CurtPalme.com Home Theater Forum

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I'm watching a movie tonight on my 9500LC and then suddenly I get a faint smell of hot electronics.

A few minutes later the smell comes back and it's a bit stronger.

I'm not the kind of guy who waits for the fireworks. I shut down the whole system and start sniffing
for the source.

It's in the PJ. It's in the HVPS. I pop off the HVPS cover and it's apparently toward the middle of the board,
and as best as I can tell the parts that were getting hot are the two big 5 watt carbon comp 200 ohm resistors
in the middle of the board that are stacked on top of each other.

The HVPS (34.9 KV model) works as of now. But I do tend to believe that it's going to eat itself if I don't take
care of an impending failure.

So who's good with these units and can troubleshoot them before they explode? Shocked

It'll be cheaper and easier to fix it NOW than AFTER the fireball, I think.

Any suggestions would be appreciated. If you're confident that you can repair the unit, let me know
and we'll make a deal for your services.

There's a lot I can handle in a Marquee but I don't mess with the HVPS. No documentation, no parts support,
no desire to ride the lightning.

I'll replace components if someone with a clue makes suggestions based on experience. But I'm not going
to be the troubleshooter as I just won't work on energized equipment that runs in the thousands of volts.

CJ

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

I would at least check the solder joints on those resistors. May just need a simple resoldering. All done with power off and disconnected.

Robert A. Hill · Joined: 19 May 2006 Posts: 182 Location: Simpsonville, SC

I agree with Mac. Simple to do and costs nothing but some time.

I check all the solder joints in the Spellmans in Ampros and have found many joints needing touch-up. I do not know if they left the factory with voids and poor wetting or if these developed due to overheating and just got worse with time. I saw restarts and shutdowns before repair. On one, it was also smelly and very hot. Maybe you have already done this as I remember that you are very skilled with a solder iron/repair station.

**Curt Palme** · Posted: Wed Dec 19, 2007 6:58 am Post subject:

Those are carbon resistors and can drift. I think each one is 220 ohms, so 110 in parallel. I've seen those get hot over time, I have never seen a schematic of the HVPS, so I don't know how those resistors relate to the rest of the circuit. I'd put in 2 watt metal film and see what happens.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I'm going to measure the values of every passive component and resolder every connection as a starting point. Components that have
drifted out of tolerance will be replaced.

But I'm not so sure about replacing those resistors with metal film resistors due to voltage ratings. Resistors DO have voltage
ratings, you know. And metal film resistors often have lower voltage ratings than carbon comp resistors. It's something to consider.

Thanks.

Update coming when I have one.

CJ

mp20748 · Posted: Wed Dec 19, 2007 12:35 pm Post subject:

Those two carbon resistors should be replaced before they cause failure to the HVPS.

Replace ONLY with Carbon 'Film' or Ceramic.

That section has a high voltage pulse on it from the power FETs. In those circuits (high voltage), you'll not want to use metal film.

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

Here is some pics of my modded HVPS. see the new Ohmite ceramic resistors. replace them all the caps are an option.

Hope these will help you find the fault.

oh and i'll also attach a schematic i got form some where cant remember.

Joust · Posted: Wed Dec 19, 2007 7:33 pm Post subject:

cool
you wouldn't happen to have the other two pages would you?

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

Thats the only one i have. i forgto where i got it. I think it was on this site. I think the person who drew this up did it for his own use. the other parts are most likely the potted section which should be left alone. and maybe the other page could be that small board attached to this board in the schematic.

Athanasios

JustGreg · Joined: 07 Mar 2006 Posts: 3098 Location: Kenosha, WI

I wonder whatever happened to sly from AVS. I was hoping he would have come over here when this site went up. He's the only person I know who modded the exposed boards and dug into the potted section. He had all the equipment to repot. He also posted some great pix of his LVPS filament voltage fix.

I'll go see if I can't track him down. He was generating schematics as he went along too.

Greg

Joust · Posted: Wed Dec 19, 2007 8:08 pm Post subject:

the voltage multiplyer section is in the schematic. I'd expect that is in the potted section.

PaulB · Posted: Wed Dec 19, 2007 8:19 pm Post subject:

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

Paul, go through it over and over again. you have to because there is soooo much info to absorb. I got the HVPS upgrade from Jeahong lees posts not the marquee maintenance thread. threre are 15 resistors to change on the HVPS if you remove all the carbon comp ones. On the vertical and convergance boards some of the resistors are hard to match up exactly. that is why there are different values. most agree that same value with a slightly higher wattage is ok. and keeep the tolerance equal or lower you should be fine.

Joust · Posted: Wed Dec 19, 2007 8:34 pm Post subject:

PaulB · Posted: Wed Dec 19, 2007 8:54 pm Post subject:

I think you're looking at the wrong ones Joust, R5 and R46 are both shown as Metal Film in the guide as per picture below

The link you provided looks pretty much to be the correct resistor that should be used as per Athanasios' advice and Jeahong lees blog http://blog.paran.com/pcaudio/645731 and conforms to Mike Parkers advice NOT to use Metal Film.

Paul

Joust · Posted: Wed Dec 19, 2007 9:02 pm Post subject:

oh right.

but i don't think it says metal film. It doesn't say they are not either though....

PaulB · Posted: Wed Dec 19, 2007 9:07 pm Post subject:

Joust · Posted: Wed Dec 19, 2007 9:11 pm Post subject:

sorry, I'm looking at the master document and I cannot find this reference.
I did update it to indicate the picture is showing metal film parts and not to use metal film in the HVPS.

It certainly could use an update. I'm sure there are a lot of things in there that can be updated.

mp20748 · Posted: Wed Dec 19, 2007 9:13 pm Post subject:

not sure where your picture came from, or why you're saying that R5 and R46 are metal film, because they should not be metal film.

From the picture that you're showing, it looks like someone had replaced those resistors (not sure). But a safe rule to always follows is that metal film resistors should never be used in high voltage circuits, because they don't deal with spikes and high voltage flashes too well. And that is why they are not found in CRT focus circuits and the circuits that are connected to the CRT elements where high voltages and spikes are common.

Whatever you do, do not put metal film resistors in any circuit that deals directly with high voltage to CRT's elements or circuits that deal with high voltages and pulses.

In the very near future, we will be back with the maintenance thread, and other things as it relates to keeping our hobby alive and doing well.

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

I ordered all my parts from newark. they have most evrything.

Athanasios