Quad 34 help

Hi,

I inherited a Quad 34 pre that weirds out now and then. The preamp
comes on, with the default source selected. Either by itself, or when
selecting another source, all the selector leds light up dimly, and
the sources are lost (pre does not work).
Any one have a schematic that they may scan for me. It seems that the
tactile switches drive a row of 8 transistors that probably do the
switching part...

would appreciated any help.

BTW, does this thing sound ok? I am a bit put off by all the tl071
opamps that populate this thing. Aby recommended mods?

nicolas