This Hobby Is Actually Useful!

[Jon Elson]

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