HP-67 Card Reader became very touchy

[teenix]

Caps are cheap to change and won't hurt :-)

[Alevin]

Being tantalum caps known to be robust and eternal, but sensible to over voltage, I wonder why these are so prone to produce fails in models with card readers. One possible explanation could be the situations where the calculator is working on the adaptor but without batteries inside. Even thought that Classic series are said to be able to work only on the adaptor, the open voltage measured on the adaptor pins are 15 volts , 5 volt. May be the models Hp-65 HP-67 with card reader suffers more the consequences of voltage surges when switch on and during work without batteries, as they detteriorate the power line cap (specially if it is 6 volts cap), and this may not have much impact in the other circutry and chips, but it does in the quites sensible reading logic.

Makes it sense?

[Massimo Gnerucci]

(09-30-2023 11:15 AM)Alevin Wrote:  Being tantalum caps known to be robust and eternal, but sensible to over voltage, I wonder why these are so prone to produce fails in models with card readers. One possible explanation could be the situations where the calculator is working on the adaptor but without batteries inside. Even thought that Classic series are said to be able to work only on the adaptor, the open voltage measured on the adaptor pins are 15 volts , 5 volt. May be the models Hp-65 HP-67 with card reader suffers more the consequences of voltage surges when switch on and during work without batteries, as they detteriorate the power line cap (specially if it is 6 volts cap), and this may not have much impact in the other circutry and chips, but it does in the quites sensible reading logic.

Makes it sense?

Just one of the threads where this argument is treated.

[Alevin]

(09-30-2023 12:48 PM)Massimo Gnerucci Wrote:  Just one of the threads where this argument is treated.

Thanks for the reference from the old forum. I have not detected it. Quite on the point.

So, it is possible to conclude that being conected the adapter without batteries inside a Hp-65 or Hp-67, it may cause to make fail not only the SENSE chip and other Card Reader PCB components, but also the indicated cap at the power line in the main PCB, specially if this could be a 6 volts one.

[John Garza (3665)]

(09-30-2023 11:15 AM)Alevin Wrote:  Being tantalum caps known to be robust and eternal...

Perhaps you are thinking of ceramic disc capacitors? They have the lowest failure rate.

But you are correct, over-voltage will lead to their demise. Along with high temperature and humidity.

It's common to blow tantalum caps in old S-100 computers (Altair/IMSAI/etc.) upon startup after years of storage. One of the many reasons to use a variac and slowly ramp up the voltage. Accumulated humidity seeping in over the years and all those up/down temperature cycles weakens the structure and dielectric material. Even with an uneventful startup, their time is limited. It's best to just re-cap all of them as they will eventually fail. This preventive maintenance gives the circuit a few more decades of reliable service.

Also good to store the unused units in a temperature and humidity controlled environment. My preferred storage method is 4mil resealable anti-static bags squeezed flat to remove most of the air.

-J

[Alevin]

Her comes the update.

Finally I desoldered the suspected bad 47 nF capacitor. The measured ESR was about 2,7 Ohms, and the capacity was out of range. So for sure it was kaput.

I manage to insert a new tantalum 47 nF 25 volts, Bulk packing. 14 € each, not cheap thought. Even the diameter was larger than the original, and it barely fit in to the remaining space, it quit fits in the holes (staight "legs" 5 mm spaced). Ref is a KEMET 350K476K025AT. Measures out of the board were 45 nF, ESR 0,01 Ohms.

And It worked!!. The HP 67 started reading cards OK at first chance, with a fully charged battery. Great!!

Thanks all contributions. The subjet should have a permanent pushpin as is a common issue.

This cap change should be recommended at first instance when card error appears once repaired the gummy wheel, even before try all that kind of mechanical fixings, that mostly have no effect, or end in a mismatch of factory fitting.

[teenix]

Good news indeed :-)

[John Garza (3665)]

BAM ! ... and the world has another working 67...

Good show!

-J

[Alevin]

Update, about the crd Error reading, in the HP-97.

After solving the issue in the HP-67, I went to the HP-97. I substituted the habitual suspicious cap, indicated by Teenix some post above. Out of the board it was not so bad, measured values were 44 nF, 0,3 Ohms ESR, Replacement new one has 45 nF 0,1 Ohms ESR. Look at attached pics. New cap on board, and new vs old caps,

Unfortunately it has not solved the issue. Still, when low battery is inserted, the cards are read, but when batteries are middle of full charged, it stops reading. It feels some squeak when batteries are full. When low batt, less o no chirp is found. May be when batteries are full they produces plenty of torque and the clutch is more prone to slip?

I got the HP-97 back in 2017, with the card reader gummy wheel already substituted by o rings, but I do not know if the clutch was fixed as well.

To make thing worse, during testing, the original idle gear, the was working fine like a champ, disintegrated several tooth. I have noted afterwards that the printed head gets blocked at 1/3 position. Probably this made lose the fragile idle gear.

This is the plan.

1) To replace the deteriorated idle gear, with nylon shapeways option. I will inform about my experience about in the proper threat (https://www.hpmuseum.org/forum/thread-15...inter+gear). The paper rollers seems to require also substitution, but I am afraid the required skills are beyond my limited capabilities and tools, ending with and inoperable printer. In any case this does not refer to card reader problems of the threat.

2) To fix the clutch with the drastic glue option, if inspection show slipping, assuming that it was not fixed when the O were introduced. Other clutch fixing options seems to be unpractical for me, i..e. uncertainty in procurement of wires or tubing in EU being the stuff recommended is in inches, whereas in here we have mm standards.


3) As the calculator reads and writes at low battery level, I will not try to play a with eccentric cam (in any case it not so easy to manipulate as in Hp-65 Hp-67). No speed potentiometer exits, so it will be kept as it is.

May be you have also some clue about another components, caps?, that could be checked in relation with the specific issue. Systematic replacement of all caps is not in my mind, under the principle: If it works, don’t touch. Indeed the Hp-97 worked fine, printing, and reading/writing cards (al least when low batt), before I tried to improve things, .-D

[John Garza (3665)]

Part of the card reader refurb is to replace the clutch. Pull the worm gear off the motor shaft, and dig out all remaining clutch material inside the little cup at the end of the worm gear. Fill with RTV sealant or gasket maker, insert the motor shaft, ensure it is straight (the shaft mates with a hole at the bottom of the cup) and let dry overnight. Also square profile O-rings seem to be the best replacement for the card reader drive roller. It used to be model airplane fuel line, but production of that has moved overseas with lower quality control (as in concentric inner and outer radii). Circular O-rings have less gripping surface and seem more prone to smear pencil marks on the card face along 2 parallel lines.

HP topcat printer gears can be found on the auction site. I've replaced many over the years, they work fine. The metal ones are 'freshly minted' and can do with some wire brushing to remove sharp edges and burrs. I lube with moly-di, same as the card reader worm gear for smooth operation. While you are in there you should also remove the paper advance rollers (both ends of the shaft) as they become brittle and slick with age. Once cleaned of all the remaining roller bits, just slip on some tight fitting silicone/rubber tubing cut to size. Works great. And you can also clean the print-heads with IPA. They rarely get such an opportunity for a thorough cleaning.

It may seem daunting at first, but once you do one, the fear will subside. Be careful of the little springs flying away if they are under tension.

-J

[Alevin]

(10-17-2023 01:23 PM)John Garza (3665) Wrote:  Part of the card reader refurb is to replace the clutch. Pull the worm gear off the motor shaft, and dig out all remaining clutch material inside the little cup at the end of the worm gear. Fill with RTV sealant or gasket maker, insert the motor shaft, ensure it is straight (the shaft mates with a hole at the bottom of the cup) and let dry overnight. Also square profile O-rings seem to be the best replacement for the card reader drive roller. It used to be model airplane fuel line, but production of that has moved overseas with lower quality control (as in concentric inner and outer radii). Circular O-rings have less gripping surface and seem more prone to smear pencil marks on the card face along 2 parallel lines.

HP topcat printer gears can be found on the auction site. I've replaced many over the years, they work fine. The metal ones are 'freshly minted' and can do with some wire brushing to remove sharp edges and burrs. I lube with moly-di, same as the card reader worm gear for smooth operation. While you are in there you should also remove the paper advance rollers (both ends of the shaft) as they become brittle and slick with age. Once cleaned of all the remaining roller bits, just slip on some tight fitting silicone/rubber tubing cut to size. Works great. And you can also clean the print-heads with IPA. They rarely get such an opportunity for a thorough cleaning.

It may seem daunting at first, but once you do one, the fear will subside. Be careful of the little springs flying away if they are under tension.

-J

Thanks a lot for your recomendations.

I tried in an Hp-65 clutch repair with the silicone procedure, but I got troubles in getting the ensemble engine staff-worm aligned.

In respect idle gear, I made a previous repair in another HP-67 with a bronze gear, and my experience was not quite satisfactory. Expanding the bore to the right size an keeping well centered was not a straightforward task with my simple tools. Then it had tendency to wobble, and move back an forth over the axe, as the width is smaller than the original and the circaclip is away from the outmost external face. It causes some time to get stuck in diagonal in between the motor pinon and the printer gear, . Finally, it was really noisy.

That is why I am going to attempt now with a printer plastic one. Shapeways nowadays offers more printing materials to try. I will document the experience in the threat.


I am grateful for your encouragement to go ahead with the full printer repair, but still I am apprehensive. I have study the theory and maintenance manual, and It seems the printer paper avance rings are not easy to replace. As previous to the idle gear collapse they did the job well, unless I can detect that the printer head stuck comes from them (May be some one got broken?), I am keeping them as they are, by the way. It is a collection item, just for exhibition, trying to keep in working order, but not intended for every day desk work.

[Alevin]

(09-26-2023 10:11 PM)teenix Wrote:  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

Keeping the threat about the electronics of hp-67 hp-97 card reader, and in relation to the cited previous Teenix post showing the Hp-97 main caps in the transformer area...

My limited electronics knowledge is nevertheless enough to know that the capacitance value of caps measured when soldered on the PCB is affected my surrounding circuitry, and it can not be taken either as the real value, nor indicator of the cap condition.

Nevertheless, measuring on the board the capacitance of C2 (76 uF, ESR 0,036 Ohms) and C4 (26 uF, ESR 0,86 Ohms) these values are not very different the nominal values documented, 68 uF and 22 uF, respectively.

Surprisingly, the C6, the substituted one, gives me on the board a value of arounf 7 pF ?? ( on the contrary the ESR is the same on the PCB than individual, about 0.1 Ohms).

Could be possible the cap C6 capacitance measured, once soldered to the PCB, being so different from the nominal one? (Specially being in mind the C2 and C4 does not show so much differences).
Or may the cap has been destroyed while I was making soldering?

Checking the other discrete components I have noticed than the rectifier diodes from the card reader area (CR1, CR2, CR3, CR4) , and the diode CR5 (Zener?) located in between C6, C4 capacitors and the Toroidal transformer T1, give 700 Ohm resistance in direct polarization, but 1,4 KOhm in inverse polarization. Should they be replaced?


Regards

[teenix]

(10-17-2023 08:42 PM)Alevin Wrote:  I tried in an Hp-65 clutch repair with the silicone procedure, but I got troubles in getting the ensemble engine staff-worm aligned.

There is a method described in my Classic Notes PDF on how to make a coupler with simple tools. I have built a few and they work ok.

cheers

Tony

[John Garza (3665)]

(10-17-2023 08:42 PM)Alevin Wrote:  I tried in an Hp-65 clutch repair with the silicone procedure, but I got troubles in getting the ensemble engine staff-worm aligned.

In respect idle gear, I made a previous repair in another HP-67 with a bronze gear, and my experience was not quite satisfactory.

That is why I am going to attempt now with a printer plastic one. Shapeways nowadays offers more printing materials to try. I will document the experience in the threat.

Keep in mind silicone is not the same as RTV or gasket maker. I've tried silicone back in the early 2000's and it did not work well. I also tried the cable insulation replacement, but it's really not needed unless the coupler itself is damaged (or crushed!) by a careless previous owner attempting repairs. The goal is to have a material inside the coupler that will not break it's grip on the smooth metal shaft, yet provide some flexibility. And you must mate the shaft into the bottom of the coupler for good alignment. Optical inspection and a 'dry-run' without sealant will aid familiarization.

I never had a problem with the gears from the auction site. Sounds like you got one that was simply wrong. Was it advertised as a 97/Topcat Idler Gear? If you go the route of fabricating new plastic ones, ensure you use material that will not wear quickly or break. The hardness trade off is between broken teeth and rounded/slipping gears. Good luck!

-J

[John Garza (3665)]

(10-17-2023 09:37 PM)Alevin Wrote:  My limited electronics knowledge is nevertheless enough to know that the capacitance value of caps measured when soldered on the PCB is affected my surrounding circuitry, and it can not be taken either as the real value, nor indicator of the cap condition.

Always best to test components when extracted.

However on the overall picture...

Well... if you have time on your hands, this seems a reasonable path.

Otherwise... keep in mind these caps, even if good now, are likely to fail in the future.
So... while you have the machine apart, try some preventive maintenance and replace them now.
Don't test, don't ask, just replace them all.

But then I'm biased as I'm older (60's) and don't want to have to go back in there years later with weak eyes and shaky hands fooling around with a soldering iron !

Build (and repair) to last. It's an HP thing.


-J

[Alevin]

New update with the task of fitting the Hp-97 card reader issues.

Printer idle gear has been substituted, as first step to continue further with the card reader problem solving. As the thread is about card read, the info about the new matherial idle gear substitution will be upload soon in the specific thread

https://www.hpmuseum.org/forum/thread-15625.html

Related to printer, I point out than during light sanding one of the advance paper wheels to improve drag, one got disintegrated in nearly one quarter of circumference, Oh , Jesus!, problems does not stop growing.

Nevertheless, as the advance wheels stay in place and still make advance the paper properly, I am keeping by the moment the printer wheels as they are, hoping to come back for that issue latter on.

I found a reference for the advance wheels substitution, guide in a slide show format created by Ignazio Cara (Italy), cited in this old forum thread.


https://www.hpmuseum.org/cgi-sys/cgiwrap...ead=216173

But the link is not working, Grrrr.... Is there some other site where the slide show can be found?



Coming finally to the card reader,… the clutch show signs of some previous repair work, but not an high level job.

The aluminum sleeve is somehow deformed (it seems to have been pressed with pliers to increase grip). Some kind of wire and soft silicon was found inside.

My “practical” decision has beens to keep the joint, but just reinforce the clutch with a superglue drip inside the sleeve.

After reassembling, the light squeal some time was heard disappeared. Now the card reader noise when reading cards seems to me consistent and acceptable (can be heard in the audio on to the vids below).

Nevertheless the syndrome “only read at low batt level” still continues.

In brief, after substitution of card reader wheels, clutch fix and C6 cap replacement (mesauring a very low capacity once soldered to the PCB, see my previous post):

At normal battery charge level, the card reader error continues, as you can see in the vid

https://youtube.com/shorts/qYyeVBTgHjo

Nevertheless, when lo-battery red dot appears, the cards are read.

https://youtube.com/shorts/UJBM0eFX29w

Please, note that the noise in this last condition is different, a lower sound, but the card transit time seems to be similar, Do you agree?

May be the lo-batt condition reduces the card speed and these makes easier to read the card?

Regards

[teenix]

(10-20-2023 12:09 AM)Alevin Wrote:  After reassembling, the light squeal some time was heard disappeared.
. . . .

May be the lo-batt condition reduces the card speed and these makes easier to read the card?

Regards

The squeal can sometimes be the lubricant at the end of the drive shaft has dried out and the shaft is rubbing against the ball bearing at the end. Some molybdenum grease can help, Tamiya brand in small tubes available at hobby stores.

It could also be caused by a damaged coupler causing the motor shaft to oscillate back and forth, or the bearings in the motor have worn.

Maybe the normal battery condition is causing the card to move too fast through the reader and the HP software cannot keep up with reading it. The only way to alter the speed is to change the motor speed resistor value on the sense board.

If you have an oscilloscope, you can check the read data and make sure it has completed before the motor switch opens. The bit width is approximately 1mS (1KHz).

There are some additional service notes for the card reader near the end of the HP-97 service manual.

cheers

Tony

[Alevin]

(10-20-2023 12:57 AM)teenix Wrote:  

(10-20-2023 12:09 AM)Alevin Wrote:  After reassembling, the light squeal some time was heard disappeared.
. . . .

May be the lo-batt condition reduces the card speed and these makes easier to read the card?

Regards

The squeal can sometimes be the lubricant at the end of the drive shaft has dried out and the shaft is rubbing against the ball bearing at the end. Some molybdenum grease can help, Tamiya brand in small tubes available at hobby stores.

It could also be caused by a damaged coupler causing the motor shaft to oscillate back and forth, or the bearings in the motor have worn.

Maybe the normal battery condition is causing the card to move too fast through the reader and the HP software cannot keep up with reading it. The only way to alter the speed is to change the motor speed resistor value on the sense board.

If you have an oscilloscope, you can check the read data and make sure it has completed before the motor switch opens. The bit width is approximately 1mS (1KHz).

There are some additional service notes for the card reader near the end of the HP-97 service manual.

cheers

Tony

Thanks for your kind and patient advise.

Certainly the time of the card passthrough the card reader is different when battery pack is full charge (about 1,9 sec) or low charge ( about 2,3). - I will compare with the transit time on Hp-67 (even though they are not exactly the same stuff). (In Hp-65 its much smaller, about 1,2 secs). In my Hp-67 card reader repair, the speed was easy to modify, as it has a potentiometer, but it did not made difference regarding the reading errors.

In any case, I am considering to follow to modifying the R1 resistance.

But previously I am thinking in remove and check again the capacitance of the recently replaced C6 cap, as I measure a very low capacity (7 pF ?) once installed in the Logic PCB. Is not this strange? May be it was deteriorated during soldering or legs are in short.

More over, the indicated diode (CR5) in the pic attached, tested on the board is conducting in direct (700 Ohms) and inverse polarization (1.400 Ohms). Is this correct? The same happens is measuring the resistance on diodes on the main PCB in the area of the card reader (CR1, CR2, CR3, CR4)

PD. The info about idle gear experience with bronze and plastic materials has been upload to
https://www.hpmuseum.org/forum/thread-15...#pid178849

Regards

Ricardo

[teenix]

(10-21-2023 12:13 PM)Alevin Wrote:  More over, the indicated diode (CR5) in the pic attached, tested on the board is conducting in direct (700 Ohms) and inverse polarization (1.400 Ohms). Is this correct? The same happens is measuring the resistance on diodes on the main PCB in the area of the card reader (CR1, CR2, CR3, CR4)

I measure normal diodes across all of these. Do you have the multimeter set to Diode check?

If you don't have a solder sucker, and you need to test them out of circuit here is an easy way to remove one end without overheating the part.

If you have some small gauge wire (Eg telephone wire) bend a small u-shaped hook on one end of the wire. Hook this around the wire of the component end you wish to remove. Hold the soldering iron with slight down pressure to melt the solder from the component side. As soon as it melts, pull on the wire, the component end will come free, then remove the iron.

You can then clear the hole out with solder-wick from the solder side. If the component tests ok, just push the component end back in and re-solder.

Careful with static when handling the board.

Good luck

Tony

[Hiwi]

Hi,
measuring the elctronic parts on the board may lead to suspect results. Desolder one leg.
There are some issues witch zeners, this could be your problem as well.

I had one card reader with the the same issue and replaced the 2,2uF and 6,8 uF on the cardreader PCB. There are two 22uF in series with the read/write heads, but i never had problems with these.

The speed should be independend from supply voltage. (it has a timer) So I would not modify R1, try to adjust the exenter of the shaft first. Measure the current, it should be increased about 200-240mA when reading at 5.5 Volts.

Some people fix the clutch with CA glue, this is not the best solution it may lead to a rough drive noise, there should be a bit play / movement. Is the card pulled evenly? May be the rubbers / silicone tube is deformed minimally.

And yes many worm gears are a bit deformed by pliers, this was made to strengthen the clutch a bit. This was made from the factory and during service and should be normal.

Check the ribbon cable to the cardreader and solderjoints on the main PCB (CRC Chip) and the sensor chip on the reader PCB.

And do not let them make you crazy regarding the capacitor values. The tolerance is 20% and an
ESR up to 2 Ohm is ok. So your 76 uf and 26 uf are perfect!

And clean the contacs of the Reader thoroughly with alcohol.

If the contacts are dirty, higher voltage leads to more current => errors.

Inspect especially the write protection contact. I had some issues with it.

Ralf