Nad 3020 Modification from 1982

[crooner]

I have just purchased a late Nad 3020 with components coded 1981.

I was surprised to find the presence of a DIY board attached to the main heatsink.

Removing the bottom panel revealed a hand drawn schematic dated from 1982.

Apparently, the unit's tape input was modified by some sort of equalizer. I also see some added resistors to the board at the tape input and tone controls.

I wonder if the mod can be reversed without much trouble...

Any comments appreciated!

[crooner]

Here's the hand drawn schematic taped to the bottom cover:

[Ian Finch]

Well, it looks like a mono adapter with it's own preset tone controls in the tape input. It should be no drama to disconnect and temporarily tidy away the wires added to both sets of tape jacks, remove the 10k resistors and the wire jumper then check that the inputs work as they should.

There may be cut tracks to solder over before you have function, then remove the power leads, earth and the board also. It's unlikely that further mods to the amp were done - this is an add-on that wouldn't be effective unless you used the tape input. You still have other inputs to use that will have similar line level sensitivity for testing.

If you want a schematic to find your way about, a search for NAD3020 should bring up plenty of threads and links.

[ingenieus]

This might help.