HP150 Touchscreen again

Tony Duell ard at p850ug1.demon.co.uk
Wed Mar 23 15:00:29 CDT 2011

> > Do you happen to knwo anything abot uthe itnerface on these touchscreends?
> > The HP150 (original, 9" CRT) has a custom interface consisitng of a clock
> line,
> > sync line and data line, on a 10 pin (2*5) header plug. The touchscreen
> > contains all standard chips, mostly 4000-series CMOS.
> The interface is combined with the front panel knobs hp-hil and rotation
> resolver.
> The interface is a hp-hil device says the selftest, most of the decoding has
> been done by a mcu9818 microcontroller.

OK, that makes sesne. I assume there's the normal HP-HIL slave chip in 
there too. 

> > Sure, and if I can't find a suitable replacement at Farnell or somwewhere,
> I may
> > get back to you. But I don't think it's going to be too difficult to find
> something
> > that will work.

It never fails to amaze me how easy it is to get spares for classic 

Yo uwould ahve thougth that a spare LED for a touchscreen on the HP150 
would be somewhat hard to find after more than 25 years. Well, as I said, 
I thought that RS and Farnell did something similar. For a laugh, I 
checked Maplin (hobbyist supply of components, limited range, rather like 
Radio Shack, alas). Amazingly they listed a side viewing IR LED. Even more 
amazing, the Maplin shop I was going to go past had 2 in stock. Of course 
I bought them.

I fitted on in the touchscreen PCB and tried it on the tester again. 
Perfect. Then I put the whole HP150 back together again. The machine 
works fine, but I am having problems with the head motion of the internal 
2674 printer (and which idiot decided that printer-out-of-paper should be 
a self-test failure? I spent quite a time trying to find 'real' problems....)

Anyway,  The machien si back together for the moment, I will look at the 
printer soon...


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