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gridrunner 25th Jul 2022 3:51 pm

Re: HP 150 Touchscreen II repair
Hi Tony, I'd love to get hold of an original 150 to go alongside this unit. I particularly wanted to get a touch screen model, as I have a thing for this technology and how it's evolved. I have here a Samsung Surface table (which is the 2nd gen Microsoft Surface technology) where the IR sensors are embedded into the screen so it can 'see' hands and objects suspended above it. Really rather cool.

The keyboard does work, but there was a scare because the cable had been gnawed by mice and then fitted the wrong way round. A quick fiddle around got it working, but it is missing a key :(

The co-pro isn't playing ball again. I need to get the PCB out. I'll do that when I fit batteries to the power board. Where is the CPU by the way? Is it tucked away out of sight?


gridrunner 25th Jul 2022 3:53 pm

Re: HP 150 Touchscreen II repair
About printers, this one has a think jet that came with it. I was shocked and surprised to find you can still order cartridges for it almost 40 years later!
I believe the think jet was the first commercially available inkjet printer to reach the market.

TonyDuell 25th Jul 2022 4:23 pm

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'.

gridrunner 25th Jul 2022 4:56 pm

Re: HP 150 Touchscreen II repair
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Hi Tony,

I can see what you mean about the ink. The cartridge was left in the unit and it has ruined the cartridge although that wasn't likely to be of much use I know :)
I have been able to clean off the residue and it looks like the Flexi might have a fighting chance. It is a HP and not centronics interface on the back.

I'll see if I can attach it if I make progress with the disk drives and hard disk.

TonyDuell 25th Jul 2022 5:03 pm

Re: HP 150 Touchscreen II repair
That's the HPIB version of the printer. The microcontroller used has an internal HPIL interface, the HPIL model simply brings that out to the rear panel via the normal transformer, etc. The RS232 and Centronics models have internal interface boards that communicate with the microcontroller over a parellel data bus.

And the HPIB model? Amazingly it the same microcontroller as the HPIL version with an HPIB-HPIL interface board. Something like an HP82169 with different firmware.

I hope I am wrong, but that flexiprint is probably corroded and will be open-circuit.

gridrunner 25th Jul 2022 8:48 pm

Re: HP 150 Touchscreen II repair
Sadly Tony, you're right. The Flexi is toast. It's a shame, if only the cartridge had been put away properly. Would the printer for the 150 I you have work on this II? It would be nice to have a period correct HP printer to display with it.

gridrunner 25th Jul 2022 10:03 pm

Re: HP 150 Touchscreen II repair
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Back to the co-pro issue. I've removed the mainboard itself to have a closer look. There is a 0 ohm resistor in W1 and it's soldered in place. Now, the machine had the co-pro option fitted as can be seen from the sticker on the back. However, why would that component be present in W1?

Flipping the board over shows some pretty uneven soldering including some partial joints on the purple and gold HP IC next to the copro socket.

Would this have every worked Tony configured like this? The chap who had this machine paid for the upgrade so that he could use the co-pro for his work. I can remove the link and try to see if it boots with the co-pro attached.

gridrunner 25th Jul 2022 10:46 pm

Re: HP 150 Touchscreen II repair
I did notice when fiddling around that it's possible to fit the co-pro board in such a way that it looks as though it's attached, but it's not in fact fully seated. This may explain why it appeared to work earlier, but not if I attach it firmly into the socket (the machine hangs with all diag LEDs lit). Could it be that this chap has had an upgrade fitted for all these years that never actually did anything?! wow..

TonyDuell 26th Jul 2022 5:02 am

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?)

gridrunner 29th Jul 2022 4:42 pm

Re: HP 150 Touchscreen II repair
Hi all,

Just a quick update on this. Removing the link to W1 is now letting the machine boot with the co-pro board installed. I can only assume that the upgrade option the previous owner had installed has never worked in over 35 years. I suppose that if you never had seen the difference between co-pro and no co-pro support, you might not be able to tell if it was functioning or not. It was apparently purchased to speed up AutoCad.

I've stripped down and cleaned the keyboard so the next stage after re-assembly is to get time to look at the hard disk unit.

TonyDuell 29th Jul 2022 4:48 pm

Re: HP 150 Touchscreen II repair
Which hard disk unit do you have? The suffix letters are very important, BTW.

gridrunner 30th Jul 2022 9:53 am

Re: HP 150 Touchscreen II repair
Hi Tony, the model number is 9133D

TonyDuell 30th Jul 2022 12:51 pm

Re: HP 150 Touchscreen II repair
Looks like the controller board is much the same as the one in a 9133H which I have worked on.

What is your hard disk unit doing/not doing?

gridrunner 30th Jul 2022 2:36 pm

Re: HP 150 Touchscreen II repair
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Hi Tony,

On the dust-o-meter I'd rate this unit a 10!

I think I'll clean it up and test the PSU before trying it.
I'll keep you posted.

TonyDuell 30th Jul 2022 4:14 pm

Re: HP 150 Touchscreen II repair
With the double-head floppy drives it is_essential_to strip the disk holder and clean the hardened grease off the latch mechanism. This applies to the drive in that hard disk unit and ones in things like the 9122 dual floppy drive. If you don't, the holder doesn't latch up properly, the upper (down) head catches in the disk when you eject it and can be ripped right off the gimbal spring. I can remember roughly how to do it, if need be I'll strip a spare drive to check.

gridrunner 30th Jul 2022 8:49 pm

Re: HP 150 Touchscreen II repair
Hi Tony, this chap has a YouTube video on fixing this particular issue I think. Does it look correct?

TonyDuell 2nd Aug 2022 5:11 am

Re: HP 150 Touchscreen II repair
I don't 'do' videos for such things. I prefer to read text and see still photos.

I took a quick look at that youtube thing, as ever I got a headache after a minute or so. From what I can see it does cover the issue, but it doesn't do the way I do, which is to dismantle the drive, take the complete disk holder out, then take that apart and clean it up. Note that there are 2 versions of the disk holder, the older one is mostly assembled with E-clip and comes right apart, the later one has levers rivetted in place, there are fewer parts to remove and get mixed up but it is a lot harder to clean off the hardened grease,

If you PM me with your e-mail address I can send you something on this.

gridrunner 5th Aug 2022 7:01 pm

Re: HP 150 Touchscreen II repair
Great news Tony, the floppy drive was serviced and can read disks fine. The hard disk is also working, which is fantastic.

The clip is less than a minute.

gridrunner 5th Aug 2022 7:07 pm

Re: HP 150 Touchscreen II repair
Luckily the grease hadn’t dried up so I was able to clean up the old grease and apply some new, working it into the mechanism. I cleaned the heads with a chamois swab. The power supply has had some slight attention with a couple of capacitor changes. The only question is how to make the hard drive which seems to be drive B bootable. I’m booting off a floppy disk on A. Do you happen to know if the floppy disks are readable in a x86 MS DOS machine?

TonyDuell 6th Aug 2022 4:46 am

Re: HP 150 Touchscreen II repair
The HP150 _is_ an 'x86 MS-DOS' machine and is clearly able to read its own disks. So I assume you mean a PC-compatible machine here.

Normal PC hardware (although not those USB-interfaced floppy drives) is capable of reading/writing the HP150 disks But the format is different and the normal PC MS-DOS won't read them as standard. Back in the day there were various utilities, freeware, shareware, etc to read/transfer files. No idea where to find them now.

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