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Old 26th Jul 2022, 4:02 am   #29
TonyDuell
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Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 4,585
Default Re: HP 150 Touchscreen II repair

I would try removing link W1. The techref makes it very clear you have to do so, the ALE signal will not behave properly if driven from 2 sources (the coprocessor board and the original 8088 via W1).

No idea why there's resoldering on the IC next to the coprocessor socket. That's the 'Elmer' ASIC, real time clock + baud rate generators +... Very early machines have 50 pin header in place of it, then a daughterboard fitted. Perhaps your Elmer IC was replaced at some point.

As for the printer, the one for the orignal HP150 won't work in a 150-II. There's a special interface circuit for it on the 'frontplane' (the PCB that interconnects the other boards) and a power connector for it on the PSU board. Your best bet is to find another Thinkjet with a good flexiprint (any interface version) and to swap the flexiprints or to have one made (are there companies that do that?)
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