Triplett 3432 Signal Gen - working again!

[dewdude]

Hey guys,

So, a couple months ago I braved the shed in the far corner of the yard looking for a couple pieces of old test equipment. I posted about the signal tracer and generator then, and I've not gotten around to the tracer. But my $11 frequency counter showed up; I had the parts; I figured it was time to make it work again.



Ythose things are a little old. But what shocked me is the inside looks practically clean! 20 years in a filthy shed; the outside looks horrible...but everything inside looked brand new. EVen the tubes looked (and tested) like new! I was going to hook up and get an ESR on the old can; but I never did. I had a schematic, but I still wondered if I was in over my head. I'd taken it apart over a month ago...didn't write stuff down, figured "Oh, I'll remember it". It's about the time I sit down to start changing things that I have the thought "oh no...I don't think i'll remember how to reassemble this thing. You'll notice the tuning cap is in the background. That sucker had seized up; plus one set of fins had fallen off. I took the cap out, lubed the bearings and got it working smooth again. The fins simply snapped back on; so it was a matter of just getting the fins lined up, snapping it back on in the proper position..then looking to make sure fins aren't touching. BTW, in case your wondering; that little circuit board to the left in that picture? That's the frequency counter. 3.5"x1"x1".



Here's the oscillator coils. This sucker turned out to be a bit of a PITA. There was a .05 cap buried between the coils and rotary switch. I hate simply tacking on caps. but there was no room in there to do anything but. I'd considered trying to remove a coil or two...but they didn't want to desolder or come out of the plate. The other issue with this are the two mica caps in the unit. I bought silver-dipped micas to replace these...and the two caps alone cost more than the 2 'lytics and 5 films *combined*. But they're located at the very BOTTOM of that rotary switch. Yeah, radio guys always said don't change those micas unless you had a specific reason; I guess I will have to go with that.



With all but two mica caps changed; resistors checked, and a fuse added; I managed to leave myself enough notes on the chassis and parts to see what went where and how it all went together. All I had to do now was fire it up; see if it was making b+ and RF.



Sure enough, it was! And the counter started flickering telling me there was RF. At first, it wasn't giving me any real values; and I thought maybe the counter was defective. Turns out if you don't have enough RF going in to it; it gets confused. Likewise, if your RF level is too strong it can overload the front end and everything between 400khz and 1000khz reads double frequency. I had thought about going through the alignment procedure; but I've decided I'm not going to. For starters, the last thing I did was carefully break the dial indicator off the housing that attaches over the dial. The only thing I can see that does is align the dial to the oscillators; which I don't actually need since I can read the frequency directly with the counter.

The guy that taught me how to do antique radios taught me to adjust and tune IF's by simply peaking the levels; and that was the real reason I wanted to fix this. However, after reading about it; I'm finding out you really need a sweep generator and scope to do it properly; which makes me wonder if I'm ever going to actually use this for that purpose. I think I've seen a few sweep generators that use a frequency generator as the source...but I got a lot of research to do in that area.