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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Re: New silicon diode, no sound posted by Damir on July 26, 2002 at 10:14:35:
Todd,To follow-up upon what Damir said---the bias voltage MUST be negative with respects to ground. If the measured voltage applied is positive, you risk thermal runaway with the power tubes. This could lead to much more damage to the amplifier.
Be sure that not only the diode, in the bias circuit, has the correct polarity---but also ALL electrolytic capacitors you may have replaced. These also will appear to be placed "backwards" when compared to the filter caps in the main power supply. That is, positive side to ground and negative side to the bias power rail.
I'd pull the power tubes and check the bias supply voltage points. Before venturing further. Next point, -48 VDC is a lot of negative bias voltage for an EL84 amp (if it's in AB1 mode). I've seen this range of negative bias voltage in 6L6 amps.
An EL84 usually has about (-)20-30 VDC applied to the grid, for idle bias. I suppose that your amp may be Class B mode. You should double check those values.
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Follow Ups
- Re: New silicon diode, no sound - steven oda 10:37:36 07/26/02 (1)
- Nevermind (for those Nirvana fans) - steven oda 10:48:07 07/26/02 (0)
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