83 My radio is supposed to have 295 volts on the screen of the 6L6 amplifiers. I read 303.5 on my digital voltmeter. Is something wrong?
Description
This article is from the Antique Radios And Phonographs FAQ, by Hank van Cleef vancleef@netcom with numerous contributions by others.
83 My radio is supposed to have 295 volts on the screen of the 6L6 amplifiers. I read 303.5 on my digital voltmeter. Is something wrong?
Yes, both your expectation that the screens are supposed to read 295
volts, not 295 +/- 20%, and that your DVM is precise just because it
gives you a lot of digits. When was that DVM last calibrated (or was it
ever calibrated) against a known standard of some sort?
Most shop test equipment is wildly inaccurate to begin with, and has had
enough use and abuse (and time) since last checked that you can't trust
the readings at all. At best, they will tell you "around 300 volts" or
"around 455 Khz" unless you have some way to check against standards.
Don't trust anything to be telling you other than "approximately" unless
you have had it checked against standards recently, know what accuracies
you can expect, and things that can affect accuracy. Most major cities
have services which have standards against which to check test
equipment, and if you have something like a GR 650 bridge that is
working properly, it may be worth the tariff to have it's calibration
checked by one of these shops.
When selecting test equipment, keep in mind that that nice old Tek scope
may have 35 or 30 tubes and 50 adjustments, and pose much more of a
maintenance problem than any radio.
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