"Jules Richardson" wrote in message
...
On Thu, 14 Mar 2013 21:42:25 +0000, Ian Field wrote:
Open it and look for bad caps by the power supply.

That's all I've ever had to replace on a Mag.

Good place to start

Well... it is looking like caps. There weren't any that were showing
visual signs of failing, but then of course that's often the way. Sadly
my ESR meter's 4,500 miles away (so I've put it on the to-do list to buy
another).

Anyway, I've replaced the PSU's main smoothing cap and those on the
outputs of the 104V and 52V lines using parts from the junk box (which
aren't necessarily in the best of shape themselves!), and - so far - that
seems to have just about cured things; there are some *very* slight signs
of picture instability when scrolling display contents, but far better
than before and certainly at a level that I can put up with. I'll give it
a week or two and if it's still OK I'll order some new replacement caps.

Its worth seeing how many caps run hot after replacement as well as when
determining which ones need to be replaced.

The ones that get hot obviously won't last long - sometimes you can take the
edge off the ripple current with a polycarbonate on the print side (in
parallel with the electrolytic).