Agilent 53132A Counter Repair (FIXED and Upgraded)

[richard.cs]

Ah, so you think it may be an overload problem on the counter rather than a fault with the PSU itself. Not something I had considered but quite plausible. Hmmm, lots of tantalum capacitors on the counter that I am now suspicious of.

I think my next step will be to separate the PSU and the remainder of the board so I can test them independently. Probably need to do that anyway for the cleaning.

[richard.cs]

PSU board removed and cleaned. Tested in isolation with resistive loads on 5V and 12V - still faulty so not overcurrent from the rest of the counter. Scoping the outputs shows full-amplitude ripple on the 5V output and about 6V of ripple on 12V output. The PSU is appears to be starting up and running for around 15 ms, every 60 ms (the 60 ms being mains-synchronous). This could be controller Vcc or perhaps the tripping of a protection circuit.

Probing around shows the controller Vcc swinging between 16 V and 10 V with that same 60 ms period. These voltages are completely consistent with the controller datasheet values. I infer from this that the fault lies either with the aux winding and its rectifier, or with the IC3/Q25 circuit (JF2014 component IDs).

As I side note I have observed that something on the PSU board is capable of holding (a small amount of) charge for several days. I am not sure what I touched - probably a line-earth EMC capacitor as everything else has a bleed path.

[richard.cs]

And the answer is... R26B is open circuit. R26A is a little high but within tolerance. It looks to be a 0.5 or 1 W part, though worst case dissipation should be under 100 mW, probably for voltage rating. As I don't stock those I have temporarily replaced it with two 1/4 W components in series and the supply now operates with the outputs in specification.

@ Jf2014 Thank you very much for the reverse-engineered schematic.

Perhaps before I put it back together for good I'll do as others on here have and source a quieter fan.

[HighVoltage]

Nice, that you fond the culprit, congratulations.

Agilent power supplies have a problem from time to time on many of their instruments and most of the time its is a single component failure. May be a good idea to install a little higher wattage resistor.

An a better fan is always a good idea.

[pizzigri]

So I am working on the 53131a ps as well, and got curious while I am waiting for some components. I decided to post here since it is more related to this general post than my specific repair problem.
The point is, I have noticed the PS has a -9 / -9VG output, and I cannot understand what is that for. Actually, I even found a video on YT in which I think Gerry Sweeney experiments with leaving this line disconnected and the counter boots and works fine; and this, to eventually build a linear PS for the counter. He never followed up in this project, but I was still very curious to learn what does the 9v Power is needed for..... anyone knows?

Plus, since the Delta PS is so unreliable, maybe it could be a good idea to make a linear ps for it. Replacement Delta PS go for 250-350 Euro which together with the VFD going prices, is totally crazy...

[HighVoltage]

Plus, since the Delta PS is so unreliable, maybe it could be a good idea to make a linear ps for it. Replacement Delta PS go for 250-350 Euro which together with the VFD going prices, is totally crazy...

This was discussed before in a different thread also in a Keysight scope thread since the PSUs in some Keysight gear are not very reliable.
The positive aspect of this is that we can find broken test gear for low cost and repair it for fun.

[f14]

sorry for bump old topic.
I have two error QSPI  fail and INTERP fail. it suddently happens. My 53131a is "newer" version ( diffirent A1 board with agilent service doc)
Have any idea with this fail ?. power supply is good. voltage output within specs

[HighVoltage]

The service manual gives these indications:

QSPI: FAIL
A1 Motherboard Assembly, or A2 Display Board Assembly

INTERP: FAIL
A1 Motherboard Assembly, or A4 AC Power Supply Assembly

So, most likely something is wrong in the A2 motherboard assembly

What are the symptoms of the instrument?
Do these fails show up doing starting of the instrument?

[f14]

The service manual gives these indications:

QSPI: FAIL
A1 Motherboard Assembly, or A2 Display Board Assembly

INTERP: FAIL
A1 Motherboard Assembly, or A4 AC Power Supply Assembly

So, most likely something is wrong in the A2 motherboard assembly

What are the symptoms of the instrument?
Do these fails show up doing starting of the instrument?

it suddently appear when power on self test.
I have read service doc from agilent but Im not clear about they explain this errors
now my 53131a like a brick it appear INTERP:FAIL when hit RUN or enter
I have test A1 mainboard. and I got something strange for me . C60 C61 cap. votage not stable (changing ~2v <->5v) I remove both caps and check the voltage it stable at 5v but the caps is fine (I check with LCR)
thanks for your anwers

[HighVoltage]

Check all DC voltages and rails for AC ripple and stability.

[f14]

Im checked . all rail stable and AC ripple ~<300mV for 4 rails 5V/12V/-12V and -9V. I measured on power input connector  (A1 mainboard)
I just remove some E-cap from A4 power suppy to check value with LCR meter and it still within specs

[HighVoltage]

If I look at an older manual, it says:

INTERP FAIL
Interpolator calibration failed on the last measurement; therefore, no valid measurement was taken.


So, I would start at the signal input and work my way through signal path until you find something that makes no sense. Sometimes this can be tedious.

[f14]

If I look at an older manual, it says:

INTERP FAIL
Interpolator calibration failed on the last measurement; therefore, no valid measurement was taken.


So, I would start at the signal input and work my way through signal path until you find something that makes no sense. Sometimes this can be tedious.

I use a Printer ON via RS232 to see more details about this error and I have 4 line:
-Interpolator : A , MRC mode Fail
-Interpolator : B , MRC mode Fail
-Interpolator : B , CC mode Fail
-QSPI : HEX DAC Fail
Because I have only one 53131a so I can't check a good 53131a signal to compare

 

[HighVoltage]

It is not easy to give advise at this stage.
All I know from experience is that you start looking at signals and suddenly you come to find one culprit.

Maybe you can borrow the same counter and compare signals.