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Unresponsive 9100B - Printable Version

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Unresponsive 9100B - dfnr2 - 02-23-2015 02:52 PM


I recently acquired an HP9100B which was working before shipping, but on arrival does not respond. The fuses are intact, and I can hear the power supply humming on power up, but there is no CRT output, and I cannot activate the error light (for example, by STOP-CLEAR-/ to get a divde by 0 error.) The register label backlight also doesn't light, but apparently did not light before shipping, when the calculator otherwise worked.

I have Tony Duell's excellent schematics, which I'm grateful for. I also have a service manual, and plan to go through it, but it seems a bit short on theory and detail. I'm not in position to swap out boards.

My plan, once I am able to get some time at the bench, is to start out by checking the power supply voltages, clocks, and move on from there. However, since apparently something changed during shipping, I'd be interested in any suggestions that would help inform a smarter investigation. I am hopeful it's not the CRT, as I would expect the error light to come on. Any suggestions would be very much appreciated.


RE: Unresponsive 9100B - MarkHaysHarris777 - 02-24-2015 10:53 AM

(02-23-2015 02:52 PM)dfnr2 Wrote:  I am hopeful it's not the CRT, as I would expect the error light to come on. Any suggestions would be very much appreciated.

Where I would begin with this beast is to re-seat all of the cards and connectors; assuming its something simple that came loose in shipment (hopefully no connectors broke, and hopefully the CRT did not crack.

Be sure to remove power (and let it sit for a while) before you open it. Remember that the HV caps on that thing can hold a charge for a while that will kick your butt if you get across it (or stop your heart)! Carefully unplug every connector and plug it back in (maybe a couple of times). Carefully unplug each vertical board and plug it back in (and by carefully I mean VERY carefully. Sometimes the old connectors will be brittle and will crack or break (which is a bad thing permanently).

Make sure there isn't an internal fuse on that thing that may have gone bad; or a breaker (I don't know, I'm not familiar with the details).

If the connectors on the cards are oxidized you'll need to clean them (they are probably not gold so its a pretty good bet you've got some work to do. I suspect once you get the connectors and cards re-seated (and|or cleaned up) things will work again.

PS. I had an old Data-dog one time that quit working and what had happened was that one of the connectors on ONE vertical board had cracked so that there was not adequate pressure on one side of the card... we wedged a piece of foam against the board to get the right pressure and voila! (hopefully that has not happened to you... look carefully over all connectors

Good luck,

RE: Unresponsive 9100B - dfnr2 - 03-06-2015 08:05 PM

Just as a follow-up, after removing and replacing the right connector board, the system appeared to work just fine. I have already completely disassembled and thoroughly cleaned the chassis assembly, power supply, HV circuitry and CRT. The only things left are to paint the top case, clean the keyboard and replace the o-rings, and then get the card reader and printer working. This machine is a thing of beauty, no doubt!

I am in the process of looking for a suitable replacement for the CRT, so I can be prepared when this one eventually goes.