SOS My QL is dying

[Qampero]

Recently, I recovered a QL. A few days later, it started crashing at startup, and now it doesn't work at all.

The symptoms are as follows: when I connect the power supply, the video pattern appears on the screen, but unfortunately, it never completes. At the end of the random pattern, a white strip appears at the top of the screen, while the rest of the display remains in a random pattern. And that’s it—no further response.

It doesn't respond to the reset button. Occasionally, it reaches the F1/F2 screen, but the keyboard doesn't register any input, and it still doesn’t respond to reset.

Before replacing any ICs, I’d like to confirm where the fault is. Unfortunately, I currently only have a multimeter and a 200kHz oscilloscope.

Does anyone have any suggestions or ideas?

Thanks in advance!

[techy]

Start by re-seating all ic's , and verify if the 68 is warming up .

be very carefull when lifting them !!

[jobdone]

Which Rom are you using? I think my first thought is ZX8302 that would cause all those issues.

[Qampero]

Thanks! My QL has a JM ROM and it's an Issue 6 board. I’ll try replacing the 8302—fortunately, I have a spare one.

I suspect there may be a bus-related issue. The last time I powered it on, after the random pattern appeared, it made some unusual noises and displayed a vertical pattern before crashing. Also, the microdrives activate randomly during startup, which doesn’t seem normal.

I think the 8301 is working, since the graphics appear to be generated correctly—VSync, HSync, and all video signals are present.

[Qampero]

I’ve replaced both the 8302 and the 8049. There's been a slight improvement—now it occasionally manages to boot, and sometimes even responds to the reset button.

However, after a few seconds (no more than 5), the system starts to degrade and eventually crashes, showing random values in memory (and video, of course) and becoming unresponsive again.