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Old 1st October 2012, 12:03 PM   #11
nkg is offline nkg  Australia
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6SL7
Pin 2 268V
Pin 5 55V
I have checked both resistors and they are within their values re soldered the joints just to make sure but yes odd .
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Old 1st October 2012, 12:10 PM   #12
DF96 is offline DF96  England
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Check the driver grid voltages. Something is making one side of the valve take all the current.
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Old 1st October 2012, 12:21 PM   #13
nkg is offline nkg  Australia
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Pin1 -.059
Pin4 -.0 something multi meter won't settle down to a fixed reading .
Nigel
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Old 1st October 2012, 12:50 PM   #14
DF96 is offline DF96  England
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Check the wiring around the phono control pot. There may be a ground connection missing, which would explain the wandering pin 4 voltage. The diagram is puzzling, as it seems to have that pot back to front.

Pin 1 seems a bit high at 59mV - could the valve be gassy?
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Old 1st October 2012, 01:15 PM   #15
nkg is offline nkg  Australia
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During the rebuild I left the phono circuit out . As far as the tube being gassy there is no visible blue glow and I don't have a valve checker but do suspect it could be a bit of a problem , may have to change it back to a 6SC7 and see what happens .
Thanks
Nigel
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Old 1st October 2012, 03:22 PM   #16
DF96 is offline DF96  England
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If you left out the phono circuit then you also left out the grid bias for pin 4. You need a 470k to ground, to take the place of the missing pot.
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Old 1st October 2012, 11:58 PM   #17
nkg is offline nkg  Australia
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Ok will do that tonight when I get back from work.
Thanks Nigel.
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Old 2nd October 2012, 12:02 PM   #18
nkg is offline nkg  Australia
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Thank you for your advice DF96 it's been running for about twenty minutes now and all is fine . I will put the phono circuit back in and have ordered some better quality pots , these one's don't even fully turn off . I have made two two amps and a active crossover from scratch all of them worked so have not been able to develop any trouble shooting skills . I now can put my nos 6L6G's to see how they sound .
Thanks Again
Nigel
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Old 2nd October 2012, 12:40 PM   #19
DF96 is offline DF96  England
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Glad it is now fixed.
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