30 Jan
2012
30 Jan
'12
4:50 a.m.
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.
30 Jan
30 Jan
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.
31 Jan
31 Jan
11:53 a.m.
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
Ditto. In fact many of mu classic computers (some are 40 years old) are
running on all their original electrolytics.
Of course I've replaced some aluminium aleectrolytics over the years.
I've also replaced tanatalum electrolytics, fetal film capacitors,
resistors, signal diodes, rectifier diodes, transsitors, simple ICs, LSI
ICs, switches, connectors, etc, etc, etc. I don;t find that aluminium
electrolytics are the problem that soem make them out to be.
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
Tektronix used to say that the best tube tester (valve tsster to me :-))
was the circuit the valve was usewd it. If it works correctly, the valve
is good. If it doesn't, the valve may be the problem. Replacing valves
that a conventional tester says are below par won't cure all probems, and
may introduce problems. Similarly a valve tester may not pick up the
reason a valve fails to work in a particular circuit that requires some
particualr porperty.
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.
If a cpaacitor could cause more damage if it fails (either electrically
or mechancially (say it'll hit somethign deleicate if it blows its top
[1]), then I'll test it and change it. If not, then I'll only change it
if it's causing problems.
[1] A concrete example that applied to me. The 2 mains smoothing
capacitors in myh HP120 CP/M machine were 'doming' on top. They tested
fine, but they're physically located on a pCB alongside the CRt and if
they blow up, they are likely to hit the CRT neck. Since gettign a
repalcemetn CRT is non-trivial, I replaced the capacitors before anyhting
happened
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
Yes. You may be 'prefect' and never fit the wrogn part, and never make a
dry joint. You may also be lucky and enver get a defective new component.
For the rest of us living in the real world, it seems better not to
change things unnecessarily.
If you ware worried about the reliability of the old capacitors, then
IMHO it's better to get the thin working properly first (changing any
capacitors that you have to), and then change the others one seciton at a
time and test the machine after each set of repalcements, Then if there's
a mistake soemwhere you'll know where to look. But I think you're wasting
time and money to repalce working capacitors in such amchines.
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.
Agreed... I find it strange... When I learnt faultfindign all those years
ago, every book told you to _think_ about it. To make measurements and
deduce waht the problem is. Nowadays I somethimes think I'm the only
person left who does that. But since it works for me (and other methods
most certianly don't), I am not changing.
I ahve no idea whay the standard method changed, but if I ever find the
idiot who came up with it, I'll be tempted to insert a logic analyser
rectally...
-tony
4:19 p.m.
On 31/01/12 19:53, Tony Duell wrote:
I ahve no idea whay the standard method changed, but
if I ever find the
idiot who came up with it, I'll be tempted to insert a logic analyser
rectally...
Ugh, that would be downright cruel.
To the logic analyser.
I mean... the only LA I'm aware of which would stand a chance of fitting
would be the HP LogicDART, and I can think of far better uses for one of
those.
Now a DSO-Nano on the other hand... XD
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/
1 Feb
1 Feb
1:21 p.m.
On 31/01/12 19:53, Tony Duell wrote:
I thoguth there were some USB instruemtns that claimed to be logic
analysers... One of those might be a sutiable enema :-)
And I didn't say how hard I was goign to force it in. I am sure either
myu K100D or HP1630 could be used for this if pushed hard enough. And the
instruemtns won't mind (I've sat on both of them without problems...)
I ahve no idea whay the standard method changed,
but if I ever find the
idiot who came up with it, I'll be tempted to insert a logic analyser
rectally...
Ugh, that would be downright cruel.
To the logic analyser.
I mean... the only LA I'm aware of which would stand a chance of fitting would be the HP LogicDART, and I can think of far
better uses for one of
those.
Oh so can I. I use mine almost every day,
Actually, I noramly use it in the single probe 'investigate' mode where it
acts as a voltmeter, frequency meter and a logic probe with the ability
to capture the waveform. The 3 channel 'analyse' mode sure is handy
though. But I rearely use the continuity tester mode.
-tony
4659
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