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Put a multimeter across an emitter resistor.
(P/F) Slowly adjust the preset PR1 so that you get 4.5mVDC (+/-0.5mVDC)
reading.
Check Quiescent Voltage across all Emitter resistors.
(P/F) The emitter resistor voltages shall be 4.5mVDC (+/-2.0mVDC).
[Setup for next test]
4.
Initial AC Checks :
4.1.
Signal check and gain of amp
Setup
Signal generator = 1mVAC, 1kHz
Signal in = Ch1 XLR
All channel pots = min (CCW)
Bass/Treble = centre
Master pot = max (CW)
Output metering = 4ohm out
Load = 4ohm
Procedure
Turn up Ch1 volume control to full. Watch for irregularities with output.
(P/F) Output voltage shall be 31.6VAC +/-2VAC.
4.2.
Emitter current check
Setup
Signal generator = 1mVAC, 1kHz
Ch1 pot = max (CW)
Ch2-4 pot = min (CCW)
Bass/Treble = centre
Master pot = max (CCW)
Output metering = 4ohm out
Load = 4ohm
Procedure
Set output to 22VAC using master volume control. Check voltage across
emitter resistors of power devices.
(P/F) Voltage shall be between 300mVDC – 400mVDC.
[Setup for next test] Reset Ch1 volume pot to min. Set master volume to
max.
4.3.
Inputs
Setup
Signal generator = 1mVAC, 1kHz
Signal in = Ch1 XLR
All channel pots = min (CCW)
Bass/Treble = centre
Master pot = max (CW)
Output metering = 4ohm out
Load = 4ohm
Procedure
Check the output for all XLR input channels. Watch for irregularities with
output while turning up each channel volume pot.
[Setup for next test] Set the signal generator to give 31.6V on output.