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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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Meanwhile i found a bad (high resistance) hf transistor Q219, located in the amp. It is a MM4018, which is not available. Can I use a 2N5160?

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This is from the specs a similar type: PNP, 40V,hfe 10, ~400Mhz.?

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And I was wondering that the SINE amplitude calibration still passes, I thought it would use the amp and attenuator as well.

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Ralf??

I changed Q219 and its complementary transistor. Now I can adjust the 7.5Volts on F3. The amp is now fixed, but the A-CAL Fail error for square and triangle is still present.

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The output is correct, sync out as well, amplitude into a 50 Ohm load is ok, on sine, square and triangle & ramp

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When switching to ramp function something curious follows: The display goes off, the ramp function is visible on the scope, but it 'sweeps'.

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Picture 1: relay board, relays are clickking, are these types they reliable? The yellow relays are often mentioned to be cleaned, my could not be opened.

Picture 2: sinus 1kHz, lokks as expected.

Picture 3: ramp moving with about 0.5Hz.

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here is a video: shows the moving of the ramp and then flips to the correct curve? for a second.

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Outputs at the analog switches are as expected, all voltages as well.

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The self test works except the AC fail, FAIL 2, FAIL 3

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The manual says this is 60% of the controller.?

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Any advices waht to test now? ROM/RAM?

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Or has anyone spare? boards for the 3325A to exchange and for testing ?

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Hi all,

I spent some more hours with my 3325A.

I made a new effort and studied the service manual from scratch. The main trouble shooting flowchart directed me to group J, so I thoroughly examined everything around U28 to U40.

At least U39 was the culprit! ?It is another analog switch. 1826-0879, hard to find. My REV C Board has many can type opamps and ics. I found a replacement a DG301 from Harris or an TL460 from TI. But the pinout is different. I had to mount the TI reverse and soldered the pins in place.

Now it is working perfect again. I have to calibrate this nice generator, but this is not a big thing. A member here has sent me a detailed calibration guide.

Ralf

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