Marathon car amp idea current draw

[cm961]

Hi guys,

I'm repairing my brothers car amp for his birthday.

My lab supply maxes out at about 2A output, and the amplifier is triggering the current limiter. I know SMPS draw a lot of idle current. Is it possible that the amp draws more than 2A of current under normal conditions (no input, no output connected)?

For reference, the amplifier is a Marathon USA model US-2100H. From what I can tell, its a pretty high power and high quality unit, but the manufacturer exists no more I believe.

Thanks,
Pete

 

[djQUAN]

most car amps that I have tested (and the one I built) all have around 1A of idle current draw. ranging from 100watts RMS total to a 340watt RMS total car amp. not sure about high power ones though. if they have dual supplies inside, it may have a higher idle current.

 

[cm961]

I know it has four ultra fast diodes (two devices, each with dual centre taps, NTE6244, NTE6240). But I think its just push-pull type. It uses the 494 PWM controller, is there any pins on it I could check to diagnose something?

Pete

 

[cm961]

Ok, I just learned that it is a class AB amplifier. I believe class AB draws a lot of idle current does it not? I think I'll put 5A fuses in it and try it from a more powerful supply, but then I can't really monitor current draw.

Any thoughts?

 

[djQUAN]

you could try to see if the output transistors of the amp are blown or shorted.

the TL494, check the pins 9 and 10. they are the output pins.

 

[sss]

Ok, I just learned that it is a class AB amplifier. I believe class AB draws a lot of idle current does it not? I think I'll put 5A fuses in it and try it from a more powerful supply, but then I can't really monitor current draw.

Any thoughts?

almost all amps are class ab 🙂
i think 2A is too much
dont use more current , u can damage more things
try to find the problem first ,disconnect the power supply from the amp if its possible and test it .

 

[djQUAN]

hmmm. class AB? I have checked all my car amps (well they are low to middle priced ones, I don't have high end stuff) and the emitter resistors of the amp stages don't have any voltage which means they are running at class B operation. a reason why I built myself a dual P3A car amp.

 

[JamesHill]

Hi!,

I have had experience with car audio smps not starting on a current limited supply, then seem to need high current for a small time to start. on a current limited supply they just pull the full current without starting up.
Just a though....

James