Printer help?

From: der Mouse <mouse_at_Rodents.Montreal.QC.CA>
Date: Thu Sep 9 14:22:46 2004

> 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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Received on Thu Sep 09 2004 - 14:22:46 BST