|Re: HP-41C PCB Repair Question.|
Message #7 Posted by Kerem Kapkin (Silicon Valley, CA) on 19 Nov 2011, 11:02 p.m.,
in response to message #1 by Kerem Kapkin (Silicon Valley, CA)
Thank You All for your valuable comments and suggestions! Very much appreciated.
I have taken your suggestions and comments spend several hours today, troubleshooting as much as with what I had available.
- Verified Batteries are OK, contacts are fine and clean. Cleaned all gold contacts with a pink eraser very gently, and removed the entire residue.
- Zebra strip looks ok, I think the round plastic in the zebra strips is supposed to be round, but with many years of pressure on it, it is somewhat square, however I traced the lines with PCB in place and verified the electrical connectivity.
- Another reason I was suspecting the transistor, because I found a repair sticker in the back of the calculator dating 1990. Also that transistor had relatively new solder contacts and unlike other two transistors, had a non-HP part number 53-0482-952. I had this calculator since 1992 and was working OK until recently, except every key stroke resulted in display blinking with several segments turning on across the display since I owned it. I contributed this problem to the early 41C's bugs and issues. Especially how the CAT command operated... Never had to open it until now. However I understand the argument about the transistor and how unlikely it could be the cause.
- Posts are fine, no cracks, or issues.
Final Result: It no longer turns on. No response at all.
I agree with Randy that it seems like a bad D/S circuit.
I will stop wasting more time with it, perhaps I can use the original board which will become available after upgrading my 41CV to CL in the future.
Thanks and Best Regards,