Restored HP-97 Card Reader WRITE ISSUE

[James Linder]

I have refurbished a 97 card reader. It reads cards just fine and it acts like it is writing to cards fine according to what appears on the display (Crd after first time through and current program step on the 2nd time through, and there are no error messages unless you try to write to a card with the corner clipped which is proper behavior).

The problem I'm having is that no code is being written to the card when it passes through the card reader/writer. I have tried two different mother boards and I installed a new card reader ribbon cable, so I'm wondering if any of the capacitors being bad could lead to this behavior. I replaced R1, R2 and R3 with new ones, however this did not resolve the problem. It has a new gummy wheel and a new worm gear to motor coupler, so the cards are pulling through the card reader just fine.

I have adjusted all the reed switches in the manner I always do so that everything should work, however I have not been able to get the code to actually write to a card. Since it has done this with two different motherboards, I'm convinced there is a component on the card reader control board that is not functioning correctly. If anyone can offer any advice it would be sincerely appreciated.

[teenix]

The 97 doesn't actually check if data has been successfully written to the card, so it is possible that there is nothing being written, or it is in error.

Yes, the capacitors could be bad, but as it is reading ok, I'm not sure that is the problem. You could try changing them if you wanted. They are 22uF Tantalum types. Make sure they are soldered in the proper polarity as they will be destroyed if soldered back to front.

It seems like you have checked everything, and the voltages to the card reader must be ok for it to read, so I guess the only real way to check is if you have access to an oscilloscope to check that the data appears on the WA WB pins of the sense chip and also that it appears on the magnetic head. Also the WE pin should be about 6V when writing and 0V when reading.

cheers

Tony

[James Linder]

I have a working 67 that confirms nothing is being written to the cards. Should I replace the sense chip? What components can prevent the data from being written to the cards? Those I need to replace one at a time. I have tons of spare parts. Thanks

[teenix]

If you have a spare sense chip, it may be worth while to change, or if you have a complete sense circuit board to swap over, even better.

Have a close look at the pins on the sense board. One may be broken or bent.

The WA and WB pins are pins 4 and 5 counting from the bottom towards the top.

WE is the 4th pin down from the top.

cheers

Tony

[James Linder]

Thank you VERY MUCH for your help! I hope you have a wonderful day.

[AndiGer]

To connect to my oscilloscope I once stuck some small wires inside the connector with ribbon cable installed. When wires were removed the ribbon cable didn't connect inside the connector.
So: when mounted check all connections at the connector pins when the ribbon cable is installed. Bending back the connector springs is not easy

[James Linder]

Thanks. I’m going to insert some small solid metal pins in there!

[teenix]

(06-21-2021 03:14 PM)teenix Wrote:  If you have a spare sense chip, it may be worth while to change, or if you have a complete sense circuit board to swap over, even better.

Have a close look at the pins on the sense board. One may be broken or bent.

The WA and WB pins are pins 4 and 5 counting from the bottom towards the top.

WE is the 4th pin down from the top.

cheers

Tony

Apologies, I was thinking of the 67 connector for some reason.

From front to back on the CPU board, the pins are:

1 Ground
2 Ground
3 6V
4 Switched battery
5 Motor On/Off
6 WB
7 WA
8 WE
9 RA
10 RB
11 HDS
12 MTRS
13 Write Protect SW

cheers

Tony

[Hans Brueggemann]

also, have a look here:
HP-67 Mag Head properties

[James Linder]

It was the motherboard. Tried a 3rd one and card reader both reads and writes now. I guess the first two motherboards have defective CRC chips. Thank you everyone for your help![/php]

[AndiGer]

Thank you for reporting back