HP41C with the wake-up issue

[husmus]

Does anyone know how to trouble shoot these PCB's? Any circuit diagrams out there? This one works most of the time, but sometimes after leaving it sit for an hour it won't wake up. Removing the batteries and shorting out the end terminals cures it again for a while. I know it's a common problem in the literature. Thanks.

[Hiwi]

Hi,
there are some things to test:
Are the screws under the rubber feet are tight enough? Are the posts damaged?
Another problem is the port / battery bay, the contacts may be bad, because of the old sponge, which has not enough tension to make contact from the battery to the pcb.
Are the battery contacts clean and not worn through?

The ON key may be bad, a bit of iso alcohol may help. I dont recommend deoxit or so called contact solvents, because it contaminates the whole calculator and may affect the plastic and the pcb. less is more :-)
Ralf

[BobVA]

I had a 41 with this problem and it turned out to be a defective board interconnect.