More or less dead HP-67

[Bernd Ulmann (Germany)]

Hi -
I recently acquired a HP-67 in non-working condition and was hoping to restore it, but I have to admit that I have run out of ideas by now.
The symptoms are as follows:

- Display shows 00000.0 at power up.

- No numbers can be entered, pressing most keys just causes the display to go blank for a blink and then 00000.0 is displayed again.

- Switching the RUN/PGM-switch to PGM causes the display to flicker rhythmically as if the machine were executing some program.

- The top-row keys cause the display to go blank and stay blank, pressing the division key results in the display of Error (maybe it tries to divide by zero which is in the display).

I checked this:

- +6.2 and -12V are there and there is no noticeable ripple on either voltage.

- PHI1/2 are there, swinging from +6.2 to -12V.

- The keyboard lines KCx are all high as long as no key is pressed.

What puzzles me is that I can see a nearly saw-tooth signal on the DATA pin (11 on the ACT) with a 5 us period. All other lines like SYNC and ISA have signal patterns that look reasonable after what I read on Jacques Laporte's pages describing the HP-35.

Does anybody have any ideas what I could/should check next? I can take pictures from my oscilloscope and post them to clarify things if necessary.
All the best - sincerely, Bernd. :-)

[Ignazio Cara (Italy)]

HI Bernd,
if the ACT is good, IMH, maybe a bad ROM (1818-0232 and/or 1818-0231). I have a test unit with easy removable component, created to test this kind of components.

Hope my post might be a valid help for you.

Regards

Ignazio

[aurelio]

Quote:

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I have a test unit with easy removable component, created to test this kind of components.

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I remember well, Ignazio, you shared the pics of this your wonderful and very useful device. But I remember even that it was so well done that nobody understood at the beginning that components were moveable and not mounted directly on the PCB, you have golden hands, my friend!

[Ignazio Cara (Italy)]

Aurelio,
thank you very much, you are too much confident about my ability.

I'm very glad to help everybody that have need an advice.

Regards

Ignazio

[aj04062]

Ignazio,

Have you posted pictures of your testing system?

[Ignazio Cara (Italy)]

Adam,
I've posted only the images of my HP-97 test-bench , but no image of my modified 67. Are you interested? I'll do it soon.

Take care

Ignazio

Edited: 10 Feb 2013, 9:10 a.m. after one or more responses were posted

[aj04062]

Ah yes,

How do you get the trimmed legs of the IC's to make contact?

[Ignazio Cara (Italy)]

Hi Adam,

no problem with the trimmed legs of the chips if you use this kind of socket:

The foolowing are the pics of the modified HP-67 PCB:

The ACT and the reader controller could be tested on the 97 test-bench.

Ciao.

Ignazio

Edited: 9 Feb 2013, 12:54 p.m.