- 2024
- Oct
- 23
A Heathkit IG-72 Signal Generator Part 1 - Observations.
I’ve decided to see about tuning up this device I purchased at The Scioto Valley Hamfest, so this will be my next project. It shouldn’t be anywhere near as involved as the last one - but we’ll see.
You’ve probably seen this picture posted here a couple of times:
The device has an output, but it’s flat on one side. The oscillator is working, is fairly close - but is out of balance. This could be tubes, the light bulb PTC resistor, or a bad capacitor. That’s what we’re here to determine.
The device was purchased at a hamfest, as previously indicated. The vendor selling it had a bunch of odds n ends:
I bought this, and another unit the guy had. The second unit had a handle, and was in poor shape overall. It sacrificed it’s handle for the ‘good’ unit.
Since much of what I’ve read points to a tube being not-bad-not-good, I picked up a fresh set of tubes:
The good unit appears to have been a factory build - everything is neat and it has the Heathkit sticker on the chassis.
The bottom uses manhattan routing and has nicely twisted lines where necessary.
It’s hard to see, but the 6CL6 tube in this one is an RCA, while the other two are Heath branded. That one has been replaced at some point - it’s a cathode follower that provides the input for the oscillator, so we’ll look at that first when it’s on the bench.
The other unit, an AG-9A, looks to have been a kit build. It’s clean inside, but not as much care was taken during assembly.
I don’t have any intention of restoring this unit for use, so it will be put back together and stashed with my other parts units. I doubt I’ll bother using the tubes out of this for anything other than display, since NOS units are still available at a reasonable price.
But first, I’m taking the time to do what I normally do with these things - take the half-loose knobs off and give them a bath:
They come out nice and clean. I’m cleaning the other unit’s knobs as well, no use in wasting time in the ultrasonic bath.
Next step is to open the device and check some things against the manual. Stay tuned!
Next part of this series: https://wereboar.com … r-part-2-suspicions/
Previous part of this series: You’re at the beginning.