HP-150 MS-DOS Computer

I don;t think it is. The obvious place to look would be http://www.hpmuseum.net/ . I think the service manual is there, but that's a boardwsapper guide, no schematics. The Techref 150 Techref contains schematics of the whole machine _apart touchscreen. The -II supplement includes the 150-II mainboard scheamtic, but not the PSU/video board, keyboard or touchscreen (the last 2 are standard HP-HIL devices). I did trace put the schematics of the PSU/video board in my -II, though. What's the problem with your unit? Does it appear to be a digital problem, or a problem with monitor circuit? We've discussed this many times at HPCC meetings. My feeling is that the 'golden years' of HP were about 1965 to 1987. The real 'death' came when they split off the test equipment division as Agilent. At one time HP were known for making some of the best test gear available [1], now they're known for cheap and nasty inkjet printers. A great pity if you grew up with their great products. [1] Although I always thought Tektronix made better 'scopes :-) I have an _old_ -- over 40 eyars old -- HP frequncy counter. Apart from a very clever design (how about making a decade counter, latch and nixie tube driver in 8 transistors (and no ICs), I am always amused by the fact that the _low precision_ timebase is the intenral oven-stabilised crystal oscillator, good to 3 parts in 10^9 after warmup and calibration. The high precision add-on was, of course, a rubidium beam. That's the HP I knew and loved :-) Needless to say I am addicted to their (old) calculators. I still routinely use HP41s. There's an HP16C on my workbench. I regard the HP9100 as the most elecgant piece of electronics that I've ever had the pleasure to work on. THe HP98xx series (all of them -- 98x0 and 98x5 machines -- are interesting, ingenious, and still work well with minor repairs30 years after them were made. And as I mentioend I like the 9000/200 series. I am not a great fan of the HP80 series. Yes, they work. They do what they claim (which is more than I could say of some manufacturer's offerings!). But there's too much custom silicon inside, the expansion bus is plain strange (and at 6V voltage levels), etc. Not really my first choice. -tony