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I am still working on my 453. The HV transformer is mounted with some sort of clear grease. I think this is heat sink compound but may just be silicone insulating grease. What is recommended here? I am also replacing Q-930 and wonder what compound is recommended for it.
I have clear silicone grease intended as a HV insulator by GC chemicals, is it OK for the transformer. I can get regular heat sink compound locally if necessary.
--
Richard Knoppow
dickburk@...
WB6KBL
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I read that silicone is somewhat conductive so you need to be careful with the transistor. I use arctic silver 5 (which is not silicone based) but you should be able to use any silicone based compound that is formulated for heat sinking such as Dow Corning 340 or the equivalent. Best, John On Thu, May 3, 2018 at 4:05 PM, Richard Knoppow <dickburk@...> wrote: I am still working on my 453. The HV transformer is mounted with some
sort of clear grease. I think this is heat sink compound but may just be
silicone insulating grease. What is recommended here? I am also replacing
Q-930 and wonder what compound is recommended for it.
I have clear silicone grease intended as a HV insulator by GC
chemicals, is it OK for the transformer. I can get regular heat sink
compound locally if necessary.
--
Richard Knoppow
dickburk@...
WB6KBL
|
Arctic MX-4 is non-conductive. It's the metal filled thermal pastes that are risky to use. IIRC MX-4 is ceramic based. On Thursday, May 3, 2018, 3:17:05 PM CDT, JJ <jajustin@...> wrote: I read that silicone is somewhat conductive so you need to be careful with the transistor. I use arctic silver 5 (which is not silicone based) but you should be able to use any silicone based compound that is formulated for heat sinking such as Dow Corning 340 or the equivalent. Best, John On Thu, May 3, 2018 at 4:05 PM, Richard Knoppow <dickburk@...> wrote: ? ? I am still working on my 453. The HV transformer is mounted with some
sort of clear grease. I think this is heat sink compound but may just be
silicone insulating grease. What is recommended here?? I am also replacing
Q-930 and wonder what compound is recommended for it.
? ? I have clear silicone grease intended as a HV insulator by GC
chemicals, is it OK for the transformer. I can get regular heat sink
compound locally if necessary.
--
Richard Knoppow
dickburk@...
WB6KBL
|
The clear stuff I have is recommended for HV insulation. It does not have a particularly high heat conductivity, probably due to not having any filler. Whatever was on the HV transformer is clear. I wanted to ask before changing the oscillator transistor. I thought I had regular heat sink compound but can't find it.
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On 5/3/2018 1:21 PM, Anthony via Groups.Io wrote: Arctic MX-4 is non-conductive. It's the metal filled thermal pastes that are risky to use. IIRC MX-4 is ceramic based. On Thursday, May 3, 2018, 3:17:05 PM CDT, JJ <jajustin@...> wrote:
I read that silicone is somewhat conductive so you need to be careful with
the transistor. I use arctic silver 5 (which is not silicone based) but you
should be able to use any silicone based compound that is formulated for
heat sinking such as Dow Corning 340 or the equivalent.
Best,
John
On Thu, May 3, 2018 at 4:05 PM, Richard Knoppow <dickburk@...>
wrote:
? ? I am still working on my 453. The HV transformer is mounted with some
sort of clear grease. I think this is heat sink compound but may just be
silicone insulating grease. What is recommended here?? I am also replacing
Q-930 and wonder what compound is recommended for it.
? ? I have clear silicone grease intended as a HV insulator by GC
chemicals, is it OK for the transformer. I can get regular heat sink
compound locally if necessary.
--
Richard Knoppow
dickburk@...
WB6KBL
--
Richard Knoppow
dickburk@...
WB6KBL
|
Hi Richard. It's amazing how some 'old wives tales' never die. There was recently an excellent link on eHam about heat sink compounds. The author worked as an EE for a large cable Co. So, he dealt with weatherproofing/heat sinking every day.
Bottom line was: good ole Dielectric grease from the auto parts store works in both cases. Used in moderation!
My own pet peeve is this: I built nuclear weapons while in the Navy. Went to school at the Sandia Corp in New Mexico. The weapons always used O-rings for obvious reasons. We used Dow Corning "Ground Glass Compound" on these O-rings. It meant: "for use on ground glass fittings" such as you would find in a lab. It had NO F'N ground glass in it!
I even visited MT after the Challenger disaster, in a different capacity. Could not believe they used O-rings on the Shuttle.
But I digress.....
ron
N4UE
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-----Original Message----- From: Richard Knoppow <dickburk@...> To: TekScopes < [email protected]> Sent: Thu, May 3, 2018 4:05 pm Subject: [TekScopes] Heat Sink Compound I am still working on my 453. The HV transformer is mounted with some sort of clear grease. I think this is heat sink compound but may just be silicone insulating grease. What is recommended here? I am also replacing Q-930 and wonder what compound is recommended for it. I have clear silicone grease intended as a HV insulator by GC chemicals, is it OK for the transformer. I can get regular heat sink compound locally if necessary. -- Richard Knoppow dickburk@... WB6KBL
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Heat dunk compound is zinc powder or sometimes silver. Never silicon grease.
Can¡¯t imagine why a transformer would need grease nor , with its mass even need to be ¡°sinked¡±
My 2 cents.
Ray
KD9CCZ
Heaven goes by favor.
If it went by merit,
you would stay out and
your dog would go in.
-Mark Twain
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On May 3, 2018, at 15:17, JJ <jajustin@...<mailto:jajustin@...>> wrote:
I read that silicone is somewhat conductive so you need to be careful with
the transistor. I use arctic silver 5 (which is not silicone based) but you
should be able to use any silicone based compound that is formulated for
heat sinking such as Dow Corning 340 or the equivalent.
Best,
John
On Thu, May 3, 2018 at 4:05 PM, Richard Knoppow <dickburk@...<mailto:dickburk@...>>
wrote:
I am still working on my 453. The HV transformer is mounted with some
sort of clear grease. I think this is heat sink compound but may just be
silicone insulating grease. What is recommended here? I am also replacing
Q-930 and wonder what compound is recommended for it.
I have clear silicone grease intended as a HV insulator by GC
chemicals, is it OK for the transformer. I can get regular heat sink
compound locally if necessary.
--
Richard Knoppow
dickburk@...<mailto:dickburk@...>
WB6KBL
|
The HV transformer is clamped to a heat sink underneath it (actually above it when the scope is upright). Both sides are coated with thin grease. The same stuff was on the transistor when I took it out.
What I am using (because I have it) is MG Chemicals 8462.
I did some research on heat sink compounds on the web. Says pretty much what you do, mostly zinc oxide or sometimes silver. I don't know why silicone is to be avoided.
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On 5/3/2018 1:38 PM, Raymond Cote wrote: Heat dunk compound is zinc powder or sometimes silver. Never silicon grease.
Can¡¯t imagine why a transformer would need grease nor , with its mass even need to be ¡°sinked¡±
My 2 cents.
Ray
KD9CCZ
--
Richard Knoppow
dickburk@...
WB6KBL
|
The stuff I am using is MG Chemicals 8462 grease. Has very good insulation properties but not high heat transfer. The original material was thin, clear, grease of some sort both on the transformer and on the transistor. I used a very thin coating in both places.
I am replacing all the transistors in the HV regulator circuit, four in all, cost about $12 at Fry's for NTC parts. May not cure the problem but I hope it does. Ohm meter testing shows all the transistors to be good but I am not quite sure I believe that. If there is no change I will have to look elsewhere but I thought it necessary to change these parts.
I will also repost in either case, either to brag or to yell for help. I really want to get this thing going again.
The ground glass grease sounds like its meant for keeping ground glass chemical apparatus caps from sticking.
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On 5/3/2018 1:35 PM, bonddaleena@... via Groups.Io wrote: Hi Richard. It's amazing how some 'old wives tales' never die. There was recently an excellent link on eHam about heat sink compounds. The author worked as an EE for a large cable Co. So, he dealt with weatherproofing/heat sinking every day.
Bottom line was: good ole Dielectric grease from the auto parts store works in both cases. Used in moderation!
My own pet peeve is this: I built nuclear weapons while in the Navy. Went to school at the Sandia Corp in New Mexico. The weapons always used O-rings for obvious reasons. We used Dow Corning "Ground Glass Compound" on these O-rings. It meant: "for use on ground glass fittings" such as you would find in a lab. It had NO F'N ground glass in it!
I even visited MT after the Challenger disaster, in a different capacity. Could not believe they used O-rings on the Shuttle.
But I digress.....
ron
N4UE
-----Original Message-----
From: Richard Knoppow <dickburk@...>
To: TekScopes <[email protected]>
Sent: Thu, May 3, 2018 4:05 pm
Subject: [TekScopes] Heat Sink Compound
I am still working on my 453. The HV transformer is mounted
with some sort of clear grease. I think this is heat sink
compound but may just be silicone insulating grease. What is
recommended here? I am also replacing Q-930 and wonder what
compound is recommended for it.
I have clear silicone grease intended as a HV insulator by GC
chemicals, is it OK for the transformer. I can get regular heat
sink compound locally if necessary.
--
Richard Knoppow
dickburk@...
WB6KBL
|
Richard, forgive this silly response to your question because I don't know if there is a specific type of heat sink compound used in your application. But... Desitin cream for diaper rash is just about the same ordinary zinc oxide based heat sink compound you buy from Digikey or Mouser. I keep a tube on hand in case of emergencies. The "it's 2:00 AM and I need heat sink compound" kind of emergency anyway. Not the other kind you'd use it for. -Bob N3XKB On Thu, May 3, 2018 at 2:05 PM, Richard Knoppow <dickburk@...> wrote: I am still working on my 453. The HV transformer is mounted with some
sort of clear grease. I think this is heat sink compound but may just be
silicone insulating grease. What is recommended here? I am also replacing
Q-930 and wonder what compound is recommended for it.
I have clear silicone grease intended as a HV insulator by GC
chemicals, is it OK for the transformer. I can get regular heat sink
compound locally if necessary.
--
Richard Knoppow
dickburk@...
WB6KBL
|
On 5/3/2018 5:16 PM, redarlington wrote: Richard, forgive this silly response to your question because I don't know
if there is a specific type of heat sink compound used in your application.
But...
Desitin cream for diaper rash is just about the same ordinary zinc oxide
based heat sink compound you buy from Digikey or Mouser. I keep a tube
on hand in case of emergencies. <snip> Hello-- One morning years ago, my office mate came to work in a bad mood (unusual for him), and I asked what has happened. "I mistook the tube of diaper-rash ointment for toothpaste," he said. Be careful out there<g>. 73-- Brad AA1IP
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My understanding is that there were two reasons. First of all, they had to build the engines in sections, and secondly they had different thermal expansion rates.
The so called 'O-rings' were very thick, custom molded seals' They were only designed for a certain operating temperature range. The lost shuttle violated NASA's own safety rules, but they went for a launch after too many launch delays.
Michael A. Terrell
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-----Original Message----- From: "bonddaleena@... via Groups.Io" <bonddaleena@...>
I even visited MT after the Challenger disaster, in a different capacity. Could not believe they used O-rings on the Shuttle.
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There are only 2 reasons I can see you would need HV insulating grease between the surfaces.
1: The surfaces need to be electrically insulated. If there is no insulation between the parts, then obviously this cannot be the case. I don't know what you're looking at but if there is metal to metal contact between the surfaces then the conductivity of the grease is moot.
2: The grease should not short out any traces it comes into contact with, if for some reason it gets runny. If it is mounted metal to metal, then this is probably the only reason they would specify HV grease. If a mica or other kind of thermal pad is used, conductive runny grease can short out the pad. On Thursday, May 3, 2018, 5:03:14 PM CDT, Michael A. Terrell <mike.terrell@...> wrote:
My understanding is that there were two reasons. First of all, they had to build the engines in sections, and secondly they had different thermal expansion rates.
The so called 'O-rings' were very thick, custom molded seals' They were only designed for a certain operating temperature range. The lost shuttle violated NASA's own safety rules, but they went for a launch after too many launch delays.
Michael A. Terrell
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-----Original Message----- From: "bonddaleena@... via Groups.Io" <bonddaleena@...>
I even visited MT after the Challenger disaster, in a different capacity. Could not believe they used O-rings on the Shuttle.
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Have you been to MT? I have. And I've assembled many nuclear warheads. Have you?
ron
N4UE
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---Original Message----- From: Anthony via Groups.Io <keantoken@...> To: TekScopes < [email protected]> Sent: Thu, May 3, 2018 6:12 pm Subject: Re: [TekScopes] Heat Sink Compound There are only 2 reasons I can see you would need HV insulating grease between the surfaces. 1: The surfaces need to be electrically insulated. If there is no insulation between the parts, then obviously this cannot be the case. I don't know what you're looking at but if there is metal to metal contact between the surfaces then the conductivity of the grease is moot. 2: The grease should not short out any traces it comes into contact with, if for some reason it gets runny. If it is mounted metal to metal, then this is probably the only reason they would specify HV grease. If a mica or other kind of thermal pad is used, conductive runny grease can short out the pad. On Thursday, May 3, 2018, 5:03:14 PM CDT, Michael A. Terrell <mike.terrell@...> wrote: My understanding is that there were two reasons. First of all, they had to build the engines in sections, and secondly they had different thermal expansion rates. The so called 'O-rings' were very thick, custom molded seals' They were only designed for a certain operating temperature range. The lost shuttle violated NASA's own safety rules, but they went for a launch after too many launch delays. Michael A. Terrell -----Original Message----- From: "bonddaleena@... via Groups.Io" <bonddaleena@...>
I even visited MT after the Challenger disaster, in a different capacity. Could not believe they used O-rings on the Shuttle.
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Richard, I just finished restoring a Tek 647A using a HV transformer from a 453. The transformers are nearly identical except to pin-out arrangement. Both transformers require heat sinking to the chassis using suitable thermal grease. I prefer non-silicon compound such as Wakefield 126 series or one of the popular PC processor thermal compounds that have better spec's. The thermal compound on the ferrite core is there to remove heat, not for any electrical purpose. I avoid silicon-based thermal compounds, because they tend to creep and may eventually lead to electrical issues. George On Thu, May 3, 2018 at 1:05 PM, Richard Knoppow <dickburk@...> wrote: I am still working on my 453. The HV transformer is mounted with some
sort of clear grease. I think this is heat sink compound but may just be
silicone insulating grease. What is recommended here? I am also replacing
Q-930 and wonder what compound is recommended for it.
I have clear silicone grease intended as a HV insulator by GC
chemicals, is it OK for the transformer. I can get regular heat sink
compound locally if necessary.
--
Richard Knoppow
dickburk@...
WB6KBL
|
I already replaced the transformer but its easy to get to so I will get some correct compound and re-install it. The original does not seem to have any filler in it, its clear. Same stuff on the oscillator.
I misplaced a nut. Plain 6-32 nut. Stopped because when I start losing things or droppings things its a sign of fatigue. Very frustrating.
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On 5/3/2018 3:43 PM, George Kerber wrote: Richard,
I just finished restoring a Tek 647A using a HV transformer from a 453. The
transformers are nearly identical except to pin-out arrangement. Both
transformers require heat sinking to the chassis using suitable thermal
grease. I prefer non-silicon compound such as Wakefield 126 series or one
of the popular PC processor thermal compounds that have better spec's. The
thermal compound on the ferrite core is there to remove heat, not for any
electrical purpose. I avoid silicon-based thermal compounds, because they
tend to creep and may eventually lead to electrical issues.
George
--
Richard Knoppow
dickburk@...
WB6KBL
|
If you already have any of the opaque "filled" types of thermal grease, just use that. The clear kind doesn't have any filler, but still helps with the thermal conductivity (way better than air) in the voids between surfaces. The filled kinds work better, but are more viscous, so be sure to work the pieces around to squeeze and thin out the layer and assure some good solid contact between the surfaces, with a thin film of the goop left in between. It's good to wipe off any excess, as it can make a mess and collect dust.
Ed
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On Thu, May 3, 2018 at 03:03 pm, Michael A. Terrell wrote:
My understanding is that there were two reasons. First of all, they had to
build the engines in sections, and secondly they had different thermal
expansion rates.
I hope not to sound too stupid here but... Why would they use materials of different thermal expansion coefficients ? Even if more heat is generated in one section than the other, I find it hard to believe that was the right choice, and I assume money was practically no object. That is was built ion sections, with limited information here I assumed it had something to do with transportation. While state law could be suspended and highways closed for such a special transport, there is still a limit as to just how large of an object can be physically transported. I think it is a damn shame they retired those without a viable replacement. They seem to be losing the last of their brain cells. Not that the shuttle did this, but now from what I understand we buy rockets from Russia to do maintenance of our satellites ??? Is that smart from a national security standpoint ? I have my doubts to say the least, even though the pundits are overblowing the differences between the two superpowers, it is not hard to become enemies in this world of pipeline wars etc. I am not sentimental but I see it as a bad time when they retired those craft, and I think they should have kept a few of those SR-71/YF17s around. These were some significant accomplishments in their time.
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You're forgetting that it was a solid fuel engine, and that the engine housing didn't heat evenly. It was hottest at the output, and coldest at the top of the engines. The differential would have cracked welds and the problems would have gotten worse each time a booster engine was reused. Below the rated temperature, the seals couldn't be certified to contain the exhaust gasses. There was a book covering the technical details of the designs, and their reasons. I read it years ago, I think it was called 'A Major Malfunction'.
Michael A. Terrell
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-----Original Message----- From: Jeff Urban <JURB6006@...>
On Thu, May 3, 2018 at 03:03 pm, Michael A. Terrell wrote:
My understanding is that there were two reasons. First of all, they had to
build the engines in sections, and secondly they had different thermal
expansion rates.
I hope not to sound too stupid here but...
Why would they use materials of different thermal expansion coefficients? Even if more heat is generated in one section than the other, I find it hard to believe that was the right choice, and I assume money was practically no object.
That is was built in sections, with limited information here I assumed it had something to do with transportation. While state law could be suspended and highways closed for such a special transport, there is still a limit as to just how large of an object can be physically transported.
I think it is a damn shame they retired those without a viable replacement. They seem to be losing the last of their brain cells. Not that the shuttle did this, but now from what I understand we buy rockets from Russia to do maintenance of our satellites ???
Is that smart from a national security standpoint ? I have my doubts to say the least, even though the pundits are overblowing the differences between the two superpowers, it is not hard to become enemies in this world of pipeline wars etc.
I am not sentimental but I see it as a bad time when they retired those craft, and I think they should have kept a few of those SR-71/YF17s around. These were some significant accomplishments in their time.
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re: Challenger o-rings. Failure was caused by low temperature at launch. The o-rings were too stiff to seal properly. Previus cold launches also experienced o-ring failures, just not catastrophic. Managers over-ruled the engineers tto keep on schedule. Richard Feynman was on the accident review committee and had little good to say about program management.
Sirry I can't help with the heat sink compound.
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Those wanting more information can refer to the study by Diane Vaughan in her 1996 "The
Challenger Launch Decision" which records in chapter 8 the grisly details of multiple
telephone conference calls right up to the final hours. My recollection is that things were not
completely polarized as "managers" vs "engineers", things were more complex.
Available used on Amazon for a few dollars.
Sorry I can't help with heatsink grease either
Ted
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On 4 May 2018 at 7:04, steve gunsel wrote:
re: Challenger o-rings. Failure was caused by low temperature at launch. The o-rings were
too stiff to seal properly. Previus cold launches also experienced o-ring failures, just not
catastrophic. Managers over-ruled the engineers tto keep on schedule. Richard Feynman
was on the accident review committee and had little good to say about program
management.
Sirry I can't help with the heat sink compound.
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Raymond Cote
redarlington
Michael A. Terrell
Jeff Urban