If no +5Vsb probably causes:
a) open resistor in the NPN of the +5VSB base (just replace it). Very offen
is a 2Watt resistor in the range of 100 to 330Kohm.
b) open resistor on the NPN emitter (this shows that an over current
condition occured). This resistor acts like a fuse. Possible values 2,2 to
4,7Ohm 2Watt.

The cap with hight esr is the one in the primary coil of the transformer of
the +5vsb (very offen 22uF/50V/105 degrees).

"Dave D" wrote in message
...

"Digi Man" wrote in message
...
I repair them (except the complettely fried ones).
Most ATX suffer in the +5Vsb power generation.
The +5Vsb is a complete small SMPS. Very offen it brokes (high ESR cap)
and
it you have not a 7805 inside the PSU, you'll get probably a fried
motherboard,keyboard and some times PCI cards!.

The working period is not very long because of excessive heat produced
by
the stand by work.
When power is off for at least 30 minutes, and caps gets cold... Then
when
power is back on the +5Vsb will become up to +40Vsb (except the presense
of
7805).

Even expensive brand models suffer from this issue.


Agreed. The last mini-ATX PSU I repaired was throwing out 7.5V on the 5V
SB
line. It appeared to work but destroyed the keyboard that was connected at
the time. It could have been so much worse!
It was, as you say, a bad electrolytic in the SB circuit. The next PSU job
I
have is a 350W ATX PSU with no 5V SB at all, when I can be bothered to
look
at it ;-)

Dave