Agilent 53132A Start-up Issue

[liviug]

I have one 53132A counter that suddenly stopped working. I press the power button, it makes the relay click noise once and it won't display anything. All front panel LEDs are OFF, display shows nothing at all.
I opened it up and looks like all power rails are good. There's activity on processor address and data busses. One thing I notice: some weird levels on data bus. Some '1' are not quite 5V, they are 3-4V levels. It may be a bus collision issue? Out of the blue busted ROM?
I checked the data on display panel. There's no activity there whatsoever. Processor does not attempt to write to the display.
Have you seen this issue before? Any ideas to try?
Thanks...

[wn1fju]

If you do get to the bottom of this issue, please post it.  My 53132A will very occasionally not start.  I press the power button and ... nothing.  Toggling it off and then back on starts it right up.  But I never poked around inside on one of those no-start occasions.

My unit also threw a ROM error, although the unit did work fine.  So I programmed up a new set of ROM chips (there are four in my early unit).  I think one could also reprogram the existing chips, but I didn't want to take a chance with those.  A dump of the faulty ROMs showed one incorrect byte in a block of FF's at the end of the address space.  My guess is that the block wasn't part of the operational program, thus the unit worked fine, but it did, of course, affect the checksum.

[liviug]

Looking back I realized my unit was also intermittent. I blamed it on the power switch, which I replaced. Things got better, but problem was still there. When it died it was connected to the AC power rail, but unit was off. When I tried to turn it ON It won't start. I have a second working unit, a 53181A. I swapped the display unit and power supplies. No change. So issue seems to be with main board. Too bad I could not find the block diagram of the counter or the power-up sequence anywhere on the net.

[wn1fju]

You wrote, "Too bad I could not find the block diagram of the counter."

Just in case you don't already have it, search for the KO4BB website and look for HP 53132A CLIP in the manual section.  That has the schematics.

[Mrfixit2]

I've got an Agilent 53132A with the same problem. Found your topic was still unanswered so here's a possible solution:
Counter would work intermittently and only after 10-minute warmup. Power supply tested good, activity on signal lines (ROM), so assumed a temperature dependent failure. Using heat gun and freeze mist, discovered SRAM (U12, U13) to be at fault. Yes, it's hard to believe warming SRAM would improve anything but my 53132A has worked fine since replacing U12 & U13. Good luck finding replacements! Mine came from Newark/Farnell PN: 2767949    Mfg PN: CY7C199D-10VXIT   

[wn1fju]

I will keep U12/13 in mind if my 53132A deteriorates.  Fortunately, the "no-start" occurs very infrequently on my unit, maybe 1 out of 50 tries.  I thought maybe it was a problem with a marginal component in the start-up circuitry of the switch mode power supply, but I never pursued it further.

And to play devil's advocate, was there a chance with your U12/13 that the chips were fine, but there was simply a marginal solder joint that was temperature dependent?  Soldering in replacement chips would certainly correct that problem.  Just a thought...