WhitakerAudio J C Whitaker 20 W Stereo Audio Amplifier, Руководство пользователя

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137
20 W Stereo Audio Amplifier
6 Initial Checkout
Before performing the following steps, review the safety precautions given in Section 9 of this
manual.
After the amplifier has been assembled, the following steps are recommended to confirm
proper construction:
1) Remove ac power from the amplifier (unplug the ac line cord).
2) Remove all tubes.
3) Connect the ac line cord to the chassis. Do not connect the amplifier to an ac outlet . Using
an ohmmeter, check the resistance between the ground terminal and either line terminals. A
reading of infinity should be found. If any resistance is measured from ground to either line
terminal, proceed no further. Recheck all primary connections.
4) Measure the resistance between the line terminals of the ac cord. It should be infinity with
the power switch off, and 4 k
Ω
with the power switch on.
5) Remove the ac power cord from the chassis.
6) Using an ohmmeter, confirm that the resistance values listed in Table 6.1 are observed. All
readings are with reference to ground. Readings within ±5 percent are considered normal.
For resistance measurements that are influenced by filter capacitors in the circuit, the value
given is the minimum typical reading. Check the right channel and then the left channel.
Table 6.1 Typical Ohmmeter Readings with Power Removed and Tubes Removed
Tube Pin No. Typical Reading Notes
V1, V4
6U8A
1 ~200 kΩ Varies due to filter capacitors in circuit
2 10 kΩ With gain set control R156/R157 fully ccw (100 kΩ fully
cw)
3 ~1.1 MΩ Varies due to filter capacitors in circuit
4 47 kΩ Heater
5 47 kΩ Heater
6 ~320 kΩ Varies due to filter capacitors in circuit
7 740 Ω
8 15 kΩ
9 ~320 kΩ Varies due to filter capacitors in circuit