WhitakerAudio J C Whitaker 20 W Stereo Audio Amplifier, Руководство пользователя, Страница: 140 / 194

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11) Using extreme caution, measure the ac line voltage between ground and the load side of
filter FL51. A reading of 120 V ac should be measured on the terminal closest to the side of
the chassis, to which the black #16 wire is connected. A reading of 0 V ac (or very nearly
zero) should be measured on the other terminal—the one with the white wire. If improper
voltages are observed, proceed no further. Remove power from the amplifier. Double check
the primary wiring and correct the problem.
12) Using extreme caution, check for proper voltages at the tube connection points listed in
Table 6.2. All voltages are measured with respect to ground using a high impedance
voltmeter. Variations within ±10 percent are typical. These measurements can be taken from
the top of the chassis by probing into the socket connection points. Take measurements on
the right channel and then the left channel.
Table 6.2 Typical Voltmeter Readings with V1/V4, V2/V5, and V3/V6 Removed
and Power Applied
Tube Pin No. Typical Reading Notes
V1, V4
6U8A
1 460 V
2 0 V
3 430 V
4 60 V Heater
5 60 V Heater
6 460 V
7 0 V
8 0 V
9 460 V
V2, V5
6973
1 470 V
2 –
3 –30 V With Bias Adj. control at mid point
4 60 V Heater
5 60 V Heater
6 –30 V
7 0 V
8 470 V
9 470 V