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HP-67 1706A00901 [RA and RB with Spike, doesn't read - doesn't write]
11-19-2021, 11:32 PM (This post was last modified: 11-20-2021 09:41 PM by albertofenini.)
Post: #1
HP-67 1706A00901 [RA and RB with Spike, doesn't read - doesn't write]
Hi everyone,

this is a working HP-67 but the card reader is not reading
Based on the suggestions received in the thread "Testing the HP65 or HP67 card reader sense amplifier" we did some tests
In the following pictures you will see the following measures :
CA (blu wave) and RA (red wave)
CB (blu wave) and RB (red wave)
We noticed that when the calculator is doing nothing (display 0.00) both RA and RB have a spike
We used the SD-14A Moon Rocket Landing card as a test
Apparently RA and RB have a good waveform but nevertheless the HP67 shows a Error Message
The same card has been tested with a couple of working HP67 and it works

Any suggestion will be appreciated
Thanks for help and take care !!!

Pictures here : HP-67 1706A00901

Edoardo & Alberto
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11-20-2021, 01:09 AM
Post: #2
RE: HP-67 1706A00901 card reader test
As long as the spike is not there when reading it shouldn't matter.

If it is, then it may trigger another pulse into the CRC chip and give a false bit. This will upset the checksum when it is checked by the Microcode and may produce the error.

The only way is to capture the whole card read and scroll through the data to see if there is one or more.

cheers

Tony
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11-20-2021, 09:30 PM
Post: #3
RE: HP-67 1706A00901 [RA and RB with Spike]
Hi Tony and thanks for the update

I have put a known working board and have seen the same behavior (though I haven't captured waves)
Don't know if this helps but I can tell you that writing a very simple program (7 ENTEr 7 X R/S) and
trying to write it on a card produces the following : the first side goes thru and then a second side is
requested, but when inserted for recording at the end of passing thru it gives an "Error" message
Also, switching from RUN to W/PRGM after a h RTN is pressed puts you in a random step and not
at the beginning of the program as you should expect
I'll do more tests ...
take care !

Edoardo & Alberto
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11-20-2021, 11:47 PM
Post: #4
RE: HP-67 1706A00901 [RA and RB with Spike, doesn't read - doesn't write]
The "Crd" request should not have occurred with such a short program. This error points to (at least) the first 28 bits from the card are not being read properly. This is the STATUS information about the card program.

When I get time, I am going to update the code for the 65, 67 (and 97) CPU replacement boards so that they can all read raw data from the cards and provide a screen dump of the information on a PC. That way users will be able to see where the errors are. Whether that actually helps finding the fault or not I don't know.

cheers

Tony
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11-20-2021, 11:59 PM
Post: #5
RE: HP-67 1706A00901 [RA and RB with Spike, doesn't read - doesn't write]
Hi Tony
Since it happens with two different cpu boards, where do you think
the problem could be ?
The card reader unit ?
The magnetic head ?
The keyboard assembly ?

Take care and thanks for all the supporto provided to me and to the forum !

Edoardo & Alberto
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11-21-2021, 12:06 AM
Post: #6
RE: HP-67 1706A00901 [RA and RB with Spike, doesn't read - doesn't write]
I would check the wiring to the sense board. Especially if the wires are the plug in type. Maybe re-solder the connections.

cheers

Tony
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11-21-2021, 03:06 PM
Post: #7
RE: HP-67 1706A00901 [RA and RB with Spike, doesn't read - doesn't write]
I have swapped the CPU board with a known working one
The spikes on RA and RB have disappeared and the original card reader worked !

I also have uploaded more pictures for this unit, and I must say that the label
on the CRC chip (which I had totally ignored) probably should have inspired me a little Smile

Also for this unit, RA and RB measured at the CRC chip with the card reader disconnected are clean
but when the card reader is connected the spikes show up.

This happens only with this CPU board.

Looks like also in this case the CRC chip is probably the one to look after ....

Updated Album : HP-67 1706A00901

thanks again for the support ! take care !

Edoardo & Alberto
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11-21-2021, 05:27 PM (This post was last modified: 11-21-2021 05:28 PM by AndiGer.)
Post: #8
RE: HP-67 1706A00901 [RA and RB with Spike, doesn't read - doesn't write]
(11-21-2021 03:06 PM)albertofenini Wrote:  This happens only with this CPU board.

Did you test the card reader together with a board of the currently non-functional 67's?
If there aren't the spikes you could at least combine two machines to one functional? ?
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11-21-2021, 06:08 PM
Post: #9
RE: HP-67 1706A00901 [RA and RB with Spike, doesn't read - doesn't write]
Hi Andi

I hadn't because all the other, or at least three (I haven't finished to troubleshoot the one
with serial XXXXA01234) have shown problems at the CPU board level but it was worth a
try, so I did it and :

XXXXA00901 chassis and card reader with CPU XXXXS02334 didn't work
XXXXA00901 chassis and card reader with CPU XXXXA01636 didn't work
XXXXA00901 chassis and card reader with CPU XXXXA01234 didn't work

I can try to de-solder the CRC chips and check if underneath there is some
corrosion, may be is a cold joint not working anymore

I also have a spare HP67 board with some ROM0 problems but maybe that CRC
is working so I'll keep up with the tests

Thanks for the support, take care


(11-21-2021 05:27 PM)AndiGer Wrote:  
(11-21-2021 03:06 PM)albertofenini Wrote:  This happens only with this CPU board.

Did you test the card reader together with a board of the currently non-functional 67's?
If there aren't the spikes you could at least combine two machines to one functional? ?

Edoardo & Alberto
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