1 Aug
2015
1 Aug
'15
10:05 p.m.
On 08/01/2015 04:24 PM, Robert Jarratt wrote:
Today I was able to repair the LCD monitor (admittedly
a cheap one) on my
son's computer by replacing some of the electrolytic capacitors.
I repaired an LCD monitor that they were going to trash at
work. You had to massively disassemble it to get to the
driver boards for the LCD panel, but there were two little
SMT Tantalum caps on a switcher circuit buried in there, and
one was shorted. I replaced them with two aluminum
electrolytics, and my kids have been using it for years.
I had another LCD that I take to shows, and lemonade or
something got spilled on it, where the buttons are in the
lower right corner. Over time, corrosion set in, and it
thinks the buttons are being held in, causing annoying mode
changes and on-screen menus. I've had to hack it twice now
to fix the problem. The tiny pushbutton switches are OK,
but they have a small SMT cap across the switch that gets
corrosion under it. I remove the cap, clean the board and
install a new cap. Still one more switch has the original
cap, but maybe the juice didn't get into that one.
PS A related question. I struggled somewhat with the
Weller Magnastat No. 8
tip, when trying to solder leads to the ground plane, I could not get the
solder to stay molten very long. I was using lead-free solder, its melting
point is much lower than the temperature which a No. 8 tip reaches. The iron
is 50W. Clearly the ground plane was taking heat away, but is it a problem
with the tip not being hot enough, the iron not powerful enough, or perhaps
some operator error?
When repairing CPU motherboards with bad caps, this is a
really big problem. I dilute the lead-free solder with
leaded solder, this helps lower the melting point to where
two soldering irons (one on each side of the board) can be
used to clear out the plated-through holes. Those are
multilayer boards, and way worse.
I now use a 65 W Weller WMP iron with WSD station, and it is
great. The larger tips have great heat conduction, makes
difficult soldering tasks much easier. (This is a fairly
expensive setup, I got my home station on eBay.)
Jon