[R-390] OT: HP-410B Tubes
Barry
n4buq at knology.net
Tue Mar 1 21:51:33 EST 2011
I have an HP-410B that I have cleaned, recapped and trying to get working properly again. The problem is with the tubes.
It came with 5814's in place of the 12AU7's. These work great, but they draw extra heater current and I would like to get 12AU7's in there again. I ordered a set of 12AU7A's but the meter will not work well at all with them. It won't stabilize, zero, or do anything else correctly (well, the ON lamp does work, but...) with them in place.
The pair of 12AU7A's check quite strong on my Hickok 752A (they check about the same uMho values as the 5814's). Is this just a case of finding a pair of well-matched 12AU7's (non-A, whatever...) that work? I'd rather not continue throwing money into tubes that don't work but at the same time, I don't like the extra stress the heaters in the 5814's put on the old transformer.
Any ideas?
Thanks,
Barry - N4BUQ
More information about the R-390
mailing list