marantz 2230 no tone control

[dishman]

My Marantz 2230 just lost tone control. The sound became very thin, and none of the bass, mid, or treble pots have any effect. It affects both channels. Volume works fine and the loudness contour still has an effect when turned on and off.

I've not noticed distortion, although it's so thin sounding I'm not sure.

Because it affects both channels, my instinct is to suspect power to the tone control board. I replaced the 100uf electrolytic (C409) and re-soldered the connections at J404, 405, &406. No fix.

Getting 7.15 volts at J404 and on the positive lead to C409,

Any ideas or suggestions?

 

[mbz]

Check J808 on P800 power supply, expect about +35Vdc.
H802,3 and maybe C806 should be looked at closely.

 

[dishman]

Getting 7.62 @ J808. Going to start with re-soldering. How would you test these components?

I'm fine with just replacing all three.

 

[mbz]

With amp powered off, use diode test function available on most multimeters.
Graphic from markthefixer.

 

[dishman]

Thanks, I didn't know you could do that. Nice tip!