Rockford Fosgate [email protected]

RockfordFIx

Member
2012-12-03 11:56 am
Hey guys,

I am working on a bd1000 and have 36v on the speaker output. I replace the powersupply fets and the output fets. I also had to replace one of the ic drivers
MIC4420CT cause it was shorted. Amp powers up fine, only thing i noticed out of the ordinary was using diode check on my meter from (+) on source and (-) on drain it read correct around .498 vdc. When i reversed the leads it would read a short 0.000vdc. I think this causing my problem not sure if the fets are leaking or if there is a bad component somewhere else.
 

RockfordFIx

Member
2012-12-03 11:56 am
Perry,

My mistake reading the pin-out of the chip wrong..

6= 0.006
7= 9.88

the output on the speaker terminal is +5.025vdc this morning. At one point i noticed the protect light was on and the output on the speaker terminals was 0.00vdc and the output pin 6 on u17 was 8.58 vdc. Pin 2 was 1.021vdc. I removed power and it went back to normal mode and was reading 5vdc on speaker terminal.
 

RockfordFIx

Member
2012-12-03 11:56 am
Perry the protect LED stays on for about 2-3 seconds. During this period the speaker terminal voltage reads 0.000v and once the protect LED light goes off the voltage starts to slowly climb. I also, just notice that the resistor on R44 gets extremely hot but can't remember if it is suspposed to be that hot or no.
 
Do you have a pot (10k ohms or greater) that you can wire as shown in the following images?
 

Attachments

  • IMG_0160b.jpg
    IMG_0160b.jpg
    122.2 KB · Views: 109
  • IMG_0163b.jpg
    IMG_0163b.jpg
    195.5 KB · Views: 108
This chip monitors the output and drives the outputs (or actually the drive circuit which in-turn drives the outputs) so that there is no (or very little) distortion in the output signal.

In the photo, you can see that R35 and R31 have been disconnected. You can leave R35 but you need to slide R31 from its pads.

What you will need to do is rotate the pot from about the 10 o'clock position to the 2 o'clock position to make the output of the output of U17 toggle from 9v to -9v. Go through the 12 o'clock position quickly. Sometimes, if you go through it slowly, it can damage the outputs. Try not to go below the 9 o'clock or above the 3 o'clock positions.

First, confirm that pin 6 is toggling as it should when you go from 10 to 2.

The pot needs to be at least 4.7k ohms. A 10k is better. Anything up to 100k should work.
 

RockfordFIx

Member
2012-12-03 11:56 am
Perry,

all i had was a 20k pot like the ones used for the crossover. I wired it like the picture and powered the unit up. i checked the output on pin 6 and it was reading 8.68v with 123v on the speaker terminal. When i turned the pot from 10 o'clock to 2 o'clock the reading changed to a -8.08v.
 

RockfordFIx

Member
2012-12-03 11:56 am
Perry i will replace U17 and seem if that fixes the voltage on the speaker terminals. I have about 26 more rockford amps to fix in my spare time. Just wondering if you own your shop, if so how do you find time to help everyone with there repairs? You definitely love what you do.