The Sinclair QL Forum

Okiez. This cannot be my problem though as pressing F1 etc does nothing, so the entire system is failing to boot. I will wait for the clock crystals to arrive and go fro there.

I noticed there is a third clock crystal on the mb near the microdrives - 4.xxx mhz - I assume this is only for the microdrives? That will be for the Colour encoder to make the PAL composite signal. It will be 4.433619MHz, standard for an analogue TV. Ahhhh. Okiez, so if THIS clock was faulty then ...

Ahhhh, didn't think of that. Okiez, will hold off until the clock crystals arrive (had to order them from overseas, but they should be here soon(. Hoping it is a missing clock signal to blame. In the meantime, I tried all the socketted chips from thus dead QL in my working QL and it runs fine - so d...

Thanks Martin, some more good avenues to explore - will start that this weekend and post back results.

Hi Martyn, good call on the oscillator crystals - I had an Amiga 1000 once arrive not working even though it was purchased working and shown as such. Turned out to be the clock crystal which had just died in transit (hard bump or vibration perhaps?). Replaced the crystal and off it went. This QL was...

Thanks Martin. Checked the expansion port - all good. Tested the reset button - all good.

Thanks guys. I will look into the logic probe.

There appear to be no HAL or PAL chips - all seem to be off the shelf logic ICs (which is good in my case - cheap and easy to replace when I find the faulty one).

Please find a picture of the board. Please excuse the quality, I took it in a hurry.

Hi Derek, unfortunately I do not have access to a logic probe so I am going to have to try and test/replace the logic chips one at a time. Which IC is the "HAL" chip (none of mine seem to be marked "hal"), also, can you suggest the order in which I should test/replace the logic c...

Just to add. On one occasion I managed to get a screen full of corruption (coloured lines and blocks) to appear, not sure how, but every other time I still get a sold stable black screen and no activity when pressing F1.

Hi Tobias, thanks for the help. I have checked the voltages on IC25 (SN75188N). Pins 14 and 1 show 12.54v and -12.48v respectively. Strange though, I removed the large heatsink that the 7805 was attached to find the other voltage regulators.... but there are none that I can see other than the two on...