Depending on what you learn about the amplifier that confirms it's fine, yes. The better you understand and set it up properly at low power, the safer will be the moment of truth. There are several voltage checks you must do before anything else, Perhaps these are first on the list:
Voltage across output the terminals should be tiny, < 100 mVDC.
Rails should be roughly equal at +/- whatever your power supply allows which, I imagine with 30VAC transformer, would mean 43VDC rails or 57V rails with a 40VAC one - measured with respect to power supply ground. The voltage across the large power resistors (Re), between the output Transistor/Mosfets and the output of the amp. itself, should be within spec. and/or adjusted ASAP with the bias current adjust, to the specified voltage and hence set the bias current correctly.
When you have run the checks that should have been specified by the kitseller, you can even hook up some sensitive speakers and play very low level audio (below the point of running out of power) and check out the sound. It will sound awful if you you play loud enough to flicker the lamp but it will give some indication of success. Otherwise, you should be able to increase the bias toward the proper level, but if you notice the bulb beginning to glow steadily, it will have to wait until you give it normal mains power.
Take great care of that bulb - one bump and "tink!" no bulb...
Voltage across output the terminals should be tiny, < 100 mVDC.
Rails should be roughly equal at +/- whatever your power supply allows which, I imagine with 30VAC transformer, would mean 43VDC rails or 57V rails with a 40VAC one - measured with respect to power supply ground. The voltage across the large power resistors (Re), between the output Transistor/Mosfets and the output of the amp. itself, should be within spec. and/or adjusted ASAP with the bias current adjust, to the specified voltage and hence set the bias current correctly.
When you have run the checks that should have been specified by the kitseller, you can even hook up some sensitive speakers and play very low level audio (below the point of running out of power) and check out the sound. It will sound awful if you you play loud enough to flicker the lamp but it will give some indication of success. Otherwise, you should be able to increase the bias toward the proper level, but if you notice the bulb beginning to glow steadily, it will have to wait until you give it normal mains power.
Take great care of that bulb - one bump and "tink!" no bulb...
"Before switching on the power, make sure that the preset R13 is set for maximum resistance and no speakers are connected to the output of the amplifier. The Vbe multiplier Q6, must also be thermally coupled to the main heatsink to prevent thermal runaway.
With the input shorted to ground, slowly increase the output of the power transformer to the working voltage of 40-0-40Vac with a variac. This should be done with an oscilloscope connected to the output of the amplifier.
If the amplifier is properly assembled, there should be no oscillations at the output as you gradually power up the amplifier's transformer. With the supply rail voltages at +-53.5V, the DC operating points should read TP1=1.65V; TP2=1.0V; TP3=0.84V; TP4=0.26V and TP5=0.79V.
Once this is established, slowly increase the bias of the output into Class AB to 100mA per output transistor. A DMM across an emitter resistor (0.39 ohms) should read 39mV. With the oscilloscope set to 5mV resolution, you should be able to reproduce Fig 1"
So I can measure all the voltage points with the light bulb inhibitor hooked up? To increase the bias of the output, I change the resistor R13?
With the input shorted to ground, slowly increase the output of the power transformer to the working voltage of 40-0-40Vac with a variac. This should be done with an oscilloscope connected to the output of the amplifier.
If the amplifier is properly assembled, there should be no oscillations at the output as you gradually power up the amplifier's transformer. With the supply rail voltages at +-53.5V, the DC operating points should read TP1=1.65V; TP2=1.0V; TP3=0.84V; TP4=0.26V and TP5=0.79V.
Once this is established, slowly increase the bias of the output into Class AB to 100mA per output transistor. A DMM across an emitter resistor (0.39 ohms) should read 39mV. With the oscilloscope set to 5mV resolution, you should be able to reproduce Fig 1"
So I can measure all the voltage points with the light bulb inhibitor hooked up? To increase the bias of the output, I change the resistor R13?
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