HP-150 Touchscreen

Yes. I have a couple of original HP150s and an HP150-II. I do like HP machines, the older ones seem to be well-designed and well-made. So do I. I also like 3 Rivers machines (PERQs), Philips machines, and a lot of others. It's jsut that theposts on DEC machines here recently have been about machiens I know nothing about (this is my problem, I am certainly not saying such posts do not belong on this list, of course they do). OK. In many ways that;s the more interesting version. It will ahve the touchscreen, all original machiens do. It was an option on the HP150-II, which apparently was not often fitted. Well, yes, it does run the monitro. It also runs the computer. The computer stuff (8088 processor, etc) is i nthe smae case as the CRT. On the back of this unit are the 2 serial ports and the HPIB port The 9121 isa disk drive. Yes, there is a processor inside, a 6809 of some flavour (I forget the clock speed, it may well be a 68B09). But t does not run user programs. It interprets commands sent of the HPIB interface and operates the disk drives. The drives are SOny _single sided_ ones. You need a signle-sided MS-DOS boot disk for this set-up. THe HP9121 PSU is quite simple. It;'s linear. There;'s a mnins transformer, rectifier diodes, smoothing cams and regulators 9on that large heatsink) on the controller PCB. The fan is a low-votlage capacitor-run induction motor. It runs off the mains tranformer scondary winding. The run capacitor is a couple of electrolytics wired in invers sereis on the PCB. The only mains stuff is on the inoput side of the trnaformer -- the connector, power switch, voltage selctoir, etc. This is a freidnly unit to work on, but you probably won't have to. They are reliable. The disk drives themselves suffer from dried up grease o nthe eject mechanism. On double-sided drives thic can result in the upper head catching on the disk when it is ejected, and then the head getting ripped off the gimbal spring. SIngle sided drives don't hav this problem, but they still often need taking apart and cleaning. It's not difficult, but there are quite a few bits. OK, back to the main unit, the one with the CRT in. On top there are some remvoable covers. Take those off. Insdie youy may see a thermal printer. This is an option, if you don't have it the machine will still run. If you do have it, unplug the ribbon cable (34 way IIRC), pull up the Nyltach fasteners and take the printer unit out. Now o nthe pack of the unit there are 2 quarter0turn fasteners on the bottom edge of the top case, near the metal cardcage backplate. Releasse these witha Phillips (not Pozidriv) screwdriver. The top case then comes off backwrds and upwrds. But be careful. The cooling fan is on the top case, It is plugged int oteh PSU board. When you get the caove free, unplug this cable and put the cover aside., Inside the machine you will see the CRT and 2 PCBS. Looking from the rear of the machine, the one on the left, with the flyback transfomrmer and the HV lead to the CRT anode cap, is the video monitor. It is fairly conventional. The one on the right is the SMPSU for the machine. This is the one with a pair of capacitors aimed at the CRT neck. So be careful. I mentioned getting insdie the card cage yesterday., You want ot do that to see what you have. It';s worth seeing if you have n expansion boards. The memroy-omnly board is not obvious from outside the macchine, you put the normal blanking pate back on after fitting it. So it may not be obvious whether you have it. The 2 expansion boards nnd the logic boarsd I mentioend all plug into a little backpalne at the fornt of the case -- HP call it the 'forntplane' in the technical manual. As well as connectors for the boards, it has connectros for cablkes ot the monitor board, the touchscreen board (aronf the front of the CRT), the PSU and the printer (20 way -- the other 14 wires of the 34 way priner cable go to a 14 pin conenctoro n the PSU board). There are a few chips on the 'frontplane', thse are the interface for the thermal printer unit. Basically, a simple parallel port. You need to read the available manuals - -alm,ost all of them. In particualr, you need to read the bit about configurign the machine. The configuration is stroed in battery-backed RAM (i nthe real time clock IC) and if the battery is flat or removed you will have to reset this. Note that the defualt, IIRC is for the machine to act as a terminal (using software in the ROMs), unless ou change thsi to 'computer' the machine will not attempt to boot from disk . -tony