Here are the relevant photos:
Shot of the PSU from the Front Topside
http://img351.imageshack.us/img351/3822/afronttopshotofpsu8ts.jpg
Shot of the PSU from the Filter Cap Side
http://img446.imageshack.us/img446/8074/asidetopshotofpsucaps6rx.jpg
Shot of the PSU from the Back
http://img446.imageshack.us/img446/7066/abackshotofpsu6rl.jpg
Shot of the PSU from the Back At R048
http://img446.imageshack.us/img446/6646/abackshotatr0483sw.jpg
Spec Sheet for KA3511
http://www.fairchildsemi.com/an/AN/AN-4003.pdf
Both resistors have one end grounded. R47 (green resistor that reads
150ohm value) is traced back to PIN 16 on KA3511 (PIN 16: PT an Extra
Over Protection Input). It also wanders out through a very small
surface mounted resistor (orange-orange-orange-gold, 3300ohm),
It is a single-sided (copper) board, there are no
surface-mounted parts at all, AFAIK.
Since it appears there was a part soldered on at the end of
the chip (it has 22 pins but there are 24 shown), it would
have been even more helpful to have indicated the pin
numbering, since there is no shot of the top of the area to
compare.
Do you think what you are calling pin 16, might actually be
pin 15?? That would make more sense. 150 Ohm load resistor
on 12V rail.
... turns
into a red wire that goes to the small board that is mounted on the top
of the right side heat sink (it is labeled "fan speed control").
You forgot to mention the thing that was important, that
besides wandering around and the other stuff, that trace
leads back to the main wire harness connection. It is a
power resistor directly between one of the output power
rails and ground, that is the sole purpose of that resistor.
What I suspect happened, is poor design and cost-cutting
resulted in long-term heat accumulation on these load
resistors, separated the copper trace from the board (part
of why those who "can" choose to spec a build, will use
plated through holes to mount such things... but this was a
budgetized PSU, not to point fingers though as practically
all of them put in PCs, are. Their second mistake was one
of layout, too little (and/or too thin) copper on the board
in that area to spread the heat, and/or cling to the board
so the entire trace didn't lift off.
Anyway, I suspect the two power resistors did short out
against each other. It's also possible this strain has
damaged something else but for the time being you might as
well throw a couple 10 cent resistors in if you have them...
but again, I wouldn't go ordering parts online to fix this
psu, it becomes uneconomical to do it.
If you can fit a larger wattage resistor, it will run cooler
due to the larger surface area. Since it is tombstoned, you
might also consider slipping some heatshrink tubing over the
exposed lead that is bend back towards the board from the
end of the resistor that sticks up. Even better would be to
enamel paint the whole thing but for a couple mm at the end
to allow soldering and then put the tubing on too, but what
lengths you go to at this point are your call to make...
again this PSU doesn't have much value at this point.
R48
(pink resistor that reads 6.8ohm) is traced back to PIN 15 on KA3511
(PIN 15: Overvoltage Protection for Output 12V).
I also suspect this is one pin off, that it's pin 14. It
too appears to trace back to another of the output wiring
harness bundles. I think it was a 6.8Ohm resistor as
measured.
It too also wanders
around, goes through a jumper and comes back to KA3511 on PIN 14 (PIN
14: Overvoltage Protection for Output 5V). Both the 12V and 5V power
are dead on the motherboard connector, by the way (the 3.3V is still
good).
It's not going to run till you connect back that torn trace.
I don't know how good you are (or what tools you have)
towards semi-precision work, so it's a bit hard to suggest
the fix that would be best for you there. Given PCB drill
bits and a drill press, it'd be possible to drill out new
holes into the existing trace, scrape off some of the laquer
and solder a jumper wire in instead of trying to rebuild the
trace. It does need trimmed off though, all of the loose
areas either glued down or cut off so there is no chance of
them later shorting out against anything adjacent.
It also looks like it "might" be helpful to move the ground
pad some... there is a lot of copper show to the left of the
board mounting hole in one of your pictures. "IF" you can
move them over that direction some (hard to tell without
good picture of the top and the resistors there to compare),
drill a new hole and scratch off the laquer to solder in the
new spot, you could put the body of the resistor towards the
board there, 'sinking away more heat to that large copper
area but it might be too close to the lid... I can't tell.
The other end could be taken just about anywhere (again I
can't tell where the space is on the top), or put down
through the original hole... and bare wire used in lieu of
the damaged trace, and finally epoxied over as mentioned
elsewhere in my post. It will have to be mechanically
secure and semi-heat-resistant though, I would not trust
multi-stranded wire for any mechanical fixing since there
will be thermal cycling (not that it would be the ideal
regardless of this but again, I dont' know what you *can*
do, feel comfortable doing, have tools to do, etc, etc.
I was thinking that these two resistors were shown in Section
6.5 OVP Block on the KA3511 spec sheet, with R101 being the 3300 ohm
resistor and R102 being the 150 ohm, but I don't think there is enough
information to verify the values are correct.
Doubtful, there is no call for a 1+W 3300 Ohm resistor in
these subcircuits. Maybe to drain the main HV cap(s) but
that's about all, and this was not used for that purpose.
By the way, can alcohol be used to clean up the backside of the board
that has the traces? If not, what is normally used?
Do you "need" to clean it? Personally, I would not clean it
now, rather wait until after you have done the repair, as
then you will have more flux residue.
It depends on what the flux was, how to clean it. Some
dissolve in water, some in water but have a petroleum base
that needs detergent, and some will need alcohol. I
wouldn't worry about getting the hardened flux off though,
if it were conductive they would not have left it on the
board as they did, and if it were clean enough to eat off
of, that won't help it run any better.
The trace is entirely lifted off, and the one where it
appears in place may have also seperated from the board as
well (hard to tell but it's not uncommon), so if that has
happened it is not a good foundation for soldering.
"Sometimes" the trace can be glued down again, taking a glue
applicator bottle with a fine tip and putting down a spot at
the edge of the trace (away from the exposed solder pad so
no glue gets on top of it), the glue will wick under the
entire trace. Obviously the glue has to be thin enough to
wick and the area tacked down till it dries.
I wouldn't generally trust that with a somewhat larger
tombstoned part that gets hot, like a power resistor. I'm
sure there's a technically "best" way to fix it but I would
probably tack down a piece of bare copper wire where the
trace was, looped where the holes for the resistors are,
solder in the resistors then apply non-conductive epoxy over
the entire area... and in that case, I would at least clean
off the flux and any residue at least on the area the epoxy
was applied to. Epoxy (the type I'd use) is quite permanent
though, you would need be sure the repair is good before
covering it.
So far as the pictures go, I was suggesting a top-down shot.
You provided an angle that wasn't as useful. The purpose
was to be able to look at two pictures side-by-side and
have them oriented the same way, with both practically 90'
from the board surface, a straight top-down view. By having
this, the components on the top of the board can easily be
compared to the traces below. Regardless, it seems these
pictures are not necessary now, it is just a suggestion for
easier troubleshooting should you ever have another similar
situation of sharing board & trace layouts with others.
I'm sure I've left out a few ideas, my post was interrupted
a few times by real life and besides that it was getting a
bit long already... but in short, yes they are load
resistors and their values determine how much load the PSU
has when there is no system connected.
In theory (probably in reality too), if you repaired that
torn trace, removed both of the resistors entirely and
connected a couple hard drives before turning it on (and
always had this load connected, or a system, whatever on
both 5 & 12V rails), the PSU would run ok without the
resistors. You should not run it without them when there is
no external load (ie- the 2 drives/etc I just mentioned).
Don't take what I wrote for granted, double-check it to be
sure the pin #s were off by one.
