Just being pedantic ... but you should've written, TT:
R1001 = 100R
R1002 =47R
C1002 = 220pF
V1001= 15v Zener.
(The Snubber Board schematic left out the extra '0' - see down the bottom of post #1 - Edit Jan 3rd, 2020.)
Andy
Hi Andy,
Since your possibly going to use the Dell FD841 CPU coolers I thought I’d pass along some information I discovered about them during a past build.
There are two versions, one has a large rectangular copper pad, the other has a smaller diamond shaped copper pad. You want the rectangular pad if you’re going to attach two devices for cooling. The easiest way to identify them without being able to see the copper pad is the shape of the aluminum fins. The more desirable one has semi circle cut outs in the aluminum fins for the screwdriver to pass down through to tighten the mounting bolts, the smaller diamond copper pad has a square relief in the aluminum fins for the screwdriver to pass.
Another clue for the rectangle pad is in the model number, “73304” must follow FD841.
Look on eBay for them, there is usually plenty to choose from.
A Noctua NF-A9pwm fan fits perfectly and are almost completely silent, I can’t hear a pair of them running from more than 4 feet away.
Wishing you good luck on your journey 🙂
Since your possibly going to use the Dell FD841 CPU coolers I thought I’d pass along some information I discovered about them during a past build.
There are two versions, one has a large rectangular copper pad, the other has a smaller diamond shaped copper pad. You want the rectangular pad if you’re going to attach two devices for cooling. The easiest way to identify them without being able to see the copper pad is the shape of the aluminum fins. The more desirable one has semi circle cut outs in the aluminum fins for the screwdriver to pass down through to tighten the mounting bolts, the smaller diamond copper pad has a square relief in the aluminum fins for the screwdriver to pass.
Another clue for the rectangle pad is in the model number, “73304” must follow FD841.
Look on eBay for them, there is usually plenty to choose from.
A Noctua NF-A9pwm fan fits perfectly and are almost completely silent, I can’t hear a pair of them running from more than 4 feet away.
Wishing you good luck on your journey 🙂
Attachments
Thanks Vunce!! One of these Dell coolers should easily cope with the 120W from two mosfets on the 4R ALPHA N, these towers move a lot of heat.......
HD
HD
Zener
Just to be clear, the zener in the circuit shown here is for the N channel correct? Also the band on the zener will be pointed in the direction of the IRFP240 chip on the snubber/
Just to be clear, the zener in the circuit shown here is for the N channel correct? Also the band on the zener will be pointed in the direction of the IRFP240 chip on the snubber/
Attachments
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As far as I know, I have only seen myself, Vunce, and a partial first sound from Jacques Antoine for the Alpha Nirvana. Did I miss anyone? Please let us know if you have built it and successfully running now.
Here is one channel first sound from J.A.
Here is one channel first sound from J.A.
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Wow, so I will be number 3 or 3.5. I'll be putting some power to it a little while, I need to mount the FETs and that's about it. Hopefully, the magic smoke shall remain after the test.
JT
JT
JT,
Wish you a smooth power on really soon, with magical sound after that, and no magic smoke! 🙂
Wish you a smooth power on really soon, with magical sound after that, and no magic smoke! 🙂
Hi X,
The second AN channel is working as well but before running extensive stereo tests I am waiting for my aluminum oxide insulators order (from ....China)!
The heat transfer using standard silicone pads is not optimal and I am afraid to blow the ouputs and/or my test speakers.
I was wondering also if Arctic MX-4 thermal paste could be used with the ceramic pads?
Cheers,
Jacques
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Jacques,
Have you done any temperature measurements that indicate that the heat transfer using standard silicone pads is not optimal?
Have you done any temperature measurements that indicate that the heat transfer using standard silicone pads is not optimal?
Hi Zman,
I routinely use silicon pads without thermal paste for AB amps.
But for class A amps I was told that these pads are not recommended.
Anyway, with silicon pads the outputs get really hot (>75°C) in a few minutes while I can still keep my hands on the heatsink without screaming after a long time (<55°C).
I haven't measured exactly but my hands are pretty accurate as daytime biochemist.
Hi Jacques,
I would recommend thermal paste with the ceramic pads, that’s the setup I use and it works very well. Temperature taken with an IR gun, the AN Mosfets don’t get above 65°C.
It’s a little messy but I feel worth the extra step.
Good luck with your final details!! 🙂
+1
Alumina ceramic pads with a very thin layer of thermal paste, works best for me
Thermal paste should not be electrically conductive.
Alumina ceramic pads with a very thin layer of thermal paste, works best for me
Thermal paste should not be electrically conductive.
Jacques,
How long will it take for the pads to come from China?
Here's an option from Farnell France:
https://fr.farnell.com/aavid-thermalloy/4180g/isolateur-oxyde-doxyde-ceram-203mm/dp/2822610?st=4180G
Maybe good option if you have other stuff to order and get the free shipping. Probably you can tell that we are eagerly awaiting your listening impressions. 🙂
How long will it take for the pads to come from China?
Here's an option from Farnell France:
https://fr.farnell.com/aavid-thermalloy/4180g/isolateur-oxyde-doxyde-ceram-203mm/dp/2822610?st=4180G
Maybe good option if you have other stuff to order and get the free shipping. Probably you can tell that we are eagerly awaiting your listening impressions. 🙂
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Can one of you tell me what voltages you have as measured with the FETs connected at Gate Drain and Source?
If you are nominally at +/-27v then look at LTSpice diagram and you can see that the drain pins will be about same as rails +/-27v and source will be about +/-375mV. Gate will be about +5v to -4.5v.
Luckily I ordered a big amount of pads from China on Jan 21st, just before the viral epidemy!
They're on their way, dirt cheap: 0.12€/each, including shipping, still waiting for them. Let's hope it's not crap!
Well, I wish I could say it went well, but it wasn't even close. One side was working for a bit and the other was not, now it's pretty much hosed. I thought I had it figured out, so I used the other side to check that out and now I have a few hundred worth of modern art.
No magic smoke or any fireworks, just no values that look right anywhere. Even with the FET disconnected nothing I get different voltages from the outputs of each.
I had to troubleshoot the supply and now this mess, for now, I need to get away from it for a bit as all I feel like doing now is firing it in the ash can.
No magic smoke or any fireworks, just no values that look right anywhere. Even with the FET disconnected nothing I get different voltages from the outputs of each.
I had to troubleshoot the supply and now this mess, for now, I need to get away from it for a bit as all I feel like doing now is firing it in the ash can.