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Discussion Starter · #1 ·
My marquee 8500 Ultra has suddenly started to act up a bit... the screen brightness fluctuates at random times, making the whole picture brighter for fractions of a second in bursts. This isn't a constant problem... it tends to come and go every 10 minutes or so and lasts for around 20 secs.


Haven't had time to run simple tests on cabling (power & vga), and the source device (PC), but it looks pretty much down to the pj.


Anyone got any ideas? ... or cures?
 

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most likely one of the 2 power supplies?
http://www.curtpalme.com/Electrohome...e_Layout1.shtm

I would pull them both out (power OFF) and clean the male socket motherboard plug at the back with a Q-tip and alchohol. They build up a lot of grunge back there which plays hell with critical voltages.
 

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Hello


One possibility is tarnished connections or crystallized solder joints inside the HVPS. Pull the HVPS from inside the front grill and remove the rear metal cover.




A small PCB sits upright to the side, it lifts out with a pull upward, we have seen where the contact pins and socket under it may benefit from cleaning.




Get a quality contact cleaner solvent, Radio Shack has one with a brush applicator in a pressure can, get some canned air also. Apply cleaner, allow to sit a minute, then blow dry with canned air.


Same for all the socketed ICs on the board, pry them out carefully one at a time, do not bend the legs, and mark the IC with felt tip to note the orientation; clean the IC legs with solvent and clean the chip sockets too, blow dry and reinsert each.




Some very large resistors live in there, resolder both legs of the six large resistors, the original solder can crystallize over time.




Clean the contacts along the rear of the HVPS and the socket inside the bulkhead that they mate to. Reconnect the anode lead firmly (pink wire) until it clicks home. Reassemble and try and good luck.
 

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Discussion Starter · #4 ·
Tested the projector late last night and interchanged all external cables. Cleaned the motherboard plugs and the external power supply connector. Left the unit on for an hour and a half and tested it again. It looks like the problem has been resolved... for now at least. Switched the external cables back to the original ones and the problem still didn't show.


I will come back with a follow up... seeing as it was a tempermental problem, it may have been a good day. Thank you both for your help... if this fails I will try the re-soldering... not something I am looking forward to considering I have it ceiling mounted!
 

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Watch it carefully. I've had the same problem on my old 8000 for years. It goes months without a sign, then acts up like crazy for no apparent reason. I haven't been able to determine any cause of it and I've swapped out everything except the mainboards and the rear heat sink boards...
 

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Glycol leakage down the back motherboard can do that. Rare with non LC sets, but I've seen a few LC MArquees do it.
 
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