Hi,
I need some help for my HP 3325A, which worked many years perfect, but know has the common FAIL 2 & 3 Error. (PASS 1, FAIL 2 FAIL 3)
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It has still sin, square and triangle output, the amplitude is ok, the range is ok (1-10Vpp) into a 50 Ohm load.
When swtichting from sin to square or triangle the a-cal error message comes up.
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The voltages are good, 5.05, -15.16, +15.16 volts, no ripple, or minor. I changes some caps in the psu some time ago.
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The integrator output looks good, the voltages are as expected on the testpoints LVL,OS1,OS2,AMPL,XDR. I interchanged already U20 & U24.
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I have a revision C board, the realays on the att board are the flat black ones.
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Alls tests were done grounding the ACD pin, 1khz and 10Vpp.
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I found something strange in the amp section. placing the jumper to detach the amp from AMP IN and measuring the DC bias voltage at F3 left and right it shows -12.73 volts.
Should be +7.5 volts.? When toggeling the jumper and playing with the amp settings, the voltage sudden comes to a normal value and I could adjust the bias with the pot to 7.5 volts.
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Should it be in any case 7.5 volts after power on and? when AMP in pin is disconnected and with any amp setting?
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I checked already soldering and diodes, resistors, fuses and caps for shorts.?? And some transitors in the amp section.
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I have the service manual, there is a huge section testing with a signature analyzer, but I don't have one.
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So are there any hints, what to test / check next? Am I right in the amp section?
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Ralf
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Ralf Rosche