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Which capacitors to replace?

Posted: Mon Mar 11, 2019 8:03 pm
by Cristian
Which capacitors on QL board are known as typically faulty?

Re: Which capacitors to replace?

Posted: Mon Mar 11, 2019 8:49 pm
by tofro
None. I have four QLs that have their ex-factory capacitors in place and have never changed any of them. The QL also has no such critical places like the Spectrum's DC/DC conversion circuit that tends to wreck all of the memory when caps go bust.

Tobias

Re: Which capacitors to replace?

Posted: Mon Mar 11, 2019 9:50 pm
by Dave
On US QLs, I have had two with failed supply caps. Both times, it was C42, positioned above the right microdrive connector, right by the EC1 port. As a precaution, I recap the 7 caps in that area, plus C4, which site between the ROM port and 8302 on US QLs. They made it 35 years but they may not make it the next 35.

Re: Which capacitors to replace?

Posted: Thu Mar 14, 2019 7:30 pm
by Cristian
Well, since my QLs are non-US, I suppose I can sleep easy.
By the way, do you think a switching type PSU might somehow overtax the capacitors?

Re: Which capacitors to replace?

Posted: Thu Mar 14, 2019 9:02 pm
by Dave
Not at all. Buck regulators about halve the current draw as seen by the caps.

The same cap with the same job is on UK QLs.

IMG_2061.jpg
Top is US.3 bottom is UK Issue 7