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Old 9th May 2012, 10:37 AM   #151
AndrewT is offline AndrewT  Scotland
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Belleville washers make excellent "springy" spacers.

They are so good, that they or similar should be used for all clamped devices. They help to hold a near constant pressure/force as the temperatures change.
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Old 9th May 2012, 12:22 PM   #152
flg is offline flg  United States
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In my bis we quite regularly line up 5-6 pair of transistors in line on a board and cover all of them with the same H.S. We use a material we call Gap Pad(trade name?). There are several brands of such stuff, 3M comes to mind also. It ussually has a dielectric rating(perportional to thickness but, high enough we don't care) and a thermal rating(naturally, also porportional to thickness). There is another material I have used that we call Body Filler(humorous). It looks like body filler you would use to fix dents in your auto. It's blue, and you mix it up like body filler. It dosent cure to a nice hard plastic though. It is removeable.
Both of these substances are designed to planerize the devices to the heat sink. That is, take up the hieght differences with a thermal spongy sheet of raz-ma-taz or goop for good contact to the H.S..
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Old 9th May 2012, 01:11 PM   #153
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Has anyone had a successful F5(T)v3 build yet ?

I'm intrigued to see how much heat they are ditching.

I've got a DIY Aleph 4 which gets quite - but not excessivley - hot.

I'm wondering wether I can't use it as a donor for a dual mono build. ie keep the chassis, heatsinks and power supplies. +/- 48V may be too high even for the V3 ???

Last edited by KatieandDad; 9th May 2012 at 01:20 PM.
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Old 9th May 2012, 01:26 PM   #154
AndrewT is offline AndrewT  Scotland
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The F5T is not much different from an F5, nor an F5x.
The heat they all give out is still related to bias current and supply rail voltage.
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Old 9th May 2012, 01:32 PM   #155
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Quote:
Originally Posted by KatieandDad View Post
Has anyone had a successful F5(T)v3 build yet ?

I'm intrigued to see how much heat they are ditching.

I've got a DIY Aleph 4 which gets quite - but not excessivley - hot.

I'm wondering wether I can't use it as a donor for a dual mono build. ie keep the chassis, heatsinks and power supplies. +/- 48V may be too high even for the V3 ???
there is no problem running the v3 on +/-48V
your aleph4 dissipates around 200W pr channal?
thats around 2A bias on +/-48V supply.
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Old 9th May 2012, 01:39 PM   #156
AndrewT is offline AndrewT  Scotland
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But !

2A bias in a Push Pull output stage limits the maximum ClassA output current to <4Apk.

4Apk from ~48Vdc limits the load for ClassA operation to >=12r0.
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Old 9th May 2012, 01:58 PM   #157
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My A4 has only got 2 x 500VA transformers - it is in dual mono configuration.

The 6 x IRFPs are biassed at a combined 2.4A (ie 400mA each) with ROCK STEADY 48V CLC rails.

The Aleph 4 has four groups of 6 x IRFP. 2 x Current Sources and 2 x SE Amplifiers.

Last edited by KatieandDad; 9th May 2012 at 02:08 PM.
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Old 9th May 2012, 02:03 PM   #158
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2A bias will give 64W in 8ohms.
if you can get bias up to 2.6A, you will have 108W in 8ohms.
but i don't think your heatsinks is up for the job.

mine will be +/-42V and 2.4A bias.
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Old 9th May 2012, 02:04 PM   #159
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2x500VA is fine for 2x200W consumtion.
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Old 9th May 2012, 02:07 PM   #160
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The Heatsinks currently keep it about 55 Degrees C on a warm day.

It should be producing approximately 100W/Channel in true Class A as per Nelsons original schematic.

Last edited by KatieandDad; 9th May 2012 at 02:10 PM.
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