Re: Waterlogged monitor

["Mark Cummings" <NOTfigjams@primus.com.au>]

> >as for the monitor, i would have to say you could do the same things with
> >dissembling it and washing it in water HOWEVER!!!!!! a monitor will store
up
> >to something like 100,000 volts in the tube which might decide to follow
the

err no, the tube is ONLY (if thats the right word to use) 24-25KV. And
normally a tube will discharge by itself, however there is no guarantee that
it will so it is always wise to discharge it using correct procedure of
course. I use a screwdriver with unsulated handle and a lead with aligator
clips both ends. One alligator clip goes on the shaft of the screwdriver and
the other goes onto stranded wire that goes around the picture tube. After
connecting the alligator leads and holding just the insulated handle,
carefully sneak the tip of the screwdriver under the rubber ring that holds
the thick (usually red or black) wire that connects to the back of the
picture tube. Push it under until you get a crack or until you hit metal
near the middle clips. Be prepared for the crack as it can jump about an
inch and you may jump when you hear it. You also need to discharge any big
voltage caps on the motherboard, some could be holding up to 400ish Volts
depending on what country you live in.

BTW even static electric charge on your body will only get to 10-20KV
depending on humidity. Of course this is completely different than a picture
tube which can hold enough charge to boot you, while the static equivalent
will only tickle.

> >path of least resistance which just might happen to be the water that you
> >decide to wash it out with.  honestly i would just keep looking for a
good
> >old composite monitor such as one of the commodore composite monitors or
a
> >magnavox rgb 80 (i found 3 of them in the wild for 3 bux a piece).

it would be a big job to dry out a monitor, and if the EHT transformer got
water in it I'd forget it as it would be nearly impossible to dry out.

> >probably the voltage has drained out of the monitor with the water that
has
> >gotten into it so far, but still i don't think i would attempt it.

I agree that water or moisture would likely (but not absolutely guarantee)
discharge any stored charges.

> FWIW, the actual anode voltage is in the 12kv to 20kv range, and is
> easily grounded at the anode connection (carefully).

colour monitors are araound 24KV, I think monochrome (ie green) monitors may
be lower like you say it's been a while since I looked at one. Hey... how
many TVs do you see these days in B/W huh :)

> The major issue will be the purity of the water used to wash it (and the
> computer).  If the water is deionized or distilled, you don't need to be
> nearly as careful with using air to get rid of it--just let it evaporate.

Yep, although I'd use an air compressor to force anyu extra out, then
closely examine the board & tracks.

> A bigger issue is the soluble and "clumpable" dirt on the board getting
> washed into places where it will still be deposited when the board has
> completly dried.  "Dust mush" is somewhat conductive, and could be
> especially problematic around high voltages (in the HV section of the
> monitor) and in high impedance circuits (none in the computer, but
> perhaps a few in the monitor).  Just be sure to rinse it several times
> and to get rid of all the dirt, etc.  And let it dryyyyy....

this happens a lot under Surface Mount chips like those on the GS mobo,
that's why I like to use compressed air to force it out. If after drying the
board out you then see growths around the legs of the chips (caused by soap
or impurities) simply clean the board again in water and re-dry. I normally
remove all socketed chips before cleaning because they don't normally
require more than a wipe over with a bit of alcohol or just a damp cloth. I
also spray moisture repelling spray or contact cleaner (which evaporates)
into jacks and connectors on the back edge of the board as well as the Apple
expansion sockets.

Mark