HP-67 Card Reader became very touchy

[YoungerThanThat]

The card reader on my HP-67 was working perfectly. I would get an error reading once in a while but it would almost read a card correctly.
Now I have the opposite condition. Most of the time I get an error message and a card is read correctly once in a while. It seems that something is no longer adjusted properly.
The wheels have been changed a couple of times, and a card running through seems to have no problem.
Is this a common issue? Is there someone that could fix my reader (for a fee)?

Thanks for your help,

Michel

[teenix]

(08-27-2022 09:53 PM)YoungerThanThat Wrote:  The card reader on my HP-67 was working perfectly. I would get an error reading once in a while but it would almost read a card correctly.
Now I have the opposite condition. Most of the time I get an error message and a card is read correctly once in a while. It seems that something is no longer adjusted properly.
The wheels have been changed a couple of times, and a card running through seems to have no problem.
Is this a common issue? Is there someone that could fix my reader (for a fee)?

Thanks for your help,

Michel

The power supply capacitor may be failing.

Prior to reading this, I added an answer to this and another issue as a PM

cheers

Tony

[YoungerThanThat]

I have replaced the power supply capacitor but it did not fix the problem. I have the feeling that the engine is slipping at the end of reading a card. There are few cards where it stops correctly at the end but most of them seem to be spinning longer than it should and then I get an error.
Anybody wants to buy an HP-67?

[teenix]

(09-03-2022 02:14 AM)YoungerThanThat Wrote:  I have replaced the power supply capacitor but it did not fix the problem. I have the feeling that the engine is slipping at the end of reading a card. There are few cards where it stops correctly at the end but most of them seem to be spinning longer than it should and then I get an error.
Anybody wants to buy an HP-67?

This operation is normal. It has to do with the HP microcode, which controls the reader, and when it detects a card read error. If an error is found, it takes a little longer to turn the motor off.

This will most likely be a checksum error where the card data does not match the calculated checksum, which is the last record on the card.

One thing that doesn't get mentioned much is the magnetic head. These are quite old now and can also suffer wear and tear. Some that I have seen are quite badly worn from cards rubbing over the top surface and I guess this reduces the pressure of the head slightly against the card surface and maybe just enough to reduce the signals that are read from the card. The writing may work fine because of higher magnetic signals, or errors could still be introduced. Unfortunately, writing poor quality data to a card does not produce an error.

You could try adjusting the concentric shaft that supports the helical drive gear to increase the pressure slightly (if it isn't at max already)

My Classic Notes has details on adjustments on page 34.

cheers

Tony

[YoungerThanThat]

Hi Tony,

I spent lots of time testing and I found out that lots of the cards (from the Standard Pack) I have been using for testing were corrupted. I have been able to restore most of them using copies that I had (and the trick of using another card cut at 90 degrees to disable write protection). There is only one card I could not restore as I did not have a copy. I will try to ask for a copy on the Classified forum.

It seems that replacing the capacitor fixed the problem. For some reason, lots of my Standard Pack cards got damaged while the reader was behaving and it got me very confused (too emotional about this calculator given the history).

On another note, I played with the concentric shaft but I could not feel any difference.
I am going to leave it the way it is right now.


Thanks a bunch for all your help,

[Alevin]

I bring up the topic of the old forum “A weird HP-67 card reader problem” `posted in June 2001 where Viktor Toth documented the case (and Tony Duell proposed the solution) were the card reader reads/writes with low batt, but not a high or normal level. After going through the entire card reader mechanical settings protocol, I believe that my machine shows similar symptoms, that is: it reads prerecorded cards, and reads and writes cards, but only when the battery voltage is low.

Similar behavior is observed in one Hp-97 I got. Card reader, low bat reads and writes, but not at normal voltage.

The thread concluded to solve the problem replacing a capacitor (15 uF or 47 uF not clear) that communicates the battery with the SENSE Vbatt ( I guess Vbatt it is pin 20 noted VB on page 36 schematics, in Tony ClasicNotes).

Please, could someone clarify me where this capacitor is located? Is the one connecting the SENSE chip pins 17-18 to ground in the same pag 36 schematics?. (small blue one in the below linked video). Or it is another one going thought the main logic board or elsewhere?
Also a confirmation of its type (tantalum?) and characteristics (cap value, voltage) is welcome

The following short video shows the calculator and the main PCB and the card reader PCB.

https://youtube.com/shorts/0pGET7dNivI

The next one shows the error when reading with full or medium battery level

https://youtube.com/shorts/v-pWB6EqYsw

A this last, with a low battery light on, successful reading (not always, thought)

https://youtube.com/shorts/H29nE7X0NYY

I have also noticed, that in the Error readings, the card travels further (with no effort to extract) than when the reading is OK (it does not advance so much, at it takes a little effort to extract), as Tony as pointed out.

Equipment description, and settings tried

The serial number is 1710A1266, with PCB Korean chips seems dated at 1977. a relatively early model. However, the PCB of the card reader is the type of the later series (Perhaps the calculator was repaired and the card reader changed in 1986?).

On the card reader PCB you can see a blue potentiometer (variable resistor for the motor speed control, as I have tested) and two yellow capacitors and the afore mentioned small blue on, in different configuration from the three parallel cylindrical capacitors that appear on the HP65 and early HP-67 models.

Its cosmetic condition is quite good with the electronics completely clean, without a trace of corrosion.

After cleaning the goo of the gear wheel, the nylon piece was substituted for two O-rings. The cards pass smoothly and without strange or squeak noises. But I get a read error permanently.

I have worked on all the usual mechanical aspects:

Clutch fix (it was not necessary, but I added a little super glue just in case, since I previously tested other recommended procedures; insulation wires and silicone,. on a HP-65 ,and I could not make them work).

Lubricating the worm and fulcrum with silicone grease.

Playing with the gear the eccentric cam.

Playing the blue potentiometer.

Applied Deoxit to card reader connections.

I have not touched the reed switches,. since they seem to work fine, as the card passes and stops without problem.

But I can't read or write cards except with low battery, namely:

I have been able to read the pre-recorded Standard PAC cards, and and write and read blank cards when the battery is low and the dot on the bottom left of the screen, that indicates low battery starts to light up.

[teenix]

The HP-97 capacitor that matches the one that you changed in the HP-67 is marked on the attached image as C6 - 47uF. The image refers to later model 97's, earlier ones have the parts in different places.

C6 - 5V Battery bypass
47uF, 16-25V Tantalum

C4 - Vss (+6V filter)
22uF, 16-25V Tantalum

C2 - Vgg (-12V filter)
68uF, 25V Tantalum (Not sure what the original type was though)

Note the polarity of each as they are polarized and inserting new ones the incorrect way will damage them. (Lots of unpleasant smoke).

Also note that the HP-97 service manual has the +ve marking for C6 to the top of the capacitor, but it should be to the left side as in the image as the capacitor pins are horizontal not vertical.

cheers

Tony

[Alevin]

May be in my previous post 1st paragraph I induced missunderstanding.

I am not the OP on the thread, but another else guy, and I have not yet changed any cap in my HP-67 ( I suffer of this syndrom in, both Hp-67 and Hp-97). Indeed my very first question is about the location of this power line capacitor in the HP-67, and still is open.

In any case, thanks Tony for your kind and detailed replay about Hp-97, that will be useful when going to solve the HP-97 problems, after picking up the ones in HP-67

Regards

Ricardo

[teenix]

Apologies, crossed wires on my part :-)

I had posted this HP-67 capacitor location image before (not sure where) but here it is again.

cheers

Tony

[Alevin]

(09-26-2023 10:55 PM)teenix Wrote:  Apologies, crossed wires on my part :-)

I had posted this HP-67 capacitor location image before (not sure where) but here it is again.

cheers

Tony

Great, I could not find this usefull pic.

Mesuring on the circuit the ESR it gives a 2,7 Ohms vaule, that is a large one for a 16-25 v 47uF cap.

So I will procede to serarch for a tantalum 47uF 25 volts or 16 volts.

I will inform on the results

Thanks a lot


Ricardo

[Hiwi]

Hi,
there are some cardreaders which write always fine but could not read any cards.
Reading cards shows always ERROR.

Aside from of a high ESR of the capacitors, there could be a problem with the contacts.
Please try to clean the PCB and the contacts carefully.

The older HP67 cardreader PCB had three silver tube tanatalum capacitors, they are high quality and usually never fail. The newer PCB has a different layout with epxoy resin tantalum capacitors.
There are two 22uf across read/write head and one in the supply line, i think it was 22uF too.

I replaced this capacitor in many cases and sucessfully solved the reading problem.

Ralf

[AndiGer]

(09-26-2023 10:11 PM)teenix Wrote:  Note the polarity of each as they are polarized and inserting new ones the incorrect way will damage them. (Lots of unpleasant smoke).

Also note that the HP-97 service manual has the +ve marking for C6 to the top of the capacitor, but it should be to the left side as in the image as the capacitor pins are horizontal not vertical.

What I learned lately: HP from some time marked polarity (i.e. orientation) of components by a square pin hole. Pin 1 of chips, anode pin of capacitors, cathode pin of diodes, left pin of transistors. Very cool.
(Before that there is a little triangle on the board you can find in e.g. 35/45/55's.)


Andi

[John Garza (3665)]

Dare I mention preventive maintenance?

We could all take a tip from the vintage radio crowd. RECAPPING

As part of the 'refurb process' on these machines, we can simply replace the capacitors as standard procedure - regardless of if they work or not. If they do work, they are old and likely to fail anyway - so while you have the machine apart replacing the drive roller wheel, take it a step further and avoid a failure in the near future by replacing them now.

-J

[Hiwi]

Polarity of tanatalum caps with colour rings:

there is always a small colourpoint on one side (defining the voltage range), if you can see it, then the right pin is the positive.

On some tantatalums (with a flat surface) this colour marking is on top but a bit out of the middle, here the pin which is nearer to this marking is positive.

Ralf

[Johnboy]

Does a similar "cap" issue exist with the 41c card reader ?

Thanks
John

[Alevin]

(09-26-2023 11:18 PM)Alevin Wrote:  

(09-26-2023 10:55 PM)teenix Wrote:  Apologies, crossed wires on my part :-)

I had posted this HP-67 capacitor location image before (not sure where) but here it is again.

cheers

Tony

Great, I could not find this usefull pic.

Mesuring on the circuit the ESR it gives a 2,7 Ohms vaule, that is a large one for a 16-25 v 47uF cap.

So I will procede to serarch for a tantalum 47uF 25 volts or 16 volts.

I will inform on the results

Thanks a lot


Ricardo

Thanks you all given great tips and advice.

Looking for replacement tantalum cap for the power line, as indicated: 47uF 16 or 25 volts, I have found in present catalogs (KYOCERA, KEMET,...), they have a dip diameter aroun 9 mm, whereas the original is about 4,8 mm. So they will not fit in the tight space around the cap in the HP-67 PCB.

May be I am missing something? may be there some particular specification I should look for?

Thanks in advance.

[teenix]

The smallest 47uF looks to be about 6mm diameter with a 6.3V rating. Since the battery supply is under 4V, this should do.

cheers

Tony

[Alevin]

(09-29-2023 10:32 PM)teenix Wrote:  The smallest 47uF looks to be about 6mm diameter with a 6.3V rating. Since the battery supply is under 4V, this should do.

cheers

Tony

Thanks again for the advice.

In the one hand, as it was metioned the 16-25 volts in reference to the power line capacitor in the HP-97, I assumed the same voltage specification for the HP-67.

In the other hand, Hp-97 is plenty of space to accept a 9 mm dip cap. Indeed the one I have got has exactly the same circutry lay out than in the pic you shown above, in a previous post.

Regards

[teenix]

The 97 has a 5V battery so the capacitor for it would be best rated for 16 or 25 volts.

You might even be able to remove the original 67 capacitor and solder a surface mount type to the circuit board pads. I think the through hole capacitor pads are spaced at 0.2 inches, so a 47uF 10V 1411 or larger 2312 type might do - nice and compact and around a dollar each.

cheers

Tony

[Alevin]

(09-30-2023 01:22 AM)teenix Wrote:  The 97 has a 5V battery so the capacitor for it would be best rated for 16 or 25 volts.

You might even be able to remove the original 67 capacitor and solder a surface mount type to the circuit board pads. I think the through hole capacitor pads are spaced at 0.2 inches, so a 47uF 10V 1411 or larger 2312 type might do - nice and compact and around a dollar each.

cheers

Tony

I am afraid my soldering skills and avalaible tools are not enought to do the job without messhing something else, as a "forest" of tall components grow around the cap. For me, desoldering and soldering throuhg the PCB holes seems easier. Any way, It is a great suggestion to think about.

Some point out. The 47 uF 6 volts, dip format, has a ESR about 2 Ohms in catalogs. So, not so different for the ESR I measured on board (with a Chinese "ESR meter" ), 2,7 Ohms, for the suppoused failed Cap. Then may be is it not so faulty if the present cap is not 16 or 15 volts but 6 volts? I guess, I will not know up to change it.

Regards

Ricardo