Bottlehead Forum

General Category => General Discussion => Topic started by: RPMac on March 01, 2010, 11:14:06 AM

Title: 2A3 filament ?
Post by: RPMac on March 01, 2010, 11:14:06 AM

I have 2A3Cs in my PG IIs. While shutting down one night, I noticed only two of the four filament in one tube were not glowing. I can't tell any difference in sound between the two amps. What issues do I have, if any?

Title: Re: 2A3 filament ?
Post by: Paul Birkeland on March 01, 2010, 01:20:12 PM

You might check to be very sure that the wires are actually not glowing, as they may be glowing more dimly. 

If you don't have a tube checker, I would advise that you get out your meter and measure the plate and cathode voltages on both 2A3's.  If the voltages are pretty close, you may not really have an issue.  I suspect, however, that the dimmer 2A3 may pull through less current, and may be on its way out.  It kind of sounds like part of the filament is no longer connected.

Title: Re: 2A3 filament ?
Post by: RPMac on March 03, 2010, 04:05:57 AM

I see why Doc pays you the big buck...other than pointing out the obvious to a dummy like me.
The bad tube...4.8mA @ 35V
The good tube...10.2mA @ 35V
Superior TV-12

At less than full volume, would the two tubes sound similar?