Sinclair ql black screen

[martyn_hill]

'Proclivity'!

That must win our Word of the Day award, Dave!

Those darn 2-tone CPU sockets... How many have I trashed!

[Pr0f]

It would have been interesting to see how many QL's had to be repaired because of 'dodgy' chips, and compare with the cost of socketing some of the more common chip failure areas - in other words - was it worth the cost saving

I can see why the ROM's were socketed - but even there - Sinclair missed a trick by not following completely the JEDEC standard - so although each socket does actually provide 64K addressing - you can't just throw a 27512 in the socket and be done with it.

[Derek_Stewart]

Hi
I have replaced IC 21 today and all is good and now working fine It is a shame that I did not replace it before I ordered the replacement ram but it might come in useful in the future.
I would like to thank all those who have took the time to try and help me I would not have been able to get it working without you.

Hi,

Great news on repairing your QL.

Did you fit a socket for IC21?

I am updating the QL Service Manual, and trying to expand the fault finding section.

I have draft flow chart of action to take to find faults on the QL.

If you have time, could you briefly list the actions you took to find the fault?

[Traindriver69]

I did order some new memory thinking that it was a possibility what was wrong but on looking at the replys to my request one stated he thought IC21 was at fault so I ordered a replacement and did socket it as why would you not as if it failed now why would it not fail in the future.

[tofro]

I did order some new memory thinking that it was a possibility what was wrong but on looking at the replys to my request one stated he thought IC21 was at fault so I ordered a replacement and did socket it as why would you not as if it failed now why would it not fail in the future.

Bus drivers and memory are indeed the most failure causes on QLs.