Hi Folks:
My Marquee 8500 LVPS was dead last week, but in checking it out I realized that one of the fuses had blown (the 1/2 amp fuse). I replaced it and now it seems to work and everything engages and sounds normal. However the tubes now output very very dimly. It's like they're suddenly all dead. Any suggestions on what may have happened? Any options I can try to revive things or am I done for?

Thanks!
John.

Hello

Take off the side panels, there is a row of connections under the blue tube, see if the connectors are carrying the voltage they are marked for. Measure filament there also, it needs 6.3 vdc. Take off a neckboard cover and measure G2 at the tip of R76, it should be 500-600 volts dc.


.

Thanks Tim. Quick question (I know this is a beginners question, so bear with me). I have a device that I think can/will test voltage. It's a Gardner Bender Multitester (GDT-200A). It has two leads (A red and a black) and choice of three inputs to connect to (10adc, Vohm mA, and 'COM'. Do you know which lead goes where? Also, what setting should I select the twist/setting to (there is DCV, ACV, DCA etc). Sorry if this is a stupid question - this stuff is not so intuitive for a layperson.

Thanks in advance,
John.

Ok, with a bit more online research I think I'm testing P14 correctly now (using multimeter to test between HRTR1 and HTR2 connections on P14), I get a reading of 3.6 when the projector is fully initialized. So, I know that's way off from 6.3. I only had the projector on for like 1 minute after I had the LVPS up and running again. Can that have killed the tubes? P14 mod had been done before on this LVPS (and it has the toggle on the side of the LVPS, which may allow changing of voltage, or is it too late now anyways? :(

I'm not sure what to connect where for the G2 and other connectors, Tim. I know I can put one end of the Multimeter to R76 and can try the other settings above P14 on the base of the projector next to blue tube, but where do I put the other end of the multimeter?

Thanks,
John

Thanks Tim. Quick question (I know this is a beginners question, so bear with me). I have a device that I think can/will test voltage. It's a Gardner Bender Multitester (GDT-200A). It has two leads (A red and a black) and choice of three inputs to connect to (10adc, Vohm mA, and 'COM'. Do you know which lead goes where? Also, what setting should I select the twist/setting to (there is DCV, ACV, DCA etc). Sorry if this is a stupid question - this stuff is not so intuitive for a layperson.

Thanks in advance,
John.

John, here is a ten cent tour of a multimeter :p


"COM" stands for common, or ground, which is your black lead.
The red lead is for the voltage. The meter should be set to DCV, which is DC volts
ACV stands for AC volts and would be used for testing AC voltage, such as from a house outlet. Everything after the powersupplies in this projector is DC.
DCA stands for DC amps, and is used to measure current.

Once you have your meter set up (dial to DCV, black plugged into 'COM' and red plugged into VOhm, your ready to measure the voltages. The black lead should go to a ground point, the red lead goes to the test points that Tim mentioned.

Hope this helps, and good luck!

Paul

Thanks Paul. It worked perfectly. Well, so far, the voltage between HTR1 and HTR2 is 3.6 which does seem way off. I checked the other voltages close by under the blue tube and all are accurate (A good sign I hope). I can't find R76 on the neck board. I see lots of other "R" values, but can't find 'R76'. Any tip on where I can find it?

Will an updated LVPS do the trick (I happened to have found a used one for cheap from another member who mailed it to me, so I can try that. Or am I already done for? ;-(

This is a good excuse for me to get one of the Longbows ;-)

Thanks,
John.

You still have a bad LVPS.

Thanks Curt. I'll see if this other LVPS (which is properly modded) will do the trick, when it arrives.

Yep.. when a fuse blows in a Marquee LVPS, it usually means the LVPS is defective.

I can't find R76 on the neck board. I see lots of other "R" values, but can't find 'R76'. Any tip on where I can find it?
Thanks,
John.

It is one of two upright resistors closest to the tube end cap, middle of the neckboard.

It sounds like the low filament is the problem.
.

if its the filiment line problem check not only the Trim pot but the cap and diode.

I replace the 1000uf 10V cap with a 2200uf 25v cap

Check C126 and D64

http://homepage.mac.com/nashou.66/.Pictures/Marquee%20Upgrade%20Pictures/LVPS%20Cap%20Upgrade%209.jpg

If cap 126 shows signs of leaking or bulging its bad, check the diode with a diode test section of a multimeter.


Athanasios

Nashou to the rescue....AS always

God I love this forum

Martin

John, did the new LVPS do the trick?

Athanasios

Hi Athanasios:
thanks for checking in. Indeed, I am up and running again now. The replacement LVPS did the trick. However, I checked the voltage and it's at 6.6 on P14 rather than what I believe should be 6.3. Is that too far out of spec or ok?

Thanks!
John.

Hi Athanasios:
thanks for checking in. Indeed, I am up and running again now. The replacement LVPS did the trick. However, I checked the voltage and it's at 6.6 on P14 rather than what I believe should be 6.3. Is that too far out of spec or ok?

Thanks!
John.

6.6 = DANGER Will Robinson
no joke, that's a Cathode killer