CurtPalme.com Home Theater Forum

[ronhowes]

So, first off, happy to be new to the forum!

Second - so I just became the proud owner of a Marquee 8500LC, HD8 lenses, multiformat decoder, contrast modulator add-in, looks to be in generally good shape. Got it for free from my company, which was replacing it with a newer LCD model.

However, it won't light up. Reseated the HDM board and focus board, no diagnostic LEDs on the back, I can hear the HV crackle as it powers up, everything looks normal, tube filaments are lit, etc, etc.

Then I noticed a burned electrolytic capacitor on the multidecoder board. C100 has turned black and vented. looks like it's in the +12V -12V supply on the board.

So, what might this indicate? Can I just assume the cap failed after many hours and get the board repaired or should I be looking for other problems? Can the set run without the decoder board? I tried it with this board unplugged but no joy that way either. (I'll be using the RGBVH input anyway) Otherwise, if you're out there, Curt, you probably have a new customer!

Ron

[Zebu Fellenz]

How is it LC if it has HD-8 lenses, the HD-8 is AC only and was used on all 8xxx Marquees except the 8500LC

[Nashou66]

Welcome to the forum!!!!

First off LC's can not have HD8's so either you read the lens wrong or its not an LC model.

Second don't worry about the multi decoder and remove it, it will use power off the rails and it could be the cause of your PJ not lighting up.

You did the right thing about reseating the board but on the HDM there is a smaller daughter board, that need to be removed and reseated also.

Also there are diagnostic lights on the low voltage power supply(LVPS) its behind the front panel, you can some times see if any are lit through the grill.

if this has been sitting and not in use for along time you may need to do a complete cleaning. Get an IC chip remover and some Caig cleaner and conditioner at radio shack. Pull out the CLM and clan all the removable chips and the daughter boards . and some denatured alcohol and clean all baords with a soft tooth brush and the denatured alcohol.

And congrats on a great PJ !!!!!

Also where are you located? Ad it to your profile signature


Athanasios

[ronhowes]

The nameplate definitely says 8500LC - the lenses are stamped "HD8B" - I'm new to these animals, so that's what it says at the moment. I have done the chip clean and reseat thing on all boards, also reseated the tube socket boards, both power supplies, CLM board, just about everything I have found in the various hints and tips online. Found the bad cap while doing the decoder board, the last one I pulled out.

The unit was ceiling mounted in a conference room where I work and was running at least as late as about three months ago before it was taken down. I can't deny, however, that the reason it was replaced may be because it died, rather than being just old technology. It was sitting no more than two days after it was removed before I got it home. Not sure what abuse it may have received during the removal process. The unit itself is clean and shows no obvious signs of dirt, moisture, etc.

I'll get 'er working - can't beat the price!

I'm a degreed EE by trade, so I have the skills and tools to do repair, but no experience (yet) on these beasts.

I'm in Minnesota, I'll add that to my profile.

[Nashou66]

Th 8500LC could be a new rear heat sink assembly from an LC added as a repair easier to just replace the whole back section then each individual board.

Click on my marquee stuff link i have some things you might need to help you out.

Athanasios

[draganm]

you have an 8500AC, most likely with a bad high voltage power supply. The multi decoder board is trash, even when it's working. Not good for anything except watching video from an old VCR= YUCK!

[Nashou66]

There is one more place to check, under the red tube on the back plane there is a few more connections, one is the High voltage power supply umbilical cord, that can come loose. you can access it by either removing the red tube or taking the side panel off on that side and going in from the side.

Athanasios

[ronhowes]

To Nashou66 - schematics! Woo Hoo! Thanks! I'll pull out the oscilloscope and start tracing my way through this thing. I'll also check the HVPS. I do seem to hear the crackle of this supply starting up, but I will double check for sure. My intent is to use a HTPC running the VGA output to the RGBVH input, so the multidecoder board will not get used.

Ron

[Nashou66]

You will need to make a set of extender cards or you will end up soldering wires to the pins you need to test. Read through the protection processing circuitry section for places to look. but first check the connector under the red tube. And Id go through and reseat all the boards again for good measure. and double check the conections on the VDM and CVA, if they are not exactly on the pins(one off) it wont start the tubes but you'll hear alt he rest as it sends a HVSP shut down signal to the HVPS. I say this since the rear heat sink section seems to have been changed and who ever put it on may have connected those connectors wrong, thus not allowing the PJ to fire up.

Athanasios

[ronhowes]

Thanks to everyone for the suggestions so far.

Status - I pulled all the external panels off to get at the electronics and such. All LVPS voltages are present at the main connector at the right rear corner of the top motherboard. I borrowed a 40KV high voltage probe and multimeter from my work and have verified there is steady HV at the splitter block - undid one of the CRT connectors and measured right inside the terminal connector itself. All socketed ICs on all boards have been reseated at least once. All boards and daughterboards have been reseated at least once. The CLM responds to commands via the RS-232 interface and an external PC running the Marquee remote control program. I have verified all CRT cable connectors are routed to the correct connector on all boards. CRT filament voltage is at a steady 6.15 V (bit low, I'll tweak it up a bit). The only thing I have not done yet is pul all the CRT assemblies and start reseating connectors on the motherboards. (something I don't want to do unless absolutely neccessary!)

So, I'm beginning to suspect , based on what I can glean from the forums and other info, is that the most likely culprit is a bad HDM - does that make sense at this point?

BTW, it is indeed an air coupled set - no idea why the 8500LC exterior rear panel is on the thing - some confused repair person at the end of the day in a dark shop perhaps!

Regards, Ron

[Nashou66]

Hi Ron, It most likely is the HDM but you can also check the CVA, a shorted CVA could cause a no tube light up situation. Pull teh CVA's connector to the mother board and try ti fire it up, do not remove the VDM cables!!!!!! That could cause scan trace to burn across the tube face.

Athanasios

[draganm]

[Nashou66]

[Curt Palme]

Check the filament voltage. If you have HV, then the HDM is fine. THe VIM might be dead though.

Check the filament, I'll bet this is a high hour set with drifting filament voltage which has killed all of the tubes. I've seen that a few times, and it's very misleading when everything seems to work, but there's no light output.

[Curt Palme]

Check the filament voltage. If you have HV, then the HDM is fine. THe VIM might be dead though.

Check the filament, I'll bet this is a high hour set with drifting filament voltage which has killed all of the tubes. I've seen that a few times, and it's very misleading when everything seems to work, but there's no light output.

[David_Web]

If you have the wired remote, check for shorts in relation to that cable. Connector is under the blue tube.