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Old 1st Aug 2007, 9:31 am   #36
jjl
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Join Date: Jan 2003
Location: Ware, Herts. UK.
Posts: 843
Default Re: Rigonda Stereo - Reviving the beast

Hello Zel

You can expect the EL84s to run hotter than the other valves; in single ended output stages they run at more or less their rated anode dissipation all of the time. The blue glow is not uncommon with the EL84 but can sometimes be a sign of distress. The cathode to chassis voltage you have measured seem surprisingly low for a correctly biased EL84; you can expect to see around 10 to 12V across the typical 270 ohm cathode resistor. There may be a problem with these resistors, the electrolytics across them or the screen grid supply to the EL84s.

Hope this helps.


John
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