Rockford Fosgate Power 1501BD

[caraudioguy2100]

Replaced the opamps and regulator .

The hum is still present but I noticed the voltage changes on the pins of U17 if I mess with the gain pot

 

[Perry Babin]

You can't do anything until you get the proper supply voltage on U1-U3. All get power from the same supply. How can you have different voltage on their power supply pins? A burned trace seems like the most likely fault.

 

[caraudioguy2100]

Here are the voltages I get on these

U9 A 2211

Pin 1:0.00
Pin 2:4.59
Pin 3:3.22
Pin 4:0.00
Pin 5:-10.23
Pin 6:0.08
Pin 7:6.19
Pin 8:9.17

U8 LM6171

Pin 1:0.00
Pin 2:-5.21
Pin 3:0.00
Pin 4:-9.77
Pin 5:0.09
Pin 6:7.84
Pin 7:9.73
Pin 8:0.01

U7 LM6171

Pin 1:0.04
Pin 2:0.02
Pin 3:0.01
Pin 4:-9.77
Pin 5:0.03
Pin 6:-5.62
Pin 7:9.72
Pin 8:0.10

Do these voltages appear to be correct or do I have a problem with one of them since I can’t find anything else defective

 

[Perry Babin]

Did you see post #22?

 

[caraudioguy2100]

Back to this amp .

I have proper supply voltage on pins 4-8 of U1 thru U3 + - 13 volts

U4 I only have 9 volts on pins 4 and 8 is this correct or is something pulling the voltage down or I have a bad connection or part somewhere ?

 

[Perry Babin]

±13 is probably a bit high but may not be a problem.

U4 voltage is OK.

 

[caraudioguy2100]

I replaced all of the Tl072’s in the preamp section .
Replaced the outputs checked all the resistors in the preamp section everything tests fine.

I get distorted audio still and the audio cuts in and out .

What am I missing here I’ve checked a lot of components and they all seem fine but the problem is still there

Anyone have any ideas ?

 

[Perry Babin]

Is this new? I thought that the amp only previously had a hum.

Post a photo of the distorted waveform.

 

[caraudioguy2100]

The hum went away .

Now the audio is distorted and the audio cuts in and out .

I will post a waveform when I get home .

 

[caraudioguy2100]

Ok my scope won’t lock onto a waveform yet I think it’s time for a new scope .

I measured directly across the speaker terminals and I get 1 volt of DC and you can see it push out the test speaker also .

So my problem is that I have DC on the output

All of the outputs are brand new .

Any ideas where to check to see where the DC is coming from ?

 

[Perry Babin]

Post the DC voltage on all terminals of U17.

 

[caraudioguy2100]

Pin 1:0.00
Pin 2:0.75
Pin 3:0.00
Pin 4:-9.76
Pin 5:0.00
Pin 6:-7.80
Pin 7:0.00
Pin 8:9.67

 

[Perry Babin]

What's the DC voltage on pin 1 of U4?

 

[caraudioguy2100]

Don’t know what happened but no I have full rail voltage across the output terminals but all outputs still test fine and amp is stuck in protection mode

 

[caraudioguy2100]

It blew the outputs so I will replace them and go from there .

If I remember correctly pin 1 of U4 had like 9 volts on it .

Do either one of those U17 or U4 appear to be defective ?

Since I have to order outputs wondering if I should order anything else ?

 

[Perry Babin]

Discharge the rail caps and desolder the rectifier end of the red/black wires for both supplies and leave them disconnected. Solder a jumper across pins 2 and 6 of U17 and get a good drive signal at all FETs before you reinstall the outputs.

 

[caraudioguy2100]

Ok both MIC4420’S are brand new .

I get good drive signals on half the outputs the other half of the outputs the drive signal is missing .

Any ideas on where to start checking ?

 

[Perry Babin]

In the diagram, where do you lose signal between U17 and the outputs?

 

[caraudioguy2100]

I have drive signal back to the other half of the outputs had a broken solder connection .

But now the drive signal is very distorted so I will have to go they the circuit and see what’s causing the issue

 

[caraudioguy2100]

Should I get identical drive signal on all of the outputs ?

I don’t get it half the outputs drive signal is fine the other half looks like it’s ringing