Author Topic: Airline JDR 8439  (Read 1617 times)


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Airline JDR 8439
« on: August 13, 2015, 02:21:10 AM »
A signal will pass through three jacks marked "Sting Instruments" in the center but the others to the right marked "Microphone Accordion" will not pass a signal. The Vibrato/tremolo does not work and I am not sure if the jacks labeled so are for foot switch or for an instrument. What should I try first ? I hope the schematic is close, if anyone has a better one please post it. I believe that this is a 1955 Wards Danelectro amplifier.
« Last Edit: August 13, 2015, 02:46:29 AM by memoryman »


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Re: Airline JDR 8439
« Reply #1 on: August 13, 2015, 03:38:25 PM »
When you say "a signal will pass through" is it measured with oscilloscope or heard through the speaker?

If you do not have an oscilloscope i would replace the 12ax7 with one that is known to be good.


If you heard sound from instrument channel and not from the mic channel, then everything after the phaseinverter is good, or good enough.
Take an audio probe (a coax cable with a multimeter test probe in one, end and two hooks or clamps in the other end, for signal and one for ground/screen, and a capacitor in the signal path for picking ip audio with a DC offset)

Connect hooks to groung and instrument channel volume pot, apply signal to mic/acc channel and follow this signal path with test probe end.

Use a multimeter test probe with a short pin or insulate it so max 4mm are exposed, limits the possibility for making a short cuircuit.

Usual disclaimer tubes=high voltage=fire death and destruction


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