Subject: Re: Monitor Problems
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From: Rubywand <rubywand@swbell.net>
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Date: Sat, 20 Mar 1999 16:49:04 -0600
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Supertimer writes ...
> 
 ....

> 
> Thanks for the info, Paul!  I opened the case and took a look at the
> bottom of the base circuit board.  I don't see any cracked solder,
> but I do see discolorations here and there.  In fact, it looks like
> some component(s) leaked.
>

     Goo, slime, ... could indicate a blown electrolytic capacitor nearby.

 
> One thing I do notice is that some time ago, when the screen
> began to exhibit symptoms (at that point, the vertical would shake
> and stabilize after the monitor warmed up, followed progressively
> by longer and longer collapses to a horizontal line until one day,
> the monitor no longer recovered), I followed the instructions in
> the monitor repair FAQ and resoldered the big holes in the HV
> module.  Today I noticed that these holes were discolored and
> some white encrustations enveloped some of them, almost (or
> maybe even) reaching to neighboring solder connections.
>
> Did I do something wrong?  Does one have to clean a solder
> connection that was made using rosin core flux?  I sort of just
> soldered the connections and closed the case.  Now I fear that
> the white encrustation is conductive and may have precipitated
> the end.

     A fractured solder connection (such as those which can be a problem with
the HV module) may have a grey appearance. Other times, though, the fracture
will be a nearly invisible line surrounding the pin and the solder will remain
shiny.

     To repair this sort of thing you must use good quality rosin core solder--
something around 60 tin ("Sn 63")-- and get the old solder remelted along with
the new solder. The parts you want to connect-- i.e. a pin from the HV module
and the copper in/around the circuit board hole-- should be 'wetted' with
solder. The result should be a shinny connection which looks like the solder is
'sticking to' the copper.

     One safety note: It is best to assume that some charge may remain on any
point of a monitor circuit board even after unplugging the power cord, letting
the monitor sit several hours, discharging the anode (as described in the
FAQs), and touching numerous circuit points to some metal 'ground' point on the
monitor. So, avoid touching two circuit points at once. For example, avoid
touching some metal frame or shield while applying solder.


     The white encrustation business is not a good sign. It may just indicate
that a poor grade of solder (high lead) was used. Connections made with this
sort of solder often fracture. The usual fix is to re-heat the connections and
add-in good solder. If there is a lot of crummy solder involved, you should
probably try sucking off most of the stuff (old + new) with solder wick and,
then, doing the connection with good solder. (For really crummy solder, you may
find that it's easier to pick off globs using a good pair of long-nosed
pliers.)

     For large gaps between a pin and the surrounding hole, it may help to bend
the pin slightly toward the hole edge in order to get a stable solder 'fill
in'.

     A less happy possibility is that acid core solder was used. If so, clean
the area with an ammonia-dampened swab and knife blade and procede as above to
remove most of the old solder. (Be sure to clean off the acid from tools and
fingers.)  Re-swab and, then reconnect using a good rosin core solder.



Rubywand