In article ,
Calvin Sambrook wrote:
I've just come back from testing things, and my colour bar generator
into one of the composite inputs gives the problem - so it is the
projector itself.

Sorry, I didn't mean it wasn't the projector I was mentaly splitting the
projector into an analogue front end and a digital back end as they are
radically different parts of a DLP.

No - I understood that bit ok.

The digital stuff from the A/D right through to the DMD is very unlikely
to give anything wavy and certainly not anything crawling through.
Those sorts of thing are however characteristic of faults in the
analouge domain.

My thoughts too since the internally generated test patterns are fine. I
couldn't check the DVI input to the beast easily - as there was nothing
there that had one. But I'm sure there could be a fault on the analogue
inputs but not on the digital.

In a relatively cheap DLP [trust me 5 years ago £10k for a DLP was at
the cheap end] I wouldn't expect massively complex analogue circuitry
which is good news really as it means there's less to go wrong. You
have seen the effect with two sources and presumably two different
leads. The composite and the S-VIDEO almost certainly get commoned
together very early on inside, maybe even simply wire-ored together,
you can test for that easily.

I would hope they were kept separated - not much point in S-Video
otherwise.

Between the connector and the A/D
there's probably only a small collection of components - some ESD
protection if you're lucky, a DC blocking cap, a 75R termination bridge
and into the A//D I'd guess.

The other likely area for noise introduction is the power supply. Just
like in a PC the power supply is a highly stressed component and as it
starts to fail it can introduce noise into the supplies to the PCB.
Obviously noise around the analogue parts is not good and esspecially
so around the A/D. Insufficient or failing smoothing caps on the PCB
can contribute to problems (or rather not remove them as they should).
I don't know this projector at all but some have a PSU for the lamp and
another for the electronics whereas some combine the two for cost
reasons. WARNING: Lamp PSUs can and will bite very hard, they put out
thousands of volts to start the lamp and then lots of current to keep
it going. Don't go there.

Any SMPS can bite hard. ;-)

Without a proper manual I wouldn't attempt a repair on someone else's gear
of this nature. If it were mine and the repair expensive, I probably
would.

[snip]


I can't I'm afraid - not my area of expertise. I'm surprised you can't
get spares for a 5 year old projector though.

I meant that the maker doesn't seem to want to supply apart from to its
dealers, etc.

--
*Xerox and Wurlitzer will merge to market reproductive organs.

Dave Plowman London SW
To e-mail, change noise into sound.