The Sinclair QL Forum

Hi I have a QL connected to a monitor with a composite out, after some time when it gets warm the picture turns B/W and the picture starts moving up or down while displaying black horizontal moving lines. When I press reset the computer continues to do the same while if I unplug it then everything comes back to normal.
Any ideas will be greatly appreciated.
Tassos

It "smells" like the MC1377P video out ic.

Is there any way to make sure that the MC1377P is the problem before I start desoldering ?
Tassos

I think that MC1377P is placed in ic socket.

Is there a possibility to be the Z8301 (IC22)? from what I remember it was notorious to break down.
Tassos

cybervet wrote:Is there a possibility to be the Z8301 (IC22)? from what I remember it was notorious to break down.
Tassos

Yes, there is!

Also test the supply voltage that feeds the MC1377P

Mark

Hi,
a poster in the German forum said she solved a video problem (no video at all) with replacing C23 C24 and C25. Those Cs have the nasty habit of leaking their electrolyte shortly after the box is out of warranty.

Your symptoms, however, look more like a faulty ZX8301 to me, mainly because your video circuitry seems to be losing sync after some time.

Another thing to check would be:
If your QL looses sync, does a (blindly) typed 'dir mdv1_' still whirr a drive? If no, it's most probably the ZX8301, if yes, that hints towards the rest of the video circuitry.

Regards,
Tobias

Thanks for the replies I will check the mdv1_ trick next time it does it and let you know what it does.
The strange thing was that was not doing it from the beginning, only after it was getting warm and then after unplugging the power cord and re-plaging it immediately was back to normal again.
Tassos