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Testing a 211 in an 845 amp

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DAK

I am fixing my buddies 845 powered ASL amp and was wondering if I could use the amp to test my 211 tubes. I understand that the 2 tubes have different requirements but are similar. maybe I can adjust the voltages to make this work? I do have a variac. But the main thing is I do not want to blow up my friend's amp. Any suggestions? regards, Dak

Follow Ups:

RE: Testing a 211 in an 845 amp - Blackdog 17:48:59 03/16/14 (4)
You probably won't get the bias low enough for the 211. It will be running very cold, and probably won't tell you anything.
You can try though without hurting the amp.
What's wrong with the amp?
Dan Santoni
- RE: Testing a 211 in an 845 amp - DAK 22:02:14 03/16/14 (3)
  Hi Dan, I changed a pair of the ps caps in the voltage doubler circuit. There was popping sounds and the one pair of caps were getting noticeably warmer than the other pair. I installed some Kemet caps which I think have a higher surge rating than the originals.
  The amp is an Antique Sound Labs 845 with fixed bias , so I do have some adjustment leeway. What is the bias necessary for the 211? regards, Dak
  - RE: Testing a 211 in an 845 amp - Blackdog 04:03:31 03/17/14 (2)
    You need about half the negative voltage for the 211. It also has a lower plate dissipation. This is an AQ1006 I assume. You grid, is probably around -125 VDC, you would need to lower it to around -60 I'm guessing. Atleast the 211 will be running light. So you won't damage anything. The other way around you risk over current.
    
    Dan Santoni
    - RE: Testing a 211 in an 845 amp - DAK 08:43:24 03/17/14 (1)
      Hi, on the amp is a milliamp meter. Right now it is set to about 700ma. So, just to be clear, I would have to turn down the bias adjustment to around 350ma if possible. regards, dak
      - RE: Testing a 211 in an 845 amp - Ed Sawyer 12:14:35 03/17/14 (0)
        
        In Reply to: RE: Testing a 211 in an 845 amp posted by DAK on March 17, 2014 at 08:43:24
        
        That's actually reading 70ma even though it says 700. I had a pair of these amps for a while. there's not enough adjustability in the fixed bias to get it anywhere near that low for 211s. Additionally, the output transformers will not have the primary inductance needed to properly load 211s. You could see if they light up but that's probably about it.

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