WhitakerAudio 60 W Stereo Power Amplifier, User And Assembly Manual

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WhitakerAudio
40) Measure the voltage on pin 5 of V2 on the left channel amplifier. A reading of –40 V dc is
typical.
41) Switch the amplifier off.
42) Install the left channel amplifier tubes. Connect another speaker to the left channel output
terminals and apply power to the unit. Observe for any unexpected behavior as detailed
previously for the right channel. If a program source is available, connect it to the RCA input
terminals and check for undistorted audio reproduction from the right and left channel
speakers. If a problem is noticed on one channel (but not the other), try swapping tubes.
Before making any such change, remove power and let the tubes cool completely.
43) With all tubes installed and no program material applied, the amplifier should draw about
1.25 A from the line. If problems are experienced, disconnect power and recheck the
installation of all components, particularly the input stage (V1) of the amplifiers.
44) Remove all power from the amplifier. Turn the chassis over to provide access to the PWBs.
Note: The following step is optional and intended only for experienced technicians.
Dangerous voltages exist.
45) Confirm that a speaker (or a resistive 8
Ω
load of 30 W or more) is connected to each
speaker output. Apply power and check the operating voltages detailed in Table 6.4.
Table 6.4 Typical Operating Voltages for Right and Left Channel Amplifiers with
No Signal Applied
Tube Pin No. Typical Reading Notes
The following readings are with a B+ supply voltage of +495
V1, 6U8A 1 275 V
2 0 V
3 55 V
4 28 V Heater, varies with setting of hum balance control
5 28 V Heater, varies with setting of hum balance control
6 125 V
7 1.4 V
8 130 V
9 125 V