"Dave Plowman (News)" wrote in message
...
In article ,
Calvin Sambrook wrote:
From your description it will likely be a "SIM2" IIRC, possibly even a
3-chip at that price, not that that makes a whole lot of difference in
this case. For sure (well 99.9% sure) the problems you state aren't
anything to do with the DLP-ness, ie the digital back end but rather
the analogue front end. Standard analogue video rules apply so it's
likely to be either board level interference or something dying around
the A/D or the PSU.

Think SIM2 rings a bell.

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. 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.

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. 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.


I'm not clear what you mean about the DVI/S-video but if you are saying
that the projector has a DVI input then the very best thing you can do
by far is to use it.

Oh, indeed. However now I've sussed out the system it's not possible. The
rest of the installation consists of a Linn (spit) home movie thingie -
with built in DVD and surround amps. And the best that can output is
S-Video. The SCART on it doesn't give RGB. There are some strange looking
connecters which are for connection to other Linn things. Look like RG45
or similar. Other versions of this unit do output components, though, by
the handbook. If there is a later version presumably HDMI.

It avoids all of the analogue front end nastiness
and (should, provided the projector is designed well) map the pixels
directly onto the DMD so no sampling and resize sillies. If the DVI is
talking EDID to the player and the player is listening (both of which
should be the case but it's a 50/50 call as many manufacturers don't
follow the rules) the player should output the right size image so no
resizing. Check that though as it's a common problem. A really good
test of whether you have it right is to display a pattern from your
source which is pixel-on/pixel off (a very fine checkerboard), if it's
set up right it will look good, if it's not you will see resize bands
in the image.

Right. But he's not about to spend serious money replacing everything else
other than the projector.

Too late to tell you now but many lamps can be a bit dangerous if you
don't handle them correctly, I guess you survived!

Know that one. Was careful not to touch it - but it is built into a glass
or whatever box with a plastic mounting frame. Hence the cost, I'd guess.
I didn't even need to get the cotton gloves out. ;-)

If your friend
isn't a smoker and doesn't use stage smoke then cleaning the filters
should be all you need to do.

Didn't even find any filters so confined the cleaning to using a camel
hair brush and vacuum on the bits I could get at.

If there are smoke/grease deposits then
you are a bit stuffed without specialist kit as cleaning the prism and
DMD(s) is v.diff

Don't suppose you can recommend a fixer? SIM or whoever don't seem keen on
supplying spares and manuals otherwise I might have had a go at changing
the board - assuming it's not all in one.


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.