HP41 Card Reader problem



#8

I have a 41 card reader (Rev 1G) that displays "Malfunction" when reading a card. The problem is definately in the electronics, as I have substituted the "mechanics" (motor/head/switches) from a good working reader, and it still "malfunction"s. Any clues ? - Thanks, John


#9

Hi;

maybe you should try demagnetising (degaussing) the head.

Also, try recording a card and reading it back in one of the nonworking readers and in another, good one. Maybe they can write but read cards.

Also check if the cards are good...

Success.

#10

I wonder how similar the electronics in the 41 card reader are to the 65/67/97? David Smith describes a tantalum capacitor in those card readers that often causes the unit to write but not read successfully.

I wonder if "malfunction" is the normal message for a bad read, such as of a blank or damaged card? I'm thinking of the sequence of the switches as a card is inserted. If one of the switches had a high resistance, the sequence of switch closures might be illogical and might lead to that message. My 97 card reader wouldn't even turn on the motor at first until I cleaned the PCD pads and the gold plated spring metal part (make sure you don't bend it) that make up the switches.


#11

Hi;

you're right. Ellis. In fact, blank or damaged cards lead to CRD ERR message. I also have two working 41's card readers and when I left the newest one (G-version) stocked for some days (about two months), I tried pluging it in and using it. Any sort of operation involving cards led to MALFUNTION message. I realized that a tiny high-frequency sound was getting from inside the reader. I plugged the 41's battery pack off, removed the reader, plugged it back in and then the batteries. MEMORY LOST got to the display.

I wonder about the tantalum capacitors till today... and where was that sound comming from. The reader? The 41?

Who knows!

#12

One of the switches on the HP41 card reader is actually a power switch to the DC-DC converter on the main PCB, so if that's dirty, the reader certainly won't work. The other contact is the conventional card-on-head contact, the optical sensor is for write protect.
IIRC, you do get a 'MALFUNCTION' if the swtiches don't close properly. Certainly that's a common cause of 'MALFUNCTION' when writing a card. But the original poster says he's swapped out the mechanism with no change.
I have a few questions :
(1) Whad did you swap out? Did you swap out the PCB on top of the mechanism with the switch contact traces? What about the little PCB at the back containing the sense amplifier chip?
(2) Does the card go through the reader at about the right speed?
(3) Do you get 'MALFUNCTION' if you try to write on a (blank, unclipped) card? If not, is the card readable on another 41?


#13

Thanks for the postings guys. To answer Tony's questions 1) I swapped the whole reader slot/switches/motor assembly, i.e. by pulling out the two motor wires, and five head wires. 2) Card seems to go through at about the right speed (can it be adjusted anyway ?).3) I haven't tried writing a card with it only reading. I can try this an get back. I could also try some swapping of the various pcb boards, but I can't figure out how you get the whole electronics bundle out. How does the cardreader case come apart around the contacts with the calc ??. Thanks - John


#14

Firstly, yes the motor speed can be adjusted, but it's not really like a 67 or 97. The HP41 reader does not use the motor control circuit in the sense amplifier chip to control the motor (it uses it for thr write-protect LED IIRC).
The motor control is based round one of the 8 pin chips on the mainboard -- the one that's not the NUT-bus ROM. It's actually.... wait for it ... a 555 timer (!).
Anyway, there's a little preset on that board that sets the motor speed.
To get the unit out of the case, take off the top cover and the latches (you've done this -- you must have). The top part of the HP41 plug unclips from the base (it's not glued on, but it is a tight fit). Then remove the screws holding the mechanism down and pull the whole lot out (mechanism and boards). The sense amplifier chip (same chip as in a 67 or 97) is on the little PCB at the back. There are 3 chips (IIRC) on the main board. The NUT-bus ROM, the 555 used for motor control, and the card reader interface chip (about 20 pins).
The 2 boards can be separated by pulling the sense amplifier board upwards, out of the contact clips, but make sure you line the contacts up with the pads when reassembling.
Do try writing -- if it manages to do that without a MALFUNCTION then the card reader swtiches are working. If the card is readable on another machine then the head wiring, etc, is also right.


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