HP 97 card reader - tantalum capacitors
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11-23-2021, 10:18 PM
(This post was last modified: 11-23-2021 10:20 PM by teenix.)
Post: #8
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RE: HP 97 card reader - tantalum capacitors
(11-23-2021 02:58 PM)AndiGer Wrote: Flogging a dead horse, I know ... old thread. It is still good information :-) This would make sense as C4 and C6 filter the Vgg and Vcc power rails from the switching power circuit. The sense chip is powered from the Vcc rail, so if it is overly noisy maybe the amplifier and level detector circuits won't work properly giving card errors. From what I've seen, the sense chip is also finnicky about the supply voltage being close to 6V. Maybe for HP-65's and HP-67's with card reader problems, it might be worth changing all the capacitors in their power supplies - 4 used in 65 and 3 for 67. cheers Tony |
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