a different color.

James

Howdy James!

Yes, this is my first set. I've done a couple tube radios, and a wind up phono (completely different tech!) The reason I've got this DuMont is because it's a family heirloom. I've run into some pretty good luck with it so far.It's nice to know it's history, and it's been in my possession for over 25 years, and I've been pretty protective of it.

As it started getting darker outside, I was able to look at the tubes as you suggested. No pink plates, so that was good. The darkness is also what led me to noticing that the CRT was apparently "coming back to life". I could see some VERY faint flickering, and started moving the ion trap around, and was able to brighten up the CRT immensely. I was pretty encouraged by that. Now I just have to figure out how to introduce a a signal so I have something to actually see.

We actually still have at least one UHF analog station broadcasting here..but alas, this DuMont has no UHF!

Thank you for the "system" for checking the resistors. I figure There's going to be some that need replacing. There's a LOT of them in there!

I do not have a tube checker. I've met a couple people who say they have one "somewhere", and say I can use it when they find it, but no one has dug one up yet. I'm starting to get enough tube driven stuff around here that buying a checker might be worthwhile. I do have a few extra tubes now. TV tubes are remarkably cheap, so buying them in lots is almost as cheap as buying one. I've got a couple 6J6's, 6BA6's, and several spare 6AU6's.