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Barco 808s Powers Up, but no image.

bpasco

Standard Member
I just replaced a bad quad in my 808s, but now I have a new problem. With the new quad it comes out of standby, but the tubes won't illuminate. I have a good video feed attached to 1, 2, and 4/5. No red LEDs at all. Green LEDs on all three tubes. Adjusting G2 pots does nothing to the green LEDs on the tubes. The controller board has the stdby, main power, and block match LEDs on for ports 1, 2, and 3/4. I swapped out the horizontal board, vertical board, port three board, RGB switcher board, and quad decoder. No change. I checked the 17v point on the SMPS, and it was high - 17.82 - and dialed it back. I've seen reference to a 48v check point, apparently referenced in the service manual, but I only have the owners and installation manuals which I don't believe discuss it. I'm not sure what else to try at this point. Any ideas are warmly appreciated!
 
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Tom.W

Active Member
Check the fuse on the EHT module and you can download the 808 data service manual. Should be pretty close to the 808s. See the service manual thread.
 

barcoed

Banned
808S and 808Se had different HVPS bits and are incompatible (unless you mod a few things) - Are you sure the replacement part has EXACTLY the same part number?
 
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bpasco

Standard Member
Thanks very much for the feedback. I greatly appreciate it. I've pulled the EHT board again, and retested the fuse in the black holder. It has connectivity. In any event, there have been no red lights on the EHT board since I swapped the quad - which means I'm not in EHT hold down, I think?

I've rechecked the part number on the quad. The quad I had in the machine originally was R7722091 Index 1. The one I put in is R7622091 Index 5. I had seen the chart on Curt Palme's website, ( http://www.curtpalme.com/docs/BarcoServiceBulletin_R762716_New_EHT.pdf ) and noted that the R7722091 wasn't on the list at all. But my EHT is the old style, R7617427, which should work with a R7622091.

Additional thoughts?
 

bpasco

Standard Member
Thanks for the suggestion. I've detached the quad from the projector, and reinstalled it. There are three connection points, to the HV splitter, the G2 power supply, and via a white plastic strip connector (don't know what that is properly called.) All are tight. When I power up, it comes out of standby, and I can hear the CRTs charge, but no signal. I have a DVD player hooked directly up to Port 2 using S-Video, which is on. Pressing 2 (or any other port) makes the relevant LED light on the RGB switching board, but no illumination on the tubes.

I've downloaded the Barco Data 808s Service Manual from the service manual thread. I'll start digesting that, but in the mean time I value your willingness to help me out.
 

Tom.W

Active Member
Also put the original boards back if the only thing wrong in the first place was the quad. Have you replaced the G2 board also ?
 

bpasco

Standard Member
Okay, I've swapped out the G2 board too. No change.

Internal test patterns do nothing (hitting the adjust button does not bring up internal menus), and the filaments on the tubes are not lit. Looking in the tubes, they look identical to when the set is turned off.

I hope I am overlooking something obvious.
 

Roland @ B4

Active Member
I'm wih Tom
By the sound of it you have EHT but one of the voltage rails is down
There are two standard replacable fuses and whole load of fixed ones test them all.
After that I would suspect a transistor has shorted out. Most common will be the big one next to the main fuse on the power supply.
 

Tom.W

Active Member
See page 267 of the service manual for the fuse locations. You will need an ohm meter to test the fuses.
 

bpasco

Standard Member
Bingo - That did it. :clap: That is an interesting one for me. In the past, if I've had trouble with the SMPS, I had no eht. Thanks a lot for the generous assistance!

I've been reading through the service manual for the 47v adjustment. I've found where it says to adjust it, but I'm not really sure I understand what the adjustment is for. What symptoms indicate a problem in that area?

Thanks again!
 

Roland @ B4

Active Member
48 volt adjustment is P2 genrally used to contol Max screen width.
It is rarely measured as most of us are pushing the projectors into the higher frequencies and need to get the most width out them so genrally they are turned up full.

However on a lower frequency particulary 15Khz video this can be over loaded and the screen width will dramatically start opening and closing about twice a second if P2 is set too high. Eventually forcing the PJ into scan fail.

I tend to set it like this. select your maximum resolution you are sensibly going to watch. set the H width in the Geometry screen to about 90-95 then turn P2 up so that the width fills the screen required. (making sure all the things like keeping it off the crt faceplate sides have been observed and the correct projection distance etc)
That way you still have 5-10 to play with.
If you come down to a 15khz source or test pattern and it starts doing an impression of an accordian try to reduce the width with the geomenty menu else get that P2 pot turned down again
 

bpasco

Standard Member
I didn't quite go far enough. Once it came on, I declared victory and powered off. Another glitch, although a different one.

Well, not quite a Stephen King cult classic, but the blue CRT is in wild Maximum Overdrive. If I put a lens cap on blue, I can see and make adjustments through the menus, but with the cap removed everything is completely washed out. Thoughts on the likely culprets? (I mean, other than operator error...:rolleyes:)

Thanks for the benefit of your thinking!
 

Tom.W

Active Member
Sounds like a bad video amp on blue. Try swapping the Blue and Green video amps or try a replacement if you have one,
 

bpasco

Standard Member
Is a good thought, but no dice.

I have one extra video amp, and swapped it out. No change. Since these old boards could easily have faults on them, when that didn't work I swapped it for the one on Green, which was working fine. While it worked on Green, on Blue it is still in Max Overdrive. :confused: Thoughts on the next step warmly welcomed...
 

bpasco

Standard Member
Yes, the set was working fine. I've had this projector for a couple of years. This is the 2nd quad I've replaced. The blue tube is 7626576, which is I believe a Sony tube.

Do I likely need a new tube?

Not sure what has launched this cascade of problems. But I do appreciate your bending your pick to help me figure it out!
 

Tom.W

Active Member
Check for a filament to cathode short using an ohm meter or a cathode to control grid short.Page 2 of the above pdf.
 

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