ICL OPD 3 vertical white stripes fault

[Chr$]

Just got my Merlin Tonto out to try out Stephens' C1 disk interface clone. I didn't get as far as plugging that in though, as I get a chequered pattern and then this screen with 3 vertical lines on boot:

It was working a few months ago when I packed it away.

Likely RAM issue? I can't find any info that mentions 3 white lines as a diagnostic aid. I had a spare CPU so swapped that, no difference. I pushed down on the socketed chips and also removed and re-plugged the daughter board, no difference. I felt the chips to see if anything was unusually hot - it wasn't. I piggybacked a 4164 RAM chip on each of the soldered RAM chips, minor pattern changes occasionally, but no real difference, still 3 vertical bars.

[stephen_usher]

Here are the diagnostic stripe meanings. I'm pretty sure I posted them elsewhere.

Three stripes = "Data Registers" whatever that means. Maybe some flop-flops somewhere?

[Pr0f]

I'm wondering if this is a fault with ZX8302 (9v battery) power circuit?

[Chr$]

Thanks. I did try unsuccessfully to find that info...

Hmmm, data registers.

I happen to have a spare NOS main board, so swapped them over (using the same daughter board) and the 3 stripes are still there exactly the same, so that's either a coincidence and both main board have the same issue or it points to something on the daughter board.

As a sanity check to remind me - to boot, the telephony module needs to be plugged in but the ROM packs and 9v battery don't have to be attached (I seem to remember the OS reports an error when there is no 9v batt attached). How vital is the small 3v cell on the main board?

[stephen_usher]

You need the ROM pack and the telephony module to fully boot, it will hang at a blank screen otherwise. It doesn't matter about the 9V battery, that merely keeps the real-time clock going.

The 3V battery keeps the "Permanent Store" SRAM energised. It isn't required to be OK. If the contents are corrupt the OS will give an error message and clear it, but that happens well after three bars.

The screen stripes are set a very early part of the boot sequence from what I've seen. Three stripes happen even before the memory test, as do the ROM CRC checks. I hope it's not the ULA on your CPU board that's gone bad.

[Chr$]

Some progress...

I had a spare NOS daughter/CPU board but that was just giving me a black screen. I tried various combinations of ROM chips (ICs 4-7) and with one combination it gets much further but goes into a boot loop, thus:

Chequer pattern
Black screen/white screen a couple of times
Vertical stripes with some colour
White thick vertical stripes

Then very briefly (I had to video it and pause the video to read it) it flashes up with:

INITIALISATION
(c) ICL 1984
SYSTEM RESET AH3V
(at bottom) a Date and time

and then it repeats that process. And it does the same using the other daughter board with the same ROM combination.

No idea what 'AH3V' means. I wonder if the ROMs are dying and/or the single-wipe sockets are crap. Has anyone got known working dumps of ICs 4 - 7? I did dump them a while ago but no longer trust them now as they were from the board that just resulted in a black screen. Then I will 'burn' all 4 twice onto 27C512 EEPROMS and see how that goes. I don't have enough 27C256's.

That other larger chip on the daughter board, that's the speech synth chip isn't it, I don't think that's too critical and as I have the same fault using both daughter boards I mean it must be something ROM related or a massive coincidence.

[Pr0f]

Seems odd you get a ROM fault when it had worked before you put it into storage. I noticed that on both my daughter boards - 3 of the ROM chips are mask ROM's and the last one closest to the processor - the one that's in position '7' of the LS137 decode at address 0xA8000 - is an EPROM. It would be the only one of these who's contents could degrade over time. It's ROM D in the documentation.

The only other thing to try would be to remove / clean and reseat the chips - but the sockets seem quite tight on mine.

[stephen_usher]

If the ROMs were damaged then you'd get 4 lines as this is when they fail their CRC check.

If it's getting to the Iinitialising page then it's actually booting "fully" before resetting. i.e. it's passing the power on tests, including memory test (but this is rudamentary at best).

I would reseat the ROM pack at this point. It's possible that the ROMs in the ROM packare having issues. You would get a blank screen witout the ROM pack connected.

However, it could also be a memory fault as the memory test is similar to the QL's from the look of things and that could miss addressing errors and the like.

[Chr$]

Thanks for the suggestions. After much re-seating, cleaning etc, I do sometimes get a different message:

INITIALISATION
(c) ICL 1984
SYSTEM RESET AHPk
(at the bottom) AA CTRL - FAIL

Then that message goes away but the bottom AA CTRL - FAIL remains and it says 'Loading saved store', then it resets itself and that's as far as it ever gets.

AHPk? AH Pack? AA CTRL?

In the 2 daughter boards I had a mixture of PROMs and EPROMs. The 'working' configuration is now made up of 1 EPROM and the rest are PROMS. I did notice some hazy traces and solder due to the battery leaking down the wires on onto the m/b. I've checked everything I can, re-touched some solder joints etc and it looks ok. There was also corrosion on the rom pack m/b pins, nearest the battery connection, so I scratched/cleaned that off and have verified by testing from m/b to the ROM pack that all connections are good. I also read the ROM pack ROMS and they all match the saved data that I saved from them a couple of years ago (one is EPROM, the rest PROM).

With the mostly working daughter board and the other (NOS) m/b it always goes white then presents 5 bars indicating SRAM issue. So I'll assume that board has an entirely different issue.

[stephen_usher]

SRAM issue I found on my machine was the lack of the POWER-GOOD from the power supply, listed as "shutdown" on the pinout.

Check VCC (from the 3V battery) and /CE (from PSU via MOSFET on the left of the board) on the SRAM chip.