I needed to replace a switch on back of my HR824 powered speaker.
Behind the speaker is a metal enclosure which has power amplifiers and
other circuitry. After removing the main back metal enclosure, I
realized that the circuit board and heatsinks were attached to an inner
metal frame which was screwed to the outer frame. After removing the
screws, the thing wouldn't budge, until I realized it was "glued" on and
I was able to yank it off with some effort.

The adhesive is white and greasy. It attaches the circuit board frame
to the outer frame by glueing 2 heatsink rails to the outer frame, for
more heat dissipation I assume (these are pretty powerful speakers, with
2 amps per speaker).

I learned about some stuff that's called Thermal Adhesive, but
apparently that stuff is supposed to be permanent, so mine can't be
that. I read that grease has no adhesive properties, so it's not that
either.

Maybe it doesn't matter, if I don't have to clean the old and apply new
- that would be great! I don't really see why I can't just screw the
frames together and leave the old stuff where it is.

But if I have to clean and reapply, can you please help me to 1)
identify the compound and 2) figure out how to clean off the old stuff.

Very, very much obliged!

CitizenRuth wrote:
Maybe it doesn't matter, if I don't have to clean the old and apply new
- that would be great! I don't really see why I can't just screw the
frames together and leave the old stuff where it is.

I'm betting it's epoxy of some sort, designed to keep the screws from
vibrating loose. Don't know how you'd identify it for sure.

--
If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.

"CitizenRuth" wrote in message
news
I needed to replace a switch on back of my HR824 powered speaker.
Behind the speaker is a metal enclosure which has power amplifiers and
other circuitry. After removing the main back metal enclosure, I
realized that the circuit board and heatsinks were attached to an inner
metal frame which was screwed to the outer frame. After removing the
screws, the thing wouldn't budge, until I realized it was "glued" on and
I was able to yank it off with some effort.

The adhesive is white and greasy. It attaches the circuit board frame
to the outer frame by glueing 2 heatsink rails to the outer frame, for
more heat dissipation I assume (these are pretty powerful speakers, with
2 amps per speaker).

I learned about some stuff that's called Thermal Adhesive, but
apparently that stuff is supposed to be permanent, so mine can't be
that. I read that grease has no adhesive properties, so it's not that
either.

Maybe it doesn't matter, if I don't have to clean the old and apply new
- that would be great! I don't really see why I can't just screw the
frames together and leave the old stuff where it is.

But if I have to clean and reapply, can you please help me to 1)
identify the compound and 2) figure out how to clean off the old stuff.

Very, very much obliged!

If it's white, and gets all over your trousers as soon as you walk in the
same room as it, then it's silicon grease, also known as thermal grease, or
heatsink compound. Contrary to what you believe, the surface tension
exhibited by this stuff over a large area, causes it to stick surfaces
together like the proverbial, and it is often necessary to get a screwdriver
in between the two sheets of metal to get some air in between to ' break '
the bond.

Thermal adhesive, on the other hand, is just that. It sticks heatsinks
directly to the tops of ICs, with a thermal conductivity similar to that of
silicon grease. The difference is that once it has done this, you would need
a crowbar to separate them again.

Provided there is still a reasonably even film of grease on both surfaces,
and it has not dried out and gone ' chalky ', then you can go ahead and just
reassemble with the old grease. However, be aware that this stuff seems to
attract workshop debris, and you should examine both surfaces CAREFULLY
before reassembly, as anything that stops the surfaces bolting back together
totally flat, will ruin the heat conductivity between the two surfaces,
through the grease.

Arfa

"CitizenRuth" wrote ...
.....
I learned about some stuff that's called Thermal Adhesive, but
apparently that stuff is supposed to be permanent, so mine can't be
that. I read that grease has no adhesive properties, so it's not that
either.

Maybe it doesn't matter, if I don't have to clean the old and apply new
- that would be great! I don't really see why I can't just screw the
frames together and leave the old stuff where it is.

Not advisable. The act of disassembly looses the "excess" that
squeezed out from the surfaces, and you can't really effectively
recover all of it to reuse. Besides if it got very hot, the compound
may have partially "dried up" making it more difficult to get the
thermal coupling the second time around.

But if I have to clean and reapply, can you please help me to 1)
identify the compound and 2) figure out how to clean off the old stuff.

Should be able to use standard heatsink compound (gooey,
white stuff) which is widely sold to people constructing their
own PCs. It is used between the CPU chip and the heat sink
in the computer. Should be able to buy this stuff anywhere
computer CPUs, heatsinks, etc. are offered.

I usually clean off the old stuff with alcohol and a rag (or Kleenex, etc.)

"CitizenRuth" wrote in message
news

The adhesive is white and greasy. It attaches the circuit board frame
to the outer frame by glueing 2 heatsink rails to the outer frame, for
more heat dissipation I assume (these are pretty powerful speakers, with
2 amps per speaker).

I learned about some stuff that's called Thermal Adhesive,

Ifg the heatsink was also screwed on, then probably NOT tthermal adhesive,
but thermal heatsink compound which could be either silicon or Berrylium
Oxide based. If the latter, it is highly toxic.

geoff

"Arfa Daily" wrote in message
...

"CitizenRuth" wrote in message



If it's white, and gets all over your trousers as soon as you walk in the
same room as it, then it's silicon grease, also known as thermal grease,
or heatsink compound.


Sorry if this seems pedantic, but silicone (not silicon) grease and heatsink
compound are not the same thing at all. The former is a clear grease, often
used for HV insulation and sometimes for lubricating plastic gears. The
latter is a silicone *based* compound with additives for conducting heat
efficiently.

Contrary to what you believe, the surface tension exhibited by this stuff
over a large area, causes it to stick surfaces together like the
proverbial, and it is often necessary to get a screwdriver in between the
two sheets of metal to get some air in between to ' break ' the bond.

That is true.

Thermal adhesive, on the other hand, is just that. It sticks heatsinks
directly to the tops of ICs, with a thermal conductivity similar to that
of silicon grease. The difference is that once it has done this, you would
need a crowbar to separate them again.

Provided there is still a reasonably even film of grease on both surfaces,
and it has not dried out and gone ' chalky ', then you can go ahead and
just reassemble with the old grease.

I would advise against this. It is by far the best course of action to
thoroughly clean both surfaces of old heatsink compound and reapply new. It
is after all rather cheap and readily available. Semiconductors OTOH can be
pricey, difficult to obtain and can cause widespread damage when they short
;-)

Dave

"CitizenRuth" wrote in message
news
I needed to replace a switch on back of my HR824 powered speaker.
Behind the speaker is a metal enclosure which has power amplifiers and
other circuitry. After removing the main back metal enclosure, I
realized that the circuit board and heatsinks were attached to an inner
metal frame which was screwed to the outer frame. After removing the
screws, the thing wouldn't budge, until I realized it was "glued" on and
I was able to yank it off with some effort.

The adhesive is white and greasy.

What you have there is very common, it's just silicone heatsink compound,
used to increase the efficiency of transfer of heat from component to
heatsink. If it were thermal *adhesive*, they probably wouldn't have used
screws to secure the assembly. Thermal adhesive is generally used instead of
mechanical fixing methods, and the adhesive itself is rather pricey. It is
very common for thermal heatsink compound to age and can become quite
stubborn to break, which might lead one to believe it's adhesive, but it's
easy to spot the difference as thermal heatsink compound will be softish and
sticky as opposed to rock hard. Thermal adhesive is *very* sturdy though,
it's epoxy based, sets rock hard and can require serious force to remove.

You should clean off all the old compound and reapply new. You *might* get
away with reassembly without new compound, but I don't think it's worth the
gamble. If it isn't convenient to get to an electronics shop for a tube of
heatsink compound, the stuff available for CPU heatsinks, which is readily
available from computer shops, is the same thing. White or silver compound
will work great. You don't have to plaster it on like mortar as some people
believe, just apply a nice even coat to one surface and reassemble.

Dave

I'm betting it's epoxy of some sort, designed to keep the screws from
vibrating loose. Don't know how you'd identify it for sure.

It is "thermal grease" aka "heat-sink compound".
Remarkably poor epoxy if he could just pry it apart.

If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.

Your political "thinking" needs work as well.
Thought about just moving to the PRC? I'm sure you'd love it.
Curious why all those people spend 10s of thousands of US$
to get away from there, though. Makes you wonder.

"Richard Crowley" wrote in
:

"CitizenRuth" wrote ...
....
I learned about some stuff that's called Thermal Adhesive, but
apparently that stuff is supposed to be permanent, so mine can't be
that. I read that grease has no adhesive properties, so it's not
that either.

Maybe it doesn't matter, if I don't have to clean the old and apply
new - that would be great! I don't really see why I can't just screw
the frames together and leave the old stuff where it is.

Not advisable. The act of disassembly looses the "excess" that
squeezed out from the surfaces, and you can't really effectively
recover all of it to reuse. Besides if it got very hot, the compound
may have partially "dried up" making it more difficult to get the
thermal coupling the second time around.

But if I have to clean and reapply, can you please help me to 1)
identify the compound and 2) figure out how to clean off the old
stuff.

Should be able to use standard heatsink compound (gooey,
white stuff) which is widely sold to people constructing their
own PCs. It is used between the CPU chip and the heat sink
in the computer. Should be able to buy this stuff anywhere
computer CPUs, heatsinks, etc. are offered.

I usually clean off the old stuff with alcohol and a rag (or Kleenex,
etc.)




WHITE HS compound contains either alumina or beryllium [oxide?];that's what
makes it white and thermally conductive(no silicone,AFAIK),and there are
clear -silicone- greases made by Dow Corning.The white compound has some
solvent that dries out after some time. Silicone grease will not dry out.

--
Jim Yanik
jyanik
at
kua.net

"Dave D" wrote in
:


"CitizenRuth" wrote in message
news
I needed to replace a switch on back of my HR824 powered speaker.
Behind the speaker is a metal enclosure which has power amplifiers
and other circuitry. After removing the main back metal enclosure, I
realized that the circuit board and heatsinks were attached to an
inner metal frame which was screwed to the outer frame. After
removing the screws, the thing wouldn't budge, until I realized it
was "glued" on and I was able to yank it off with some effort.

The adhesive is white and greasy.

What you have there is very common, it's just silicone heatsink
compound, used to increase the efficiency of transfer of heat from
component to heatsink. If it were thermal *adhesive*, they probably
wouldn't have used screws to secure the assembly. Thermal adhesive is
generally used instead of mechanical fixing methods, and the adhesive
itself is rather pricey. It is very common for thermal heatsink
compound to age and can become quite stubborn to break, which might
lead one to believe it's adhesive, but it's easy to spot the
difference as thermal heatsink compound will be softish and sticky as
opposed to rock hard. Thermal adhesive is *very* sturdy though, it's
epoxy based, sets rock hard and can require serious force to remove.



If the white compound had silicone grease in it,it would not dry out.
I believe the white compound has some other petro-based grease.


There is a silver-loaded thermal epoxy adhesive,and 3M(IIRC) makes a
thermal 2-part adhesive for gluing on heat sinks.

--
Jim Yanik
jyanik
at
kua.net

"CitizenRuth" wrote in message
news
I needed to replace a switch on back of my HR824 powered speaker.
Behind the speaker is a metal enclosure which has power amplifiers and
other circuitry. After removing the main back metal enclosure, I
realized that the circuit board and heatsinks were attached to an inner
metal frame which was screwed to the outer frame. After removing the
screws, the thing wouldn't budge, until I realized it was "glued" on and
I was able to yank it off with some effort.

The adhesive is white and greasy. It attaches the circuit board frame
to the outer frame by glueing 2 heatsink rails to the outer frame, for
more heat dissipation I assume (these are pretty powerful speakers, with
2 amps per speaker).

I learned about some stuff that's called Thermal Adhesive, but
apparently that stuff is supposed to be permanent, so mine can't be
that. I read that grease has no adhesive properties, so it's not that
either.

Maybe it doesn't matter, if I don't have to clean the old and apply new
- that would be great! I don't really see why I can't just screw the
frames together and leave the old stuff where it is.

But if I have to clean and reapply, can you please help me to 1)
identify the compound and 2) figure out how to clean off the old stuff.

Very, very much obliged!


It's heatsink grease, you can get it anywhere that sells electronic
components, even Radio Shack has it in little tubes.

CitizenRuth wrote:
I needed to replace a switch on back of my HR824 powered speaker.
Behind the speaker is a metal enclosure which has power amplifiers and
other circuitry. After removing the main back metal enclosure, I
realized that the circuit board and heatsinks were attached to an inner
metal frame which was screwed to the outer frame. After removing the
screws, the thing wouldn't budge, until I realized it was "glued" on and
I was able to yank it off with some effort.

The adhesive is white and greasy.

This is almost always a grease made of silicone oil and zinc oxide
powder, and some is thick enough to hold the parts together firmly to
require tools to separate them. Don't substitute it with a heatsink
grease containing silver powder, commonly sold for computer CPU
cooling, in case there's high voltage (silver powder is also very
messy).

Jim Yanik wrote:
"Richard Crowley"

WHITE HS compound contains either alumina or beryllium [oxide?];that's what
makes it white and thermally conductive(no silicone,AFAIK),and there are
clear -silicone- greases made by Dow Corning.The white compound has some
solvent that dries out after some time. Silicone grease will not dry out.

I'd be very surprised if any consumer product made in the past 30 years
contained anything as toxic as beryllium. Even the oxide form seems to
be considered hazardous.

Mackie used to be a very service oriented company.. I haven't dealt
with them lately, but I suspect if you called them up they'd send you a
little of whatever it is they use free of charge. They should at least
telll you what it is and where to get some. Especially since you paid
like 1500 bucks for those speakers.

wrote in message
ups.com...


This is almost always a grease made of silicone oil and zinc oxide
powder, and some is thick enough to hold the parts together firmly to
require tools to separate them. Don't substitute it with a heatsink
grease containing silver powder, commonly sold for computer CPU
cooling, in case there's high voltage (silver powder is also very
messy).


Shouldn't be an issue with the voltages one would expect to see in a
transistor amp. Cheap white compound will dry out over time and lose its
effectiveness, whereas something like arctic silver shouldn't. I wouldn't
necessarily recommend silver loaded compound mind, but I see no reason not
to use it for this kind of job. It's possible in this case that the
transistor is directly mounted anyway, ie without an insulating pad.

Dave

"Jim Yanik" wrote in message
.. .

If the white compound had silicone grease in it,it would not dry out.
I believe the white compound has some other petro-based grease.



That's probably true, I often wondered how a silicone based product could
'dry out'. I read somewhere these compounds were based on silicone/synthetic
oils, maybe there's something else added as well which dries out.

Dave

"Dave D" wrote in message
...

"Arfa Daily" wrote in message
...

"CitizenRuth" wrote in message



If it's white, and gets all over your trousers as soon as you walk in the
same room as it, then it's silicon grease, also known as thermal grease,
or heatsink compound.


Sorry if this seems pedantic, but silicone (not silicon) grease and
heatsink compound are not the same thing at all. The former is a clear
grease, often used for HV insulation and sometimes for lubricating plastic
gears. The latter is a silicone *based* compound with additives for
conducting heat efficiently.

Contrary to what you believe, the surface tension exhibited by this stuff
over a large area, causes it to stick surfaces together like the
proverbial, and it is often necessary to get a screwdriver in between the
two sheets of metal to get some air in between to ' break ' the bond.

That is true.

Thermal adhesive, on the other hand, is just that. It sticks heatsinks
directly to the tops of ICs, with a thermal conductivity similar to that
of silicon grease. The difference is that once it has done this, you
would need a crowbar to separate them again.

Provided there is still a reasonably even film of grease on both
surfaces, and it has not dried out and gone ' chalky ', then you can go
ahead and just reassemble with the old grease.

I would advise against this. It is by far the best course of action to
thoroughly clean both surfaces of old heatsink compound and reapply new.
It is after all rather cheap and readily available. Semiconductors OTOH
can be pricey, difficult to obtain and can cause widespread damage when
they short ;-)

Dave

Hi Dave

Yeah Yeah - you're right ! The missing ' e ' on the end of silicone was a
typo. I probably should have put it the other way around like " It's
heatsink compound, otherwise known as thermal grease or silicone grease ". I
know that it's not actually the same stuff as silicone grease - I have a big
tub of that which I use for all sorts of plastic lubricating. But I think
that you've gotta agree that for as long as any of us in the business can
remember, this hateful stuff has been known generically ( albeit
erroneously ) as ' Silicone Grease '. ( probably because it's based on
silicone, and greasy ... )

As far as replacing the compound goes, I would absolutely, definitely and
without question, agree with you to always always always replace compound
between semiconductors and their heatsinks, first cleaning off all traces of
the old, chemically. However, where the compound is between a true heatsink,
and a secondary ' belt and braces ' piece of metal such as a back panel,
like the OP seems to be suggesting, then in my experience, there is no need
to cover yourself, the kids and next door's cat ( for if any of them are
within 30 yards of you, they will get covered ... !! ) in the stuff, just
for the hell of cleaning it off and replacing it. Compound in this sort of
position doesn't normally get to a high enough temperature to dry out and go
powdery. : -))

Arfa

"Arfa Daily" wrote in message news:qOL2f.4930

Yeah Yeah - you're right ! The missing ' e ' on the end of silicone was a
typo.

You must be a silicone't (!)

geoff

"Geoff Wood" wrote in message
...

"Arfa Daily" wrote in message news:qOL2f.4930

Yeah Yeah - you're right ! The missing ' e ' on the end of silicone was a
typo.

You must be a silicone't (!)

geoff

Ohhhh That's baaaad !!!!

Arfa ;-)

Richard Crowley wrote:
clifto wrote:
I'm betting it's epoxy of some sort, designed to keep the screws from
vibrating loose. Don't know how you'd identify it for sure.

It is "thermal grease" aka "heat-sink compound".
Remarkably poor epoxy if he could just pry it apart.

For some reason I appear to have missed a few clues in his text. I got
the impression that the stuff was between the mounting brackets and the
speaker cabinet, and missed where he said it was gooey stuff.

If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.

Your political "thinking" needs work as well.

Not at all. The Dems will be running a socialist. If the Repubs run a
leftist like McCain, then I figure I might as well go all the way.

Thought about just moving to the PRC? I'm sure you'd love it.

You've got the wrong guy. I'm busy trying to keep the PRC from moving
in here.

--
If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.

"Arfa Daily" wrote in message news:ngQ2f.13404

Ohhhh That's baaaad !!!!

Arfa ;-)


One of my worst ever !

g.

"Geoff Wood" wrote in message
...

"Arfa Daily" wrote in message news:ngQ2f.13404

Ohhhh That's baaaad !!!!

Arfa ;-)


One of my worst ever !

g.


Years ago ( Jesus, about 40 actually ... ) a buddy of mine in chemistry
class, got asked by the teacher, what the chemical symbol ' Sn ' was. Quick
as a flash, he said " Silicon, sir ! "

After a suitable pause, the teacher said " Aye, Smith, you really are a
silicon, aren't you ... ? "

His name wasn't actually Smith ...

Arfa |:-o

Dave D wrote:
wrote in message
ups.com...

This is almost always a grease made of silicone oil and zinc oxide
powder, and some is thick enough to hold the parts together firmly to
require tools to separate them. Don't substitute it with a heatsink
grease containing silver powder, commonly sold for computer CPU
cooling, in case there's high voltage (silver powder is also very
messy).

Shouldn't be an issue with the voltages one would expect to see in a
transistor amp. Cheap white compound will dry out over time and lose its
effectiveness, whereas something like arctic silver shouldn't. I wouldn't
necessarily recommend silver loaded compound mind, but I see no reason not
to use it for this kind of job. It's possible in this case that the
transistor is directly mounted anyway, ie without an insulating pad.

I have a Leach audio amplifier built in the 1970s, and a few years ago
its Radio Shack or GC silicone grease hadn't dried out. So I wouldn't
worry about this, and I don't see why Arctic Silver would be more
resistant to drying out (it may use ester instead of silicone grease).

wrote in message
oups.com...

I have a Leach audio amplifier built in the 1970s, and a few years ago
its Radio Shack or GC silicone grease hadn't dried out. So I wouldn't
worry about this,

It depends on how hot the semicondictor runs. It's possible the
effectiveness of thermal compound can deteriorate as it changes state.

and I don't see why Arctic Silver would be more
resistant to drying out (it may use ester instead of silicone grease).

It is based on polysynthetic oils. The manufacturers apparently claim it
won't dry out, and my experience with it certainly backs their claims up- I
have never seen dried Arctic Silver.

In any case, I am not advising anyone to rush out and buy Arctic Silver for
electronic work. I merely meant that for the OP's purposes, any form of
thermal compound he could get his hands on would do the job. Plain old
white, silver, whatever. Many people build their own PCs these days, so I
thought perhaps he may have a tube of CPU compound lying around, or have a
nearby computer shop he could get it from.

Dave

In article .com, wrote:

Dave D wrote:
wrote in message
ups.com...

This is almost always a grease made of silicone oil and zinc oxide
powder, and some is thick enough to hold the parts together firmly to
require tools to separate them. Don't substitute it with a heatsink
grease containing silver powder, commonly sold for computer CPU
cooling, in case there's high voltage (silver powder is also very
messy).

Shouldn't be an issue with the voltages one would expect to see in a
transistor amp. Cheap white compound will dry out over time and lose its
effectiveness, whereas something like arctic silver shouldn't. I wouldn't
necessarily recommend silver loaded compound mind, but I see no reason not
to use it for this kind of job. It's possible in this case that the
transistor is directly mounted anyway, ie without an insulating pad.

I have a Leach audio amplifier built in the 1970s, and a few years ago
its Radio Shack or GC silicone grease hadn't dried out. So I wouldn't
worry about this, and I don't see why Arctic Silver would be more
resistant to drying out (it may use ester instead of silicone grease).


I have seen the white stuff dry out plenty of times. Its sure easy to
spot and feel. If you can't smear it then it must be removed.
If its still good, I would just even out the stuff and reapply components.

greg

"GregS" wrote ...
I have seen the white stuff dry out plenty of times. Its sure easy to
spot and feel. If you can't smear it then it must be removed.
If its still good, I would just even out the stuff and reapply
components.

I agree in theory. But in practice, thermal grease is so
cheap compared to what it prevents that it is foolish
economy IMHO.

"Richard Crowley" wrote in message

"GregS" wrote ...
I have seen the white stuff dry out plenty of times. Its
sure easy to spot and feel. If you can't smear it then
it must be removed. If its still good, I would just even
out the stuff and
reapply components.

I agree in theory. But in practice, thermal grease is so
cheap compared to what it prevents that it is foolish
economy IMHO.

Agreed.

If there is some small particle in the thermal compound, it
would separate the component from the heatsink and could
dramatically decrease cooling.

The best plan is to carefully clean both surfaces and use
new, clean compound.

In article , "Arny Krueger" wrote:
"Richard Crowley" wrote in message

"GregS" wrote ...
I have seen the white stuff dry out plenty of times. Its
sure easy to spot and feel. If you can't smear it then
it must be removed. If its still good, I would just even
out the stuff and
reapply components.

I agree in theory. But in practice, thermal grease is so
cheap compared to what it prevents that it is foolish
economy IMHO.

Agreed.

If there is some small particle in the thermal compound, it
would separate the component from the heatsink and could
dramatically decrease cooling.

The best plan is to carefully clean both surfaces and use
new, clean compound.

I was building amps from STK modules. I studied the mating surfaces.
Ideally metal to metal contact is best, even the anodized surfaces
should be milled down. So I was taking the STK module and
sanding it down flat. It really wasn't very flat. I had to start out
with a flat surface for the sandpaper! After much work, I got it
to the point I felt was OK. Even a flat etched surface is worse than a mirrored
flat surface. Very very little grease is needed if everything is smooth and flat.

greg

GregS wrote:
I have seen the white stuff dry out plenty of times. Its sure easy to
spot and feel. If you can't smear it then it must be removed.

I noticed the CPU temperature on my main computer going a bit high a few
months ago. I checked, and sure enough the heat sink grease had dried
out. Replaced it and all was well.

If its still good, I would just even out the stuff and reapply components.

Disagree. Where it's needed, it's critical; it's cheap enough that
replacing it in critical places is well worth while.

--
If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.

"GregS" wrote in message news:dijfd2

I was building amps from STK modules. I studied the mating surfaces.
Ideally metal to metal contact is best, even the anodized surfaces
should be milled down. So I was taking the STK module and
sanding it down flat. It really wasn't very flat. I had to start out
with a flat surface for the sandpaper! After much work, I got it
to the point I felt was OK. Even a flat etched surface is worse than a
mirrored
flat surface. Very very little grease is needed if everything is smooth
and flat.


They don't suffer from thermal problem when mounted conventionally, with a
dab of heatsink compound, so why bother ?!!!

All a bit OTT consuidering the STK modules don't sound that great in the
first place.

geoff

In article , "Geoff Wood" wrote:

"GregS" wrote in message news:dijfd2

I was building amps from STK modules. I studied the mating surfaces.
Ideally metal to metal contact is best, even the anodized surfaces
should be milled down. So I was taking the STK module and
sanding it down flat. It really wasn't very flat. I had to start out
with a flat surface for the sandpaper! After much work, I got it
to the point I felt was OK. Even a flat etched surface is worse than a
mirrored
flat surface. Very very little grease is needed if everything is smooth
and flat.


They don't suffer from thermal problem when mounted conventionally, with a
dab of heatsink compound, so why bother ?!!!

All a bit OTT consuidering the STK modules don't sound that great in the
first place.

geoff

Sounds good enough for the common man. Running the 200 watt modules,
now extinct, but rugged as hell. I ran at reduced voltage for 200 watts at 4 ohms.
I was actually driving nearer 3 ohms at one time.

greg

In article , clifto wrote:
GregS wrote:
I have seen the white stuff dry out plenty of times. Its sure easy to
spot and feel. If you can't smear it then it must be removed.

I noticed the CPU temperature on my main computer going a bit high a few
months ago. I checked, and sure enough the heat sink grease had dried
out. Replaced it and all was well.

If its still good, I would just even out the stuff and reapply components.

Disagree. Where it's needed, it's critical; it's cheap enough that
replacing it in critical places is well worth while.


i suppose the fluid helps to also fill in gaps having to fit into the compound mix
of dry materials. Having dried out may not always be a problem. There should be very little actual
compound that sits between flat surfaces. Its almost totally trapped in. if the surfaces
are poor, and the strength of the compression is poor, I think it would dry
out quicker. Probably a good choice for gasket type pads.

greg

"Richard Crowley" wrote in
:

"GregS" wrote ...
I have seen the white stuff dry out plenty of times. Its sure easy to
spot and feel. If you can't smear it then it must be removed.
If its still good, I would just even out the stuff and reapply
components.

I agree in theory. But in practice, thermal grease is so
cheap compared to what it prevents that it is foolish
economy IMHO.



What dries out (white stuff) is not the thermal conducting material.
It should be reapplied solely for best thermal contact.
And the thinnest,most even layer is most optimal.

--
Jim Yanik
jyanik
at
kua.net

If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.

Makes me feel good that Usenet is available even to the insane.