Hello,
i see that You have a lotz of experience for repairing QL Computers.
Can You please take a look of this picture?
http://www.mediafire.com/view/t3qe1al898ilqh7/QL.JPG
My QL gone broken and Insert of Minerva rom doesent help me further to diagnose it.
All i know that the 74LS245 is ok, and it doesent seem to be a ram fault. I’ve took a working QL from my friend, and tested ULAS, CPU and all chips, all work as it should on other computer so im stuck and need a little help..
with best regards,
Viktor

@xAD / nIGHTFALL
Hello and thank You very much for Your reply,
Yes, it was first iv’e checked, i have replaced it with new one, i noticed, that one capacitor (470uF) was burned out, thick one under the Heatsink, so i replaced it, ive checked the power on RAM & ROMS, it is 4.9v on VCC so i think there is nothing wrong with power circuit.
also i have got a Minerva rom from Rich, to make a RAM test possible, but installing it makes any difference – i see same squares, no changes. there are changes when i start the QL without ROM chip – i have black screen then, with no squares.
I forgot to say, it is a Issue 5 motherboard, and actually i have buyed it broken, so i dont realy know what exacly previos owner have done with it. I see that there are some changes and modifications done. IC17 is removed, the JU2, JU3 and JU4 are dridged, and JU1 & JUt5 are removed. I realy stuck and i don’t know where to start, i have many ZX Spectrum repairing experience but i have not repaired QL’s till now…

Ciao,
Repairing two MDV units, due to faulty R/W heads, one head replaced with a spare salvaged from otherwise dead units. I am looking for one more head. Can be extracted from faulty QL/ZX drives. Should measure 16/16/96 ohms across 2xRead a 1xerase coils.
Can you help?
Grazie tanto.
T.

I have a ql. that when i plug it into the monitor the screen says f1 for f2 when I push the monitor its not working the tv works i think the color is off though? do you fix them still?