Help with Tube Testing? (Admiral 17T12)

[Winky Dink]

I picked up an Admiral 17T12 with good audio and video a couple of years ago. At that time, I pulled the chassis for a quick look and a few pictures, then put it away. I took it out two days ago, but now it has no video at all.

I thought this would be an easy fix even for me with little expertise in electronics.

So I started with the tubes (I got an EMC 213 last year). I found one bad 6AU6 and replaced it with a spare used tube. Then the HV rectifier 1B3 showed shorts in two positions where it shouldn't be shorting. I pulled a 1B3 from a non-working set. This 1B3 was apparently OK two years ago, and it passed the short test, but on the emissions test the needle didn't even budge. I tried the tubes back in the set, but after several minutes there was no glow and no heat from either one.

Is the test failure of both tubes a coincidence, am I making an error in testing, or is the test instrument failing? I had no problem with a couple of dozen other tubes.

I'll be grateful for any advice. I've apparently forgotten how to embed images, but here are some picture links.

- Winky

My EMC 213 set up:
https://picasaweb.google.com/lh/phot...eat=directlink

Testing instructions and 1B3 data:
https://picasaweb.google.com/lh/phot...eat=directlink

Excerpts from Frank's Tube Data:
https://picasaweb.google.com/lh/phot...eat=directlink

[ohohyodafarted]

First off I love your avitar. I haven't heard mention of WinkyDink since I was a kid in the 50's. In addition, I had an EMC 213 tube tester when I was about 13. First one I ever owned. Bought it from Olson Radio. It was in kit form. It's a cute little tester and tests most of the common types of that era.

Sorry I can't give you much help on your issue, but someone here will no doubt be able to give you some expert advise.

Good luck!

[Eric H]

If I'm reading your picture right you have the heater voltage set to 6.3 or higher? (Fil volts should be on "a" and you have it on "d") That would instantly destroy the heater/cathode on a 1B3.

In normal operation you won't see a glow or feel any heat from a 1B3, it get's it's voltage from the Flyback so if there's no High Voltage due to no Horizontal Oscillator, it won't light.

Check to see if you have any high voltage coming out of the flyback by holding an insulated and ungrounded screwdriver next to the cap (disconnected from tube) coming off the flyback, if there's voltage you should get a nice healthy blue arc from the cap (not from the tube)

[Winky Dink]

Eric, thanks. I may, indeed have fried a something. I think the heater takes 1.25V. I set up the picture to show the short test, and the tester is not switched to "quality," so I don't know if I was actually applying the "d" voltage. In any case I'll have to be more careful.

Bob, I was also a Winky Dink fan. I still have the 1950 Motorola that I used to watch Winky Dink.

- Winky

[Winky Dink]

Quick follow-up. Spent some time with the EMC 213 and a multimeter instead of sticking tubes in. Measured and labeled the filament voltage settings. Finally I started using a switched outlet and keep the machine turned off while I check and recheck the settings for each tube. Pulled the "no good" tubes out of the trash and retested. New results with the two 1B3's--one is perfectly good and the other fails the emissions test. Thanks again, now I can move on to the other mysteries of television.
- Winky