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benareeno
Joined: 22 Mar 2006
Posts: 1614
Location: ottawa, canada
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| Posted: Mon Feb 23, 2009 10:07 pm Post subject: thermal compound and heatsinks.... |
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Has anyone added this to the stk chips or any other hot running chips on their pj's? This may allow me to pursue my fan mod in a slightly safer manner...Couldn't find much in the search function, so I thought I'd get some discussion through this thread.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Feb 23, 2009 10:15 pm Post subject: |
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Do you mean adding heatsinks to things that dont have them or using compound on a device that already has a heatsink ?
Last edited by macgyver655 on Mon Feb 23, 2009 10:15 pm; edited 1 time in total
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Mon Feb 23, 2009 10:15 pm Post subject: |
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A whole bunch of sets are affected by poor quality thermal compound. Some of the boards end up with hardened compound and I attribute that to causing failures on the board. If a chip is bad, I take it off, chip off all the hardened material, wipe/sand down the heatsink block and put new stuff on. I've never had a repaired board fail a second time around. I think adding new compound t on top of old stuff is not a good idea, or at least it won't do anything.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Feb 23, 2009 10:21 pm Post subject: |
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Adding new compound on top of old is worse then none at all. Many people dont know how to use compound. Thinkness is bad. Its proper use is only to fill voids in the 2 surfaces to help in heat transfer. To apply properly you merely add a thin layer to cover the area in contact. When you place the component on the heatsink you move it back and forth to smear the compound until you hear the 2 scraping each other. That is the proper amount.
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benareeno
Joined: 22 Mar 2006
Posts: 1614
Location: ottawa, canada
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| Posted: Mon Feb 23, 2009 10:24 pm Post subject: |
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Would the stk chips in an 808 already have heatsinks? I'm wondering if it would be worthwhile, or possible to add some...with thermal compound (if necessary).
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Robert A. Hill
Joined: 19 May 2006
Posts: 182
Location: Simpsonville, SC
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| Posted: Mon Feb 23, 2009 10:33 pm Post subject: |
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Like Mac said, a you should not apply a thick coating of any thermal grease. I have been trying to get a sample of Indium Corp. Heat Spring material to try with the power transistors on my Ampro 3600. This material would have superior thermal properties compared to standard silicon grease with lower thermal resistance being one property than could help in high thermal density areas. See their website for more info:
http://www.indium.com/TIM/solutions/heatspringtim1.php
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DrKnow65
Joined: 14 Jan 2009
Posts: 118
Location: Carbondale, CO
TV/Projector: Vidikron Vision One
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| Posted: Tue Feb 24, 2009 4:22 am Post subject: |
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Just be careful that you don't get a conductive thermal paste (Arctic silver for example) it can cause you problems...
I haven't done any thermal stuff on my PJ, but I have done some extensive work on RC car speed controllers and voltage regulators. I use MX-2, it's a 2 part thermal epoxy that is di-electric, but expensive. The grease tends to lose it's bond with any kind of vibration even with a decent retainer.
www.arctic-cooling.com
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Tue Feb 24, 2009 4:26 am Post subject: |
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| benareeno wrote: | | Would the stk chips in an 808 already have heatsinks? I'm wondering if it would be worthwhile, or possible to add some...with thermal compound (if necessary). |
They have massive heat sinks with fan cooling. In all the 808 sets I've seen, only two STK chips have ever failed... and that's a lot of 808's that have been through here.
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benareeno
Joined: 22 Mar 2006
Posts: 1614
Location: ottawa, canada
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| Posted: Tue Feb 24, 2009 5:33 am Post subject: |
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Interesting...so what chip or chips are at biggest risk if doing some sort of lowering of the fan voltages?
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David_Web
Joined: 02 May 2007
Posts: 418
Location: Sweden
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| Posted: Tue Feb 24, 2009 10:16 am Post subject: |
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It's usually the caps that will go bad with heat.
RIFA has some good info on it's site. Although they are hight quality caps so the once in the PJ might be a lot worse.
_________________
SNR of people are ridiculously low.
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Ile
Joined: 09 Mar 2006
Posts: 1491
Location: Jyväskylä, Finland
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stefuel
Joined: 07 Mar 2006
Posts: 3353
Location: Green Harbor MA USA
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| Posted: Tue Feb 24, 2009 11:13 am Post subject: |
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As Curt is the one most likely to have them, I'd like him to perform a experiment. Take two identical projectors, mount one exactly per manufacturers instructions and the second, really F'd up running side by side on the same size screen.
Wanna bet which one runs way hot 
The point is, if you take the time to mount them correctly you won't have to make the time to figure out how to get them to run cooler later. That and a little good house keeping...... 
_________________
Chip
A Barco is only a AmPro with training wheels
Card carrying member of the AVS chain gang.
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kal
Forum Administrator
Joined: 06 Mar 2006
Posts: 18114
Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
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| Posted: Tue Feb 24, 2009 3:34 pm Post subject: |
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| macgyver655 wrote: | | Adding new compound on top of old is worse then none at all. Many people dont know how to use compound. Thinkness is bad. Its proper use is only to fill voids in the 2 surfaces to help in heat transfer. To apply properly you merely add a thin layer to cover the area in contact. When you place the component on the heatsink you move it back and forth to smear the compound until you hear the 2 scraping each other. That is the proper amount. |
Exactly. You're just trying to fill in any air gaps that may exist when the two metal surfaces are pressed against each other.
What I do is put VERY thin smear of compound on one of the two clean surfaces and then press the two together tightly and move them around a bit. Then I pull them apart. If the compound isn't over the entire surface of the clean surface you didn't use enough compound. Just put a tiny bit more and repeat....
Like quoted above, you're trying to use as little as possible - just enough to fill in any inperfections/cracks.
Kal
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draganm
Joined: 08 Mar 2006
Posts: 8990
Location: Colorado
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| Posted: Tue Feb 24, 2009 4:48 pm Post subject: |
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| DrKnow65 wrote: | | Just be careful that you don't get a conductive thermal paste (Arctic silver for example) it can cause you problems... |
exactly, you want electrically insualting but Thermally conductive. I think that white stufff they used on our PJ's in the 90's is crap. Dow makes a good pure silicone paste for this purpose, i'ts called Dow Corning Molykote, Dow Corning 5 Dielectric Compound but it's not cheap, 5.3-oz Tube is $20.
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