HP-67 - 1612A03018 - Card Reader Advice Requested (was HP-67 - strange behavior)

[albertofenini]

Hi everyone,
couple of updates on this post ...

We have received a working CPU board (thank you very much !!!) and thanks to this we have been able to test the card reader.

We have been able to assemble three different card readers:
two HP-65 style (no variable resistor to adjust the speed) and one HP-67 style.

One strange thing common to all of three is this :
if the motor is powered directly (attaching a battery) it runs to a good speed.
but when the engine is engaged from the logic board because a card has been inserted it runs to
probably at one third of that speed.
Any idea why this is happening ?

We also have tried a different keyboard logic, we have had some incompatibilities between card readers
and keyboard pcb with the HP65 so we thought this was the case.

However, on this other keyboard PCB we had broken the transistor that sits between the anode and cathode drivers,
it is marked M624 3-393, does anyone knows a good equivalent part ?

We have recovered the transistor from the original keyboard, but this does not allow us to test the
old keyboard again.

Of the two first card readers, one has good RA and RB, and also good DATA but keeps giving Error.
The other one, seems to be physically blocking the card.

The third one to our surprise works.
We have assembled it litteraly from the worst of the spare parts we had,
and it runs so slow that the card barely passes thru, however we tested it with the SD-04A card which
is a two sides card from the standard pac, and is about dates, we tested the DOW program and it works.

Tomorrow we will post videos and pictures.

On the board side : we took some measurements on the broken CPU board.
This is the one that has a suspected ROM0 not working.
We have found good Phi1 and Phi2 on the ACT, the CRC and the ROM0.
However, the side of the ROM0 that handles the segments of the display is dead.

Also, when compared with a working board, Idisp and Ibias are different.
The array of resistors looks good, and is about 24K Ohm for each resistor.
What should try ?
We will open a separate thred for this one

Thanks to everyone !!!