Dead 1987 HP-41CV



#5

Hi all,
i would like to have an 'expert' opinion on a dead 1987 built HP-41CV. i don't know how long it has been stored without batteries (must be years!). However after inserting new batteries, i can't get that nut awake. I've already tried the usual measures (as discussed here in the forum) to reanimate it, but had no success. power supply gives just below 5V after inserting the batteries and 6.35V after ON has been pressed and released ( measured on the cap next to the choke).
any pathological hints about it? What are the usual suspects? I have scope, voltmeter, etc., so there is no prob to do measuring on the internals.

tia for your help!

Hans


#6

The HP41 service manual is available on the HPMUSEM disk set.

Clean the CPU board and all the keyboard contacts with 91% isopropyl alcohol. Also clean the ON switch through the little hole on the keyboard under the key contact dome. Use a tiny wire brush dipped in alcohol. If the ON key contact is dirty, for some strange reason the machine won't turn on...

#7

Since there is a voltage change when you turn it on, something is going on in there. While you have it apart to clean it; you can check the 16 screen connectors by gently prying up on them with a pin or toothpick. That is a possibility.


#8

pardon me for not mentioning it: it's a halfnut. what i found out so far is, that current consuption in OFF mode is just some mikro-amps. after ON pressed and released, current goes up to 4.5 mA, which is imho far too high. after ON being pressed again, current consumption keeps staying on that level. only chance to get level down is by removing batteries.
unfortunately, i do not have the diag module and i could not find any appropriate schematics on the mohp cd set ver. 3.1. does anybody know, whether the newer mohp set contains a halfnut 41cv schematic?

cheers, hans


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