CurtPalme.com Home Theater Forum

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Well lets see how well this thread goes.

There seems to be a lot of opinions on capacitors on here so some things have me curious. I'm also curious as to the responses and also who responds.

So I'll start off with this question. What are the internal operating temps of a projector? Are there areas that are hotter then others and if so where?

Dont be shy to respond. I think this should be discussed openly and with no hard feelings amongst anybody. It may answer questions that many here have.

**Curt Palme** · Posted: Tue Nov 03, 2009 4:57 pm Post subject:

Hot ambient temperature = short component life. That holds true for semiconductors as well generally.

WHat's strange is that NEC USS 6010 switcher I recapped had 30+ bad caps, although the switcher output card mostly runs cool. I'm guessing it was jammed in a rack somewhere? All caps I changed were the higher grade 105 degree caps, and had leaked onto the board.

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

I love threads Like this As I am always up for learning new theories or practices.

To be honest My Pj's do get hot, but not so hot as to cause a capacitor to fail outside of its temp rating. But if there are any 85c caps those i might change out to 105 temp.
The rear convergence amps get the hottest on the marquee, then possibly the focus boards heat sync.

However in some cases doesn't the specified values , ripple current and ESR rating change with an increase in Temperate, so couldn't that be another reason to go to higher rated temp caps.

Am I right on that one Ron?

Also what about shelf life ratings on caps? shouldn't a piece of equipment that has been idle for years and
years be re caped ? Just to be safe.

So what do you think, since you are the one asking the question?

nashou

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

there's too many variables to make a definitve statement about CRt's in general. I know on a Marquee, which has excellent cooling AFAIC, the caps don't generally fail to the point of leaking crap on the boards. The marquee also uses 85C rated caps almost exclusively in every location. All 85C caps i've seen are rated for 2,000 hours at 85C before they start to degrade. the caps i like to buy are rated for 5,000 to 10,000 hours at 105c.
I also don't think outright failure is the biggest issue, some degree of internal voltage leakage in an old cap beyond the rated 20% will also cause parts up-stream to run harder and hotter.

Ile · Posted: Tue Nov 03, 2009 7:31 pm Post subject:

Air temperature coming out of my BG808s is about 40 celcius.

Hottest heat sinks are about 50-60 celcius.
https://www.curtpalme.com/forum_archived/viewtopic.php@t=13103.html

Even in worst case scenario (85 degree cap near hot heat sink) hottest caps are least 25 degree under rated temp.

So I think 85 deg caps are just fine by temperature. But still I have feeling that 105 ones would last much longer if both are used in 50-60 degree. Also some special caps like low impedance ones are only available as 105 deg version.

jkruger · Joined: 24 Oct 2007 Posts: 2435 Location: Carlsbad, CA

No to hijack the thread, but does anyone else think that image does something strange to your eyes? It looks like it's shrinking to me.

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

what are those area's at 90 to 125?

**kal** · Posted: Tue Nov 03, 2009 10:18 pm Post subject:

An important thing to remember too is that heat doesn't just kill things faster such that they all of a sudden stop working. Heat will cause convergence drift and stability issues as the parts age faster too.

Keep your projector cool and it'll not only last longer, it'll be a lot more stable from turn-on to turn-off. I got my current projector new and it's well cooled and always stable from turn-on to turn-off. No waiting for it to stabilize. Only thing is it takes about 5 minutes for the contrast ratio to get to the best. Just enough time to get a beer, put in the movie... etc... Wink

Kal

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

So should caps be changed just because of how old they are?

Or because of there rated hours based on the rated temp?

How about because of there placement on a board in comparison to other components generating heat? Of course because of location to a heat generating component would the temp of that location matter? What if its location is in a cooler area?

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

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

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

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

Age of years, especially if not used, as the electrolytic type capacitor deteriorates over time being unused that if having a voltage biased in normal use.
this i read somewhere when i first began getting in to this Hobby a few years ago.

Also getting back to heat , over time if exposed to heat the oxide film will dissolve into the electrolyte , and as temperature increases so does the rate of dissolving.

under normal temperature conditions and if used frequently they will perform well but any prolonged non use or extreme heat will deteriorate
the cap.

I had not read up on this since long ago and had to look back on some bookmarks in my browser for a "refresher" course

Nashou

Ile · Posted: Wed Nov 04, 2009 10:59 am Post subject:

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

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

Here is a good site on Capacitors of all types and cons and pros of each, along with aging properties, cause of failures, and other characteristics.

http://my.execpc.com/~endlr/reliability.html

An excerpt on reliability of Aluminum caps

Aluminum electrolytics have a reputation for being troublesome in some electronic equipment. NASA, for example, does not allow them to be used in flight hardware because of the risk of failure and outgassing. Tantalum capacitors can be used instead. There has been some work in designing aluminums that could be used in space applications however.

In general, close attention has to be paid to their application if you expect good long-term reliability. The higher the operating temperature the shorter their life, and running aluminums too hot seems to be a common design mistake. This can be caused by things like excessive ripple current, poor ventilation, too high a system ambient, and/or locating them too close to a hot power supply component. Over time the oxide film tends to dissolve into the electrolyte and every 10C rise in temperature doubles this effect. The rate of deterioration is much faster in storage than if the capacitor is kept voltage biased in normal use. Actually, the most common failure in aluminum electrolytics (at least for through-hole aluminums) is not loss of capacitance or leakage, but increase in ESR, due to loss of water from the electrolyte. This is also temperature dependent. Operating life is less dependent on operating voltage than with some capacitors. A generally accepted formula for estimating electrolytic capacitor life is:

LT=LR*(ER/EO)*2(deltaT/10)

Where:
LT = operating life under stated temperature and voltage (capacitor core temperature, not just ambient)
LR = the life at rated limits
ER = rated voltage limit
EO = operating voltage
deltaT = difference between rated operating temperature and capacitor core temperature in C

Athanasios