Search found 225 matches

by Erm
Mon Nov 23, 2020 5:42 pm
Forum: ZX Spectrum Lounge
Topic: 128k +2 Mysterious Videos issue.
Replies: 36
Views: 17651

Re: 128k +2 Mysterious Videos issue.

Fixed! It totally was the 40058. It now has the PCF1306P fitted... which is of course even older than the original, but that's fine, there's a socket in case that dies.
by Erm
Mon Nov 23, 2020 2:12 pm
Forum: ZX Spectrum Lounge
Topic: 128k +2 Mysterious Videos issue.
Replies: 36
Views: 17651

Re: 128k +2 Mysterious Videos issue.

The multiplexer for all the DRAM chips is IC10 (which goes by one of these part numbers depending on when it was made: PCF1306P, ZX8401, 40058). Mark Aha. I do actually have a broken issue 6A 48k board that had an issue and I've been using as spares. It has it's PCF1306P present, but obviously I do...
by Erm
Mon Nov 23, 2020 1:04 pm
Forum: ZX Spectrum Lounge
Topic: 128k +2 Mysterious Videos issue.
Replies: 36
Views: 17651

Re: 128k +2 Mysterious Videos issue.

With my 'scope out I had a look at the ram address lines. The top row (IC17 - 24) all have nice square activity (the top row in the pic below). The bottom row (IC25 - 32) shows weirdness, not proper square waves and some that peak in the middle somewhere, neither high nor low (bottom line in the pic...
by Erm
Sun Nov 22, 2020 10:44 pm
Forum: ZX Spectrum Lounge
Topic: 128k +2 Mysterious Videos issue.
Replies: 36
Views: 17651

Re: 128k +2 Mysterious Videos issue.

I just tried the Brendan Alford diagnostic ROM and the screen is illegible and then there are all 8 red bars in the border. Deary me.
by Erm
Sun Nov 22, 2020 10:06 pm
Forum: ZX Spectrum Lounge
Topic: 128k +2 Mysterious Videos issue.
Replies: 36
Views: 17651

Re: 128k +2 Mysterious Videos issue.

Can you burn EPROM chips? Mark Yes. You think it's the ROM? Or you mean to burn a diagnostic ROM? I do actually have the original saved ROM data somewhere. I have the plug in DiagRom and that is obviously more focussed on 48k models but I did manage to get through to the 128k menu and it reported a...
by Erm
Sun Nov 22, 2020 5:27 pm
Forum: ZX Spectrum Lounge
Topic: 128k +2 Mysterious Videos issue.
Replies: 36
Views: 17651

Re: 128k +2 Mysterious Videos issue.

I swapped all the RAM (fortunately I'd socketed it all a while ago as this is my main tinkering Spectrum) and that changed nothing. I checked all the original RAM in another Spectrum and it seemed fine. When I start it I get variations of this: 20201122_172121_resized.jpg Sometimes there are a lot o...
by Erm
Sat Nov 21, 2020 11:52 pm
Forum: ZX Spectrum Lounge
Topic: 128k +2 Mysterious Videos issue.
Replies: 36
Views: 17651

Re: 128k +2 Mysterious Videos issue.

Well it certainly fixed the screen using an original PSU for now, but I seem to have done some damage to something else now as I get random patterns and junk on the (perfect) screen! Going to have to investigate.
by Erm
Sat Nov 21, 2020 2:53 pm
Forum: ZX Spectrum Lounge
Topic: Dumping Microdrive Cartridges reliably.
Replies: 0
Views: 2131

Dumping Microdrive Cartridges reliably.

No, not actually dumping them in the bin, but dumping the contents of them properly, i.e. sector by sector to make an exact duplicate of the original.... I have a vDrive ZX which is probably the most convenient way of copying data from original mdvs to an SD card (and then to a modern computer) but ...
by Erm
Sat Nov 21, 2020 2:48 pm
Forum: ZX Spectrum Lounge
Topic: 128k +2 Mysterious Videos issue.
Replies: 36
Views: 17651

Re: 128k +2 Mysterious Videos issue.

Today I had nearly the same problem with "crawling dots scrolling over the screen". Tested an ZX Spectrum Issue 6a PCB. But an other Speccy, wich worked fine before also shows these dots. I used an adjustable bench top power supply and after I took an other power supply every thing works fine. Seem...
by Erm
Wed Sep 30, 2020 8:37 pm
Forum: SALES
Topic: RS232 Interface (8255 Chip) £30
Replies: 7
Views: 9462

Re: RS232 Interface (8255 Chip) £30

YannFr wrote: Wed Sep 30, 2020 8:44 am Hello,

I'm interested by your card, could you contact my PM to discuss about it?

Thanks
Yann
Done that.