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Old 25th Jul 2022, 3:23 pm   #23
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 don't think I have any complete spare 150's, sorry.

The HP touchscreen with its scanned array of IR beams was an interesting way to do it, but ultimately it was too limited in resoultion so died out. I remember Steve Ciarcia had a project based on it in his Circuit Cellar articles in Byte magazine some years before the HP150 came out, said article metions a patent owned by one of the American universities, I forget which but it might be worth tracking down.

The touchscreens are quite different electronically between the 2 machines. The HP150 one has a custom interface that links to an 8041 on one of PCBs. The HP150-II is an HP-HIL peripheral, as I mentioned it also fitted at least one HP video monitor and was used as such with some HP9000-series machines.

The HP150-II processor is roughly in the middle of the motherboard I think.

Which Thinkjet do you have? I assume either the HPIB or RS232 version, to use the HPIL or Centronics ones with a 150-II would be perverse at best. I have the full service manual for that unit too, BTW. NEVER leave the cartridge in the Thinket when you are not using it. If the cartridge leaks ink, it will drip onto the flexprint that connects the cartridge to the control PCB and corrode the traces. Replacement flexiprints are very hard to find, the easiest source is another Thinkjet where the custom processor chip has failed.This is even worse on the HP Integral, the flexiprint there is longer than the one in a normal Thinkjet.

The microcontroller in the Thinkjet is a custom 8 bit HP thing with internal firmware. It has external RAM and font ROMs, oddly these connect using the 'Saturn bus' as in the HP71B handheld computers. Very strange. And yes the Thinkjet was probalt the first commercial inket printer, the name is officially a contraction of 'THermal INKJET'.
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