From: uhclemLOSE.mar06@nemesis.lonestar.org
Doug_M wrote:
: Hi, I have a 4D with an Astec power supply. The power supply "sizzles"
: first for about 30 seconds before the system comes on. Once it is
Sounds dirty. Disconnect & Remove from system, wait half an hour, and
spray down solder side and component side (from multiple angles) with
Dow Bathroom cleaner, eg the scrubbing bubbles. Wait about 30 seconds
and rinse several (at least seven) times using fresh water each time.
Fresh distilled water for the last two rinses is recommended. Shake
vigorously and then let unit stand in full sun for at least a day,
shaking and turning to dislodge any remaining water every hour. Keep
component side facing sun. Do not leave outside over night as any dew
may cause rust.
After 24 hours, shake again looking for any hint that water remains
under capacitors and under other parts. Put back to bake in the sun
if uncertain.
Once satisfied that there can't be a molecule of water remaining
anywhere on the power supply, re-install.
I have found the Dow Bathroom cleaner to be unusually effective at
removing the dust & grease combination that initiates most power supply
and video driver board HV arcing, but it can't be left on the components
for long. It can ruin paper labels and remove markings from some
plastic labels and case components, so it should not be sprayed
liberally on CRT deflection coils and such, particularly avoiding
places where you can't rinse them and get them good and dry quickly.
Don't get it on things that have lubrication unless you plan to
relubricate later.
: I'm stumped. Any hardware gurus out there that can point me in the
: right direction?
Unplug any external peripheral wiring, notably any RS-232 or printer
cables. Also check for a hot neutral on the 120V power line. One of
those three-lamp outlet testers will give you the answer on this, or
you can check with an AC voltmeter.
The power supply has a safety circuit that can be confused and
refuse to start if it sees a voltage potential on any of the output
lines before the power supply turns itself on. This potential
can be caused by leakage up the parallel printer or serial cables
from another device and/or if the machine you are working on or
the remote device has a hot neutral.
The Tandy supply is more touchy about this outside leakage than the
Astec supply, but if you have a hot neutral, you need to fix that
immediately. Most unsafe, and can cause equipment destruction.
Another possibility is that the supply has no load, or the +5V or
+12V output lines (any of them) are shorted. The power supply will
instantly shut down in a shorted output condition, and can't function
properly with no load.
Make sure edge connector to video driver board is fully seated.
Being sidewise can short connections out, making the power supply
refuse to run in some situations.
Disconnect all but one thing from the power supply (it does require
some load), and see if the power supply starts working by measuring
voltage. Then reconnect things (with the power off then turning back
on after next device re-added) until the supply stops again.
The last item added is the one to investigate.
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| with incompetence and crime. Stop
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