The reverb stopped working in my '79 Fender sf Vibrolux Reverb.
While troubleshooting, I saw that the12AT7 reverb driver (V3) has glowing plates. Is this a symptom of bias gone nuts, I suppose?
Furthermore, the cathode voltage is around 30V instead of 6V shown in the original schematic.
This amp has the stock late-70's arrangement with a 680 ohm cathode resistor and no bypass cap. Earlier versions of this amp had a larger cathode resistor with 25/25 bypass cap.
My questions:
- what makes the plates glow?
- should I use the earlier bf-style arrangement, or am I better off leaving the stock plain 680 ohm therein?
While troubleshooting, I saw that the12AT7 reverb driver (V3) has glowing plates. Is this a symptom of bias gone nuts, I suppose?
Furthermore, the cathode voltage is around 30V instead of 6V shown in the original schematic.
This amp has the stock late-70's arrangement with a 680 ohm cathode resistor and no bypass cap. Earlier versions of this amp had a larger cathode resistor with 25/25 bypass cap.
My questions:
- what makes the plates glow?
- should I use the earlier bf-style arrangement, or am I better off leaving the stock plain 680 ohm therein?
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