Sanusi model 2000 left chanel almost dead

J.casebeer

New Member
Hello.
I am new to vintage audio. I was recently given a Sanusi model 2000. It's not the 2000x or 2000a. The guy who gave it to me didnt even know if it would power up. When i connected it and powered it on, there was no sound coming from the left channel. I turned the balance knob almost all the way to the left and turned the volume 1/3 of the way to full volume. This produced an even volume from both channels, but obviously something is not working correctly. Adjusting the bass or treble knobs or pressing the loudness or mono or reverse buttons has no significant effect on the weakness of the left channel. I have thoroughly cleaned the pot's and switches with deoxit D5, but it made no detectable difference. The cover had previously been removed from the unit and several screws were missing. I was told by a local audio guy that my output transistors might be the cause. I replaced all 4 Toshiba 2sc493 with 4 new MJ15015. This also made no difference for better or worse. What do I try next?
 
As a test, you can try this.
Remove the jumper plugs in the back for pre-out and main in. Get a pair of audio cables and use them by plugging the left pre-out to the right main in, and with the other cable connect the right pre-out to the left main in.
Test the unit. If it is still the left channel that is weak, you have a problem in the left main amplifier (power amp). If the problem moved to the right channel, your problem is a bad/dirty switch or a problem in the control amps tone amps etc.

If the problem stays in the left, you can try the main speaker coupling Capacitor mounted in one of the cans (2000uf @50v), or the input transistor 2sC458 (TR801) which is notorious for going bad, or the 5uf capacitor (C804).
If the problem moves, you may want to try the small coupling caps on the preamp, tone amp, and control amp boards. They are usually 1uf, 2.2uf, 4.7uf (or 5uf), or 10uf. You can actually test these to see if they are bad by jumping a new one in parallel with the one in circuit as failure wise they usually open. Just be careful to observe polarity, and keep volume down as it may blast you. Other things to look at are there is other 2SC458 transistor (TR602) used in this receiver in the amp sections that could be causing this issue if the problem has moved with the audio cable swap.

Note that on Semi (fairchild) KSC1845 are good replacements for those 2SC458's. And I would replace the ones in the right channel especially if they were the cause of the problem in the left.
 
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