audioregenesis wrote:What instructions did you follow when you bypassed the tone controls? Proper instructions should include the addition of a 1.0uF coupling capacitor to prevent excessive DC voltage from appearing at the output of the PAS. Power amplifiers, like the ST-70, which are not AC coupled at the input, may become unstable if too much DC is present. A stock PAS (non X) will exhibit about 100mV of DC at the output, which the ST-70 will tolerate, however, bypassing the tone controls without including the capacitor will elevate that to about 800mV, which can be a problem for the ST-70.
I followed curcioaudio's directions
Refer to figure 1 and proceed with the following steps.
We will begin with the Left Channel.
4. Refer to figure 1 and connect a jumper from terminal 4 to terminal 6 on the foil
side of PC-5.
5. Connect another wire jumper from terminal 6 to terminal 7 of PC-5.
6. De-solder the wire connected to terminal 3. You will find that it is connected to
the center lug of the Left Treble Control and once desoldered from PC-5 terminal 3, you may cut it at the connection to the Left Treble control.
Next we will make the same changes to the Right Channel.
7. Refer to figure 1 and connect a jumper from terminal 11 to terminal 13 on the foil
side of PC-5.
8. Connect another wire jumper from terminal 12 to terminal 13 of PC-5.
9. De-solder the wire connected to terminal 10. You will find that it is connected to
the center lug of the Right Treble Control and once desoldered from PC-5 terminal 10, you may cut it at the connection to the Right Treble control.
10. The tone controls are now removed from the circuit.
11. Replace the bottom plate and top cover and secure with the four screws