Good day. I am working with a Rockford 801s. Signal is coming out on the output normally @ 50HZ with clean audio as well. Except when powering up it is drawing up to 10amps or more I believed amps then goes down to 4.5 amps at the input power supply of 12 volts. Is this high current drawn normal without any load.
Not normal unless you're referring to a sharp spike that lasts a fraction of a second.
The 4.5 amps could be a biasing problem.
What work was done to it?
The 4.5 amps could be a biasing problem.
What work was done to it?
yes a sharp spike of more than 9 amps a fraction of second, then goes back to zero and starts to build up current until 7 amps then goes down gradually until 4 amps. It stays at 4 to 4.5 amps/ I tried to put load, check the audio, ok and it stays at 4 amps more or less.
yes, it has a clean audio, my only concern was the 4 amps drawn current at the power supply load of 4 ohms.
I tested it with audio for a long time and it is working normally , the heat from the mosfets are normal as well.
actually no work was done yet on the electronics side , i just replace the broken terminals of the power supply. is this the trimmer to adjust the biasing?
Blue potentiometers, marked (oddly) R412 and R413. with amp semiconductors tightly clamped to the heatsink and a low-rated fuse (10 amp) or a current limiter in the B+ line, slowly turn the pots counter-clockwise. The current should go down. Try this for both channels.
There are a very few Rockford amps that have one or more pots reversed (clockwise reduces current draw) and that's why I'm recommending that you turn slowly to confirm that CCW is lower current.
This is the best photo I have of the bias pots. PC board #4333.
There are a very few Rockford amps that have one or more pots reversed (clockwise reduces current draw) and that's why I'm recommending that you turn slowly to confirm that CCW is lower current.
This is the best photo I have of the bias pots. PC board #4333.
Attachments
Just an update Perry, yes I was able to reduce the idle current 4.5 amp. to 1.12 amp. by reducing the biasing thru the potentiometer trimmers R412 and 413, turning CCW. That was the lowest current I can come up with. I believe the amp now is normally in its safe state. Is it?
I think its a little low, do you have a scope? Adjusting bias with scope is what i do with a high frequency signal like 15-20kHz and a load of 4 or 2 ohms per channel.
Then i check for crossover distortion, if you dont see it, its fine. you will see crossover distortion if bias pots are completely in counter clockwise position.
If you encounter crossover distortion turn it slowly clockwise until its almost disappeared. i leave a very small notch, nobody will hear this.
I had a very similar amp ( punch 800a2 ) biased and i landed at around 1.7- 2 Amps of idle current.
BR
Andi
Then i check for crossover distortion, if you dont see it, its fine. you will see crossover distortion if bias pots are completely in counter clockwise position.
If you encounter crossover distortion turn it slowly clockwise until its almost disappeared. i leave a very small notch, nobody will hear this.
I had a very similar amp ( punch 800a2 ) biased and i landed at around 1.7- 2 Amps of idle current.
BR
Andi