11.
Current Limit
Setup
Signal generator = 0.5VAC, 1kHz
Signal in = Ch4 RCA
Ch pots = max (CW)
Bass/Treble = centre
Master pot = min (CCW)
Output metering = 100Vout
Load = 40ohm
Procedure
Change the load to 20ohms. Increase the signal such that at ~65VAC you can see
the overload protection coming on with a rounding of the sine wave. If it is there
then reduce the voltage to 30VAC out. Switch off the unit and connect a shorting
link to the 100V output. Switch the unit on.
(P/F) The mains current shall be < 3.5Aac.
Leave the unit shorted for ~10sec. Release the shorting link and check for the
output.
(P/F) The output shall be reading 30VAC +/-1V.
[Setup for next test] Change the load back to 80ohm. Set all volume pots to centre.
Remove the signal from Ch4.
12.
Noise floor / SNR
Setup
Signal in = none
Ch pots = centre
Bass/Treble = centre
Master pot = centre
Output metering = 100Vout
Load = 40ohm
Procedure
Put dummy lid on. Check for Hum & Noise.
(P/F) The output shall be reading < 6mVAC (-85dBr ref 100V).
Values to be recorded
Value
Pass
Range
12.
Noise floor
0mV – 6mV
Set Ch1 volume to max. Set master volume to max. Connect signal to Ch1 RCA.
13.
Fan/Thermal check
Setup
Signal generator = 0.5VAC, 1kHz
Signal in = Ch1 RCA
Ch1 pot = max (CW)
Ch2-4 pot = centre
Bass/Treble = centre
Master pot = max (CW)
Output metering = 100Vout
Load = 40ohm
Procedure
Adjust channel 1 volume pot to an output reading of 70VAC. Connect a
thermometer to the temperature sensor. Wait the unit to heat up. A heat gun may
be used to speed up the heating of the heatsink.