Most encountered problems on HP97 ?

[Olivier TREGER]

Hello,

I've just found 2 HP92 on eBay. One was advertised as non working. The other was unknown state but when I put in a brand new battery (bought from watershoko on eBay) nothing happens until I plug in the power supply.

The strange thing is that on the second one (the one that works), I get nothing but strange display, nothing to do with normal behavior: zeros at different places and that's it.

The question: what are the common issues on the 97? What do you suggest I check/dismount/solder/blast first?

Thanks,
Olivier

Edited: 22 Nov 2006, 5:29 p.m.

[Olivier TREGER]

No one on this subject??

[Thomas Radtke]

Ok, if no one else does: These calcs simply go bye bye when runnig from their adaptor w/o recharchable batteries inserted.

Correct me if I'm wrong.

[David Smith]

They need good batteries installed to work properly.

[Tony Duell]

Actually, the topcat series (HP9x) have a circuit which loads the battery line if it tries to reach a higher voltage than the Vss logic supply. You won't damage these machines if you connect them to the AC adapter without a good battery installed, but the printer and card reader (on a 97) will not work properly.

There is an exception to that. The circuit only functions when the machine is turned on. The (very rare) HP95C has the same problems as Woodstock and Spice continuous memory machines in that the RAM supply voltage will go sky-high if the machine is turned off, there's no battery installed, and you connect the AC adapter. This can damage the RAM chips. So if you're lucky enough to have a 95C, I'd charge the batteries in some other machine.

To get back to the original poster's problem, the common failures on the Topcats are the ACT (CPU) chip -- the 22 pin one on the logic board, and ROM0 (the 18 pin chip). The former can be obtained from any Topcat or Woodstock machine apart from an HP27, the latter is specific to the particular type of machine.

[Olivier TREGER]

Quote:

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To get back to the original poster's problem, the common failures on the Topcats are the ACT (CPU) chip -- the 22 pin one on the logic board, and ROM0 (the 18 pin chip). The former can be obtained from any Topcat or Woodstock machine apart from an HP27, the latter is specific to the particular type of machine.

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Do you suggest that I open it and try to locate the chips? What can help me to determine which one could be out of order?

[Olivier TREGER]

Quote:

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They need good batteries installed to work properly.

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I did that, as stated in the original post: new batteries from watersokho (seller on eBay).