HP 41CV Power On



#7

I know I'm coming in very late - I just joined the forum. I have 41CV that I've used since the mid 80's (I earlier had a 35, 65, and 67). Recently it has often been reluctant to turn on, even though the N cells are fresh and the battery contacts are clean. I've heard this is a known problem. What is it? HP no longer suppoirts this calculator, but I have come to depend on it.

Ed Grens


#8

Hi Eager,

It could be that your calculators internal interconnects are
giving trouble. The calculator can be disassembled and cleaned
but can also be wrecked by static electricity damage.

I am able to safely repair these machines. Happy to quote you if
you like. This is NOT a plug... ;-) Just trying to help.

Speaking of which, you could check out my pages on repairing the
41CV at either: www.furlow.org or my own pages at:

donwallace.customer.netspace.net.au

I have 20 years experience in electronics repairs and have similar
timespan of experience in electronics engineering.

Good luck!

Don Wallace


#9

Nice photo spread there!



Most of the 41s I've opened don't have the nuts on the screw posts, (I did open one that had that arrangement.) It seems like a much better plan than using the gripping power of the screws exclusively to press the processor PCB to the keyboard PCB, particularly given the tendency of the posts to crack with age and abuse. I also recognized a symptom you mentioned as being caused by static discharge - the strange behavior on "SIZE" and storing to registers. I have one calculator that starts showing garbled program lines when size exceeds a certain value. I had concluded that this was a RAM problem, or possibly something with the CPU. Can you comment on whether one or the other is more likely? How would you go about distinguishing the two? (I might send it to you for repair, but mail between OZ and the US takes forever. 8)


#10

Hi,

Just a quickie: Is the black plastic piece for the electrical isolation still in place between the keyboard and the CPU board, I forgot to replace it one time myself and then I had also some strange behaviour on certain keys.

Good luck

Ronald


#11

Yup. It's still there.

#12

Hi Howard,

Thank you for the feedback on my photos of the 41CV repair.
I shot them with a toy digital camera, so they are a bit rough.

Most definitely, you have a faulty RAM chip. I can replace it if
you first get a sick 41CV from ebay and send me your machine and the one I'll use for parts to repair your calc. I will test the RAM first to ensure you get a functional system back. It's a long way to send a calculator for repair, so I would do the job properly.

Kind regards,

Don
P.S. you may want to check my pages once in a while. The website is under heavy development with a lot of new material to be uploaded
shortly. Any feedback or technical questions are welcome.


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