UK101 Resoration

[Mike52]

As mentioned in my introduction, over the coming weeks I intend to restore my Compukit UK101 to working order if possible, it may take a long time as I have other ongoing projects.

The UK101 was packed up and put into storage in the mid 1980's in fully working condition, and has not been seen for some 30 years.

It had over several years been heavily modified, Original monitor MONUK01, then a modified version MONUK02, then a replacement from a company called Watford Electronics, called WEMON. A home made 16K RAM & ROM memory expansion board, and eprom programmer both built on euro-card sized boards, sadly these were disposed of years ago.

Whilst I had the eprom programmer I took the opportunity to 'future proof' the UK101 by building binary images of all the BASIC and MONITOR roms/eproms as well as the character generator. It's a good job I did this, read on ...

Some of the silicon from the 1980's does not seem to have survived very well, as when powered up the UK101 gives the normal screen full of miscellaneous characters. Pressing the 2 reset keys however does not result in any change to the display, however this proves some of the video circuitry is working. Monitoring the reset pin on the CPU results in a valid reset. The CPU has the correct 5v supplies and a 1 MHz Clock, but no data on the address lines.

Replacing the 6502, and removing all but the first 2 2114's now give data on the clock and address lines for a few seconds after reset whilst it does a partial screen clear then the unit goes into limbo.

I have removed all of the roms/eproms and checked their contents using an arduino mega and a small sketch wired as a reader. Alas WEMON is deceased, the checksum does not match the original . My next move is going to be returning the UK101 to its original spec with the MONUK02 rom (if I can find it, if not program a 2716 and swap the 2 select links). It should be easier to fault find after removing all the modifications.

I have recently found the WEMON manual and fitting instructions, created a pdf, and sent a copy to Steve Gray. I have given him permission to pass it onto OSIWEB.ORG for archiving after he has changed its format ( it is currently some 39MB due to me having to scan it at 600 dpi because of the poor quality of the original, it seems to be a photocopy of some typed pages, and hand drawn diagrams).

If you would like a copy of the rom images for archive purposes I can supply them.

The saga will continue ...

Regards,
Mike.

[bxdanny]

Yes, please post the ROM images that you have. (Actually, I have copies of the MONUK01, MONUK02, and CEGMON ROMs, but not of WEMON.)

[Mike52]

Update.

I have now removed all of the previous modifications to the pcb returning it to its original condition, cleaned all of the IC legs, found and fitted the original MONUK02 rom after checking it's contents were still correct using an arduino mega.

The ROM appears to be a 9316 or similar device, unfortunately the TOP 853 eprom programmer that I have access to does not handle this type of device without some sort of adapter, so it's less trouble to use an arduino and a patch board.

At switch on the normal jumble of characters appear, and about every 3rd or 4th time I reset the board,
the normal prompt is obtained.

So far so good, but it seems I have another problem that will not let the board reset correctly.

However if the board is operated upside down, it resets correctly more often. This leads me to think that there may be a problem with an IC socket, poor soldered joint, hairline crack in the print somewhere, or an intermittently shorted key switch.

As requested by * bxdanny * I have attached the UK version of the WEMON ROM, I will post the other files when I can retrieve them from a 5.25" floppy (IBM version not OSI)

To be continued ...

Regards,
Mike

[MK14HAK]

Good luck. Hate those intermittent faults. Any corrosion on the board?

[bxdanny]

Thanks, Mike52. I mainly had two questions about WEMON, namely whether it supported booting from an OSI-type disk (the answer is no, at least not without an additional ROM at $9800), and whether it was basically a clone of CEGMON (the answer is definitely not, so I guess Tom Graves, one of the CEGMON authors, was thinking of some other ROM in the article at http://weblog.tetradian.com/2014/03/16/ ... -the-past/.) I found a review of WEMON online yesterday (in the form of scanned pages from a magazine, not OCR'd), but I can't seem to find it again now. Anyway, this was 4 kB ROM mapped at $F000 that required moving the ACIA to $E000. And if the review was accurate, it really had a full-screen editor of the sort found in Commodore and Atari 8-bit computers (and in GWBASIC). Interesting.

[Mike52]

@MK14HAK.
The board looks in remarkably good condition for its age, no corrosion or damaged tracks that are visible.

@bxdanny.
I have supplied Steve Gray with a pdf of the full wemon installation and instruction book, he is going to try and reduce the file size when he returns from his vacation, and then post it on this forum.
If that fails, I'll pass it on to Dave in its original form.

I have recently started to disassemble the file and comment it with the subroutines and other information available in the book. Most of it goes over my head, as I am a hardware guy, software is not one of my strengths. Who knows, someone may be able to make sense of it.

Regarding the disc boot option, this was only a jump into another ROM that was part of a package *designed* by Watford Electronics, where they were aiming to sell an expansion board similer to the 610 board but with a disc interface of a different design. I originally had one on order, but cancelled it due to the lack of its appearance after 6 months. I don't know if they ever got past the prototype stage.

Regards,
Mike

[Steve Gray]

Yes, i recieved the manual and now that i'm back from my vacation i will try to clean it up a bit for posting. I was sent wemon several years ago and planned to disassembe it, and maybe port it to c4p, but sadly never got a chance to look at it. Only now have we discovered the binary was incomplete. I'm glad its been found!

I have experience with the commodore screen editor code so maybe i can help with the disassembly.

Steve

[Steve Gray]

Ok, I cleaned up the WEMON manual and made a new PDF, zipped it up along with the binary and magazine review PDF.
I have sent it to Dave so hopefully he can make it available here soon.

Steve

[Mike52]

Hi everyone, a further update.

In order to narrow down the problem with my UK101, i have removed every IC on the board, cleaned the IC legs, cleaned and re-tensioned any sockets where the contacts seemed poor, refitted the IC's and retested.

Regretably the fault is still present. Time to try a different approach. Remove all of the basic roms, and 2114's.

I then programmed a single 2764 with a combined image of the four basic roms. Hardwired this and a 6264 8K x 8 ram chip on a breadboard along with a pair of 74ls138's for address decoding, directly to the 6502 pins on the reverse side of the UK01's board.

Powered the unit up again, only to find I was left with the same results.

At least I am narrowing the fault down and may not yet know what the fault is, but at least I know where the fault isn't.

During my working career I have always found intermittant faults the most annoying type of fault to locate , so I am not surprised that this is not going to be an easy fix.

My next move will be to investigate the keyboard / keyboard scanning circuitry etcetera.

To be continued ...

Mike

[Jeff]

Mike, just to be clear, the fault you're having is that the board doesn't always reset. Or could you please describe fault you are experiencing.

/Jeff