buz21 substitute

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Sorry to bring this thread back from the dead but am running into issues with a similar amp (us acoustics ZED). I soldered IRF540N's and it seems to work but the sine waves are a bit fuzzy and within 2 minutes BOOM one of them leaks with no sign of damage.

Am guessing these amps don't like the "N", any insight on this Perry and if so should I use IRF540PBF or FQP33N10.

BTW this amp has 28 outputs so replacing them more than twice isn't fun, lol. Any help or advice is greatly appreciated.
 
I might just order 12 of the IRF540PDF and install 3 on each side (6 per channel) and see how it does under a light load. I would hate to solder 28 and have the same damn issue. If it does fine then I'll solder in the rest.

Never had much luck getting ANY info out of ZED, no matter how nice or simple the question may be.
 
As you can see it originally had 12 fets per channel, I figured since it has four extra spots for fets on each ch I would throw those in as well. I used same .1ohm 5watt resistors so right now the amp has 16 .1ohm resistors on each side/ch.



Pic is not mine..but same exact amp.
024DC4B2-5139-4479-94F8-439933D8D397_zps0mtysja9.jpg
 
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Okay tried it with the IRF540PBF (used a total of 24 just like when stock), adjusted the bias and got a final idle of 0.95amp. So I tried it with the low pass set and a bass track, I notice that the amplifier quickly got hot, after 6-7 minutes the amplifier was very hot and internal fan kicked on.

I paused the track to see if it will cool down, well even after 15min of no audio the internal fan was still spinning.

I am afraid of giving it back to the owner and for it to fail...am starting to hate these Zed amps, lol.
 
When I adjusted it to 0.95 I did so with a dmm, once I was testing it and it got warm I was monitoring the amperage with a amperage clamp meter (not as accurate as the dmm in line with B+) and the idle current was pretty high but may have been caused because of the fan being on...perhaps?

Should I let it warm at at normal levels with dummy loads then once it warms up enough cut it off and remove the dummy loads and RCA then check the idle current?
 
Will run it again while monitoring the amperage and get back in an hour or so...the transistors have plenty of compound as I rubbed it on top of kapton insulator, a nice thick layer and when the transistors were clamped you can see the compound squeezed out... I'll post some pics as well.
 
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