30 Jan
2012
30 Jan
'12
9:46 a.m.
Peter Coghlan wrote:
Most of my experience is with arcade video game monitors - we used to
analyze problems to try and determine which component was failing,
however in 99% of the cases it was one or more capacitors. So we came to
the conclusion that replacing all the electros saved a lot of customer
repair billing and fixed almost every monitor that came through.
In most cases modern monitors (ten to fifteen years old) can be
troubleshot to only a couple of bad caps quickly, but everything else
gets new caps as this has proven to reduce future service calls - if we
used good quality and proper types on monitor power supplies and
horizontal/vertical outputs.
We have been servicing games in our part of the world since the 1970s
and got tired of seeing the same ones back in every year or so. Since
replacing the caps we now only see the game once every ten years or so.
Mind you this was for games that are on for 8 to 12 hours/day, 5 - 7
days a week...
John :-#)#
With anything
over about ten years you start by replacing electrolytic
capacitors. If you want to test instead of shotgun then pick up an ESR
meter, but it usually shows more than a few are failing. If the monitor
is over twenty years old, then just replace all the electrolytics and
then troubleshoot - it there is still a problem that is.
I don't think I've got anything less than ten years old. I can't remember
having cause to replace more than an occasional electrolytic here and there
except in the case of a television from the 1970's which has required about
five or six over years of heavy use.
I'm sure if I checked everything with an ESR meter it would show up a bunch
that are below par. However, many applications for electrolytic capacitors
can tolerate very large variations and they may well have years of usable
life left in them even though the meter condemns them. There may be a case for
checking critical capacitors in power supplies etc which may be at risk of
overheating or leaking, however there is no reason to check every electrolytic.
I think replacing large numbers of electrolytics is likely to be be more
trouble than it is worth and may even introduce new problems that weren't
there before, particularly on old pcbs where the print was never well stuck
to the board, even when new. Far better to look for a schematic if available
and wade in with the scope looking for the problem with deductive reasoning.
Do take care to match the caps to the job they do
- low ESR caps for the
horizontal, and caps that handle AC ripple for the linear power supplies.
I will agree there.
Regards,
Peter Coghlan.