DLP projector

[Dave Plowman (News)]

A pal has an awfully expensive home cinema set up - perhaps 5 years old. The projector is an Italian DLP type (can't remember the make) which cost the thick end of 10 grand. Most of the rest is badged Linn. The firm who installed it all (nice job) are no longer around. The output from the projector was getting a bit dim so he decided a new lamp was needed. The quote from a dealer was 1200 quid. ;-) He got the lamp from Ebay for less than half that and asked me to fit it, as he doesn't know one screwdriver from another. ;-( Proved an easy job - but I suspect the dealer would have done a good clean at the same time. And I wasn't going to attempt a full strip down without a service manual - not available. So just carefully cleaned everything I could including the various fans.

The light output is now fine - but it seems he hoped it would cure another fault. That is moving 'diagonal' wavy lines - looks to me like RF interference.

If you put up the various test patterns internal to the projector, these are clean. Just the DVD (the only source) has this patterning.

The whole installation is built in and will need quite some dismantling to get at anything - even just to try a different DVD player.

The strange thing is it appears to use the S-Video input to the projector

- since it has DVI and components.

Anyone come across this sort of fault before I start ripping things apart?

[Adrian C]

"dlp wavy lines" seems a popular search term in Google, which suggests it's not a unique problem. Mitsubishi & Samsung feature highly, but haven't looked further into the posts for answers.

try posting to sci.electronics.repair ?

[Dave Plowman (News)]

If it were a DLP fault, wouldn't they appear on the menu or internal test charts, etc?

Looking at that forum, it appears to be only analogue inputs are affected (on a different make) so it could still be RF interference, rather than a fault.

[Toby]

That's poor, I assume since you have replaced the lamp, you can gain access to the component video and DVI ports?

I would run new component and HDMI cables if at all practical - sounds like it will be a HD PJ, and SVideo is poor compared to component or DVI/HDMI I have an old Sony that was damn expensive when I bought it, that is about 6 years old and does 1080i over the component video ports (no DVI or HDMI)

To test, just try a short component video cable.

Toby...

[dennis]

I have some, no I wouldn't know what to say without knowing what it is. the stuff I used and frequently had to realign was based on CRTs and multiple projectors on one screen!

I would suggest that a £30 hdmi DVD player from ASDA is going to be significantly better image quality than what he has if you are taking it apart. Control of said player will be the stumbling block as it cost cash for players with control interfaces which are probably being used.

[Dave Plowman (News)]

I'm going round tonight to investigate - but it seems it uses a convertor box at the screen end where the DVD/surround amp is - to feed the projector via the VGA input. But the DVD is connected to that by S-Video. Gawd knows why. The convertor box has an composite input so I'll take my colour bar generator and see if that is clean. Then investigate if I can improve things over S-Video - although to be fair it looked pretty good when I've seen it working properly.

Don't think it does the full 1080 - only 720p

The fault seems to be heat related - it starts out clean then the 'interference' gradually appears over some 10 minutes or so. Possibly a cap failing somewhere.

[Calvin Sambrook]

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.

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. 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.

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

Good luck, Calvin

[Dave Plowman (News)]

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.

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.

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

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. ;-)

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.

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.

[dennis]

Have you or anyone else cleaned the filters on the projector? They need to be done frequently.

[dennis]

How big is the screen? These days you can get big lcd/plasma sets.

If you/he do decide to replace it buy a good AV amp with built in D/A convertors and then the cheapest bluray player will give the same sound and picture as the most expensive. It is only the D/A that makes any real difference to how it sounds, not the label on the DVD player. Also a digital image doesn't depend on the DVD player either unless it is upscalling which you shouldn't need to do.

[Calvin Sambrook]

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 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.

[Clive George]

Sure you've checked who you're replying to?

[Calvin Sambrook]

IMO if he's got used to a DLP projector he'll be bitterly disappointed by the image quality of a plasma and probably cry at an LCD. 3-chip DLP is the dog's wotsits. Even 1-chip from 5 years ago is very good, certainly lots better than plasma or LCD in terms of artefacts like noisy blacks, black detail and refresh rate.

Mind you prices have fallen a lot so a new DLP of similar light output and capability might be a sensible option for anyone serious about home cinema.

Nowadays you'd be crazy to go to analogue at all, it's pointless.

[Dave Plowman (News)]

No - I understood that bit ok.

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.

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

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

[Dave Plowman (News)]

Didn't measure it - about 8 ft wide.

Indeed. The screen comes down to cover one of those. ;-)

[Calvin Sambrook]

Oh you'd be surprised. It's not as bad as it sounds actually and it's perfectly usual for signals to time-share a track on the PCB, indeed many A/Ds are pinned that way so designers have no choice. [Mind you most double up composite with G/Y of component RGB/YUV as it makes more sense that way in the A/D]. The cheap way is to wire-or in which case the user had better not plug a signal into both inputs at the same time. The more expensive is to buffer the two inputs onto the track in which case the user can have both plugged in and can select between them. In the case of composite sharing with S-video's Y you still get the advantages of s-video with it's seperate colour carrier and would never really know what's going on inside.

[geoff]

In message , "Dave Plowman (News)" writes

Ha ha

[Dave Plowman (News)]

Well, I have a Sagem DLP rear projector, and a new lamp for that costs nothing like 600 quid. And surely any type of projector requires both a precision light source and optics to give the best results?

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Calvin Sambrook" saying something like:

This isn't a DLP one. Even if it was, there's no way I'd pay the rip-off ruinous prices they want. The whole re-lamping thing is about diy, and doing it on a budget. As more used and dirt-cheap lamp-knackered projectors come on to the market via ebay the like, more people are finding out about alternative lamp solutions, including DLPs. There's been a significant growth of interest in the last couple of years and the body of knowledge is expanding daily. As you can appreciate, this is world removed from paying £10K on a gadget and greasing up and bending over for a lamp.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Dave Plowman (News)" saying something like:

Via various forums I found sources of the naked lamps, one of which is this guy...

for LCD re-lamping. I've no doubt similar can be found for DLPs, but I wasn't searching for those. I've certainly come across postings about replacing lamps in DLPs with cheaper versions, so it's being done out there.