CurtPalme.com Home Theater Forum

wbamb83392 · Joined: 16 Sep 2009 Posts: 8

I picked up a pair of inexpensive retired Marquee 8500 projectors a while back that I never got around to using until now. One of them works fine, but the other did some strange things when I first plugged it in. The red tube briefly illuminated on its entire surface, then went black. The other tubes did nothing. When I peer through the lenses with the projector running I see only one single faint dot on each tube toward the bottom center. When I push the menu buttons on the remote, nothing appears. It seems as though the beam isn't scanning since there is no noise or illumination on the tubes except for the dot. None of the diagnostics lights are illuminated. I've never seen this projector display video.

Does anyone know what the most likely problem is? I hope it's loose connection or a common problem I can fix with a soldering iron. If its not fixable, then I have another question. The working projector has burnt tubes and the non-working projector has nice tubes. Is it more efficient to swap electronics, or tubes?

thanks,
Eric

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

First clean all the contacts through out the entire Pj, also it be a good time to clean all the boards as well with denatured alcohol and a soft tooth brush.
pay special attention to the removable chips and smaller daughter boards especially on the Control module (CLM). reseat the HVPS and the LVPS as well. Open the LVPS and blow out any dust that may have accumulated. then report back.

to your question about swapping parts, since you have one PJ that works its easy to now swap boards in and out of the non working to the working PJ to find out which board is faulty. Start with the power supplies.

http://www.avsforum.com/avs-vb/showthread.php?p=14952911#post14952911

Athanasios

wbamb83392 · Joined: 16 Sep 2009 Posts: 8

Reporting back...

1. Tested bad PJ. Previously the red tube flashed, then showed only one dot per crt. Now it displays nothing.

2. Cleaned contacts and connectors. No change, no dots.

3. bad PJ LVPS works fine

4. bad PJ HVPS works fine

5. bad PJ CLM reproduces original problem in good PJ, displays dots

It seems that there are two problems, one causing the display to be one dot per crt and another new problem causing nothing to display at all. Should I continue swapping, or is it likely that one bad board damaged another? I don't want to have two bad projectors.
-Eric

**Curt Palme** · Posted: Thu Sep 17, 2009 2:34 pm Post subject:

Keep swapping boards. I'd suspect a neck board or the VIM. I can repair the one(s) that are bad.

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

wbamb83392 · Joined: 16 Sep 2009 Posts: 8

Ok I've swapped just about everything from the bad PJ into the good PJ and it still works: VIM, HDM, HVPS, LVPS, all three crt socket boards, the entire heat sink/board assembly, and the focus module. The only bad part so far was the CLM, but the good CLM does not cause the bad projector to function. It turns on and displays no error lights, but there's no picture at all and no static electricity noise like the good PJ makes.

I haven't swapped the HV splitter yet, or the board above the CLM. It looks like I'll have to completely disassemble and reassemble both machines for each further swap, so feel free to offer any shortcuts.

-Eric

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

Check the entire non working pJ's mother board for any screws or metal parts that may have got caught in one of the open connectors, especially up against the back plane. So yes do a complete tear down and rebuild of the non working PJ, use the good CLM once its all back to check and still clean the bad clm's chips and contacts first and test it once more before the tear down just in case. i had a clm not work in one PJ but worked in its original PJ after i did all the cleaning of the chips, not sure why but it only worked in that PJ? Weird huh?

Athanasios

wbamb83392 · Joined: 16 Sep 2009 Posts: 8

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

well the HV crackle is good!! I did the same thing once with the back heat sink ribbons and no issues after. Have you checked the Voltage at the P14 plug?
This is the heater element voltage, it should be 6.35 volts or close to it. if its higher than the tubes could be shot. One more thing are there any error lights
on the CLM now that it works or on the LVPS front panel?

And for shits a giggles after you hear the HV crackle wait a minute and hit the contrast button and raise it with the up arrow , you never know it might be all the way down. Also check to make sure all the G2 lines are on the correct PIN on the tubes!!!! look at the marquee set up guide here on curts site its the Top pin in the key slot of the tube socket.

Athanasios

wbamb83392 · Joined: 16 Sep 2009 Posts: 8

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

6.43 is kinda high and it could have cooked the tubes over time but I am not 100% positive that the voltage you see is enough to do that, some other person care to comment? One thing you can do next but its more work to see if the tube is cooked is to swap a tube from the bad to good PJ and see if it lights up. Oh one more thing did you switch the Vim from the good PJ to the bad one? also use the good CLM in the Bad one together with the VIM.

Athanasios

Revox · Joined: 13 Feb 2008 Posts: 158

No, 6,43V isn't to high. Its under +-5%! I red something in the bulletin messages that you should start thinking about this voltage when its under 5,5 or over 7V.

When the tubes of one PJ are burned hard (can you make a picture of them?) stop searching, offer all parts, whatch a movie instead of "wasting" time.
I understand your problem of failure search, i am always motivated in finding a bug too but afterwards i look back and namend myself a time waste basket!

wbamb83392 · Joined: 16 Sep 2009 Posts: 8

Revox · Joined: 13 Feb 2008 Posts: 158

My M was used 800hours and has a very bad green tube. I didn't wonder about this:
They put G2 to 80 and set the contrast and brightness very high. Then they destroy half of the light output using polar filters...

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

wbamb83392 · Joined: 16 Sep 2009 Posts: 8

draganm · Joined: 08 Mar 2006 Posts: 8990 Location: Colorado

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

Drags right here is the procedure for fixing the heater voltage.

Re post from my Marquee thread:

http://www.curtpalme.com/forum/viewtopic.php?p=106293#106293

The first installment I thought should be the Heater filament fix . this is to save the tubes
from over voltage to the heater elements in the tube causing premature failure.

remove the LVPS from the projector and open up the case being careful to remove all
connectors before completely opening. Locate the 6.35 voltage trim pot on the section
that houses the fans. a 470 ohm metal film resistor and a 20ohm trim pot is needed.

here is a close up pic.

remove the old pot that causes the drifting of the voltage as shown here

then I wrapped one end of the resistor around the existing resistor as shown, I did
this backward for the pics, I should have cut the trace first as in the next pic after this
one.

this pic you can see the trace cut and the resistor soldered to the other
resistor, i found it easier to keep the lead on the resistor then cutting it after its all done.

Then I fed the other lead through the whole that the cut trace goes to. Make sure all the
old solder is removed so the pin from the trim pot can also fit.

Now with the new trim pot in place.

Back side of board showing lead from resistor and trim pot leads.

Solder the pins from under and put power supply back together and test the output before
you connect P14. trim pot to get as close to 6.35 as you can.

While you have the cage for the power supply out you can cut the screen area to allow better
airflow and it could also help reduce and turbulent noise, i used a pair of metal snips then a file
to smooth it out. I also added dynamat to the inside stop any vibrations in the chasis.
A fan noise post will also be in this thread too.

Parts needed: I get mine from Newark:

http://www.newark.com/jsp/search/productdetail.jsp?SKU=62J1506

http://www.newark.com/jsp/search/productdetail.jsp?SKU=94C3568

Athanasios

Elaine Benes · Joined: 25 Apr 2006 Posts: 1416

draganm · Joined: 08 Mar 2006 Posts: 8990 Location: Colorado

Nash i like your P14 fix. I've been doing something almost identical except resistor on bottom. I really don't like the fixed resistor method. I have one here done by someone else and it's at 6.23VDC. You would think that's fine but it throws a dimmer picture. I think nailing the 6.35 within +/- .01 is the way to go and you need a trim pot for that.