Wow, it feels like forever since I posted a project thing...
Well, I’m still stuck when it comes to the Philco 39-45. Part of that is due to my test gear, which I always buy used, so it almost always needs to be repaired.
I’d already done some work on my Hickock 540 tube tester, but recently it had started misbehaving. It was giving me weird results when testing known good tubes. So today I decided I’d peek under the hood and see what might be going on.Â
As you can see from the second pic, I’d already replaced one of the resistors on the resistor board, but another one (the 1.2k at the bottom) was reading 1.6k, so it got pulled and replaced. Next there was a sneaky wax-paper capacitor (5th pic) hiding under the resistor board. I hadn’t noticed it was there till now, but it was not in great shape. So I cut it out and replaced it with a new equivalent.
Lastly there was a 100k resistor that bridges the neon lamp that indicates a tube is shorted. This resistor was way off spec, which meant that no matter how good the tube was, the tester always showed that it was shorted. I pulled the bulb socket out and replaced the old one with a new 100k resistor.
I fired up the tester and now it seems to be behaving itself. So, I’ll get it back in place on my bench, then run through the tube compliment in the Philco 39-45 to just double-check that no tubes are bad. Maybe that will tell me something...
Stay tuned for more exciting parts replacements!