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The parts from the time are such shit that it didn't really matter anyway.

The parts from the time are such shit that it didn't really matter anyway.

(post is archived)

[–] • 3 pts

Here's the whole thing. It's not worth replacing everything, although I may get rid of the tantalum crud at some point.

[–] • 2 pts

That's pretty cool for an old piece of junk. Love those hand-taped/drawn traces and the MC7441 Nixie tube drivers. Kind of surprised it's a fiberglass board instead of phenolic given the age of the parts. Must have been spec'ed for fiberglass due to its application. Was probably pretty expensive in its time.

[–] • 2 pts

It's a Heathkit IM-1212 voltmeter kit. It was probably outrageously expensive because it was sold by a school (in this case, Bell & Howell.)

[–] • 2 pts

It's a Heathkit IM-1212 voltmeter kit. It was probably outrageously expensive because it was sold by a school (in this case, Bell & Howell.)

A voltmeter with only 2 digits of display? That must have been a precision piece of test gear!

[–] • 2 pts

10K - 5%

Can't believe I still member color codes.

[–] • 1 pt

That one's silver - 10%

It was still outside of even that sloppy band at 11.7k

[–] • 2 pts

lol Damn, you're right. I mixed it up with the gold band.

[–] • 4 pts

It's carbon comp, you may as well say "Tolerance is maybe."

[–] • 2 pts

I hope the mistakes you are correcting include replacing those old carbon composition resistors with carbon or metal film resistors, particularly those half-Watt jobbies. Probably should replace those tantalum caps too while you're at it.

[–] • 2 pts

I'm in the device's oscillator circuit right now - but the whole thing is carbon comp resistors. Trying to correct some of the drift, I replaced all the associated parts with some mil-qualified metal film parts from my stocks. The device would drift 10 counts out of 85 on warmup, now it's 2 in 85.

I'm not replacing the rest since those don't really matter, it's the oscillator that does the dirty work here. The rest of that 1970s shit can stay where it's at.