Re: Autistic HP-65 needs help! Message #8 Posted by Vieira, Luiz C. (Brazil) on 11 June 2010, 11:03 p.m., in response to message #7 by Michael Meyer
HI, Doc;
I do not know the HP65 circuitry, but if you have a display with 'garbage', I'd suspect either the display driver/decoder OR the main ROM contents. As you managed to test the mainboard in another HP65 and it works fine, you are in the right way trying to find the problem in the external circuitry. So, my question would be: the LED display is driven by circuit(s) in the mainboard or somewhere else in the calculator? I have an HP55 but I do not recall how do its internals look like, neither if they remind the HP65's... Anyway, if the LED driver/decoder chips are not in the mainboard, they may also be the cause of it.
The other way to get into a conclusion would be running a pre-recorded program (mag. card) and see it the calculatorĀ“s display shows something understandable. I also do not know if the HP65 has the auto-run feature (I know nothing about this dude...), but if it has, that would help a lot.
The closer way to 'see' inside of it was through this picture:

But I did not get too much insight from it.
Sorry not helping the way I would like to...
Cheers.
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