HP-65 more on the card reader

[albertofenini]

Hi Harald,
we will not be able to do that, because in order to re-use the spare keyboard we had to move
the Anode and Cathode drivers, and we do not want to de-solder them again.
However, I can tell this.
In order to measure the Ph1 and Ph2 signals at the Anode driver we had to put the calc in lab mode.
We took it out of the case and we soldered a cable to from the power switch to the power line
and we added a switch in order to toggle between RUN and PRGM/WRITE modes.
With the calc in this condition, we measured Ph1 and Ph2 and they were good and clean,
both when reading or writing a card.
While at it, we measured in this condition WA and WB and to our surprise, not only they were
very clean, but the recorded program was readable and executable.
At this point, since we also have a spare case complete with keys, we mounted the unit
in this second case and it stopped to work, i.e WA was good and WB was bad.
We took the unit out of this case and it started to worke again.
By saying it works I mean is able to read and record cards, basic function has not been an issue ever
To cut it short, it the unit is out of a case it works, it reads and writes, if it is in a
case it doesn't.

Any idea with this happens ?
Thanks everyone !!!

   
   
   

[teenix]

(02-08-2019 11:05 PM)albertofenini Wrote:  To cut it short, it the unit is out of a case it works, it reads and writes, if it is in a case it doesn't.

Any idea with this happens ?
Thanks everyone !!!

I would suspect the WB line is being opened or otherwise upset when the pcbs are in the case. I would be checking the pins that connect the cpu board to the reader board.

cheers

Tony

[albertofenini]

It's definitely a possibility,
I will take a close picture of the point where the card reader pins get connected to the logic board.
BTW, it looks like the CPU cover is lightly shifted to the right, and in reality this keeps the final
part of the card reader not perfectly aligned with the chassis.
On the other side, this is also true when the unit is out of the case, since is a defect that is not related
to the case and the keys, but more to the logic board and card reader assembly.
I certainly agree that I have to investigate in that area.
I'll keep posting results ....
Thanks for keeping up with the support.

[albertofenini]

Here we are
The top of the CPU, which is a metal cover, is very lightly shifted to the right, compared to all the
other units we have.
As a consequence, the bottom part of the card reader hits the CPU and does not fit perfectly in the
chassis, and the pins cannot be inserted till the end.
However, it should be considered that this situation does not depend from the calculator being
inserted in the case or being left outside of the case.
It may be true that once is inserted in the case and it is fixed with the screws it may get worst,
but I would expect that is a contact gets open, not that a noise is introduced because of this.
What do you guys think ?
Would it be worth to connect the card reader using some thin cables ?
Thanks again !

   
   
   

[AndiGer]

Is it possible you get kind of short circuit? Did you try to insulate the card reader connectors by putting a piece of paper between the CPU case and the pins? In the last picture you posted it looks like the pins being very near to the CPU case which looks to be made from metal ...

[albertofenini]

We did it,
we surrounded the last part of the pcb with some insulating tape on both sides, just leaving the pins out,
but it didn't help ...

[teenix]

(02-09-2019 12:56 PM)albertofenini Wrote:  We did it,
we surrounded the last part of the pcb with some insulating tape on both sides, just leaving the pins out,
but it didn't help ...

It definitely sounds like a mechanical issue.

The card board looks under stress, so it is possible that the inside of the connector holes are not making proper contact with the pins after assembly. Using the scope, you should see steady states on the WA WB lines with the boards working out of the case. Maybe wiggling the card pcb will show up changes that you can track down.

The plating inside these holes can be quite thin and may wear away with many insertions onto the connector pins, causing problems.

You could consider filing the side of the pcb so that it fits around the cpu case, but not so much that you damage the traces.

cheers

Tony

[Geoff Quickfall]

I have checked my 65s and 67s.

Some of the keyboard PCAs are slightly warped as you indicate. All function correctly.

Could it be a trace microcrack once the board is flexed? Check the continuity of each trace with the board in place. Also check for cold solder joints on the gold prongs. These may be stressed with the flex.

Electronic noise may be introduced by your wiring at the foot of the board or are they removed prior to testing?

Geoff

[albertofenini]

Hi everyone, thanks for all the ideas.
Last weekend we worked on our HP67 units, these were also in need of a restoration, and we
will post separately what we did, as it may be of help for someone.
We didn't work on the HP65, and we will try over the next few days.

As per Geoff suggestions :

Even in our HP67 the card reader PCBs are a little warped, without any problem.
As per the wiring, we used the same system with the other HP65 we restored, without any problem.
We do this so that we can capture at the same time the two channels RA and RB or WA and WB with the scope.
However, now that we know that the only bad channel il WB we may as well remove them.
Please consider that once the unit is in the case, WB is noisy even if measured at the Amplifier pin level, which would exclude
the wiring being responsible for the noise.

We'll try to clean ad reinforce the pins, which are however well aligned and cleaned.
We may as well try this particular card reader with and HP67 and see if it works.

We'll do more tests and we'll post the results !
Thanks everyone !!

[albertofenini]

No way !
We did few tests tonight without getting any far from where we were.

At first we de soldered the wires, as said they have been of no trouble with the other units, but you never know.
By doing this, we also checked for cold joints and re-passed all the joints.
Then we cleaned the prongs and the corresponding holes in the logic board.

We assembled and powered the unit with an external battery pack, not the original.
To our surprise it worked like a charm.
I say to our surprise because in our opinion we didn't do anything special other than cleaning what was already cleaned.
We read and recorded almost the entire Standard Pac.

Then the external battery (3 X AA rechargeable Nimh batteries) died ...
We used then the rebuilt original battery pack, and the card reader began to fail in recording.
We changed batteries in the external pack and we switched back to that and
the card reader started to work again.

At this point we thought that when the renewed original battery pack was inserted something was changing (mechanical pressure maybe ?) but don't ask me what.

We also changed the rounded o-rings with some squared o-rings, trying to improve the friction between the card reader and the card, and it got worse.

Since we have an additional spare card reader, which we know it works because we have used it with the HP67 and it works 100%,
we swapped the actual card reader with this one, just to get back to the starting point. It reads well, but it never record.

We almost tried every possible position with the eccentric, and I must say that while reading is affected by this setup, while recording doesn't work regardless of the eccentric position

As always, we are opne to any suggestion .... thx for help !!!

[teenix]

(02-12-2019 11:38 PM)albertofenini Wrote:  No way !
We did few tests tonight without getting any far from where we were.

At first we de soldered the wires, as said they have been of no trouble with the other units, but you never know.
By doing this, we also checked for cold joints and re-passed all the joints.
Then we cleaned the prongs and the corresponding holes in the logic board.

We assembled and powered the unit with an external battery pack, not the original.
To our surprise it worked like a charm.
I say to our surprise because in our opinion we didn't do anything special other than cleaning what was already cleaned.
We read and recorded almost the entire Standard Pac.

Then the external battery (3 X AA rechargeable Nimh batteries) died ...
We used then the rebuilt original battery pack, and the card reader began to fail in recording.
We changed batteries in the external pack and we switched back to that and
the card reader started to work again.

At this point we thought that when the renewed original battery pack was inserted something was changing (mechanical pressure maybe ?) but don't ask me what.

We also changed the rounded o-rings with some squared o-rings, trying to improve the friction between the card reader and the card, and it got worse.

Since we have an additional spare card reader, which we know it works because we have used it with the HP67 and it works 100%,
we swapped the actual card reader with this one, just to get back to the starting point. It reads well, but it never record.

We almost tried every possible position with the eccentric, and I must say that while reading is affected by this setup, while recording doesn't work regardless of the eccentric position

As always, we are opne to any suggestion .... thx for help !!!

If I understand correctly, if a different battery pack works and the original doesn't, then perhaps the battery pack may be faulty, ie higher than normal internal resistance, poor terminal contact. When writing, the sense amplifier probably needs more current than reading and this may be affecting the battery supply, or the chip has decided it wants a low impedance battery supply.

It could be just a weird combination of this particular chip and this particular battery. Does that battery cause faults in other calculators?

cheers

Tony

[albertofenini]

Hi Tony,
I really don't know what to say,
It is a HP Classic battery pack, rebuilt with Nicd batteries that we have used for testing all the other calcs with no problems.
We have more than one pack and all generate this behavior.
The difference seem to be whether the batteries are inside the calc (original HP pack) or clamped to
the plus and minus contacts but outside of the calc.
The funny thing is that all of these components if taken one by one and combined in other units work fine,
but when put together they behave weird.
We'll go back to round oring and do more tests.
Thanks everyone for the continous support !

[teenix]

(02-13-2019 10:16 AM)albertofenini Wrote:  Hi Tony,
I really don't know what to say,
It is a HP Classic battery pack, rebuilt with Nicd batteries that we have used for testing all the other calcs with no problems.
We have more than one pack and all generate this behavior.
The difference seem to be whether the batteries are inside the calc (original HP pack) or clamped to
the plus and minus contacts but outside of the calc.
The funny thing is that all of these components if taken one by one and combined in other units work fine,
but when put together they behave weird.
We'll go back to round oring and do more tests.
Thanks everyone for the continous support !

I've got a similar problem with a HP67. If I connect leads to the battery terminals via my power supply, the calculator will not turn on although it is drawing current - way less than the power supply can source. If I use a battery pack, same voltage, it works.

cheers

Tony

[wallyt]

Alberto and I are following a parallel course! I have an HP65 that will read/record fine as long as the NiCd battery pack does not have a full charge. Below 4V it seems to work really well. If I charge the pack so that it is above 4V the card reader is non-functional. Also, If I use a pack that has three disposable AAA lithium batteries the reader will not work. This pack is around 4.5V to 5V.

For those using an external supply with clip leads is it possible that there is a voltage drop from the leads and this allows the reader to work? It would not be much of a drop but maybe the sense amp is really sensitive.

[teenix]

(02-13-2019 04:31 PM)wallyt Wrote:  Alberto and I are following a parallel course! I have an HP65 that will read/record fine as long as the NiCd battery pack does not have a full charge. Below 4V it seems to work really well. If I charge the pack so that it is above 4V the card reader is non-functional. Also, If I use a pack that has three disposable AAA lithium batteries the reader will not work. This pack is around 4.5V to 5V.

For those using an external supply with clip leads is it possible that there is a voltage drop from the leads and this allows the reader to work? It would not be much of a drop but maybe the sense amp is really sensitive.

You'd reckon a sense amp would be more sensible about things :-)

cheers

Tony

[wallyt]

Doh! It's more sensible than me. Anyway, I think I am going to try using my variable DC supply and clip lead it to the unit. Starting about 4.5V I'm going to reduce it slowly and see exactly where the card reader starts to work reliably.

I just finished repairs on a second HP65 and it is working very well. I did not need to replace the clutch, just the gummy wheel. This unit works fine regardless of which battery pack I feed it. I do think, however, that the cards transport through the unit a little slower than the problem unit.

[albertofenini]

We have modified the keyboard PCB by adding two single hole pins for the power supply.
This way we don't need to de-solder and re-solder the power cables anytime that we want to test
the unit with a different card reader.
We also have soldered the scope wires on the logic board rather than on the card reader.
We have used thinner and better quality wires to avoid any possible side effect.

We have tested the unit with three different card readers.
Two are HP-65 style, fixed resistor, one is using the old sense amplifier, and the other
is using the same sense amplifier mounted on the HP67 version of the card reader.

They both behave in the same way, regardless of which battery pack is used.

A third car reader is an HP67 style, it has the trimmer and the new version of the sense amplifier.
This particular reader was also not reading, but once we have changed the 22microF capacitors
it started to read with no problems at all.

However, all of them have the same problem, a noise WB channel, thus not recording.

We also replaced the two transistors on the logic board, we thought that given the different
behavior based on the type of battery used, it also could have been an issue with the PSU
not performing well when writing a card.

However, even with two different transistors, all of the card readers are able to read, but
having a noisy WB channel they all fails to record a card.

Would it be possibile to add a capacitor and clean (filter) the noise ?
What do you guys think ?
And eventually, where and how should we connect it ?
Thanks in advance !!!

   
   

[teenix]

(02-15-2019 12:39 AM)albertofenini Wrote:  Would it be possibile to add a capacitor and clean (filter) the noise ?
What do you guys think ?
And eventually, where and how should we connect it ?
Thanks in advance !!!

I doubt it. The noise looks like the WB output is oscillating, as it's peak voltage is the same as the WA signal. Any capacitors on the outputs might cause overshoot on the rising and falling edges and could cause more problems.

What type of transistors did you use in the power supply?

cheers

Tony

[albertofenini]

Hi Tony,
exactly the same type that were in place, we got them from a stripped logic board from another HP65 which
had a broken CPU.
They works, since the unit operates well, and read cards.
We also re-soldered the WA and WB pins of the CPU just in case, but nothing.
Take care and thanks for help

[teenix]

(02-15-2019 09:23 AM)albertofenini Wrote:  Hi Tony,
exactly the same type that were in place, we got them from a stripped logic board from another HP65 which
had a broken CPU.
They works, since the unit operates well, and read cards.
We also re-soldered the WA and WB pins of the CPU just in case, but nothing.
Take care and thanks for help

Thanks Alberto,

If I am correct in saying the card will write unless it is assembled into the case and then it fails...

Have you tried isolating the WB pin from the main cpu board to the card reader board leaving all other pins connected normally. Probably difficult to do without bending the WB connector pin and risking damaging it.

That way it might prove whether the fault is on the cpu board or reader board.
You should still be able to see the cpu WB signal even though it doesn't get to the sense chip and see if it is good or bad.

cheers

Tony