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What kind of audio wiring do you find in the changer assembly? There should be
two shielded cables with a common ground, with the inner conductors connected
to the each of the live terminals (Left and Right) of the cartridge. The third
terminal on the cartridge should be connected to the common ground (shield) of
the cables.
Regarding capacitor replacements, at least the three interstage capacitors
should be replaced. If they are leaky at all, they will allow a positive bias
on the first grids of the 6AU6 or 6AQ5 tubes, which may kill them and other
components in short order. Those capacitors are C10, C14 and C19.
The DC voltage on the grids of these tubes (pin 1 for the 6AU6 and pin
7 for the 6AQ5) should be zero at all times, as they are connected to the
ground through the potentiometers and no grid current is normally flowing.
If you choose to go with the existing capacitors, at least do hook up a
DC voltmeter and check each of these voltages. Also, do not operate
the amplifier without a load connected to the speaker outputs. A 2 watt,
8 or 10 ohm resistor connected between the 8 ohm tap and ground of each
transformer would be fine if you don't want to hook up the speakers.
Good luck!
P.S.: Another tip - do not do any restoration work yet (except replacing big
capacitors such as C5/C6/C7 if you wish) in the tuner area, it is too easy
to disturb things there.
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