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Old 11th Jan 2021, 6:31 am   #79
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Join Date: May 2018
Location: Northampton, Northamptonshire, UK.
Posts: 649
Default Re: Non-working Commodore PET 3016

Originally Posted by ScottishColin View Post
Hi all - apologies for dropping off for a few days - a few issues at home. I intend to go through this whole thread and re-do what I have done as I am starting to get an intermittent 1.00Mhz reading on UG5 pin7, but it is intermittent.

I will do some more careful cleaning as I cannot see any obvious shorts. I fear I may have a dry joint somewhere that may be beyond me.

I will go through the thread and hopefully report back tomorrow or Tuesday.
With a > 1 layer thru-plated PCB, Dry-joints are very unlikely. And it's also much less likely to have joints crack with time / heat-cycles etc. with these.
So any intermittent connections are more likely to be with connector contacts - especially if not gold-plated or that tight, but usually re-mating a few times sorts it out (at least in the short-term).

The could be a cracked passive component, but much more common with surface-mount, and quite rare on a fairly-rigid PCB with leaded parts.

I have seen crystals become a bit intermittent (especially if leads get pulled), but you have to be careful that 'scope probe capacitance doesn't stop them oscillating (probe on x1 will usually cause this)
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