[Chris Main]

Hi: I've had a Barco 808G in faithful service for about 6 years.. I always knew that our relationship might have to come to an end some day... but I thought I'd ask for help before I write her off...

Basically, in normal use, only running at 720p via an HTPC (and now the Gamma-X HD fury polarity switcher - helps when I occaisionally want to hook up my XBox)..

the blue tube has become unstable, and now goes off altogether sometimes. It comes back on (ie its not a fuse..) and sometimes it flickers... so the result is that the colour of the image washes in and out ... but it's becoming unwatchable.

While it's on.. the image is fine... no sign of any other issues.... convergence is stable, image is sharp..ish... but no worse than normal.

Is there any thing I should do as an obvious first step...?

Is there anyone left in the country who could offer advice ?

Sadly, replacing the tube isn't really an economic choice... I'd be selling the PJ for parts or scrapping the thing if I can't get her working again...

so... any suggestions to avoid that would be very gratefully received..
Chris

[ovation1357]

Hi Chris,
Welcome to the forums! There are still a few CRT gurus left in the UK who will be able to help you I am certain that they will reply to you very soon... But to start things off:

Can you describe in more detail what you mean by 'unstable' on the blue?
When the blue goes 'off': If you look inside the lens, is the tube completely dark or is it dimly lit? If dimly lit is it blank or with picture?
How often does this problem occur?
Does the same problem appear when using a different video input?

I'd be surprised if the blue tube itself is actually faulty in this case... Whatever has failed - you should be okay as there's still a whole load of 808 series spares kicking around at incredible prices.

I've got a couple of Seos (Barco) Graphics 808s projectors that I'm breaking so if you ultimately get a diganosis and need a part then feel free to PM me and I'll tell you if I have what you need.

Can you also please clarify that this is an 808 and not an 808s model?

Regards
Jonathan

[Chris Main]

Well, thanks for the quick reply... I guess there may be life left in the scene...

So...
"Can you describe in more detail what you mean by 'unstable' on the blue?
When the blue goes 'off': If you look inside the lens, is the tube completely dark or is it dimly lit? If dimly lit is it blank or with picture?
How often does this problem occur?
Does the same problem appear when using a different video input?"

Progressively more and more often.... At the start (6 months ago), maybe once or twice during a film, the colour would flick in and out of "true"... my wife didn't even notice it. Over time it became more obvious and would happen more often. I can't remember what I thought it might be at the time, but I thought maybe it was losing convergence and then regaining it... before and after the image was fine, but the colour was flickering ...wrong... and then correct again.

I tried various video sources, it seemed fine with S-Video, (and I'll check that again) but certainly two VGA sources at similar resolutions are having problems via VGA to RGBHV (with a Gamma-X in between, but the problem pre-dates introducing that)

Now, with the blue going off for long periods, it's more obviously that, and you can see that the tube is not lit at all.

I agree that it's unlikely to be a failed tube.. (it would just be dead, right ?) but something is causing it to lose the signal, or sync, or something.

Nb, when it's lit, you can look into the 3 tubes... R & G are stable and blue... well the intensity ..stutters...

That's the best description I can give...

Oh - for a while I would find that switching to adjust mode (genlocked) would help, or just switching off and on... but I knew I was kidding myself even when it seemed to be fixing things for a while.

Heartened by your comments though....

And definitely not an "s" - 808G

[ovation1357]

Hi Chris,
Thanks for the extra information.

If this wasn't affected by input type/resolution then I'd be questioning whether you've got either an issue with your EHT Splitter or part of the G2 circuitry. It would certainly be useful to know for sure whether you can witness this problem using an S-Video input at all.

It will be interesting to hear other people's opinions about this problem as I'm far less experienced than some of the others. If I was having to make my own decisions about this I'd probably do the following:

1) Establish for certain whether or not this problem happens with low resolution sources via an alternative input.

If it happens on *all* sources then I would:
2) Turn up the G2 adjustment for the blue tube (with a NON-METALLIC tool) and wait for the problem to happen again - Then check for sure whether the tube has really gone completely dark or if it still has a bright raster but no picture.
- Here I'd be thinking that the tube is either loosing its G2 voltage or loosing EHT.
I'd probably consider checking that the EHT fly-lead for the blue tube is correctly seated in the splitter and also examine the blue CRT neck board for dry joints.
***Do not attempt either of these procedures unless you know what you're doing! G2 voltage is around 700-1000volts DC and the EHT is 37.5Kv.***

If only high resolution RGBHV sources are affected I would:
2) Check that my BNC input connectors are making good contact - Wiggle the Blue input connector to see if it affects the picture. You could try swapping the blue BNC with the red and just confirm that the problem doesn't move to the other tube (I think this is unlikely) - Obviously the colour will look totally messed up if you do this but it shouldn't hurt the projector.

If we can confirm that only the blue tube is ever affected and establish for 100% certain that it only happens at higher input frequencies then we can narrow down where the problem lies.

Hope this helps
Jonathan

[Tom.W]

Sounds like a bad neck board (video amp) try swapping the blue and Green neck boards and see if the trouble travels over to the Green tube. Sony or MEC tubes ?

[Tom.W]

While your at it reseat all the boards and make sure the connectors are tight. I assume you have eliminated the source and connecting cables out as causing the flicker.

[Chris Main]

Thanks for the replies..

Additional info:

fired up this morning, and the picture was fine for around an hour, then the blue cut out. no flickering, just straight off. And to be clear, there is nothing showing at all, completely dark when you look down the lens.

Switched in a S-VHS source, but no change, so I don't think it's source dependent.

I flipped over the blue and green BNC inputs, and the blue tube stayed off, so it's not a dodgy BNC connect (of course the fact that the s-vhs shows the same behaviour makes thus moot, but I thought I should confirm)

so... it sounds like this should be a fixable thing.. the impression I'm getting is that it's the amp board that drives the blue tube.

Apologies for being overly newbie.. I installed the thing, inverted for ceiling use and set it up, maybe 6 years ago... I swapped out the fans for quiet ones maybe a year ago (using double the no of fans.. the expelled air is no warmer than before) .. but I'm not really familiar with which board is which. I try to keep the cover closed most of the time...

I'm an engineer by trade, and I work with electronics... so happy to get stuck in... but I'd need to be completely clear about which boards are the neck boards before I go swapping them...

[Roland @ B4]

Hi Chris
It is very unusuall for tubes to die but it does happen.
Tom high lighted it may be a neckcard / amplifier. I too follow that thought, from what you have described.
The BG808 amplifier is not mounted to the tube but sits on the chassis behind the tube. It is a retangular box about 5 x 10 cm with a bunch of yellow leads going to it. It is held to the chassis by two pan head slot bolts.
My very first test would be to swap the red and blue units over.
There are two plugs with yellow wires attached to each unit.
These do fail regularly and are quite easy to repair.

If the problem transfers to the red you have your culprit.

As a saftey precaution don't mess with the green
1 it brings up most of the menus
2 the green tube is the most difficult and expensive to obtain.

I have spares if you want to drop me a pm

[Chris Main]

Bingo !!

after looking at the chassis... reading your note... looking at the chassis... reading your note properly...

Swapped over the two boards, and hey presto... problem transferred to the red tube.

In fact.. there was an earlier indication... a kind of line structural flickering in the picture image, that I now note is only coming from the affected tube / amp.

will pm immediately...

Beyond my most optimistic expectations... many thanks.

[ovation1357]

See! I told you there were some gurus in here ;-)

Really glad to hear you're on your way to a quick and simple fix... Roland's a great guy to deal with - I brought a couple of boards from him a few weeks back and he was really helpful.

Good luck!
Jonathan

[Chris Main]

Not there yet, but it's looking good... and far better than I could have hoped for when I posted.. many thanks all...

[Tom.W]

As I remember the BG 808 (non S) uses the Sanyo VPH06 video amp. I would suspect you just need to replace it. The chip runs hot and needs to be properly heat sinked.

[Tom.W]

Here is a link to the Sanyo video amp in question...

VPH06 Datasheet pdf - FBET Hybrid IC Video Pack (VPH Series) Video Output Amplifiers For High-Definition TV - SANYO

[Tom.W]

Just an after thought but if the tube with the bad video amp runs just fine for awhile without vertical retrace lines and completely turns off you might just need to replace the thermal compound on the heat sink.

It can dry out and cause the video amp to overheat. What fans are you using ?

[Roland @ B4]

Blast it with hair dryer!

The Normal bright picture failure with diagonal lines is Q2 failure (check that number it may be Q1)

Tis failure of course could any one of the 50-100 other components or connectors on that board

[Barcoing Mad]

Henry is largely out of the CRT game these days, but he might have bits and pieces (if Roland hasn't!)

CRT Projectors Home Cinema Experts CRT Spares

[Tom.W]

Here is a fair price if you need one or would like spares...

Barco R7621736 RGB Output Amp Data Graphics 808/s CRT - eBay (item 270383059115 end time Sep-27-09 09:58:46 PDT)


No I am not the seller.

[Roland @ B4]

Price @ $55 is about Right the last few I sold On Ebay went for £35.
Shipping at $36 is a bit steep

[TVrepairman000]

Hi

If it is the VPH06 chip I think I have several avaliable, will have to check weather they are VPH05 50Mhz or VPH06 60MHz first (as I can't remember the numbers), saved them out of Sony VPH-1251's I had in and scrapped due to burnt tubes.

You can fit a VPH06 in place of a VPH05 but not the other way round !

Let me know and I can sort you out a good one for a couple of quid + postage assuming you are in the UK, saves spending £30 on a new neck board if your happy to change chip over.

TVrepairman000

[Tom.W]

It's nice to know that we in the CRT projector community all help each other out !

[Chris Main]

Just wanted to say many thanks for all the contributions here... well beyond the faint hope I had posting...

I thought the scene was all but dead... but I guess I've been given a new ... well chose your own cliche...

The main thing is my Barco is working again, thanks to a replacement amp board, and I'm chuffed to bits...

Thanks again,
Chris Main

[Tom.W]

[Roland @ B4]

I love a story with a happy ending