F4 power amplifier

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#2,741
my guess is (and it's merely a guess) is that the straight line layout you propose is better than the standard Peter Daniel board, but not better than using a spreader approach like Magura is suggesting, which in turn is probably not quite as good as using a pair of 6" heat sinks per side. Again, this is just guessing...

Also, yes the differential is pretty small, a few degrees here and there, but I've come to find that a few degrees can make a lot of difference.

I've also used the results to help me choose a thermostat rating as well as locating a good position to use it. I'm looking at the Sensata/Airpax TO-220 devices and will probably choose a 50C value (Digikey 723-1203-ND) placed in the center of the heat sink. Before the simulations, I had selected a 75C device, but now I know that that is way to high, as I cannot get the thermostat close enough to the "hot spots" and as a result I will derate the device and move it to another position. I think the simulations helped inform this decision.
 
#2,743
1E?

Please excuse the newbiness but what's 1E (between the output and fets)

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#2,747
Peter Daniel said:
I used copper spreader in Zv9 and heatsink temp is pretty much uniform: http://www.diyaudio.com/forums/showthread.php?s=&threadid=85590&highlight=
Click to expand...

wow Peter, looks great. Seems the price of copper will have to make this a future addition for me.

Also one question.. I cannot seem to find some large fender washers used to distribute the force on the FET cases. I see these on so many pictures, including the real-deal First Watt amps. I ordered some #4 fender washers online and was disappointed to find them only slightly larger than usual #4 washers. The ones on the First Watt amplifiers are actually larger in diameter than the width of the FETs! I'm guessing this part is something buried deep in the abyss that is the McMaster-Carr catalog?
 
#2,751
Question to help me fix a catastrophic screw up. Last night, I was assembling my F4 monoblock. I got everything wired up. All hard soldered. Everything checked, double checked. Then I realized I needed a power cord from my Neutrik Powercon connector to my power supply. No problem. I built one up. All I had was black wire kicking around, so I added some colored heat shrink for polarity. Well, I screwed it up. I ended up putting power to the ground. :bigeyes: The positive was correct, the negative was to ground and the ground was to negative.

So, my question is where do I start to fix the sad reality that it now pops fuses.
 
#2,752
The Mosfets have reverse diodes built into them, so that often
enough you can pump a tremendous amount of reverse current
through the channel without blowing anything. You will have to
isolate the damage. This is a good time to invest a few bucks in
a Variac (you won't regret it). Try Marlin P Jones on the web.

😎
 
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