Dynaco ST-70 Restoration Module
Assembly, Installation, and Adjustment Manual
Page 6
CAE Dynaco Driver Restoration Module PC-3R – R0: 7-02
D . Final Checkout & Initial Power Application
1.
Replace the power fuse (3A Slo-Blo) with a 1A AGC (quick trip).
2.
If you haven’t already, remove the rectifier tube. Plug in and turn on the
amplifier. Examine the filaments on the new replacement driver board. All three
should be illuminated. If the center tube is not illuminated, turn off the amplifier
(remove the plug from the AC socket) and reverse the wires labeled “4” & “5” on
the replacement board. Reapply power – all three driver tube filaments should be
illuminated. Remove power from the amplifier.
3.
Remove the three driver tubes and insert the rectifier tube and the two left channel
output tubes. Do not install the right channel output tubes right now. Replace the
original 3A fuse. Rotate both original Bias Potentiometers fully counterclockwise.
Connect your DC Voltmeter to monitor the current thru the output tubes by
measuring the voltage across the 15.6 resistor located at pins 1 & 8 of the output
tubes - connect the negative lead (Black) to the chassis and connect the Positive
lead (Red) to the junction of the 15.6 ohm resistor and the Output Tube pins 1 &
8. Monitor the voltage as the tubes reach operating temperature. If the voltage
begins to exceed 2.5 volts quickly remove power. Otherwise adjust the Bias pot to
obtain 1.56 volts. Remove power.
4.
Install the right channel output tubes, apply power, and repeat the procedure
outlined in step 3. Recheck the bias on the left channel. Remove power.
5.
Install the two small 7199 signal driver tubes.
6.
Replace the cover and enjoy.
