I'm totally unfamiliar with solid state, and I'm troubleshooting a circuit that uses 2N1370 transistors. On one of them, the base and emitter sit at exactly the same voltage.
My cheapie component tester identifies it as a single diode, but that's in circuit.
Could this be a short between base and emitter? Or some other failure mode?
My cheapie component tester identifies it as a single diode, but that's in circuit.
Could this be a short between base and emitter? Or some other failure mode?
If it’s in circuit, there may be a low resistance between base and emitter. You need to look at it out of circuit.
You're absolutely correct. I pulled it out and it checks out fine. So I've got other problems messing with the voltages. Maybe all those 60-year-old Transi-Lytics? 😀
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From a dark corner of my brain, I seem to remember that most dead germanium parts had a collector to emitter short, or a collector to base short, unless the circuit could furnish enough current to blow that short open, or pop the emitter resistor.
I blew up transistors as a kid too, most were the Poly Paks bag full for a dollar untested junk, which was all I could afford. The big fat germanium output transistors found on the backs of car radios were hard to blow, unless you used a Lionel train transformer for a power supply. Alkaline batteries were not yet invented when I played with germanium.
I blew up transistors as a kid too, most were the Poly Paks bag full for a dollar untested junk, which was all I could afford. The big fat germanium output transistors found on the backs of car radios were hard to blow, unless you used a Lionel train transformer for a power supply. Alkaline batteries were not yet invented when I played with germanium.
It was the electrolytics, of course. There were ten, in values from 5uF to 175uF - I replaced all of them and things are working fine now.
A couple of them are super bulgy. I'll post a pic if I get to it.
A couple of them are super bulgy. I'll post a pic if I get to it.
Behold, a super failed 1963 100uF/35V Transi-lytic! (With an equally failed, but non-bulgy one for comparison).
Gross!....I guess the safety vent didn't work - or maybe it didn't even have a vent. I'd hate to be working on the gadget when and if it blew though. In high energy circuits like power supplies and amps, those old electrolytics can go off with a deafening blast and a hell of a mess of tiny foil fragments to clean up.
Generally, rather than simply applying power to old, unused gear, I would first replace any large, deformed or obviously leaky or corroded electros with other, similar rating but working ones that I keep around in a jar for this reason. Your ears are too valuable to destroy or impair for want of due care.
Generally, rather than simply applying power to old, unused gear, I would first replace any large, deformed or obviously leaky or corroded electros with other, similar rating but working ones that I keep around in a jar for this reason. Your ears are too valuable to destroy or impair for want of due care.
It seems from comments elsewhere, that Transi-lytics had a rather volatile electrolyte that gave them great performance but it could slowly permeate through the plastic case, leaving a dried-out cap which probably became increasingly hot as the amount of electrolyte dwindled. The heat may well have softened the plastic and been the reason for the "bulgy" shape that cap has now. Antique Radio Forums • View topic - Sprague Transi-lytic capacitors?
No vent on these guys. Luckily, this is a low-voltage small-signal circuit (reverb driver and recovery for a vintage Wurlitzer organ). So there's not a ton of energy in play.
Part of me wants to put on the safety goggles and puncture it, just to see if it's actually still under pressure.
Not likely, I'd save any effort. It was probably long ago and the pressure would have dropped and levelled to local air pressure as any remaining electrolyte cooled off and condensed back to liquid. Even that will probably have vanished completely over the years since.