CurtPalme.com Home Theater Forum

barclay66 · Posted: Tue Jan 10, 2012 8:20 pm Post subject:

barclay66 · Posted: Tue Jan 10, 2012 8:28 pm Post subject:

Uh, lots of posts to answer...

HK-Steve · Posted: Wed Jan 11, 2012 2:27 pm Post subject:

Michael, sorry to say it, but,
Pop goes the HVPS, again, and again, and again.

replaced the fuse, powered up with no tubes connected, splitter only, fuse blew straight away.
Same symptoms as the last 2 HVPS's.

Will see if I have a working A Revision.

Cheers

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

Are you sure the 390 volt line is not compromised? Do you have a spare Wiring harness you can replace Michael's with? It just seems wrong that its blowing all the time. Or maybe the back plane has a problem in the traces or the connectors. I would just do a tear down
to check it out. I hate seeing HVPS being eaten up by this machine.

Maybe replace his chassis with another one from an 8500.

Athanasios

HK-Steve · Posted: Wed Jan 11, 2012 2:58 pm Post subject:

Thanks for the suggestions Athanasios, but,

I had Michaels chassis at my place, replaced the loom, and also checked the LVPS output,
It sat stable for 8hrs at 383 to 385volts, as I data logged it when running for a full day.

Back plane board was also checked, but looked perfect.

I do not have any other chassis to change-over, don't see how it would help??

Appreciate your comments, but looks like I will loose even more hair with this problem.

Cheers

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

Steve when checking the 390 volt line are you checking it where it comes out of the LVPS location or on the output socket to the HVPS?

Id check it at the HVPS end.

This is f*ck*** up, I read back and see it worked with the 34kv PS but it got too hot to touch and you had to shut it down.

I wonder if there is anything under the mother board or behind the back plane that you cant see causing a short.

If it was me id tear down the entire chassis and double check everything with a fine tooth comb .

The reason id try another chassis is because there has to be a short somewhere with the 390vdc line/trace or one of the G2 lines/trace.
that chassis has bad JuJu now!!! Wink

EDIT: I had a set that kept showing a fail led on the 24 volt line. i couldn't find the issue. so i tore the set apart to part it out and there was a sheet metal screw behind the Back plane. I put it all back together and the LVPS had no error lights.

Athanasios

**Curt Palme** · Posted: Wed Jan 11, 2012 3:17 pm Post subject:

I haven't joined in here, because I have nothing really to add.

Other than the 390 volts input, there's nothing here really on the backplane or control circuits that affect the HVPS other than turning it on and off.

Here's the thing though about the shorted MOSFETs: It takes a LOT usually to create shorted windings in a transformer, as in the one that couples the output of the MOSFETs to the potted HV section. It's a coupling transformer. I know I had a bunch in the older Ampro 2000 HVPS, and have indeed seen some in the Marquee supplies, but it's sure not a consistent failure.

As I said above, I've had one Marquee do the same thing, and it never got resolved. Unless Scott has something to add here that they may have seen at the factory, I got nothing, sorry!

HK-Steve · Posted: Wed Jan 11, 2012 3:23 pm Post subject:

Appreciate any help Curt, and you have helped, like everyone else who has replied.

So what did you do with the Marquee that had same kind of HV problem?

Cheers

**Curt Palme** · Posted: Wed Jan 11, 2012 3:36 pm Post subject:

I don't know what the customer did with it. It was a HVPS sale only, 30 days later he told me it failed again, I sent a second replacement. 30 days later he called again. I asked how many he'd gone through, and he said 5 or 6. IN 6 months. (!!) Yeah, no warranty, sorry!

He did send me one of my sold ones back along with one of his other ones, but he'd hacked his potted section apart and damaged a bunch of the parts, so I had no idea what the problem was. I believe one of mine that he'd sent back had the 'ticking' sound in the potted section, so I threw it out.

WIth shorted MOSFETs, I've had about 50% success in replacing just the MOSFETs again. 50% of the time, they run red hot, indicating a shorted output transformer. I used to scope the gates of the MOSFETs to see if the input waveform had changed, but I think I've only ever had one bad HVPS driver board, and that caused a dead HVPS.

flipdog · Joined: 22 Dec 2011 Posts: 156

Possible arc back through the G2 line.........

HK-Steve · Posted: Thu Jan 12, 2012 10:15 am Post subject:

Would an arc through the G2, damage the VNB?

Next step, is to work out which tube,
Tubes were test using the Sencore which checked out all good.

Don't know what to do now.

Cheers

HK-Steve · Posted: Thu Jan 12, 2012 10:32 am Post subject:

Athanasios,
I might get the projector down and back to my place,
but I pretty much checked everything the first time, as per your suggestion,

might be the only choice to finally work out the problem.

Cheers

**Curt Palme** · Posted: Thu Jan 12, 2012 3:33 pm Post subject:

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

I still say its the 390 volt line, or the back plane connector for the HVPS. Something is causing a short to the HVPS form the outside.

Athanasios

barclay66 · Posted: Thu Jan 12, 2012 4:28 pm Post subject:

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

What i meant it is not caused inside the HVPS, all the HV supplies would work in another chassis i bet and would not blow as would their LVPS's. So what I meant was what you're saying is the back plane connector at the 390 volt output must be shorting the HVPS. I couldn't see it being the G2 connections on the Back plane. It blows the fuse to fast, and I assume not giving the G2 time to cause the failure/Short.

Athanasios

barclay66 · Posted: Fri Jan 13, 2012 9:12 am Post subject:

HK-Steve · Posted: Fri Jan 13, 2012 10:29 am Post subject:

PM, right back at you.

Chers

HK-Steve · Posted: Fri Jan 13, 2012 10:41 am Post subject:

The contacts on all 3 HVPS's are perfect,
shiny, no burns, no tarnish, nothing, see pic, just a nice pressure contact mark.

all look exactly the same.

Keep the ideas comming, we are going to get this worked out.

Cheers

barclay66 · Posted: Fri Jan 13, 2012 2:30 pm Post subject:

Hi,

The backplane connector is part of the wiring harness which is located below the belly fans. Although the connector itself seems to be ok it could be possible that one of the wires hasn't been crimped to it correctly. This could be checked. Another idea could be changing the complete harness (maybe some can take one out from a scrapped set)...

Regards,
barclay66