Re: [help] Only noise being seen while IQ balance / phase lo / phase hi.

Ronald Taylor

Jose, since you got a good setting of the BPF, that means the signal is getting as far as the IQ balance control/CW filter input area of the board. The BPF tone measuring point is in that location. The monitoring point for the balancing and nulling adjustments is at the input of the last audio stage, IC10A. So the signal is being lost somewhere between the input of the CW filter and the output of IC 10B. 

I couldn't tell from the thread but if you haven't yet measured all the DC voltages around ICs8, 9 and 10, you should do that next. Expect the approximately 2.5 volts on1,2,3,5,6 and 7 of IC8 and 5,6 and 7 of IC9. I,2 and 3 of IC9 might be a little different as it is no longer part of the DC coupled circuitry like all the opamps  preceding it. But its still somewhere in that range I think. Pins 1,2,3,5,6 and 7 of IC10 will be somewhere around half the supply voltage.

If any of those are off, re-check connections in that area. If all is right, then you need to find a way to trace the signal through those stages. With the unit in the alignment mode (test tone present), flow it back from the last stage, output, input, next to last stage output, input etc till you find where it stops. Don't replace an opamp until you are certain it's not something else... Hope this helps

73 ... Ron

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