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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: HK Citation 2 rebuild questions posted by DAK on April 13, 2015 at 01:45:39:
Don't do any of the things you mentioned. And no offense, but if you don't know what to do with that resistor then you should not do any re-design work to the bias circuit without guidance - it puts the power tubes and the OPTs at risk if bias is lost. If you ever see all four power tubes run wide open on a Cit II you'll never forget it!
Why not do what you mentioned? First off, the bias winding on the Cit II power trafo is suspect. We've had enough intermittent failures (which damages/destroys the power tubes - and of course the tubes get blamed if they are new production!) of an internal solder joint that we recommend a complete replacement of the bias supply including its own dedicated transformer. Maybe someone here has installed it already and can fill you in.
Second, reducing the decoupling capacitance may even make the amp unstable! We recommend a major increase in the size of the decoupling caps, and it pays off big in sonics. Those V1/V4 tubes alone draw about 18-20 ma EACH - you aren't dealing with wimpy little 12AX7s here! Do not reduce the capacitance, we use and STRONGLY suggest good quality caps, along with a large increase in value.
My comrade and bench tech Don Sachs and I have done HUNDREDS of these amps. What I'm passing along is not conjecture, it is proven techniques based on my 40+ years of experience with these amazing amps.
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Follow Ups
- RE: HK Citation 2 rebuild questions - Jim McShane 05:19:51 04/13/15 (10)
- RE: HK Citation 2 , seperate bias supply - DAK 11:20:17 04/13/15 (5)
- Bias supply - Triode_Kingdom 12:08:26 04/13/15 (1)
- RE: Bias supply - DAK 12:18:54 04/13/15 (0)
- RE: HK Citation 2 , seperate bias supply - PakProtector 11:38:28 04/13/15 (2)
- RE: HK Citation 2 , seperate bias supply - DAK 12:15:47 04/13/15 (1)
- RE: HK Citation 2 , seperate bias supply - Triode_Kingdom 13:01:51 04/13/15 (0)
- RE: HK Citation 2 rebuild questions - DAK 09:52:03 04/13/15 (3)
- RE: HK Citation 2 rebuild questions - Jim McShane 12:45:31 04/13/15 (2)
- RE: HK Citation 2 , bias supply requirements - DAK 12:52:30 04/13/15 (1)
- RE: HK Citation 2 , bias supply requirements - Eli Duttman 13:20:46 04/13/15 (0)
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