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HP-67 1805S02334 - albertofenini - 03-20-2021 11:08 PM
The Keyboard
Hi everyone
after a few SR-52s and some TI-59s we are now back working on an HP-67
This one had a broken battery contact but it was shown working so it was a go
Once opened however the oxidation was worst than we thought
Basically the key domes were all broken and few traces on the back corroded
The 50% water and 50% vinegar did his job, than from a non working keyboard
we recovered the metallic strips and soldered them rebuilding the keyboard.
Almost all of the keys have the classic click except the h and the enter
will see if we can do something about that but at least is now working
By doing so the pcb has become a little curved and while this is not a problem for the
keys, once screwed to case everything was fine, it may be an issue for the card reader ...
The card reader chassis was also quite damaged so it will be challenging ...
Any idea or suggestion is welcome
Take care !
Pictures here : HP-67 1805S02334
RE: HP-67 1805S02334 - teenix - 03-21-2021 01:38 AM
The only thing I can think of is if the PCB has warped a bit, the card contacts may not function properly. As far as I know though, the board should stay fairly flat once properly secured into the calculator case.
cheers
Tony
RE: HP-67 1805S02334 - albertofenini - 03-21-2021 09:42 PM
The Faceplate
Hi Everyone,
not much to say on the faceplate, keys and faceplate have been washed
but it will be necessary to spray the TS80 to bring it back to the original
aspect, that will be done as the last thing
The Card Reader
The card reader has been completely stripped of all the components
this is one of that latest version, it can be taken out without de-soldering
thanks to the pins
Cleaned with the usual mixture, two traces needed to be restored and
they are the Motor and the RB traces
The wheel has been restored with two o-ring and the clutch has not been
done has it keeps (for the moment) a good strength
It has been mechanically tested and a card goes thru regularly
However, sad to be said, it doesn't work ...
The problem seems to be in the RA and RB channels, though we have not tested the
writing feature for the moment
Both RA and RB are noisy once the calculator is powered on, even if the card reader
is inactive.
When disconnected from the logic board it looks ok, also RA and RB on the logic
board are ok when the card reader is not connected
We have put this logic board in a working unit and it can read just fine,
so we presume the card reader controller on the logic board is fine
We changed the amplifier on the card reader with a known good one and it behaves
like this.
When a card is passing thru you can see the correct wave in between the noise
Please be aware timing has been set differently when it was not reading vs
when it was.
Also, keep in mind that on the keyboard pcb the two traces that have been repaired
are SB and SC
We could not test the impedance, but we have measured the resistance and it is :
between red and yellow : 44 ohm
between blu and orange : 43,6 ohm
these values are comparable with values measured on other magnetic heads
As always, any suggestion is very welcome !
Take care !!
Updated album : HP-67 1805S02334