Questions about tubes and gear that glows. FAQ
In Reply to: Whats the purpose of these funny bulbs? posted by Mike B. on November 30, 1999 at 11:59:13:
Don't know for sure, because I am unfamiliar with the circuit, but sounds like voltage regulator tubes in a shunt reg config. It's an odd thing (good, but odd0 to find in a commercial product, since the tubes have to be NOS since they have been out of production since the advent od SS regulators.
Another possibility is that they are damper doides than function just as you describe. If you trace them back to the center tap of the secondary of the power transformer, they are indeed damper diodes. If they are sitting on the B+ rail, they are voltage regulators.
Out of curiousity, are the labelled and with what number? And are they plugged into 7-pin sockets?
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