CurtPalme.com Home Theater Forum

nidi · Joined: 17 Aug 2008 Posts: 305 Location: Switzerland

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

Did you guys check Scotts suggestion here?

mp20748 · Posted: Mon Oct 18, 2010 5:41 pm Post subject:

I'm really puzzled on this one trying to figure out how a tube could cause the HVPS to blow its FETs.. Confused

The power supplies in the Marquee are both smart supplies. Meaning, they just don't fire up without first confirming the load on them.

The LVPS when you turn it on, it senses a load on each of the rails and if that load is off, the projector will shut down. And its rails put out a lot of current once it settles. Think about it, when have you ever seen a burnt trace or wiring in a marquee from a short?

The same people who set the design goal for the LVPS did the same thing with the HVPS. It to will do a current sense before firing up. If you notice, when you fire up a Marquee, you should notice a brief high voltage noise or sparkle as what's common when high voltage gets to the CRT's... a few seconds later, you'll here that noise again, but loader. That's because the HVPS initially fires up, before it really fires up. If there's a load (tubes, splitter,etc) on the 34.9kv line, you will not hear the second and final noise.

I know the Marquee is not the most advanced of the CRT projectors, but it'll be hard to find one with more advanced circuit and tube protection than a Marquee.

This is a strange problem indeed.. Sad

HK-Steve · Posted: Mon Oct 18, 2010 5:44 pm Post subject:

All the chassis wiring has been checked, visually and also for electrical insulation, plus continuity.

The VNB are good, as I have tested with a 8inch tube which fired up no worries for the 3 VNB.
Which also test the splitter.

Cheers
Steve

HK-Steve · Posted: Mon Oct 18, 2010 5:47 pm Post subject:

Thanks Mike, But I know what you mean with the start up of the HV,
But when the projector starts, we get the normal clicks of the CLM, then the last click is the HVPS.

for which we get the fuse exploding, no crackle at all.
it is pretty much as soon as the relay turns the HVPS on, BANG.

Appreciate the replies and advice.

Cheers
Steve

mp20748 · Posted: Mon Oct 18, 2010 5:53 pm Post subject:

The only thing I would suggest is to either replace the FETs and see what happens, or try another HVPS in it, but do so starting out with the anode lead not connected to the splitter and floating away from touching anything.

HK-Steve · Posted: Mon Oct 18, 2010 7:03 pm Post subject:

I have 2x HVPS which I have replaced the FET's, but they are non repairable now, as they just don't fire up any more,
so looks like more damage than just the FET's.

Tomorrow I will take some video of when I power up and show what happens.

Keeps the suggstions going, Much Appreciated

Cheers
Steve

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

Steve have you looked closely at the Connector where the HVPS plugs into ? It just has to be a short somewhere, this is bewildering us all . It is hard to look
at it through the bay to make areal assessment, is there any way to remove it and do a closer inspection. I think its just best to get this out of the way and move on to the next likely place.

Athanasios

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

mp20748 · Posted: Mon Oct 18, 2010 7:25 pm Post subject:

HK-Steve · Posted: Mon Oct 18, 2010 8:08 pm Post subject:

OK 3 post, and 3 replies in 1 back.

Wiring loom is perfect, connectors perfect, even tested with new loom. still problem.

VNB and splitter put into another test chassis, no problem in test chassis, original chassis still a problem.

Replaced Fet's 2x times, plus some other resistors, diodes and caps, still a problem.

I am going gray, just thinking about this problem,
if I only had hair ")

Cheers
Steve

mp20748 · Posted: Mon Oct 18, 2010 8:14 pm Post subject:

HK-Steve · Posted: Tue Oct 19, 2010 6:18 am Post subject:

Yes, it still blew the fuse.
Looks like it has damaged something else further down the line.

Cheeers
Steve

mp20748 · Posted: Tue Oct 19, 2010 7:43 am Post subject:

stefuel · Posted: Tue Oct 19, 2010 9:00 am Post subject:

To early in the AM for me. I'm not sure of a way to test a tube for internal HV shorts. There's three pages to read here so this might have been asked already. You have looked through the lenses for any visual tube damage? I have first hand experiance with what happens when a tube face cracks and coolant fills the tube. A HV short due to fluid in the tube bell can be read with a DMM. Not sure what the readings would be but it should be close to that of putting both test leads in a glass full of coolant.

HK-Steve · Posted: Tue Oct 19, 2010 9:48 am Post subject:

All the cables for the tubes and HVPS are all in good condition, so I don't think there is an issue there.
This why I am really hessitant at putting another HVPS in just to see it blow, not a cheap way to fix.

The tubes are all good visually, glycol is in the LC chamber, no cracks, or glycol in the neck of the tube.

I put a multimeter onto all tubes and they all had the same readings.

So Which Color tube do I put in first, to see if the HVPS blows again????
Flip a coin??

Appreciate all the advice.

Cheers
Steve

stefuel · Posted: Tue Oct 19, 2010 10:35 am Post subject:

"So Which Color tube do I put in first, to see if the HVPS blows again????
Flip a coin??"

NONE!!!

Pull the HV from all three tubes and see if HV comes up normal (not sure if a Marquee checks for HV connection to tubes).
Then connect one at a time.
The odds are in your favor of not blowing the HVPS on the first try (66 2/3rds %). If you get past the first one then it's
50/50 on the next try Laughing

tse · Joined: 03 May 2006 Posts: 1014 Location: Sweatbucket, Fl.

Replace fuse with two 100W, 220V incandescent light bulbs connected in series. If everything is ok the HVPS will come up and bulbs will have slight glow. If problem, lamps will light up bright but nothing should break. Might help to find the problem.

Scott

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

Aren't Incandescent light bulbs now Illegal in Europe!!! And soon to be here? Damn Global warming BS!! Now i need to buy a lot of those to have incase i run into the same issue.

Athanasios

HK-Steve · Posted: Tue Oct 19, 2010 2:39 pm Post subject:

Thanks for all the suggestions,
Today I am exhausted after a day of work and looking after my 2x boys who are on school holidays.

I will give some more feedback tomorrow on what I find with the lamps in series, Thanks Scott and Chip.

I repaired one of the supplies, but I don't think 100% because when I just had the splitter and no tubes connected, the fuse blew.
Splitter tests OK with the 8inch tube and also in my own projector, 9500.

Cheers
Steve