|I/O subsystem not working on HP-41CV?|
Message #1 Posted by Philippe Lasnier on 17 Feb 2011, 9:17 a.m.
I've just received a very good looking HP-41CV from 1983 (Singapore). I have been told it was well looked after, and it looks it, but unfortunately it doesn't work very well.
My diagnosis (possibly flawed) is that the I/O subsystem is faulty.
I deduced that from the following observations:
- Start from fresh. Batteries have been in for a while, but the calculator hasn't been turned on for hours.
- Turn on. The calc on its own (no module, no card reader, nothing inserted in the ports) works fine. I haven't found any problem with it.
- Plug in a card reader (81104A), and a CAT 2 doesn't report anything. Nothing happens if you try to insert a card in the reader (the reader works fine in any of my other HP-41's).
- Plug in a TIME module (with or without the card reader still plugged in), and the calculator goes mad, with random characters (including lots of "@" for some reason) flashing on an off, and no real keyboard control. The calculator usually cannot be turned off except by taking the batteries out.
- After a while of on/off/batteries out and messing around with the keyboard, the calc slowly "stabilises", and eventually things start to work. A CAT 2 correctly reports the TIME module and the card reader. Things look peachy. The stopwatch works, and the card reader reads cards properly.
- Turn off the calculator (and go to bed in my case).
- Turn on the calculator some time later (as short as 1/2 hour) - mayhem again...
A layman's speculation is that something needs to "warm up". I thought maybe a faulty capacitor would be the cause?
In the absence of Geoff's repair book (I'm signed up for when it comes out), I am reduced to asking for your help (and Geoff's, if he is reading this).
Any precise idea what this could be? Is that repairable?
Of course, if it's not repairable I could just "sacrifice" it to become the shell of a HP-41CL :-)