u-test-m tube tester

[bandersen]

That's a pretty sweet sign

http://chicago.craigslist.org/sox/atq/1705212011.html

(no affiliation)

[ohohyodafarted]

I sent him a note asking if it was still available. Thanks for the heads up.

Bob


EDIT: I got it, and thanks again. Will pick it up within the next two weeks. I hav always wanted one of these for my TV display room.

Bob

[bandersen]

I'm glad you got it. I was tempted, but don't have the room.
I can't believe how many sets have popped up this week. I just might have to start renting a storage locker!

[ohohyodafarted]

I know this is a long shot, but does anyone have any idea where to get a schematic for a U-test-M tube tester.

It is a very simple unit underneath. I already replaced the rectifier diodes and the electrolytics. Still dosent work. When you hit the test lever, the needle goes negative. The thing seems simple enough. Looks like all the various voltages from the multi tap transformer are wired directly to the appropriate sockets, and it appears that when you hit the test switch it completes the common side of the transformer and power supply circuit.

Sometimes simple gets very complicated without a schematic. If I had a schematic I could probably get it running in nothing flat.

If anybody can help, with any information on who built these testers, or where to get a schematic I would be most greatful for the help.

Thanks!

[leadlike]

I have a very similar drug store tester. Mine was made by Mercury. Like yours, there isn't a whole lot to the underside. When I first got mine, it was very dirty and the needle would swing slightly negative of zero when the test function was pushed. The short lights would also come up. I found it was just a bent lead shorting to the case of the unit.

It could be possible that your diodes were wired in backwards as well. My crt tester had that done and it would not function at all until that was done.

As for a schematic, this gentleman has posted to Audiokarma in the past saying he would give out any service info for his similar self-service tester if asked. I'd probably get in touch with him for a schematic. They can't be that different:

http://www.tuberadios.com/eico660/

[ohohyodafarted]

Thanks, I dropped him a note requestiing help if possible.

I don't think the diodes are in backwards. It had the original ones in the unit and the polarity was plainly marked. Very wierd looking in a 1/2" bakelite cube with 2 terminals out the top and a mounting stud on the bottom, and they did not register when I tested them on my meter. So I went ahead and replaced the 2 diodes and the electrolytics. I got the same results with the new parts installed.

I also cleaned up the multi section rotary selector switch with de-ox-it.

Tube testers are a pain to work on. Very hard to follow the wiring. Last time I fixed a Hickok tube tester I tore my hair out for days and I had a schematic. Eventually I found a cold solder joint, probably was that way right from the factory.

Thanks for your help.

[Tubejunke]

I have a table version of a very similar, if not the same tester. I used to use it at the store as a kid, then years later I bought it from them. It has some issues as well. I wish I could get rid of it.