Owner`s manual
9
composite of modern reliable capacitors. Both the voltage and capacitance
ratings are raised giving higher reliability and performance.
c. Return tow of the four output tube – one channel’s pair. Select DC Volts on
your digital voltmeter and a voltage range of 2 volts and monitor the voltage
across the 15.6 ohm bias set resistor (for the channel that now has the output tubes
installed). Adjust the associate bias potentiometer fully counterclockwise. Apply
power and as the amplifier begins to warm up, carefully monitor the voltage.
• If at any time the voltage reading exceeds 1.5 volts, immediately disconnect
the power. Proceed to the next step.
• If the bias voltage does not climb, wait a few minutes and adjust the bias
potentiometer until the voltage reading indicates approximately 1.0 VDC. Now
power down and proceed to step (e) below.
d. Remove power. Lift both coupling capacitors on the driver board associated
with the channel being evaluated and power up again.
• If the tube bias current climbs above 1.5 volts replace the output tube socket.
CAE offers a complete hardware replacement kit (P/N S7-HDWR) that includes
four new high quality tube sockets, input connectors, and power switch.
• If the current in the output stage does not climb, replace the driver board
assembly with either the CAE PC-3U or high performance PWB-3A.
e. Switch the two output tubes from the channel just evaluated to the remaining
channel and proceed again through steps ( c) and (d) above.
B. NO SOUND
1. If your Stereo 70 has sound in ONLY ONE CHANNEL and the filaments are
illuminated – follow the steps in this section.
a. Reverse the signal input plugs connected to the input of your Stereo 70. Apply
power and an input signal.
• If the no sound condition has reversed channels, the problem is not with your
Stereo 70 and perhaps is with your preamp, or the interconnects
• If the no sound condition remains with the same channel, go to the next step
b. Check to be sure that the bias is correctly set in both output stages
• If the correct bias is too low and cannot
be reached, proceed to section e
below
• If the bias can be correctly set in both channels, set the correct bias level
(according to the Dynaco Owner’s manual available at our website
www.curcioaudio.com
), and proceed to the next section