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Re: Tube data notes on the 6SH7......any thoughts?

11/16/1998 9:23 AM
Re: Tube data notes on the 6SH7......any thoughts?
From the Clubman schematic it's hard to tell where that 6SH7 is operating. The cathode resistor is much higher than one normally sees, for instance.  
Since you built the circuit, would you measure the supply voltage (schematic shows 410v), the plate voltage at pin 8, the screen grid voltage at pin 6, and the cathode voltage at pin 5?  
This looks like a really high gain circuit.  
About the tube:  
What brand are you using? I think GE was the last company to produce metal tubes, but a lot of them are problematic. For instance, I bought a group of new 6SJ7s that were GEs, and they are highly microphonic. I needed them for microphone preamps. They're obviously no good for that application. The old RCA or Ken-Rad seem to be much better tubes. 6SH7 was not as prevalent as 6SJ7, 6SK7. You may not have much to choose from. I'll bet matchless had to go through many samples to find some suitable for clubmans.  
I'd appreciate if you could post the voltages, so we can maybe suggest a substitute that may sound somewhat similar.  
11/16/1998 9:49 AM
Benjamin Fargen

Doc, Thanks for your help.  
I am using a GE 6SH7 and I have one other that I have not tried yet. I will measure the voltages you requested and post them as soon as I get home from work tonight. I am assuming that Matchless redesigned the newer Clubmans with a EF86 in the second stage due to lack of good non-microphonic 6SH7's.  
11/16/1998 7:01 PM
Benjamin Fargen
Re: Voltage readings from the Clubman's 6SH7.
Doc, Here are the readings:  
Plate = 215.9v  
Screen grid = 113.3v  
Cathode = 3.1v  
I was mistaken about the brand of tubes I am using....they are not GE's....they are nos RCA's that come in the red and black sleeve.  
Thanks for all your help and I look forward to your suggestion on what I should do!  

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