bias current on rockford punch 200.4

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Hello

i repair a punch amp 200.4 (4x25wrms)

the guy who have this amp before burn the mosfet in the supply and he modify the bias current :rolleyes:

i find information to set the correct bias current here

Rockford Corporation Technical Library CD

but I do not know which way to turn the potentiometer to set it to the minimum before turn on the amp and procede to the bias set :confused:

is it in clockwise or counterclockwise ?

and what are the resistors to set the bias because i must put my multimeter on it to mesure 4 or 5 millivolt on each (rockford say that in the service manual)
I surrounded the resistors if you can confirm me if it is good please ?

An externally hosted image should be here but it was not working when we last tested it.


I think the amp was build in 2000 :confused:

Thanks for your help :)
 
Turn them counter clockwise. I watch the idle current of the amp using a .005 ohm resistor in series with the amp B+ terminal. If you turn the pot slowly the idle current will increase quickly, then I back it off. You can find the knee at which the current takes off. I usually set it there and let it warm up and verify current doesn't increase.
 
Hello :)

Thanks brandes.cm :)

Yes the current increase quickly :eek: i move a little and the current increase...

i use a 12 volts supply with 5 Amp to set up the bias current i set up to 4.5mv on the 0.1ohms resistor and now the amp works fine and without heat :)

I mesure before adjust the bias and i have for channel front Left 17.5mv and 2mv for channel front right :rolleyes:

for the rear channel i have 3mv and 18 mv :rolleyes:

the guy who have this amp before me make nonsense :(

Now i run the amp in my car and works better :)

The bias was verry difficult to set :eek: 30 minutes to do because I am a perfectionist :)
 
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