Quote:
Originally Posted by Yamamaya42
On that RCA schematic it's C118a then, ( I did not see it at the bottom)
I still prefer the Sams, cause it's easier to see, and has much more info, like waveforms.
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If C118A, then I would expect a sawtooth and that ripple magnitude sounds about right. That sawtooth is just the capacitor discharging as load current is drawn and then recovering as the rectified AC input waveform recharges it. The ripple is high here since this is the first filter capacitor.
For checking tubes, substitution is always your best bet. It would make sense to have on hand spares for most of the tubes in that set. Drugstore testers were more about tube sales than thorough tube testing.. for a really good test, a mutual conductance type tester is always best, but not really worth getting until you're surrounded by tube equipment needing repair. If you want to find one locally, figure out where audiophile, ham radio enthusiasts, or antique radio collectors hang out, you'll probably be able to borrow one, or at least bring your tubes to someone to check.