Hi All, I really could do with some help here! I retrieved my A4000/030 from the loft a couple of weeks ago. It had been up there for over 25 years. When I opened it up there was signs of battery leakage and capacitor leaks. On powering it up I got a black screen unsurprisingly. Anyway, I identified broken traces and repaired them and it booted. The issue seems to have been broken traces from U177, flip flop IC. I’ve been gradually fixing other issues like no fast ram (now fixed), and I was trying to get the RTC going when I think I had a short between a couple of the traces wires that I had used to repair U177. It now won’t boot, black screen again. I replaced U177 as it was pretty corroded, and replaced all the trace wires, but it still won’t boot. I’ve checked the voltage on all of the pins, which look fine apart from the clock pin which is only reading 0.5V. Unfortunately, I don’t have an oscilloscope so can’t look at the wave pattern to see whether it looks right however 0.5V does seem quite low for a clock signal. I’ve had a look on PCB explorer and it appears that another flip flop IC (U354), and when I measure the voltage on its Clock pin it is also 0.5V. I’m really not sure what this means. Is U354 not working properly or is 0.5V normal for a clock signal? I don’t particularly want to pull and replace chips unless I am pretty sure that they are faulty.
