9 Sep
2004
9 Sep
'04
7:13 a.m.
From: "der Mouse"
<mouse(a)rodents.montreal.qc.ca>
Duh, I forgot to say: I've more than removed the dead cap.
The bottom of the cap is visibly damaged; it has lost a good deal of
some black material. The baord is also visibly damaged; the
component-side etch under the capacitor has lost its coating, and the
board is significantly pitted, too.
I replaced it with a 220/35 cap from my parts drawer; when I put the
result in place, turning it on produced another flash of light from
that area. I removed it again and cleaned the area with water and an
old toothbrush and let it dry overnight.
Now, the power supply no longer does the tick-tick-tick overload thing;
it comes on and stays on. But it doesn't work; I get the usual walking
lights, then the 05 SELF TEST display, then SWITCHING TO PS; after a
bit, it changes to 55 SERVICE. This may be because I still have all
the covers off - there may be sensor switches - or it may be because
the pc board damage has broken a critical etch run or something. I do
note a very faint ticking noise, disturbingly reminiscent of the one I
mentioned before - but far less frequent (maybe every five seconds) and
a great deal softer; I had to listen closely to be sure I wasn't
imagining it.
I think one of you said something about having a service manual; does
it happen to say what 55 SERVICE means?
Hi
I think most of the error messages are listed but sometime it
just says something like "replace the xxx board under the main board".
If you know what I mean. Look at the board carfully. It sounds like
you had a small electrical fire. Remove any charred PC board and
look to see if traces are burnt through. Missing solder mask is not
an issue but missing copper is.
I'll look for my manual to see what it says( not here so will
report back tomorrow ).
This sounds like a PS board. Not having the drawings here, this
might be the case. If so, the diode or diode bridge may shorted.
This would wipe out the cap and maybe a few more parts.
Dwight
I would
guess that replacing the cap should put it back in working
order.
I've now removed the cap. [...]
Failing that, does anyone happen to have a spare board? It's the
smaller of the two digital logic boards - the one that measures
something like 6 by 8 inches, the one you have to remove the big one to
get at. (I don't _like_ boardswapping, but absent the tools and doc
I'd need to diagnose this one, I see little alternative.)
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9 Sep
9 Sep
7:22 a.m.
I think most of the error messages are listed but
sometime it just
says something like "replace the xxx board under the main board". If
you know what I mean.
Yeah - but even if it does, it would be reassuring to know that the
selftest agreed with me about what's at fault here. Or it could say
something like "such-and-such sensor switch is stuck open", in which
case I know I probably need to replace a cover or plug something in or
some such. (There are two sockets with no cables to plug into them as
far as I can tell; I don't _think_ I have any cable ends hiding,
but....)
Look at the board carfully. It sounds like you had a
small
electrical fire. Remove any charred PC board and look to see if
traces are burnt through.
It's not clear whether there is any charred PC board. There certainly
is _missing_ PC board, but it's not clear whether the black substance
is charred board or just gunk from the capacitor that I haven't
scrubbed away yet.
There is at least one via that is damaged; I can see the little copper
cylinder sticking up every so slightly from the damaged board around
it. It's connected to a power wire on the foil side, though, so it's
not clear whether it's essential or whether perhaps the capacitor
lead's hole substitutes acceptably.
It's not that easy to look very closely at the damaged area; it's
surrounded on three sides by components tall enough to get in the way
of things like cleaning efforts. I may remove the cap I added and see
if that lets me scrub it any cleaner.
Missing solder mask is not an issue but missing copper
is.
Obviously - though if there's any copper missing on the top layer, it
appears to be part of a high-area fill, probably ground, and thus
relatively inessential.
I'll look for my manual to see what it says( not
here so will report
back tomorrow ).
That would be appreciated. No hurry, though; I'm about to take off
tomorrow and won't be near the printer for a week or two if I can't get
it fixed pretty early tomorrow morning.
This sounds like a PS board.
It's not. The caps are right next to the only heavy wires that connect
to it; I'm sure they're incomng power (the board they connect to _does_
look like a power supply board) and the caps are just for local
decoupling.
Also, with the replaced cap, as I said, there are no more pyrotechnics
and the main power supply does not go into its overload failure mode,
so there doesn't seem to be anything still shoretd out. The flashes of
light, though, indicate _something_ was shorting; the one after I
replaced the cap leads me to fear that there was a short and some
conductor acted as a fuse. I may get out a voltmeter to see if the
various chips are getting power (some of them are stock 7400-series
logic, so finding ground and +5, at least, will be easy).
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