Hp-41C card reader - dead

[Vintage63]

I used a multimeter one probe on the vertical knife and the other on the copper strip on the upper PCB. There is continuity so the knives are all connected properly.
When you guys launch the Catalog 2 command do you also get as a first line of the list the entry I get on the photo? Thank you
Marco

[do2]

(05-20-2022 07:56 AM)Vintage63 Wrote:  When you guys launch the Catalog 2 command do you also get as a first line of the list the entry I get on the photo? Thank you
Marco

Hi Marco,
this is as it should be
It means that your calculator successfully recognized your card reader. Yours is version 1E.

[Vintage63]

thank you!!!
so now I have to investigate why when I put a card in nothing happens ?

[Vintage63]

these are the 'forks', that are pressed by the PCB. how are they used by the reader

[Vintage63]

   

[teenix]

(05-20-2022 09:26 PM)Vintage63 Wrote:  these are the 'forks', that are pressed by the PCB. how are they used by the reader

They detect when a card is inserted into the module and allow the inbuilt CPU to control the read write process. If they are faulty, the system won't work properly. They are delicate and care should be taken not to bend them out of shape if cleaning is required.

cheers

Tony

[Vintage63]

Teenix thank you very much. Are they in the correct position, both pointing in this direction pr do they have to be angled differently with each other?

[Vintage63]

I have also discovered that all the cables are not solderd onto the various PCBs but they are inserted in some sort of plugs. I have checked them and they are all plugged in correctly.
What does trigger the motor when the card is inserted?
Cards are inserted from the right, correct?
Not that inserting them from the left changes anything either.
Thank you
Marco

[teenix]

(05-21-2022 04:25 AM)Vintage63 Wrote:  Teenix thank you very much. Are they in the correct position, both pointing in this direction pr do they have to be angled differently with each other?

They look ok in the picture. You can see a small indent on the leaves where they contact with the gold plated circuit board when the card is inserted. This can also be seen when the board is screwed in place.

cheers

Tony

[teenix]

(05-21-2022 09:46 AM)Vintage63 Wrote:  I have also discovered that all the cables are not solderd onto the various PCBs but they are inserted in some sort of plugs. I have checked them and they are all plugged in correctly.
What does trigger the motor when the card is inserted?
Cards are inserted from the right, correct?
Not that inserting them from the left changes anything either.
Thank you
Marco

A lot of HP calculators had this arrangement, I guess for servicing. I doubt you would find connections like this these days. The only trouble is that they can corrode and give poor connections, but I think this is mostly due to the effects of battery corrosion which is not a problem in the reader module.

There are 2 contacts in the reader, one detects the card insertion and the other is for starting the read write process. There is also an optical sensor for the write protect switch.

If you don't have it already, this is the circuit for the HP82104.

http://www.hpcc.org/cdroms/schematics5.0...p82104.pdf

This will allow you to see the switch connections and if you have a multimeter you can test them when the card is inserted.

Insert from the right, and the card should feed out of the left side. It will make a difference because the switches are on the right side of the R/W head.

If you look at the connection holes in the PCB top, imagine them numbered left to right 1 - 5.

As you push the card in pins 4 and 5 will short, then as you push the card in further, pins 2 and 3 will short just as the card touches the drive wheel. The first one starts the motor running, the second starts the read write process. The write is allowed or inhibited depending on when the optical LED detects the card. This will occur later if the card is write protected with the corner cut off.

The card processes are controlled by the CPU chip on the circuit board. There is also a small ROM chip for the CPU instructions. Obviously if these are faulty the module won't work. You said the 41 displays correctly, so maybe the CPU is working.

There is also a motor driver based on a common 555 timer IC (1826-0180). Some of this circuit may be faulty also.

An oscilloscope can help with fault detection.

cheers

Tony

[Vintage63]

the 'tunnel' I insert the card into seems void of any sensors though. There is a clear LED under the tunnel and above it, soldered to the PCB, what I believe an optical sensor.
The motor by itself with a battery works. So it could be that the sockets where the motor cables are inserted could be oxidised? WD40 for electrical contacts could work?
Thank you
M

[AndiGer]

Post #86 shows the forks with the PCB off. If you insert a card you should see the forks springing upwards. This way they concect to the PCB.
With the PCB installed you can also see them spring upward if you look under the PCB from the side. If they are up you should get the shorted contacts of the golden fingers as stated above.
HTH

[Vintage63]

my forks seem all to be touching the pads on the underside of the PCB without any free movement. maybe this could be the problem?

[AndiGer]

(05-22-2022 08:16 AM)Vintage63 Wrote:  my forks seem all to be touching the pads on the underside of the PCB without any free movement. maybe this could be the problem?

So if you measure with the multimeter pin 4 and 5 are shorted always even without a card inside the slot?

[Vintage63]

Hi AndyGer, if you can look at picture in post #79 and tell me which are pins 4 and 5 it would be helpful. But the forks are at present all pressing on the PCB pads. There is no 'air gap' between them and the pads. I will try, once back at home, to remove the PCB and insert the card from the right to see which forks do move when that happens and I will bend them down a bit more.

[teenix]

Here is a short video of a card moving in and out of the reader. You can see the closest spring moving easily, the rear one is a bit harder to see, but operates first.

The springs move upward to contact the circuit board.

http://teenix.org/card_41.MOV

cheers

Tony

[AndiGer]

(05-23-2022 01:18 PM)teenix Wrote:  Here is a short video of a card moving in and out of the reader. You can see the closest spring moving easily, the rear one is a bit harder to see, but operates first.

The springs move upward to contact the circuit board.

http://teenix.org/card_41.mov

cheers

Tony

Tony,
I get a 404 error ... also when i try to connect to the modified HP-97 service manual at your site from the other thread Duane opened

[teenix]

I changed the .mov to .MOV in the link, should be ok.

I thought I deleted the 97 file as the later service manual was available, although I think that has some errors too.

cheers

Tony

[AndiGer]

You are right with the errors. Page 95 e.g. Connection left of R7 to VB is wrong for instance.

[Vintage63]

unless I'm totally blind I can't see a card moving nor the forks ?
but thank you anyway ??