Tektronix AFG-3022C - power supply issues

[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?

[Paulo Peres]

  Hmmm.
For a moment I thought I was going crazy.
I was reading the 071-1640-04 manual. The correct manual for this instrument is 071-1640-02.

If I didn't measured the voltages before, I would think someone exchanged the power supplies.

Anyway, now I know I need more information about 119-7153-00 power supply. Does anybody can confirm if it really corresponds to 7001318-J000 I have?

[m k]

Check if the PSU has an obvious internal/external regulation setting.
Maybe some models need more and internal regulators are not enough.

Newer manuals have PSU revision as -xx, so there are more than few.
Bypassing internal regulators would mean backward compatibility and is easy to make.

[lern01]

Hmmm.
For a moment I thought I was going crazy.
I was reading the 071-1640-04 manual. The correct manual for this instrument is 071-1640-02.

If I didn't measured the voltages before, I would think someone exchanged the power supplies.

Anyway, now I know I need more information about 119-7153-00 power supply. Does anybody can confirm if it really corresponds to 7001318-J000 I have?

I have an AFG3101, and the power module is also Artesyn 7001318-J000. The A72 is 672-5815-04, the A31 is 671-6052-01, and the A51 is 672-5953-02. The machine starts up normally, but Diagnostics reports error 2303 and Calibration reports error 1103, both of which are related to DC bias. The no-load outputs of the power module are 7.2V, 4.32V, +18.73V, and -18.92V. When connected to the A72, the voltages are 7.21V, 4.4V, +18.34V, -18.79V, -4.99V, and -4.91V. According to the service manual (071-1640-02), it should be ±15V. Is the output of the power module normal now? Is it ±18V or ±15V? Looking forward to your reply, thank you!

[m k]

Manual 071-1640-02 page 3-2 has a block diagram, there power supply is +/-15V.
A bit above that is a local regulators rectangle, clearly a separated and different thing.

Next page defines power supply as +/-15V.
Next page from that defines A11/A12 board local regulator also as +/-15V.
Two different things.

It's possible that all final voltages are from local regulators, but obviously no definitive answers available.
So check the power supply visually, if you can't find any texts then maybe components can give some directions.
Though net pictures are clearly not very promising.

[lern01]

It has been fixed. The power supply is fine, it is a soft fault of the amplifier tube on the amplifier board. I hand-drew the amplifier board circuit diagram, if you need it, please contact me.

[hitecelec]

Hi

have a AFg3021B with the same symptoms
Can you share the amplifier diag that you mentioned

Thanks in advance

[hitecelec]

hi

further investigation revealed a resistance of 8 ohms across c1107  capacitor on the CPU Board 672-5815-13
There area whole lot of capacitors in this path. Looks like i have to junk this as replacement board even if available will be expensive.
a better option is to buy tek AFg1022 with a std warranty of 5 years

model is AFg3021B


Regards

Anand