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Old 18th Dec 2008, 3:56 pm   #11
hmv1944
Tetrode
 
Join Date: May 2006
Location: Sheffield, South Yorkshire, UK.
Posts: 76
Default Re: Sound Sales PX4 Amplifier

Thanks guys. Another silly mistake on my part. The coupling caps for the output valves should be as Peter describes. I must admit I thought it looked a bit odd but my electronic theory was not up to working out why. And I should have checked the hardware again!
Using an 800Hz sine wave and measuring the AC voltage across the 470R cathode resistor with a DMM I wasn't able to find a clear minimum reading. I'll try again with a lower frequency. No spare time over Christmas!
Alan.
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