Electronics > Repair

Tektronix AFG-3022C - power supply issues

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Paulo Peres:
I'm repairing a failed Tektronix AFG-3022C with an interesting problem at power supply.
The power supply is an Artesyn 7001318-J000 module.
At first, it was not turning on.
Suddenly, it started to work (and I checked the voltages with the poor diagrams of the service manual and was everything ok)
But in this condition, the equipment was resetting if it suffered a minimal movement.
After a disassembly and reassembly, it started to work without resetting, but now it stopped to recognize the ASICs (was working even with the resetting issue).
I checked the PS again and discovered that the voltages are altered (5V to 7,1V, +/-15V to +/-18V; the 4.3V keeps almost the same). Weird detail: at the parts list section of the manual, the power supply is described as having these altered voltages as features.
Does anybody have a clue about what is happening here?

m k:
First it had a clear contact problem.
Now it probably has another contact problem.

Maybe you should disassemble it again and check places.
If there are pinheader type connections, check their pin surfaces.
Maybe there are some oxidation and new connection point is just over one.
Weak solder joints can also have given up.

Paulo Peres:
I did it, actually.
I checked also the electrolytic caps, the solder joints, the opto couplers in the feedback loop... everything ok.
The PWM controller appears to be ok, too. One of the tests I did was slightly change the impedance of the feedback voltage divider (i added a parallel resistor). As result the voltages read had a proportional change.
Everything looks ok, but the PS behavior remains the same.

Vovk_Z:
"It was not working and then started to work" it could be bad electrolyte caps in power supply. They work better when energized for some time (you may heat them too it would help until they became cold again). Mine GDS-806 had similar behaviour.

m k:
Fixed 5V chips have hard times with 7.1V supply.
Missing ASiCs can be a protection against overvoltage.

What manual you are reading?

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