Electronics > Repair
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...
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