This amp had a shorted output and blown power supply.
I have installed four new outputs where the shorted one was.
I have installed new power supply drivers and 47 Ohm gate resistors.
Found R99 burned open and I could not read its value. One end connects to the main ground and the other connects to the secondary ground. I have installed a 0 Ohm resistor there.
Amp goes into protection without power supply mosfets installed.
494
1) 0V
2) 5V
3) 4.457V
4) 0V
5) 1.483V Saw tooth is present
6) 3.62V
7) 0V
8) 14.3V
9) .034V
10) .034V
11) 14.3V
12) 14.3V
13) 5V
14) 5V
15) 2.046V
16) 3.911V
393
1) 5.132V
2) 5V
3) 8.135V
4) 0V
5) 2.581V
6) 2.111V
7) 5.132V
8) 14.3V
Taking Pin3 of the 494 to ground does force it to work and I have good drive to each gate pad.
I have checked each transistor for leakage and none are defective.
I could use a little help finding the fault on this one.
I have installed four new outputs where the shorted one was.
I have installed new power supply drivers and 47 Ohm gate resistors.
Found R99 burned open and I could not read its value. One end connects to the main ground and the other connects to the secondary ground. I have installed a 0 Ohm resistor there.
Amp goes into protection without power supply mosfets installed.
494
1) 0V
2) 5V
3) 4.457V
4) 0V
5) 1.483V Saw tooth is present
6) 3.62V
7) 0V
8) 14.3V
9) .034V
10) .034V
11) 14.3V
12) 14.3V
13) 5V
14) 5V
15) 2.046V
16) 3.911V
393
1) 5.132V
2) 5V
3) 8.135V
4) 0V
5) 2.581V
6) 2.111V
7) 5.132V
8) 14.3V
Taking Pin3 of the 494 to ground does force it to work and I have good drive to each gate pad.
I have checked each transistor for leakage and none are defective.
I could use a little help finding the fault on this one.
Attachments
This amp has protection that shuts down the drive if there is no rail voltage.
Does the amp work when the PS and output FETs are installed?
Does the amp work when the PS and output FETs are installed?
OK, I did not realize that. I was wanting to ensure good drive before installing them.
Yes, amp powers up and comes out of protection with them installed. I will put it back into the heatsink and test it further.
Thank you Perry.
Yes, amp powers up and comes out of protection with them installed. I will put it back into the heatsink and test it further.
Thank you Perry.
OK I have it back together.
It powers up and has good audio at the speaker terminals with minimal DCV offest.
However it does draw ~4.8A at idle with my current limiting resistor inline. Does that sound normal? It seems like it should be a bit lower. Checking drive signal at the power supply mosfets looks normal and nothing seems to be getting hot.
One thing nice about this amp over some of the other amps of this design is it has bleed off resistors so the rail caps are drained fairly quickly.
It powers up and has good audio at the speaker terminals with minimal DCV offest.
However it does draw ~4.8A at idle with my current limiting resistor inline. Does that sound normal? It seems like it should be a bit lower. Checking drive signal at the power supply mosfets looks normal and nothing seems to be getting hot.
One thing nice about this amp over some of the other amps of this design is it has bleed off resistors so the rail caps are drained fairly quickly.
If nothing gets hot if left on at idle for 15/20 minutes, it's likely OK.
Have you looked up the owner's manual to see if it gives the idle current?
Have you looked up the owner's manual to see if it gives the idle current?
One pair of IRF3205 was heating up while the others remained cool. Drive signal was showing them not turning off as fast as the others.
Changed out the drivers for that set and now the amp idles at 1.6A and now everything remains cool.
The manual for the amp just states a maximum current draw of 300A, nothing about draw at idle.
Changed out the drivers for that set and now the amp idles at 1.6A and now everything remains cool.
The manual for the amp just states a maximum current draw of 300A, nothing about draw at idle.