Hp-41C card reader - dead

[Vintage63]

thanks to Tony for showing me were the trimmer is!!! I tried changing the position of the trimmer but nothing improves. Rotating it counter clockwise it goes faster and the card advances with a ripping noise, i.e. not fluid. Rotating it clockwise the movement is fluid but still get the MALFUNCTION message. Only once I got a "RDY 1 OF 1" message but never got it back. Hopelss :-(

[AndiGer]

Hi Marco,

I can feel with you because I now also have a card reader that always reports malfunction :-(.
The card is running very quiet and smooth thru the reader (tried many). And also another calculator.
After I got the cover off and could take out the board I soldered some wires to GND RA and RB to measure with the oscilloscope. Signals IMHO look very good.

   

@all:
Anybody another idea what to check? Measure lines to the calculator? If yes - what exactly can I measure there?

Thank you
Andi

[teenix]

Hi all,

This seems to be a common problem, although I don't know how common.

It may not be the card reader or sense chip, it could be the CRC or ROM chip at fault. The only way to test is to monitor the Is and DATA busses to see if the card data is being transferred to the 41.

I plan to do this soon with a faulty one I have here.

This testing might also reveal poor Port connections between the reader and 41.

cheers

Tony

[Vintage63]

the poor connection between reader and port 4 on 41C could be enhanced by squeezing the 'clips' in the hidden part of the card reader connection tunnel, i.e. where the trimmer is?