Rockford Fosgate Power 500bd no output.

[rhempz01]

The amplifier sounds as if everything NJ is functioning as intended. Yet there is no audio output. I have oscillation, a healthy power supply.

 

[rhempz01]

Correction, has audio, with static and thumping from the switches.

 

[Perry Babin]

Have you tried cleaning the pots and switches?

Is the audio clean at U4, pin 1?

If the switches thump loudly when switching positions, it could be due to an op-amp with significant DC on its output.

 

[rhempz01]

Looks like there is some noise surrounding it. Grounded at the rca sheild.

 

[rhempz01]

U4 pin 1 40hz 5v

 

[Perry Babin]

Are the RCA shield grounds intact?

With no RCAs plugged in, what's the resistance between the RCA input shields and the main ground terminal?

 

[rhempz01]

.980kohm

 

[Perry Babin]

Are the RCA shield grounds intact?

 

[rhempz01]

Yes rca sheild grounds are in tach. It has a very distant static sound. Something is wrong. Its like it has a bad signal ground

 

[Perry Babin]

Do you read 0 ohms between the signal source RCA shield ground and the ground terminal of the amplifier?

 

[rhempz01]

No .981kohms

 

[Perry Babin]

That's the amp's resistance. shield to ground terminal.

What's the resistance from the source unit shield to the amp's ground terminal?

 

[rhempz01]

Yes that's with nothing plugged in, from source sheild to ground .979kohms

 

[Perry Babin]

Without the RCAs plugged into the amp, source RCA shield to the main ground terminal of the amp?

 

[rhempz01]

.979kohms

 

[Perry Babin]

What is your signal source?

 

[rhempz01]

Signal generator is what im measuring. But the clearest for audio testing 8s always my cell phone 3.5mm jack to rca jacks.

 

[Perry Babin]

Why isn't the ground of the signal generator connected to the 12v power supply ground?

 

[rhempz01]

I have them all connected to the same common ground. Same strip same plug. Only difference is the third ground plug type. Both of my scopes grounds read 0 ohms. Even if i use a seperate signal source it sounds distant and static like.

 

[Perry Babin]

Does the amp make the noise with no RCAs plugged in?

Use a jumper wire to connect the RCA shields to the main ground. Confirm that you read 0 ohms between the RCA shields and the main ground with the signal generator plugged in.

This may not solve the problem but the amp is expecting a grounded shield from the signal source.

How does the noise (on scope and audibly) change with and without the jumper wire for the shield ground?