jgab
Well-Known Member
Hi,
My 86' Canadian JCM 800 2204 died on me. I turned on the power and there was no indicator light (6vac powered off the first power tube). Tubes didn't light up. No sound at all through the amp. Here is what I did:
- Shut off the amp and plugged it in through my light bulb limiter. With the amp fully on, I don't have any shorts.
- Took the amp off the limiter.
- Measured 120vac at my plug connector, through my mains fuses (Canadian Version has two HV fuses). - Measured 120 vac on both sides of my power switch.
- Measured 120vac out of my mains selector.
- Getting ~360 vac (2X's) on my high voltage secondaries measured at my diodes, and ~470 vdc rectified and on my plates (screens about the same).
- Measuring 3.30 vac (2X's) on my heaters (heaters don't light up on any of my tubes- cool to touch).
I am getting ~470vdc on my screens and then almost the same voltage after my two first 10K droppers. Usually I have about 327-330 vdc dropped after the two 10 droppers and going to my PI. Instead I have about the same voltage throughout.
If I had current, the voltages would be lower right? I don't seem to have any current. I tried plugging into my variac and direct into the wall. Also used a couple IEC connector power cords to rule out the cord.
Not sure what to do right now. Can a bad filter cap cause this? If a 50uf/50uf goes bad?
Any advice?
J
My 86' Canadian JCM 800 2204 died on me. I turned on the power and there was no indicator light (6vac powered off the first power tube). Tubes didn't light up. No sound at all through the amp. Here is what I did:
- Shut off the amp and plugged it in through my light bulb limiter. With the amp fully on, I don't have any shorts.
- Took the amp off the limiter.
- Measured 120vac at my plug connector, through my mains fuses (Canadian Version has two HV fuses). - Measured 120 vac on both sides of my power switch.
- Measured 120vac out of my mains selector.
- Getting ~360 vac (2X's) on my high voltage secondaries measured at my diodes, and ~470 vdc rectified and on my plates (screens about the same).
- Measuring 3.30 vac (2X's) on my heaters (heaters don't light up on any of my tubes- cool to touch).
I am getting ~470vdc on my screens and then almost the same voltage after my two first 10K droppers. Usually I have about 327-330 vdc dropped after the two 10 droppers and going to my PI. Instead I have about the same voltage throughout.
If I had current, the voltages would be lower right? I don't seem to have any current. I tried plugging into my variac and direct into the wall. Also used a couple IEC connector power cords to rule out the cord.
Not sure what to do right now. Can a bad filter cap cause this? If a 50uf/50uf goes bad?
Any advice?
J
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