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dave-in-kc · 05-09-2023, 12:59 AM

I picked a 110 (and a portable plus) up recently. I hooked both up to a 6v power supply and the 110 seems to "work" but the screen is garbled. I can navigate to the memo writer and the keyboard works but it alternates characters (pressing "rrrr" gets "2r2r"). I've taken the boards out and cleaned and reseated all cables and chips but no luck. The portable plus machine works fine. Any suggestions?

TallKey · 05-09-2023, 04:14 AM

SWAG:
Faulty display RAM
Failing or failed capacitors

I see a display adapter port on the 110.

Same display problem with the monitor?

Martin Hepperle · (This post was last modified: 05-11-2023 12:18 PM by Martin Hepperle.)

Code:

r   01110010   "rrrr"

2   00110010

     ^ bit=00

a   01100001   "Battery"

!   00100001

     ^ bit==0

It looks like every other byte has bit 6 stuck at zero. Probably not a RAM fault, but in the display addressing logic.

Martin

dave-in-kc · 05-09-2023, 05:48 PM

Well, I dug my old mono monitor out but I'm getting nothing on the screen. I tried it on the portable-plus machine with same results. Is there a switch or setting that's needed to use the external display port on the 110?

dave-in-kc · 05-09-2023, 06:06 PM

I tried attaching a mono monitor to that port but get nothing (same result on the portable plus, too). In reading the manual, it says this is a serial port. I'm not seeing any reference to an external display.

TallKey · 05-09-2023, 07:21 PM

(05-09-2023 06:06 PM)dave-in-kc Wrote: I tried attaching a mono monitor to that port but get nothing (same result on the portable plus, too). In reading the manual, it says this is a serial port. I'm not seeing any reference to an external display.

9 pin female port, some serial, some CGA. Bad old days of computing (my opinion).

Good luck to you in solving the display issue.

dave-in-kc · 05-09-2023, 07:49 PM

Well, thanks for your help. You might be seeing this machine on ebay "as-is"!

Jim Horn · 05-09-2023, 08:22 PM

The HP-110 Portable's 9 pin D connector is a serial port, not a video one. If you wish to have a video display with it, you will need an HP-IL video interface along with two HP-IL cables to connect it, all of which are not very common.

Fortunately, the '110 Service Manual is available with schematics and such. Disassembly for access to the main processor circuit board is very simple once you access the Torx screws on the bottom. I opened mine many times and modified it a lot before giving it away to another Forum member here.

Let me know if you need help - I hate to see these machines not working!

TallKey · (This post was last modified: 05-09-2023 10:29 PM by TallKey.)

Thanks for pointing out the HP-IL interface. This makes the 110 a bit more interesting.

It is not only the HP-IL parts are not too common, the HP-IL video 'adapters' tend towards the 'not too affordable.'

Jim,
Can you comment on the utility of the 110 or 110+ communications with a 41 or 41 peripherals, printer, tape etc?

dave-in-kc · 05-09-2023, 09:54 PM

Thanks Jim, I took the boards out and reseated the chip and cables. But Martin thought the problem may be in the "display addressing logic", which is way beyond my capabilities. Guess I will put it back together and sell it. I'm still glad I bought it!

dave-in-kc · 05-10-2023, 01:20 AM

I took the display apart and found two crusty caps on the board. Not sure if this would cause the screen problems but I will replace them. Tomorrow!

TallKey · 05-10-2023, 01:42 AM

(05-10-2023 01:20 AM)dave-in-kc Wrote: I took the display apart and found two crusty caps on the board. Not sure if this would cause the screen problems but I will replace them. Tomorrow!

It may not be the repair, but it is a negative finding.

Sadly, I have seen much much worse from leaking caps.

Martin Hepperle · (This post was last modified: 05-10-2023 12:19 PM by Martin Hepperle.)

(05-10-2023 01:20 AM)dave-in-kc Wrote: I took the display apart and found two crusty caps on the board. Not sure if this would cause the screen problems but I will replace them. Tomorrow!

Yes, I would surely replace these electrolytic capacitors and inspect the PCBs for damage.

Martin

Jeff_Birt · 05-10-2023, 02:53 PM

(05-10-2023 01:20 AM)dave-in-kc Wrote: I took the display apart and found two crusty caps on the board. Not sure if this would cause the screen problems but I will replace them. Tomorrow!

Definitely need to take care of those caps and corroded traces. If you don't clean off all the corrosion it will keep eating away at the traces.

dave-in-kc · 05-10-2023, 08:49 PM

I replaced those two caps on the display board but don't see any difference. I tested the whole keyboard and attached a photo. I pressed each character 2 times. The numbers and special characters seem to work fine but not the letters.

Any thoughts before I slap it back together?

Klaus Overhage · 05-11-2023, 06:05 AM

As far as I know the display board gets the data to the single picels. The decision how to display a character is already made in the LCD controller board in the lower main part of the computer.
In the Hewlett Packard Journal July 1986 is a photo of it on page 27.
Fig. 2 "Photograph comparing LCD controller board space in The Portable (I) to the size of the 25-line LCD controller hybrid used in the Portable Plus (r)."
https://www.hpl.hp.com/hpjournal/pdfs/Is...986-07.pdf

On Page 25 the is this sentence "To support a full screen of graphics, it is necessary to have more memory than the single 64K-bit static RAM used in The Portable."
Maybe this 8 kByte RAM or a connection to this board causes the problem.

Martin Hepperle · 05-11-2023, 12:25 PM

(05-10-2023 08:49 PM)dave-in-kc Wrote: I replaced those two caps on the display board but don't see any difference. I tested the whole keyboard and attached a photo. I pressed each character 2 times. The numbers and special characters seem to work fine but not the letters.

Any thoughts before I slap it back together?

As already noted above: bit 6 seems to be zero all the time.
All characters that have bit 6==0 are displayed correctly (everything up to the ASCII question mark).

This could be due to a logic chip fault or a broken trace. You could first ring out the path of data bit 6 , and later try to trace signals with an oscilloscope to find out, where the fault enters the chain. It may well be that the bit is never written to the RAM so that the fault lies somewhere upstream, e.g. in the bus drivers/buffers.

Martin

Jeff_Birt · 05-11-2023, 12:40 PM

(05-10-2023 08:49 PM)dave-in-kc Wrote: I replaced those two caps on the display board but don't see any difference. I tested the whole keyboard and attached a photo. I pressed each character 2 times. The numbers and special characters seem to work fine but not the letters.

Any thoughts before I slap it back together?

This sort of looks like a stuck bit problem. Presuming they used standard ASCII encoding for characters the alpha characters start at $40 (with @ symbol, then $41 is A) and continue through $7F (actually $7B-$7F are { | } ! ).

If you were to type 'a' ($61) and bit 6 stayed low you would get $21 which is '!'. This does not look exactly like what is showing up on your LCD but perhaps something similar.

ThomasF · (This post was last modified: 05-11-2023 01:39 PM by ThomasF.)

(05-11-2023 12:40 PM)Jeff_Birt Wrote: If you were to type 'a' ($61) and bit 6 stayed low you would get $21 which is '!'. This does not look exactly like what is showing up on your LCD but perhaps something similar.

As already mentioned before, this seems to be exactly what happens.

All numbers and ":;<=>?" (column 3) shows up correctly (since bit 6 is low (0x30-0x3F), actually all characters from column 0-3 shows up correctly, but all characters in column 4-7 (ie 0x40-0x7F) is shown as from column 0-3 (ie. 0x00-0x3F) instead.
So "qwerty" in the attached picture is shown as "17%249", and line 2 should be read as "Line: 4 Column: 21".

But the interesting part is that this only applies on every other character.
If we have a 16-bit bus, then 1 stuck bit could show up like this, but not with an 8-bit bus.

If RAM is collected from two different chips or dies (ie even bytes from one and odd from another), then we might also explain it, but it only seems to apply to the display (not RAM in general).

Anyone has schematics for the HP110? Service manual? It might give a clue ...

Just my 2 cents ...

Edit: Answering my own question ...

I found schematics on this site (where else ... ?): HP110 documents

Page 14 (of Tony Duells schematics document) shows the LCD-driver, and there is actually a 16-bit to 8-bit latch here.
The latches (82C82 - U11-12, U23-24) latches 16-bit data down to 8-bits to the LCD.
So if I had the device in my hands, I would check the pins for bit 6 or bit 14 on these, and if you are lucky you will find a bad solder or something that shorts any of these pins.

Good luck bit-hunting!

Cheers,
Thomas

Jeff_Birt · 05-11-2023, 02:07 PM

(05-11-2023 01:25 PM)ThomasF Wrote: All numbers and ":;<=>?" (column 3) shows up correctly (since bit 6 is low (0x30-0x3F), actually all characters from column 0-3 shows up correctly, but all characters in column 4-7 (ie 0x40-0x7F) is shown as from column 0-3 (ie. 0x00-0x3F) instead.
So "qwerty" in the attached picture is shown as "17%249", and line 2 should be read as "Line: 4 Column: 21".

What is the Line/Column nomenclature you are referring to? I have not come across this before. In most of your explanation the 'column' seems to be the high nibble. I would assume then that 'line' refers to the low nibble. When you say "Line: 4 Column: 21" though I have no idea.