Owner`s manual

c. Remove power. Exchange two of the output tubes from one channel with other

two output tubes from the other channel. Reapply power and adjust the bias

according to the Dynaco Owner’s manual.

• If the no sound condition has reversed channels, replace the output tubes.

• If the no sound condition remains with the same channel, go to the next step

d. Remove power. Exchange the small signal tubes (7199’s) from one channel to

the other. Apply power and an input signal.

• If the no sound condition has reversed channels, replace the 7199’s

• If the no sound condition remains with the same channel, the problem is

confined to the driver board and it should be replaced.

e. Remove power from the amplifier. Remove the output tubes. Follow the Quad

Electrolytic Discharge Procedure as described above. Locate the 15.6 ohm

Bias adjustment resistor. This resistor is located under the amplifier chassis near

the output tube sockets. It is shaped like a 1/4” diameter white ceramic cylinder

and has one lead connected to the amplifier chassis and the other lead connected

to pins 1 & 8 of both output tubes (for that channel). Pull the output tubes and

using the Resistance setting of your Digital Voltmeter, set to its lowest reading,

measure the value of this resistor.

• If it measures greater than 16.3 ohms

, it should be replaced. It will be

virtually impossible to find a replacement for this resistor however this is a

minor problem. Replace it instead with a 10 ohm 3Watt Metal Oxide resistor

BUT be certain that you now set the Bias Voltage to read 1.0 volts (not the

original 1.56 Volts. If you change this resistor, you should also make the same

change to the resistor on the other channel regardless of its condition (to

preserve channel to channel balance).

• If it measures correctly

, proceed to the next step.

f. Do not reinstall the output tubes

. Apply power to the amplifier. Using your

digital voltmeter set to the DC Volts function, measure the voltage at pins 3, 4, &

5 of both output tubes, relative to chassis (negative lead of your voltmeter

connected to the chassis). As you measure the voltage on pin 5 of the output tube,

rotate the bias adjustment potentiometer from one end to the other and note the

effect. You can identify the tube pin by first locating the notch in the tube socket

(looking from the bottom side of the socket) and counting clockwise from the

notch. The first pin after the notch (counting clockwise) is pin 1. This continues

until you reach pin 8 and then the notch again. Note that pins 1&8 are connected

together – this should help give you a visual clue.

• The voltage at pin 5 should vary from negative 26 VDC to negative 39 VDC.

If you do not obtain this reading replace the bias components (selenium rectifier,

2 X pots, 2 X electrolytic capacitors, and 2X resistors) with CAE P/N S7-BIAS.

• The voltage on pins 3 & 4 should be approximately 450 to 500 VDC (be

careful). If this voltage is less than 300 VDC, make the measurement on the

same pins of the other channel. If the other channel reads correctly, the output