Where is NOP on the HP-67 ?

[albertofenini]

Thank you very much Tony for all the tips
We’ll try and let you know !
Take care !!

(01-07-2021 11:36 PM)teenix Wrote:  

(01-07-2021 09:49 PM)albertofenini Wrote:  Thank you guys !!! It works !!!
Thanks everyone!!!

Still I have to figure out why the 10th digit is off ...

I assume 10th mantissa digit...

Failed connection inside LED package #3
Open circuit pin 1 of LED package #3
Open circuit pin 3 of cathode driver
Open circuit on PCB track between pin 1 and pin 3 mentioned above
Failed cathode driver

Knowing me, probably none of the above ;-)

cheers

Tony

[albertofenini]

Just a quick update
It has to be a cold joint of some sort
When we took the keyboard pcb out of the shell and we connected everything to start the tests the 10th digit started to lit correctly
Depending on how much torque we apply on the upper left screw it doesn’t lit
We’ll post soon pictures in the original thread
Thanks for all the help !

[teenix]

(01-10-2021 10:23 PM)albertofenini Wrote:  Just a quick update
It has to be a cold joint of some sort
When we took the keyboard pcb out of the shell and we connected everything to start the tests the 10th digit started to lit correctly
Depending on how much torque we apply on the upper left screw it doesn’t lit
We’ll post soon pictures in the original thread
Thanks for all the help !

I'd try to re-solder all the cathode driver and faulty display module pins. No need to remove old solder first.

If that fails, it could be a hairline crack on a circuit board track.

cheers

Tony

[albertofenini]

That's exactly what I will do as soon as possible

It must be said that the original keyboard was beyond repair or at least not repairable in the short term.
We may be investing few euro in a conductive pen to repair the corroded traces but those good cost quite a lot
Also the metallic domes needs to be removed and cleaned underneath to make it reliable

Because of this we used a old keyboard from another HP-67 which was also repaired

Particularly under the RCA chip there where two missing traces, one from the transistor that sits between the two
chips and one underneath the RCA chip itself that we fixed with a couple of thin cables

Also the card reader board that came with the unit was not reparable, we tried using thin cables but the result
was not working and so we used a board less damaged

The magnetic head we tried was not working although in a good preserved case so we used a different one
but that fact that bakelite was not as smooth as it should have been together with the copper pieces that should keep
the card aligned is making reading and writing not consistently

Last but not least, the Logic board has some oxidation, that in the long term is going to worsen,
however, last time we washed a working Logic board from an HP-67 it came out like new but it was no longer
working, so we are a little skeptical with this ...

All in all we are learning a lot from this and we'll do our best to bring it back, as always thanks to all the suggestions and tricks !!!

Let me say that the building quality of the HP65 is far far better than that of an HP-67 ...

Some additional pictures can be seen in the original post and here

HP-67 1705A01636 2nd part