Zero-loss loop in JMP 2203

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jekyll72
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Zero-loss loop in JMP 2203

Post by jekyll72 » Fri May 14, 2021 12:39 pm

Installed circuit in my friend's JMP 2203. All the connections look correct, measured 330V at the B+ point on loop circuit board. Plugged in to cabinet to test and no volume output. There is sound from the preamp section, but no overall loudness whatsoever. I swapped out power and phase inverter tubes, but no difference. I removed the effects loop and reinstalled the jumper between the treble and master volume pots. No change. Any thoughts? Thank you.

glpg80
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Re: Zero-loss loop in JMP 2203

Post by glpg80 » Mon Aug 30, 2021 10:40 pm

Where in the circuit did you try to insert it?

In mine I put it after the master volume but before the phase inverter. Does the wire you use have break in it? Bad solder joints?

You should be able to bypass the loop manually (master volume output directly to normal coupling capacitor to phase inverter) to see if the amplifier still works.

Check to make sure you inserted it into the correct location in the amplifier signal-wise.

danman
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Re: Zero-loss loop in JMP 2203

Post by danman » Tue Aug 31, 2021 5:50 pm

As glpg80 mentioned, you may have a bad wire or faulty solder joint. You should be able to use your meter (set to ohms scale) to find the faulty connection in the signal path.

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