Rockford Fosgate Pinch 400.4

[Perry Babin]

That sounds like a bias issue. I'd expect to see a high current draw if the insulator heats up quickly.

 

[S Merlington]

Don't know what happend but now I don't have any audio on both rear channels..

 

[Perry Babin]

What if you plug one RCA into the front and the other RCA alternately into each of the rear channels?

 

[S Merlington]

same thing no audio on the rear channels

 

[Perry Babin]

Post #19 of this thread?

 

[S Merlington]

I had a bad op amp U400 sound came back in the left rear channel..

Do all the op amps control the audio for the right rear channel or only certain ones ..

The problem is in the preamp section. But cannot figure out why I still have very low audio in right rear channel

 

[Perry Babin]

Post #19. Without that information, I can't help.

 

[S Merlington]

Dont completly understand post #19

Im going to use my sine wave generator with a 100hz signal and set the level so i see about a half volt of AC on the op-amps..

The op-amps are U100,200,300,400,101,103,301,401

Which ones do you need the Ac volts on ??

For example U101 all pins or which pins are you refering to since there is a total of 16 pins you want the voltages from ?

 

[Perry Babin]

The output pins. The numbers should all be at the output pins.

 

[S Merlington]

Voltage at RCA Jacks is 1.896 with black probe on Amps ground terminal..

Crossover set to full range gain fully clockwise..


Pin 1:0.814
Pin 2:0.820
Pin 3:1.794
Pin 4:1.795
Pin 5:0.820
Pin 6:2.993
Pin 7:0.821
Pin 8:0.820
Pin 9:0.823
Pin 10:0.825
Pin 11:4.01
Pin 12:4.17
Pin 13:0.833
Pin 14:0.820
Pin 15:4.01
Pin 16:4.14

 

[Perry Babin]

Measure the resistance between the RCA shield and both end of R365/465. Does one end of each read 0 ohms to all of the RCA shields (no RCAs plugged in)?

 

[S Merlington]

yes i get 0.02 ohms on 1 end of 365 and 465

 

[Perry Babin]

Do you have any intermittent connections on the RCA shields?

 

[S Merlington]

No

 

[Perry Babin]

With the input voltage you had (1.896v), I'd expect about 1.25v out of all 4 of the first op-amps.

Is there anything you see on the board or test procedure that could account for the difference in voltage?

Are the components on the diagram and in the amp around those op-amps the same?

 

[S Merlington]

Went over some solder connections heres what i get now..

Pin 1:1.43
Pin 2:1.42
Pin 3:1.68
Pin 4:1.90
Pin 5:1.44
Pin 6:1.44
Pin 7:1.44
Pin 8:1.45
Pin 9:1.44
Pin 10:1.45
Pin 11:6.00
Pin 12:4.86
Pin 13:1.45
Pin 14:1.44
Pin 15:6.00
Pin 16:6.28

 

[Perry Babin]

Is the 2/4ch switch set to 4ch?

 

[S Merlington]

Yes

 

[Perry Babin]

Either there's a problem with the measurements or there are a lot of intermittent connections.

The voltage on the first 4 points vary greatly but the voltage on the next 4 points is almost identical. That's hard to understand if the switch is set to 4ch.

 

[S Merlington]

I will look at the preamp section more closely and to see if i can find the bad connecions..

Owner just called and said i can take my time with the amp since hes dealing with a money issue right now..


So i will put this one aside for a couple of days and then look for bad connections on th board..

Thanks or your help so far greatly appericated