CurtPalme.com Home Theater Forum

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

Hi everybody,

I have a defective Marquee HVPS. I also have a spare one, but the defective one is a newer version with the better resistors etc.

So I was wondering, if there are obviously defective parts in the unpotted section, is it worth trying to replace them, or will there probably be defective parts in the potted section too?

Greetings!

Tillman

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

Hello

I have only ever managed to fix one; there was a visible arcing and a foil trace had charred. I jumpered around the bad spot and got it working.

.

Ben851 · Joined: 13 Sep 2008 Posts: 221 Location: Ottawa, Ontario

I tried to fix mine by replacing all the caps and resistors in the unpotted section - it was a complete waste of time and money... I'd say stick with your other one...

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

In my case (at least) the two MOSFET's on the side are dead. But it seems there's not much chance of getting it working again.

Thanks!

Tillman

**Curt Palme** · Posted: Fri May 07, 2010 1:24 am Post subject:

Put it in a set and put your ear to the case of the HVPS. If you hear a ticking sound, it's a writeoff. If it's dead without the ticking, there's about a 1 in 3 chance it can be repaired. I've gotten a few running.

mhalsan · Joined: 09 Nov 2007 Posts: 146 Location: Astoria, Oregon

I assume the potted section contains something similar to the flyback transformer used in vintage TV sets. What's in there that causes a ticking sound?

Just Curious. Not about to cut one apart.

Thanks, Mark

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

It takes a very rare kind of specialist who'll dig into the potted section and attempt repairs. But if he could do it economically, he'd have
a nice little niche market to serve!

I wouldn't consider potted section repairs unless I had access to the CORRECT components for repair and also had a supply of the same
sort of potting compound originally used, for safety's sake.

CJ

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

I did some research into removing the potting material a year or so ago. Although it is (arguably) doable we need to know the exact compound used in order to to select the correct removal method.

A heat gun should be the first method used as most non mil spec/aerospace potting will eventually surrender to thermal breakdown. This method allows you to precisely control the removal process compared to chemical submersion methods. This method will require many (tedious) hours of heatn' and a-pickn' but is desirable to the usage and proper disposal of chemicals.

Epoxy based potting can be dissolved using dichloromethane, methylene chloride (not methyl choride), and methylene dichloride. (All the same chemical actually) I would imagine the process would take about a week or so and may require periodic mechanical removal of surface material to expose untreated potting. Use extreme caution when using these chemicals and do NOT heat it! It boils at ~40c but I wouldn't recommend it.

If using chemicals you should adhere to the MSDS warnings as they all present hepatic, chronic cancer, neural, and respiratory hazards in addition to the obvious acute hazards such as splash introduction to the eyes. (I didn't mention ingestion because HELLL-OOOOO...) This chemical is still used in the USA and is the main ingredient in most solvent based paint strippers.
Silicone should surrender to a bath of consumer level silicone cleanup solvent with the same mechanical removal of material as it softens. Commercial silicone solvent is more aggresive but more difficult to obtain in small quantities. (< 5gal )

The biggest concern I had aside from the obvious health issues is the degredation of coil winding insulation coatings, PCB and plastics damage.

IF repairs can be affected once access to the innards has been achieved we will have to reverse the process and reintroduce a suitable potting material with suffient thermal and dielectric properties. Epoxy will generally cure to a semi rigid state in ~24 hours, ~2 hours for urethane to cure to a hard rubber (75 Shore A), and ~12 hours for Silicone to cure to a medium rubber (50 Shore A). Dielectric properties/years in use respectively: (YIU is just an FYI, but interesting)

450V per mil/31, 450v per mil/24, 450v per mil/8. (EDIT:Fixed incorrect Voltage for Silicone. I typed 50v initially)
FYI-a mil is .001"

I would hope that anyone considering chemical removal USES the necessary personal protection equipment as outlined in the MSDS.

Access to critical knowledge (potting material used and what/where everything is located) is the difference between surgical methodology; and throwing a lawn dart while blindfolded at a family reunion.

Hazards not withstanding, I STILL want to see and touch what's in there though. Rolling Eyes

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

https://www.curtpalme.com/forum_archived/viewtopic.php@t=18703.html

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

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Hey..... I was just rereading that thread and I came across this....

http://www.curtpalme.com/forum/viewtopic.php?p=217907#217907

Mostly this sentence: I've got a couple of late model Ampro 3600 LVPS coming your way along with a parts unit. THey are leaving tomorrow.

Hey Curt....... I never got these......are they lost in the mail???? Laughing

stefuel · Posted: Sun May 09, 2010 11:51 am Post subject:

dvh99 · Joined: 25 Dec 2009 Posts: 2158 Location: nederland

if the daughter board on the hvps comes loose it wont start the pj, maybe its that.
i once changed out a couple of those big polyester caps for high grade polypropyleen ones and forgot to put the daughter board back after which the pj wouldnt start without any report on the clm of an error.

dennis

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

No,
it's not the daughter board I guess. I KNOW that there are defective parts in the unpotted section, but I don't know if these took out something in the potted section as well. (defective parts I know of are Q1 and Q2)
I think there's no ticking sound from the potted section, as the fuse of the HVPS blows as soon as the LVPS is plugged in (not turned on!) .

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

If you know these parts are bad then the only way to find out is to change them. Nobody can tell you what the outcome will be. There may also be other bad parts that are not in the potted section. Just trace back the circuits off those transistors and check back a few parts locations.

When your done and ready to fire it up just make sure you have your gloves and goggles on..... Shocked

Oh, and a fire extinguisher!!!!!!!!

**AnalogRocks** · Posted: Sun May 09, 2010 3:16 pm Post subject:

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

**Curt Palme** · Posted: Sun May 09, 2010 4:30 pm Post subject:

It's a throwaway. There's a short in the potted section that has blown the MOSFETS.

You might be the first, but I've never had a SPellman HVPS that has blown the MOSFETS that doesn't also have a problem in the potted section, causing the MOSFETS to blow in the first place.

dvh99 · Joined: 25 Dec 2009 Posts: 2158 Location: nederland

if it has the wirewound resistors i would take them out, they are expensive.