The Sinclair QL Forum

Hey guys. I finally found myself a QL but it doesn't want to fire up.
When powered on it produces vertical green and red thick bars with random white clocks and black dashes on the screen, no noise from the speaker although microdrive 1 gives a little spin when first powered up.
Pressing f1 does nothing and pressing reset does nothing to the screen although a small click can be heard from the speaker.
I have tried all the removable ic's in a working QL and that continued to work fine.
Is this just likely to be down to a ram issue, will minerva run on a QL in this state and where is the best source for minerva.
I have scoped all the ram chips and they appear to be behaving exactly the same as those in the working QL or at least very similar.
Could it be a multiplexer at fault?
Bit stumped really.
Cheers , Dave.

Hi Dave,

Yes if you've tried putting the ZX8301 chip in another QL and it's working in that one, then more than likely it's an issue with either the DRAM chips or the 3 TTL support IC's - a bus transceiver and 2 multiplexers. You should check for any obvious issues on the PCB, like foriegn objects shorting tracks out, and any possible broken tracks.

If you aren't even getting the 'tweed' pattern, I doubt the Minerva ROM's RAM testing will be able to tell you anything. as the display really isn't working but it does look like it is trying to start up if MDV1 spins.

Check the edge connector on the left hand side of the QL for any bent pins.

How are you driving your monitor / TV ?

Minvera ROM - there's a couple of options for you there - place a wanted add in the forum, but there are vendors who can supply you with the rom/board you need, no doubt they will be in touch soon


Welcome to the forum by the way

Thankyou for that.
Regarding mdv1 spinning up, if I turn the power off and on within a few seconds it doesn't spin up, it has to be left for at least 10 seconds power off.
I have checked for bent pins and also checked that the correct voltages are present. I can't see anything that would pose a problem on the pcb.
It looks like I will need to do more digging.
Thanks again.

just out of interest, which ic's did you swap to the other machine?

Did you do just one at a time, or take them all across ?

daverobzippy wrote:Thankyou for that.
Regarding mdv1 spinning up, if I turn the power off and on within a few seconds it doesn't spin up, it has to be left for at least 10 seconds power off.
I have checked for bent pins and also checked that the correct voltages are present. I can't see anything that would pose a problem on the pcb.
It looks like I will need to do more digging.
Thanks again.

Welcome to the Forum and good luck with this QL.

I'm no hardware expert, so I'll just mention that if your efforts come to nothing (all sorts of QL faults have been sorted with the friendly advice you get from the members here!), Ian Gledhill at Mutant Caterpiller can do QL repairs - see here http://www.mutant-caterpillar.co.uk/sho ... p?cPath=39

Sorry for not replying to this earlier.
There is nothing worse than searching a forum for a solution to a problem only to find the op never put the answer.
It was the 2 ls257 multiplexor chips that were toast.
With them replaced it now fires up fine every time.
Thanks for the help in this.