Nakamichi TA-2 Receiver in a funk

I'm trying to troubleshoot a 1980'2 era Nak receiver that has pushbutton input switching via a microprocessor (can also be remote controlled). The button lights don't work, and I get no input connections at all. Strange, but the micro works, controlling the volume up and down. Also, the amp worksvia the pre-out and power-in jumpers. Apparently, some aspect of the switching (done via an analog switch IC) is screwed up. Anyone have ideas on how to troubleshoot this?

 

I would first check the electrolytic caps in the power supply. Noise
on the B+ lines will cause all matter of digital problems with this
model. Chuck

 

I'm trying to troubleshoot a 1980'2 era Nak receiver that has pushbutton
input switching via a microprocessor (can also be remote controlled). The
button lights don't work, and I get no input connections at all. Strange,
but the micro works, controlling the volume up and down. Also, the amp
works via the pre-out and power-in jumpers. Apparently, some aspect of the
switching (done via an analog switch IC) is screwed up. Anyone have ideas
on how to troubleshoot this?

What ident is the big an. sw. ?

 

There should be a switching IC (LCxx22 or TC9163) located on the board. Inmany cases this is the problem. You will see the signal entering the IC, but no output. I believe that the light and the audio are controlled by the same line. The few of these I have seen in the past were quick fixes by replacing the switching IC. (IIRC)

Dan

 

Did Nakamichi do the thing with the button lights that they did on some
other units? (The lights were used as the pullup resistors in the matrix
scanned keyboard or something strange like that).

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

 

I was able to download a service manual from Elektrotanya.

The site is difficult to access if you don't speak Hungarian but I can email
you the manual.

email me at:



and reverse "labolgcbs" to read "sbcglobal".

Mark Z.

 

http://diagramas.diagramasde.com/audio/Nakamichi_TA-2_2A_2E_20.pdf

- Franc Zabkar