Card Reader breaks cards on writing, reads fine

[damaltor]

After repairing my card reader, i was using it for a few days now on a more or less daily basis. It always worked flawlessly, i never had problems.

Today i read one program, modified it, and wrote it back to the same card. Doing a VERify afterwards gave me "malfunction".

I wondered why that might be, reset the calculator, tried a few other cards, wrote a short demo program to write on an empty card and so on. this is the essence of my search:

- Cards with valid programs on them get read without problems. The program on them is correctly loaded into memory.
- Cards with valid programs can be VERified without problems.
- This is also true for multi-card programs.

- known empty (new) cards will be read, and afterwards show "CHECKSUM ERR" which means they are read successfully, but contain no valid data.

- If i am in PRGM mode and put a card into the reader, it pulls through without any error. It looks like the card has been written successfully. This is also true for multi-card programs.

- freshly written cards will show MALFUNCTION on reading and on verifying (But not CHECKSUM ERR).

- If i take a cards with a valid program, i can verify it fine. I also can read it fine. After writing the exact same program back onto it, they only give MALFUNCTION (but not CHECKSUM ERR).

So, it looks like the reader reads everything fine, but breaks cards on writing. I disassembled the reader again and cleaned the head, to no avail. I also used the head cleaning card, also without any news. Any ideas on that?

[wojtek]

(05-10-2016 12:09 PM)damaltor Wrote:  After repairing my card reader, i was using it for a few days now on a more or less daily basis. It always worked flawlessly, i never had problems.
...............
So, it looks like the reader reads everything fine, but breaks cards on writing. I disassembled the reader again and cleaned the head, to no avail. I also used the head cleaning card, also without any news. Any ideas on that?

I have no that reader, so my opinion is based on my experience in repairing electronic devices only.
As you repaired this reader some time ago I suggest you should disassemble it again and double-check what you had repaired.
If cleaning of the writing head have not helped you could check all the connectors inside, pull out every connector, perhaps clean the contacts with isoprophyl alcohol, and put in again.
If above fail to fix the problem you could check the mainboard and the soldering points for short-circuits and bad solders
As the reader worked OK before you have good chances to fix the problem.

[damaltor]

thanks wojtek, This is pretty much what i did. I followed along the service manual of the reader, disassembled everything, and adjusted the motor current a bit lower to be in spec of the values named in the service manual. On that way i had unplugged and replugged every connector. It seems to work again now.

My guess: After cleaning and fixing everything (and after disassembling the motor itself), the motor was too fast. This might happen if the magnet orientation inside the motor is not correct, which could have happened by disassembling the motor itself. If the Magnet is oriented wrongly, the motor spins faster but with less torque.

Now,if the card goes through too fast, the program data is only written on the card partially, so it cannot be read back correctly. reading old cards worked, because the data was correctly written on the older cards i had written before.

I dont know if the solution was unplugging/plugging all the wires, or adjusting the motor speed - nevertheless, for the moment it seems to work fine.