If your F5 smokes and the Mosfets pop they 99% of times go short circuit so you going to get rail voltage on speakers.
You can try to ask speaker manufacturer for warranty (nothing wrong with asking).
The big issue is the look on Her face when she goes I told you so....
Or you can do things properly.
Answer those questions and you are alright?
Is non contact thermometer accurate on small area and reflecting material?
answer to this is no even whit really expensive ones first of all find out spot size / distance normally 8 to 1
Is silly laser pointer pointing in right place?
Maybe not
Is it calibrated correctly for material?
Maybe?
So simple £15 pt 100 kitchen thermometer may be more accurate.
Second thing how do you know that sink are at right temperature? (Try to measure the temperature of your bath water) 2 C lower than what you like is just cold 2 C above and it will be to hot.
That is the way we have been drawn and same all for all to the point that there is current legislation in UK that prescribe maximum water temperature out of water tap at 50 C at that temperature one body goes Fu you and all short of alarm bells start to go off in one Gully Wog
Third what is the actual temperature of the Mosfets?
Or to put it another way has you made thermal interfacing properly?
Way to answer that is to measure the temperature of the metal tab on the back but you can't do that with the Mosfets mounted.
What you can do is measure he temperature of the Drain leg which is just a piece of metal directly in contact with the Mosfets Junction (the place where all magic happens) and has very little temperature impedance (the data sheet actually gives you the exact numbers to do the math)
Can you do that with no contact thermometer?
NO chance!
😀Or you can follow same other "piece" of advised
Please read this I am being a bit sarcastic and most certainly would not recommend this
To reduce the temperature of your sinks.
Just loosen up the screws that clamp the Mosfets to the sink.
Your sink will be really cool and we can all be happy for the next 5 minutes or so
PS once you got ang of taking accurate themperature mesurament
Just stick 3 legs o the back plate of your amp and use that as botom
Maybe 5 minutes work + time for thing to warm up?
You can try to ask speaker manufacturer for warranty (nothing wrong with asking).
The big issue is the look on Her face when she goes I told you so....
Or you can do things properly.
Answer those questions and you are alright?
Is non contact thermometer accurate on small area and reflecting material?
answer to this is no even whit really expensive ones first of all find out spot size / distance normally 8 to 1
Is silly laser pointer pointing in right place?
Maybe not
Is it calibrated correctly for material?
Maybe?
So simple £15 pt 100 kitchen thermometer may be more accurate.
Second thing how do you know that sink are at right temperature? (Try to measure the temperature of your bath water) 2 C lower than what you like is just cold 2 C above and it will be to hot.
That is the way we have been drawn and same all for all to the point that there is current legislation in UK that prescribe maximum water temperature out of water tap at 50 C at that temperature one body goes Fu you and all short of alarm bells start to go off in one Gully Wog
Third what is the actual temperature of the Mosfets?
Or to put it another way has you made thermal interfacing properly?
Way to answer that is to measure the temperature of the metal tab on the back but you can't do that with the Mosfets mounted.
What you can do is measure he temperature of the Drain leg which is just a piece of metal directly in contact with the Mosfets Junction (the place where all magic happens) and has very little temperature impedance (the data sheet actually gives you the exact numbers to do the math)
Can you do that with no contact thermometer?
NO chance!
😀Or you can follow same other "piece" of advised
Please read this I am being a bit sarcastic and most certainly would not recommend this
To reduce the temperature of your sinks.
Just loosen up the screws that clamp the Mosfets to the sink.
Your sink will be really cool and we can all be happy for the next 5 minutes or so
PS once you got ang of taking accurate themperature mesurament
Just stick 3 legs o the back plate of your amp and use that as botom
Maybe 5 minutes work + time for thing to warm up?
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I am the manufacturer of the amplifier and the speakers so the warranty is good on both. 😉
I borrowed my friends non-contact infrared temperature gun to get a baseline temperature. Since the cost of these is very reasonable I have ordered new one and will compare the readings of both in the near future. Since Nelson was kind enough to offer guidance I'm going to closely follow his recommendations when I do this test.
I am using those pink Keratherm insulators for my MosFets.
Regards,
Dan 🙂
I borrowed my friends non-contact infrared temperature gun to get a baseline temperature. Since the cost of these is very reasonable I have ordered new one and will compare the readings of both in the near future. Since Nelson was kind enough to offer guidance I'm going to closely follow his recommendations when I do this test.
I am using those pink Keratherm insulators for my MosFets.
Regards,
Dan 🙂
How do you intend calibrating your temperature meters?
What if the Heatsink Supplier changes his method of anodising, or dyeing of their heatsinks?
Would you bother to recalibrate your temperature meters?
What if the Heatsink Supplier changes his method of anodising, or dyeing of their heatsinks?
Would you bother to recalibrate your temperature meters?
At my own risk I was assuming that the temperature of the heatsink and mosfet were fairly close. Once again, the beauty of a non-contact measuring device is that it offers risk free use. Are there disadvantages to them? I don't know. I've never had one before. I'm guilty of not really checking but I'm hoping (fingers crossed) that my 6" (150mm) wide x 13" (330mm) long x 3"(76mm) tall heatsinks will do the job. Below is the heatsink closest (an inch wider) I could find to the one I'm using.
Regards,
Dan 🙂
I use a contact thermistor and a clothes peg.
Which is better is open for debate.
The contact thermometer only cost me £5.00 GBP.
Which is better is open for debate.
The contact thermometer only cost me £5.00 GBP.
Agree with Zen Mod no need to split air
Only thing that I like to point out is that if thermall impedence is no good one end up with cold sink and hot mosfets.
If one is to be shure the only way to know is to mesure both for this a £5.00 GBP conctat thermometer is exactley what one need does not have to be accurate but say a 10 C difference between the 2 is about right
Only thing that I like to point out is that if thermall impedence is no good one end up with cold sink and hot mosfets.
If one is to be shure the only way to know is to mesure both for this a £5.00 GBP conctat thermometer is exactley what one need does not have to be accurate but say a 10 C difference between the 2 is about right
If you trust the $10 Walmart contact thermometer or any $50 DMM with the temp probe, I suppose there is no reason not to trust this non-contact thermo gun. I actually tried all of them with my simple mosfets matching set up. They were within 2C in 10 mins duration (from completely cold to 47C) which is quite acceptable especially I had no way to tell which one should be the "authority".
How much does using the Keratherm Red help?
http://www.mhw-intl.com/wp-content/uploads/2011/10/red.pdf
Regards,
Dan 🙂
http://www.mhw-intl.com/wp-content/uploads/2011/10/red.pdf
Regards,
Dan 🙂
Sounds like my choice of Red Keratherm would minimize the difference. Although unscientific my first measurements were 46C for the heatsink and 50C for the Mosfet. Once my new Infrared Thermometer arrives I'll try these again. With these devices being <$20USD I don't see why more of us don't have one.
Regards,
Dan 🙂
I do not have one because it can not mesure the temperature of the drain pin where it came out of the mosfet case.
1 is shiny and reflects light
2 is to small for focusing spot.
3 can not hold it steady to same spot whyle it mesure up
1 is shiny and reflects light
2 is to small for focusing spot.
3 can not hold it steady to same spot whyle it mesure up
that gives a delta T c-s of 4Cdegrees.
Using that to determine Rth c-s for your assembly gives
Rth c-s = 4C / WPq.
What was your Pq?
What does that say about the accuracy of your device Tc and sink Ts measurements?
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Have you tried running it standing on its end yet ?
It will run appreciably cooler.
OK the MOS-FETs will not be ideally placed on the heatsink but the heatsink will be approximately 100% more efficient.
It will run appreciably cooler.
OK the MOS-FETs will not be ideally placed on the heatsink but the heatsink will be approximately 100% more efficient.
If you refer to the documentation http://www.mhw-intl.com/wp-content/uploads/2011/10/red.pdf the interesting part is how much better the Rth of Keratherm is compared to Mica.
Once all my data is collected and I conclude that I am running too hot I can easily add the aforementioned fans. My on/off circuit for my Bulgin switch contains a 12vdc power supply. Perfect for my thermally triggered fans pictured earlier in this thread. Will they help? Read on.....
Regards,
Dan 🙂
What thickness of Keratherm?
What thickness of Mica?
Euvl does a very thorough article (Linear Audio) on designing heatsink to match duty.
In there, he reproduces a table that shows the comparative performance of various insulators. Both Kapton and Mica are stated as 0.05mm thickness.
Both can be procured thinner.
Kapton @ ~0.035mm and Mica 0.025mm
and the Keratherm is stated as 0.25mm.
Thin 1mil (1thou, or 0.001" or 0.025mm) Mica is only significantly bettered by Keratherm 86/82, 1mm Aluminium Oxide betters Mica, but only just. None of the other currently available materials that I have investigated can better thin Mica.
What thickness of Mica?
Euvl does a very thorough article (Linear Audio) on designing heatsink to match duty.
In there, he reproduces a table that shows the comparative performance of various insulators. Both Kapton and Mica are stated as 0.05mm thickness.
Both can be procured thinner.
Kapton @ ~0.035mm and Mica 0.025mm
and the Keratherm is stated as 0.25mm.
Thin 1mil (1thou, or 0.001" or 0.025mm) Mica is only significantly bettered by Keratherm 86/82, 1mm Aluminium Oxide betters Mica, but only just. None of the other currently available materials that I have investigated can better thin Mica.
Quick question on this topic from a hobbyist. Does thermal paste improve mica AND, will it compromise the electrical isolation?
Frank
Frank
Thanks. So OK to use something like the high efficiency CPU paste (e.g. 'arctic silver') on both sides of mica?
Careful !
If the Thermal Compound has metal in the formulation it is probably electrically conductive. Silver is a fantastic electrical conductor.
The Thermal compound must also act as an electrical insulator in most electronic uses.
A follow up on Mica and all other "hard" surface interfaces.
All these "hard" interfaces MUST use a thermally conducting compound to replace all the air in the interface.
If the Thermal Compound has metal in the formulation it is probably electrically conductive. Silver is a fantastic electrical conductor.
The Thermal compound must also act as an electrical insulator in most electronic uses.
A follow up on Mica and all other "hard" surface interfaces.
All these "hard" interfaces MUST use a thermally conducting compound to replace all the air in the interface.
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