Owner`s manual

Remove the cover and locate the power supply section. This is the area near the

Power transformer, Quad Electrolytic Capacitor, rectifier tube, Filter Choke, and

Bias Supply (selenium rectifier & two electrolytic capacitors located underneath

the chassis). Follow the Quad Electrolytic Discharge Procedure as described

below

a. Remove the rectifier tube (or diodes if your amp has been modified) and the

four output tubes.

b. Replace the fuse, connect the amplifier to the AC mains and apply power.

• If the fuse does not trip

, go to section 2 d below.

• If the fuse trips immediately

unplug the amplifier from the AC mains. De-

solder the transformer RED-Black Stripe lead connected to the selenium

rectifier.

c. Replace the fuse, connect the amplifier to the AC mains and apply power.

• If the fuse trips the power transformer is defective and should be replaced.

CAE has high quality Magnequest replacement transformers (CAE P/N MQ-

060) specifically designed to both physically and electrically drop into the

existing Stereo 70 chassis.

• If the fuse does not trip

, unplug the amplifier from the AC Mains and replace

the Bias Components (Rectifier, and both Bias electrolytic capacitors). You may

obtain a complete bias supply replacement kit from CAE (P/N ST7-BIAS).

d. Install a new rectifier tube. Replace the fuse, connect the amplifier to the AC

mains and apply power.

• If the fuse does not trip

(either immediately or after the rectifier tube reaches

operating temperature, you have probably eliminated the defects in the power

supply section. In this case power down, set the bias pots to minimum bias (full

counterclockwise), and install the four output tubes. Apply power and after a

few minutes adjust the bias of the output tubes according to the instructions in

the Dynaco Owner’s Manual. It is probable that that you have finished your

repair. Return your amplifier to your system and look for any additional

symptoms.

• If the fuse trips

as the rectifier tube begins to reach temperature (or

immediately if your amplifier has solid state diodes) proceed to the next step.

f. Now we will test the Quad Electrolytic Capacitor for shorts. Follow the Quad

Electrolytic Discharge Procedure as described above. Note – there are actually

four capacitors in this “can” each having its negative terminal connected to the

can container. Unfortunately a failure of any one suggests that failure in the others

is imminent and therefore the entire device must be replaced. Set your digital

voltmeter to measure resistance at the 2000 ohm (2 K ohm) range. Connect the

black probe of your digital voltmeter to the amplifier chassis. Place the red probe

of the digital voltmeter on the first section (indicated by a semi-circle) of the

electrolytic capacitor. The voltmeter will require a few seconds to charge the