SOME NOTES about the NAD 701 AM/FM Stereo Receiver

which may be of help to anyone working on this model

I bought mine in 1996, about the time manufacture of this model ceased. It does everything I want of a tuner-amplifier, and I commend the design, presumably done under the direction of Bjorn Erik Edvardsen. Maybe the amplifier design is similar in other NAD 25/85Watt products (does anyone know?) The product brochure can be seen here

Remote Control
The use of a motor-driven volume control for remote control is entertaining, and is only found in audio equipment of this era

I managed to blow my 701 up recently, by changing speaker connections while it was running - didn't expect that, but it is a DC-coupled design!
Servicing was easy, with good access to the boards:

One output stage had died gracefully, only the complementary power pair had failed before the fuses blew. These were a 2N3055 + 2N2955 , which are readily available in the metal can TO3 package or in plastic packages. If replacement driver devices are needed and hard to find, I recommend 2SC2238 (npn) + 2SA968 (pnp) - complementary audio driver types.
The fuses F501-504 are shown as "T" (slow-blow) on the PCB screen, but "F" (fast) types had been fitted originally, so I used 4A "F" types

The power switch button bracket had broken, so I also fixed this, using a bit of old credit card:

The display bulbs were failing, so I took the opportunity to replace them with white LEDs, two in series with a resistor - about 220ohms gives a bright display

Servicing information - schematics and PCB layouts - is available in this zipfile - 916KB



JH, Feb.2010. Last updated Sep.2012

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