Rockford Fosgate Power 800.4

[lostamps]

i got this amp after a person hooked this upto a factory wiring but forgot to disconnect the factory amp.

i belive the factory amp shot threw the RF 800.4 and now 2 channels are really distorted.

i have opened the amp and i cant find anything at all that is burnt (top and bottom traces are fine) i dont see anything burnt at all.

any help in what this might be and how to fix it??

thanks to a wonderfull forum and memebers!


1st post!!

 

[Perry Babin]

I don't have the schematic for the 800.4 but the 800a4 should be close enough. If they're the same, the first ICs in the signal line are U100, U200, U300 and U400. If you have no way to listen to the signal (signal tracer) or view the signal (oscilloscope), you can check each one to see if any one of the 4 is running hotter than the others.

If you have a test tone generator or a test tone disc, you could drive that into the amp and measure the AC voltage on the outputs of each of the op-amps (U100-400). You'd need to set the amp to full range, set the bass boost to the minimum and the gain to the maximum. You'd need to drive signal into all of the inputs at the same time or determine which op-amp is fed by each of the inputs.

You could also try measuring the DC voltage on each of the pins of the op-amps to determine if any appeared to be damaged. You would do this with no signal input. If you want to try this first, post a list of the DC voltages on each of the 8 pins of the op-amps. Place the black meter lead on the shield of the RCA jacks for this test. You would need to do it for all 4 op-amps. Look up the datasheet for the ICs (TL072) if you don't know the pin numbering scheme.


U100
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:

U200
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:

If you're new to this, read through the basic repair page (link below). If nothing else, read the text in the yellow box on that page.

 

[1moreamp]

Try this link for some RF schematics, they don't list a four channel but it will give you a idea of RF engineering by reviewing them ...

http://www.schematicsforfree.com/archive/dir/Automotive/Products/audio

 

[lostamps]

I don't have the schematic for the 800.4 but the 800a4 should be close enough. If they're the same, the first ICs in the signal line are U100, U200, U300 and U400. If you have no way to listen to the signal (signal tracer) or view the signal (oscilloscope), you can check each one to see if any one of the 4 is running hotter than the others.

If you have a test tone generator or a test tone disc, you could drive that into the amp and measure the AC voltage on the outputs of each of the op-amps (U100-400). You'd need to set the amp to full range, set the bass boost to the minimum and the gain to the maximum. You'd need to drive signal into all of the inputs at the same time or determine which op-amp is fed by each of the inputs.

You could also try measuring the DC voltage on each of the pins of the op-amps to determine if any appeared to be damaged. You would do this with no signal input. If you want to try this first, post a list of the DC voltages on each of the 8 pins of the op-amps. Place the black meter lead on the shield of the RCA jacks for this test. You would need to do it for all 4 op-amps. Look up the datasheet for the ICs (TL072) if you don't know the pin numbering scheme.


U100
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:

U200
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:

If you're new to this, read through the basic repair page (link below). If nothing else, read the text in the yellow box on that page.

ok i have the amp reopened , and im lost....lol

i looked inside and found only oe thing that i think you want me to test the dc voltage on its a tl494c 16 pin.

i found a few 8 pins (4 pins on each side) but there are 11 of them near the rca's and no markings on them at all.

would it help if i took a picture and maybe you could guide me as to what i need to test.

i want to thank you so far for your reply!!

 

[lostamps]

ok relooked and found the marking on the chips , they are the TL IC chips you said.

i could not find a U200 but i did find a u202 and u201???

also i have a crude drawing i did so that you could guide me in what i need to test.

here it is

also i ahve a ton of pics if those will help also.

thank you all for your time.

 

[lostamps]

is this what im looking for?

 

[Perry Babin]

The pin-out you posted is for a different op-amp but the numbering scheme is the same.

If you want to send me the photos, zip them into 10meg max zip files and email them to me. Please don't send multiple photos without zipping them.

babin_perry@yahoo.com

Email Rockford to get the schematic and email that to me also.