|Chips other than ACT and RAMs going bad?|
Message #1 Posted by Eric Smith on 7 July 2005, 8:08 p.m.
How common is it for HP calculator chips other than the ACT and RAMs to go bad?
In Woodstocks, the most common cause of bad chips is the use of the AC adapter without a battery pack, with a bad battery pack, or with the pack not making good contact. Due to uncharacteristically poor design, this allows the voltages to exceed the limits of the chips.
Similarly, the card reader sense amplifier of the HP-65 (and maybe the HP-67) may be damaged by use without a battery pack.
But have those of you that repair older HPs noticed many cases of other chips going bad?
I'm considering offering tiny modules that can replace the ACT of the Woodstock, Topcat, 67, and 19C calculators. The module would effectively replace the ROM and RAM chip as well, though the anode driver portion of the ROM/anode driver chip would still be required for the display to work.
But I'm wondering whether it's common for other chips in these calculators, or in the Classic or Spice calculators, to go bad. In particular, whether the CRC and PIK chips, or the series-30 CPU or ROM/RAM chips fail often.