My good old (I must have bought it in 1995 or so?) NAD 216 THX power amplifier had a strange problem for quite a while. When the balance was turned all the way to the right, the left speaker continued to play an audible signal. Not really what you’d expect from an “audiophile” Hi-Fi system of that price range.

Also, for a long time, I was thinking this whole combination of NAD216THX and NAD116 should really be completely remote-controllable from the Squeezebox Touch. The preamp can be put on standby already by the Squeezebox using the “IR blaster” solution, but not the power amp.

So…. loooong repair project started.

  1. Added a 5V relais to the power amps power switch circuit so that I can bridge it.
  2. Added plugs to both the preamp and poweramp mechanics.
  3. Identified the “green LED” signal on the preamp. And identified a place where I should be able to find 5V.
  4. Soldered a cable.
  5. Also… that “bridge mode” switch looked suspicious, it made bad contact and the LED was sometimes flickering. So… I removed it.

Then, I managed to find the problem with the crosstalk between the two channels. The fault was the protection chip TA7317P. Took me a while to identify it, but when I heard a dumb “click” when turning the poweramp off, my suspicion was awaken. Changed the chip, bingo! So here we are again, with the HiFi system ready for another decade hopefully.

The remote control isn’t quite finished yet, the 5V of the preamp isn’t sufficient to drive the relais board. So I’ll still have to solder a little power regulator. That’s a project for next month… hopefully !

This is where the “bridge mode” switch was.

Unfortunately, it was also when I realized that at 50y of age, I reallly needed a magnifying glass to solder even such relatively big contacts. Sigh.

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