DYNACO Stereo 70 Manuale di restauro - Pagina 20

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DYNACO Stereo 70 Manuale di restauro
Dynaco Stereo 70 Power Amplifier
Restoration Manual
Detailed Procedure & Guide
Page 20
R0 4-03
floating at nearly 500 VDC relative the amplifier chassis. Most DVM's are suitably
insulated however you should be advised nonetheless and take the appropriate
precautions.
11. Connect the amplifier to 120VAC mains.
12. Switch on the amplifier. Examine the Digital Voltmeter reading. It will begin at a
very high voltage (nearly 550 VDC) and begin to drop over time. This voltage represents
the normal charging of the quad electrolytic capacitor and actually is re-forming the
capacitor simultaneously via the 100K ohm resistor. Observe the reading over a 15 to 30
minute period. If after approximately 1 hour the voltage reading of the DVM fails to drop
to 10 volts or less, the condition of the Quad electrolytic capacitor is suspect and should
be replaced.
13. Switch off the amplifier, disconnect it from the AC mains, and wait at least one hour.
14. Slide back the heat shrink tubing and de-solder the 100K / 3Watt resistor from both
the red wire and lug #2 of the quad electrolytic capacitor.
15. Re-connect the red-wire from the previous step to lug #2 of the Quad electrolytic
capacitor.
16. Install the output tubes – the two small driver tubes will be installed later. Rotate the
bias adjustment potentiometers (located near the center of the chassis) completely
counterclockwise.
17. Connect the amplifier to the AC mains and apply power. Re-adjust the bias per the
Dynaco Owners manual.
18. Switch off the amplifier and re-install the two remaining driver tubes (7199).
19. Replace the covers and return your amplifier to service.
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