"James Sweet" wrote in message
news:FUphf.6802$Dx3.4099@trnddc07...
Arfa Daily wrote:
"SeventhPrince???" wrote in message
oups.com...

Did the measurement. All the rated voltages come out good.



This should have been your first check, as it would seem to indicate that
the supply is good, however, with a switch mode power supply, you can't
toatally declare that to be the case, without one further check.

Whilst the voltages may APPEAR to be correct, when measured on a
multimeter ( anolog or digital ) they must also be checked for switching
hash using an oscilloscope. It is common to see peak to peak noise as big
as the DC level of the rail, caused by poor electrolytics on the
secondary side. Microcontrollers, and other circuit sections, will not
tolerate this sort of disturbance on their rails and reset lines.

Judging by the observations you have made regarding low value / voltage
electrolytics on the primary side of the supply, you have been trying to
make use of the advice that I offered another poster further down the
list, who was having trouble with an external tape drive PSU. The advice
that I was giving there, related to a dead switcher with no fuse blows.
You will also have noticed that I said to check the electrolytics with an
ESR meter, as James has also said.

If you do not have an ESR meter, or do not know what one is, I would
suggest that you Google the subject, and acquaint yourself. If you intend
to go on trying to repair switch mode power supplies without one, you
will consistently fail. It is the single most useful item of test
equipment that you can have in your workshop for this type of work, and
will save you hours of diagnostic time. Look up Bob Parker in Australia.
He produces a very good ESR meter at very reasonable cost, and
distributes world-wide. His meter has an unambiguous digital display, and
I have been using one daily, for a number of years now.

Arfa

Arfa


Or just replace all the capacitors, unless you repair a lot of things like
I do, an ESR meter is not always a great investment, capacitors are cheap.

Bob Parker's meter retails in the US, in kit form, for around $60. You're
not going to buy too many quality caps for switchers for that money, so I
reckon that it represents a good investment for anyone hoping to make money
by repairing stuff with switchers in it. Also bear in mind that if you're
doing it for money, your time should be worth at least $15 an hour, so
changing all the caps as opposed to spending 5 minutes finding and replacing
the one that's really faulty, has got to be worth the investment in a very
short time, hasn't it ?

Arfa