NAD 3020 Series 20 mk-3 MOSFET Output Conversion

So this is the doner amp that is going to be used for the project, its in almost mint condition and i dint want to break it(unless i have to lol)

Its what i call a mk3, this is the same board they used as they moved onto the 'A' version

So things that need to be done

Modify the base of the heatsink so it will accept the FETS
Modify the print so it maches the pin out

so this is the scheme that needs to be used for this one

ive never been able to find an official 'A' service manual, but this is close

Its easily recognised by the fact the regulated supply is now on the main pcb


  • 3020 ser 20 service ver 2.pdf
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  • FET donor.jpg
    FET donor.jpg
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  • FET donor reg supply position.jpg
    FET donor reg supply position.jpg
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  • reg supply mk1.jpg
    reg supply mk1.jpg
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2007-10-10 5:21 pm
The same basic design often works with little or no modification other that the adjustment range on the vbe multiplier. You get a few watts less with the mosfets, unless the drive voltage can be enhanced to drive the gates a bit above the rails. Even thats not essential, you can just live with 3 volts or so less output swing.