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Old 8th March 2009, 12:56 PM   #2881
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Join Date: Oct 2007
Decided to replace one of the faulty board with another board.

Was finally able to fire up the F4 and set up the bias - approx 200mv resulting in the heat sink temperature of 59deg C.

Even my wife commented that the F4 sounds superb. However approx 2hours into using the F4, the fuse blew.

Checking the boards - I found 1 of the 3W resistor burnt / probably resulting from the fact the corresponding mosfet was not properly attached to the heat-sink

Other than the 3W fuse, is that corresponding mosfet also dead? (looks kinda brown around the edges) Any other components that will need to be replaced?

thanks

her shann
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Old 25th April 2009, 05:11 PM   #2882
Liliya is offline Liliya  Norway
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Join Date: Aug 2003
Location: 3370 Vikersund
Default My F4 and Aikido prosject

This is my F4 amplifier project. Later on Aikido will be added into the same chassis.


Heatsinks to a class A amplifier cost a lot of money, so I went to a junk merchant in the nearest town. Here I paid a reasonable price per kilo aluminium and for the cutting.
(I was to late to participate in the group-buy on DiyAudio)
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Old 25th April 2009, 05:14 PM   #2883
Liliya is offline Liliya  Norway
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Join Date: Aug 2003
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Default My F4 and Aikido project

Lots of screws and nuts is needed. Fortunately we have a firm in Norway, Biltema, that sell this things very cheap.
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Old 25th April 2009, 05:16 PM   #2884
Liliya is offline Liliya  Norway
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Default My F4 and Aikido project

A lot of holes to bore.
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Old 25th April 2009, 05:18 PM   #2885
Liliya is offline Liliya  Norway
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Join Date: Aug 2003
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Default My F4 and Aikido project

The first of the “units” in position.
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Old 25th April 2009, 05:19 PM   #2886
Liliya is offline Liliya  Norway
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Join Date: Aug 2003
Location: 3370 Vikersund
Default My F4 and Aikido project

One channel almost ready
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Old 25th April 2009, 05:22 PM   #2887
Liliya is offline Liliya  Norway
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Location: 3370 Vikersund
Default My F4 and Aikido project

Both power units in the chassis. 2x 36600 mF each.
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Old 25th April 2009, 05:27 PM   #2888
Liliya is offline Liliya  Norway
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Join Date: Aug 2003
Location: 3370 Vikersund
Default My F4 and Aikido project

The PCB is from “cviller from Denmark”. I found his solution to be the best on my DIY heatsink with regard to a balanced spread of heat.
No problems either with DC or bias.
The most “thrilling”: How would my selfmade heatsink behave??
Suprisingly well. After one hour I could easily keep my finger on it without any unpleasantly. The first minutes hottest where the FETs
are mounted, but after one hour very well spread over the hole heatsink.
I think I could easily increase bias setting from 250 mA to 300 mA
without problems. But I am not sure I have any benefits of doing that, or what will you experts out there says??
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Old 25th April 2009, 06:46 PM   #2889
Liliya is offline Liliya  Norway
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Join Date: Aug 2003
Location: 3370 Vikersund
Default My F4 and Aikido project

Aikido on test.
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Old 25th April 2009, 06:51 PM   #2890
Liliya is offline Liliya  Norway
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Join Date: Aug 2003
Location: 3370 Vikersund
Default My F4 and Aikido project

I use Russian tubes in both positions 6N6P. Lukas Fikuzs have through his Lampizator site learned me to love this tubes.
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