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Discussion Starter · #1 ·
Hi all,

I'm in the process of mounting my Electrohome 8501 (non LC) and can't get the blue tube to turn on. The PJ is currently on the floor (trying to determine mounting distance to the screen). I'm driving the unit with RGB into input 01 with a HTPC (1280x960 @ 60Hz resolution). The red and green tubes turn on and work, the blue does not. I have switched the blue and green input cables with the same results (wanted to make sure it wasn't a cable issue). When I go through setup (where individual tubes are turned on/off) the blue still doesn't light.


I am a total newbie to CRT PJs... I've taken the the two top panels off (lens adj. area and actual tubes / electronics). Each tube is encased in a metal cage and there is some sort of card between each tube (also in a metal cage). There is a plastic shield covering the front area of this compartment with a notch for the previously mentioned metal caged cards. The cages do NOT line up with the notches in the card (a bad thing?). On top of the green is a unit which kind of looks like a distributor cap from a car. I have no idea where to find board 'X' so if you have a suggestion please tell me where the board is located in reference to the parts I've listed. I tried to follow some previous advice like "pad the horizontal deflection board to prevent sagging" but realized I have no idea where that is or what it looks like! (insert image of me staring at PJ scratching my head).


Two more questions:

- How do I flip & invert the image for a ceiling mount (it's currently setup for floor operation)? I know I need to flip two plugs... where are they located (there are two over the green tube that look promising but I'll wait for an answer).

- Where can I get a service manual? I have the owners manual but it doesn't contain a lot of information (for example, how to turn a gun on or off).


Thanks! This forum has already been very helpful... I look forward to your advice!
 

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Say Greg


Did you just get this projector? Lack of blue emission could be an electron gun damaged by high filament voltage. Get hold of a digital voltmeter and try to measure the filament voltage at motherboard connector P14, it is behind the rear of the blue tube; filament voltage cannot exceed 6.50 volts dc or you may have damaged tubes. Go to our new website and look at this: http://www.etechvideo.com/techtip1.htm# See picture at bottom, we have opened the rear heat sink on a Marquee and we are checking the filament. If yours is too high it may have ruined the gun: http://www.etechvideo.com/techarticle1.htm Without electrons streaming from the gun, you have no image. The filament voltage comes from the low voltage power supply which is removeable with a few screws, we can repair those here by mail. Another possibility is a failed neck board, the circuit board mounted on the end of the tube which is the video final amplifier stage. Also, for scan reverse, you will need to reverse Three horizontal yoke plugs (above the green tube) and Three vertical yoke plugs (yellow/green wire pairs plugged into rear heat sink; these are visible in the first mentioned picture, under the voltmeter.
 

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Discussion Starter · #3 ·
Thanks Tim! Yes, I did just receive the PJ. I'll check the filament voltage and get back to you...


Greg
 

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Discussion Starter · #4 ·
OK, it measures at 6.41V when the unit is fully powered up. Will a different neck board work? (i.e. can I take the red and hook it up to the blue?) If so, is the neck board easily removable (it looks attached to the tube in the middle of the board?). Looking at the neck board I can see no obvious sign of damage (burnt resistors, etc.). Here's some more info:


Model #: 38-P13085-AC

SN: 079060004

S/W version: 3.4
 

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Greg. this a long shot but you said the blue wasn't working during set-up. Is this during the part where the brightness is turned down to 10% and you look directly into the lenses to center the raster. My blue didn't look like it was working at this point either but it actually was, just had to turn brightness to 30% to see it. BTW, that " plastic shield covering" is actually lead shielding to protect you from X-rays and other harmful radiation. Good luck with your E-home, the end product is worth the hassle.
 

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Discussion Starter · #6 ·
draganm,

I actually went through the mechanical setup (in the help menu) where the unit turns on/off each tube (focus red, green, blue, etc.). Does the help menu override existing settings? If not, perhaps this is the issue.


1) How do I toggle a tube on/off?

2) I tried adjusting brightness. The blue didn't show even when briefly cranking the main brightness adjustment (brite button & u/d arrows) to max (turned it back to 30).
 

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Discussion Starter · #7 ·
Who sells E-home service manuals? Tim? I'm working from the user manual right now...
 

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Guys!


Service manuals are $85 plus shipping, schematics are provided on CD ROM, add $40 for schematics on paper, 11" x 17". Greg should try swapping red and blue neck boards to diagnose this; make sure you sketch where every wire plugs in. We also have used neck boards here at $430 plus shipping plus old neck board, $830 for new.
 

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Discussion Starter · #9 ·
Good news!


I swapped the red and blue neck board and now both tubes work. Now on to actually setting up the PJ (more questions in another post).
 

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Guys!


There was likely some tarnish on a connection or mebbe a cold solder joint in the signal path.
 
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