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Post subject: Fender Excelsior Tremolo stopped working
Posted: Tue Nov 12, 2019 8:24 am
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The tremolo on my Excelsior (PR2298) stopped working.

BACKGROUND

1. The output of the amp is not changed when the tremolo is turned on. No loss of power, signal drop or noise.

2. Replaced V2 with a new 12AX7 and get same results as above. Also, if I remove the V2 tube, the amp volume decreases but still has output.

3. Checked tube socket for loose connection or bad pins with none found.

4. Checked the tremolo switch and speed pot. Switch works and pot is in range and tracks correctly.

5. Input voltage to the circuit "X" is correct and voltage to TP15 looks within range.

6. Visual inspection of the PCB shows no damage to it or any of the components and all wires are good.

7. No previous issues with the tremolo, this is the first problem.

I do not have a function generator to supply the 10mV at 1kHz to comply with the test notes on the schematic (2298CAX020, Rev. A).

Has anyone experenced this problem before?

Could the MOSFET IRF820 be the problem?

Any ideas on how to troubleshoot this issue?


Thanks for your help.


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Post subject: Re: Fender Excelsior Tremolo stopped working
Posted: Thu Nov 14, 2019 3:11 am
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Joined: Fri Feb 05, 2010 4:31 am
Posts: 14045
Location: Province de Québec, Canada
Most of the time in tube amps tremolo issue are the capacitors.

I will replace all of them C5, C8, C9, C10
Issue with the Mosfet ? I don't know, maybe


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Post subject: Re: Fender Excelsior Tremolo stopped working
Posted: Thu Nov 14, 2019 5:12 pm
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Joined: Tue Nov 12, 2019 7:52 am
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Thanks for your insight.
I plan to break the board down after I get some replacement part (caps, MOSFET, Zener diode etc.) on hand.


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