CurtPalme.com Home Theater Forum

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Sparky015 · Posted: Sat Jun 12, 2010 1:32 pm Post subject:

**Curt Palme** · Posted: Sat Jun 12, 2010 1:36 pm Post subject:

I would indeed replace the fuse first. If there's a problem in the HVPS, the fuse will blow again. Can't see a shorted HVPS damage the LVPS, which is what feeds the HVPS.

stefuel · Posted: Sat Jun 12, 2010 2:21 pm Post subject:

"Maybe the fuse blew from to much inrush current. Pop a fuse/thermistor combo in there and try it."

I like that.............."inrush current". Is this something new that you've learned or did it just POP into your head? Laughing

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

About the only thing that is going to blow a fuse like that is a large "inrush" current. Check those mosfets again. If they are not shorted look for punctured insulator between mosfet and heatsink. It could be one of the plastic caps on the power input. Something in the mosfet/input section is shorted to the chassis or shorted across the 385VDC input.

Scott

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

HK-Steve · Posted: Tue Jun 22, 2010 4:34 pm Post subject:

Hey Guy's,
A HVPS from Curt was shipped, put in, and you guessed it, POP it went.
Fuse exactly the same, so this is not a faulty HVPS.

I was on the phone when the projector was fired up,
Normal clicking of the HDM, CLM, last "On" was the HVPS, POP straight away.

No HV noise,
like the power was turned on the HVPS, then POP. not enought time to even fire up the tubes.

So, LVPS problem??
Splitter?? I looked at the splitter, but looked fine.
Tube shorted??
HV Cable shorted to ground??
G2 problem??

Now to go put that 2nd HVPS in the bin Crying or Very sad

Appreciate any comments

Cheers
Steve

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4409 Location: Phoenix

Hello

Inspect tube faces and tube necks for cracks. See if all tube filaments light up.

.

chillman · Joined: 09 Apr 2007 Posts: 134 Location: Germany, Bavaria

Before you throw it away, send it to me, I'll cover shipping Wink

Seriously, doesn't this mean that probably both HVPS's are still ok and that the problem is caused by something else, like the 385V section in the LVPS? The fuse is there to protect the HVPS, right? IIRC, the fuse inside the LVPS is rated a bit higher, which could explain why the one in the HVPS fails first.

Greetings!

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

One thing to consider is the LVPS runs from the same 385VDC that is sent over to the HVPS.

Scott

**Curt Palme** · Posted: Wed Jun 23, 2010 12:09 am Post subject:

Sorry Steve, haven't had a lot of time to answer emails. This is indeed very strange, that HVPS came out of my test set that has had 100+ hours on that HVPS while here. If the fuse POPS on both supplies, do check the MOSFETS. Strange if they would be shorted though, if there's a short in the HV block, the HVPS goes into shutdown mode, it normally doesn't blow the MOSFETs.

mp20748 · Posted: Wed Jun 23, 2010 12:43 am Post subject:

A short on the HV lead will not blow a fuse or short the FETS. It will shut down as Curt indicated.

The only thing I'm thinking is the 390 volt supply from the LVPS. That same 390 volt rail is also the sub supply source for the main rails coming out of the LVPS.

If somehow the 390 volt is higher than it should be the other switching supplies in the LVPS would most likely still regulate and you would not see a difference on any of the other LVPS rails.

So if all the other rails check fine, that would not rule out the LVPS 390 rail.

The LVPS is easy to test for this problem... the 390 volt rail is always on when the LVPS is connected to the AC line.

Remove it and connect it to AC line.

Follow where to put your meter probes in the picture, it should read 385vdc:

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

Mike the way you are probing that LVPS is exactly how I blew my first Marquee's LVPS up, it blew a hole right through the PCB board under one of the op amps near the three large fets, which also were all shot along with about 4-5 resistors and the fuse. Do not touch the case with the probes while doing that, it also melted the case to the probe.

Right after I did that everyone on AVS told me to put down my soldering iron and never to touch electronics again. Wink

But i did get one voice of encouragement. And I have them to thank for my continued interest in this hobby.

So Steve i know you know better but still be careful on that line, I agree with everything Mike said, you might have a runaway voltage there on the 385 line.

Athanasios

HK-Steve · Posted: Wed Jun 23, 2010 6:02 am Post subject:

Thanks for all the replies,
I will go throught the LVPS and check it out for the 385v output.

I pulled the LVPS when the first fuse exploded, but all visually looked OK.
Spare LVPS to install and to check the original looks like the plan.

Appreciate the help from you all.

Cheers
STeve

mp20748 · Posted: Wed Jun 23, 2010 6:41 am Post subject:

HK-Steve · Posted: Tue Jul 06, 2010 9:12 am Post subject:

OK, some more feedback on this issue,

Measured the 390v line, got 383v, so this does not look like the problem.
I used aligator clips, so no safety issues.

Looks like I need to check the tubes now, agree??

Appreciate your comments
Cheers
Steve

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

Yes do as Tim stated above. And why not try a new splitter too, you never know.

Steve, is it ceiling mounted? if so I wonder where the wires are running with regard tot he fans. I never seen it happen but what if they cam in contact with
a fan blade ever so slightly and it slowly cut through the 385v line (doubtful its pretty thick jaket) or one of the G2 lines if they go through there. Its been a while since i had those belly fans off.

Athanasios

HK-Steve · Posted: Thu Oct 07, 2010 8:44 am Post subject:

So I am revisiting this thread to finish the problem,

I have checked all other boards, no issues. Chassis wiring is all good.

So How do I go about testing a shorted tube?

Appreciate any replies and advice

Cheers
Steve

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

Steve, one thing we have not checked, the VNB's. There might be a problem on one of the G2 lines on the VNB. Aslo look closely at all the G2 lines going to the VNB's and possibly the HVPS connector on the backplane. Glycol drip?

Athanasios

HK-Steve · Posted: Thu Oct 07, 2010 12:57 pm Post subject:

Athanasios,
Definately no glycol issues, first thing I checked.
Ceiling mounted also does not cause the same issue with glycol. more mess on the floor.

VNB's have been checked, could find no issues.

Just don't want to blow an other HVPS. good for Curt, not for me. Embarassed

Cheers
Steve