The Sinclair QL Forum

Hi.

I'm going to try and diagnose a probable memory fault and was wondering, while I wait for some 15ns chips to arrive, if this chip would be suitable for a piggyback diagnosis in the meantime please?

Also, when piggybacking do you put some weight on the chip to hold it in place please? or some blu-tak? I really don't have a clue (as is obvious)

Many thanks
Tony

I think that would be fine. You'll probably have to press it down onto the chip and keep holding when testing - whatever is needed to ensure the connection is good. I've used that method before, sometimes it cures the issue other times it leads to different patterns on screen and sometimes it makes no difference, but it certainly can be quite useful.

Many thanks Chr$, will give that a go

What is the issue though, does Minerva report a RAM problem with an error screen full of large digits?

Green screen on boot (JM rom)

Have you tried booting it with Minerva? That will report some codes and from them you can (usually) work out which chip is bad.

Chr$ wrote: Thu Jan 18, 2024 2:49 pm Have you tried booting it with Minerva? That will report some codes and from them you can (usually) work out which chip is bad.

Hi Chris, I don’t have minerva…

I tried each chip and still get green screen, also tried multiple to no avail

At switch on I get top half of screen showing the twead pattern with black and white stripes below, then it quickly changes to the full twead screen then black for a moment before turning green

Can I order a minerva/tk2 from you please?

Actually slo-mo of the video I took shows it starts with black and white stripes and the tweed pattern moves down until it fills the screen

Screen then blanks and then shows full twead again

Before blanking and going green

This is what it looks like as tweed moves down the screen initially

Hi

I get a deja vu, As mentioned Minerva will diagnose any memory fault.
Others will most likely correct me if I'm wrong, but I would start with the logic circuitry for RAM/ROM and the screen could be the cabling to monitor, do you use RGB?