Re: System Saver IIgs -- ID of burned part?

[Rubywand <rubywand@swbell.net>]

Mitchell Spector writes ...
> 
>     I just opened up my Kensington System Saver IIgs to have a look
> inside (I've been wanting to replace its noisy fan for years) and just
> found something I wasn't expecting. The orange disc-like part at
> location 'V1' (there's also one at V2 and V3) split open and the
> plastic cover above it is badly scorched and burned. It looks to be
> some sort of large capacitor, resistor or regulator--I'm not sure,
> only that I've seen these on other electronics only much, much
> smaller in size. It has two points that solder to the board, probably
> a postive and negative contact.
>

     Sounds like a Metal Oxide Varistor (MOV).  They are often red or orange
and the "V1" location seems right according to a diagram. MOV's are used to
suppress voltage transients.


 
>     The fan, LEDs and power-outlets seem to be working just fine, so
> I'm wondering what this bit of electronics does and how safe is it to
> continue running with it blown.

     An MOV is placed across a line-- such as from the 'black lead' to the
'white lead' of an AC power line inside an extension cord case or 'power
center'. If you get a voltage spike above, say, 130V, the MOV conducts and
tries to chop down the spike's amplitude. The higher the spike wants to go
and the longer it lasts, the greater the energy the MOV has to 'absorb'. It
looks like the part in your SS IIgs took a pretty good pop-- maybe from a
nearby lightning strike.

     Running without the MOV won't hurt anything; but, you will not have
clamping protection from the V1 MOV across that particular line.

     A typical part for use in something like a System Saver IIgs would be a
V130LA10A from GE. (You could check the labeling of the part at V2 or V3.) 
There may be a fuse in series with the V1 MOV. If there is, it may be blown,
too. (Seems a bit unlikely since the MOV blew; but, it's easy to check with
an Ohmmeter.)



> Is it a fire hazard? I have absolutely
> _no_ idea when it blew, it could have been last week or it could
> have been 10 years ago.
>

     Since it sounds like the part has been pretty thoroughly blown, it
probably is not a fire hazard. Snipping it out of the circuit would be a good
idea just to make sure. Besides, you probably want to put in a replacement.
(It doesn't matter which lead goes to which connection point.)



>     Incidentally, can I use an ordinary 12v DC fan (say from a AT/XT
> powersupply) if/when I get around to opening it up again? The
> existing fan is huge, probably about the size of a refrigerator fan!
 ....

     The fan needs to run from the AC line. (You can't use a 12VDC fan unless
you add a transformer and rectifier or some other kind of 12VDC power
supply).  Some good AC replacement fans are listed at
http://home.swbell.net/rubywand/Csa2POWER.html#017 .



Rubywand