gswan question:Is the noise able to be sampled at the insert output with gain set to max, eq out, tape switch set to mic input, phantom off and the input socket shorted (ie all pins connected together to remove any external effects).
http://www.zshare.net/audio/543689204485ab28/ 0dB
http://www.zshare.net/audio/543689961cb56c3f/ +6dB
Audiojohn question:Check the DC voltages around the input transistors and output pins 1 and 7 of the IC and compare them with a good channel - this might give a clue.
Good chan Bad chan1 Bad chan2
Transistor 1
Base .02v .02v .02v
Collector -8.95v -8.84v -8.75v
Emitter .63v .62v .64v
Transistor 2
Base .02v .02v .02v
Collector -8.92v -8.82v -8.50v
Emitter .63v .64v .64v
IC1:
Out 1 .01v .01v .02v to -0.03v
Out 2 -.82v .10v .00v to 2.00v
IC2:
Out 1 .01v .00v .00v
Out 2 -.01 .00v to .01v .00v
Links i forgot to add earlier for this
Ive added some pics of difference:
1. Components for line input, but only on this channel not the other 2 good channels
2. Capacitor has its own track on quiet modules, but on noisy modules it is soldered on back of pcb for mid eq freq
3 Phantom resistor on good modules, non existent on bad modules
4. Larger cap 100v on good modules, 63v(i think) on bad modules
5. Different resistors(metal, i think) on good modules, normal on bad modules
6. Different bridge(not sure of correct term)wires on the 2 kinds of modules
http://www.zshare.net/audio/543689204485ab28/ 0dB
http://www.zshare.net/audio/543689961cb56c3f/ +6dB
Thanks once again
Paul