Rockford Fosgate M400-4D

Hi guys
Today I received this amplifier to repair, in which "someone" has put his hands to try to repair it ...
As you can see in the first photo, five electrolytic capacitors were completely loose from the motherboard (these capacitors had lost their capacity and are swollen)
There are also some components that have been replaced by other dubious features ...

All the base plate is covered with a special varnish, which makes it difficult to read almost all components ...

Does anyone know of a scheme?
 

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Well,

I have managed to run the power supply, I have replaced the damaged capacitors, and two resistors that were open, the rail voltage is present (49 volts).

When the amplifier is connected and signal is applied to the input, nothing happens, no sound appears.
The voltage at the audio output terminals is 0, 65 v.

I have checked all output FETS without finding anything strange, I have also checked if there is voltage supply in the preamplifier card (12.53 v are present).
Is rare...
I am a little lost, in this type of amplifiers by its condition and typology (new class D)

Does anyone have any ideas?
 
I return to this thread, after a time disconnected ...

well, I want to know if it is normal for a regulator to be missing in the bias setting zone of the fourth audio output channel.

class D topology not have bias regulation, probably this trimmer set output offset.
i think that this amp use irs20954S to create the class D stage.
So, check the VCC voltage, referring to -B voltage.
For info, VCC is intended the voltage required for low and high side (via R+D) driver and have the reference to -B.
+B and -B are the main rails voltages.
 
Ok Mario, thanks for your clarifications.

I will check the VCC voltage, to create the D class this amplifier uses the IRS2092S

I'll post the data as soon as I have it.
Good! the functioning principle is the same.
You have 4 channels available, all with the same problem.
If the rail voltage is present and there is also the pre-amplified regulated voltage, the only thing that the 4 channels share is VCC on the pin 10 and the supply voltages of the modulators (+/- 5.6v on pin 1 and 6)
 
Rail tension is present (48.8v) in the two metallic strips that are observed in the photo, I suspect that B- is the longest strip, from there taking the negative tip of the multimeter in B-, and the positive in the drain of the FETS of the out stage are observed 25v and 48.8v respectively in each pair of FETS.

Pin 10 of each IRS2092 is -24.7V with the negative probe of the multimeter to the negative of the amplifier.
On pins 1 and 6 there are 4.58v and -5.38v respectively.

The power LED on the amplifier is shown in the two colors red / blue
 
on pin 10 measured with B- with probe black is 0v.

pin 1 preamp voltajes is 5.48v
Maybe I explained myself wrong!
When I talked about pin 1, 6 and 10, I was referring to 4 irs2092S.
For this reason, on the pins 1 and 6 of all the IRS2092S there should be 5.6volt (with black probe on PIN 2 of all IRS2092S) instead, on all pins 10 (of all IRS2092S) there must be 12volt (with black probe on -B).
When I talked about "preamplifier voltages" i meant the DUAL voltage present on the preamplifier board that isn't SINGLE 12volt, but usually +/-12v (if are installed TL072) and you must see this on pin 4 and 8 of all op-amp (with black probe on pin 2 of all IRS2092S)
If u have big different voltages on pin 1 and 6 of all IRS2092S probably u have problems with this part of circuit or a defective IRS2092S.
If u have 0 volt on pin 10 of all IRS2092S (with black probe on -b) you have surely a bad regulator (and probably, this is the main cause of your issue).
Unfortunely, RF do not share schematics of this new amp model, so we have to arrange it.
 
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No, you have not explained wrong, maybe there is some point that I did not understand well ...
I've always been measuring pins 1, 6 and 10 on all four IRS2092s.
On pins 1 and 6 of all IRS2092 there is +/- 4.99v measured with the black probe on pin 2 (there is no difference in any IRS2092)
Pin 10 continues without voltage

What I do not understand is when you say:
When I talked about the "preamplifier voltages" I was referring to the DUAL voltage present on the preamplifier board that is not SINGLE 12volt, but usually +/- 12v (if TL072 is installed) and you should see this on pin 4 and 8 of all op -amp (with black probe on pin 2 of all IRS2092S)

Do you mean the preamplifier board that contains the operational circuits 4580?
 
Do you mean the preamplifier board that contains the operational circuits 4580?
Yes of course! But at this point i think that the preamp board work correctly.
-B and +B (with black probe on Pin 2 of irs2092s ) are identical and symmetric?
I dont understand but I've read this:
I suspect that B- is the longest strip, from there taking the negative tip of the multimeter in B-, and the positive in the drain of the FETS of the out stage are observed 25v and 48.8v respectively in each pair of FETS.
can you explain me better?
 
-B and +B (with black probe on Pin 2 of irs2092s ) are identical and symmetric, have a very small variation.

I was saying:
Taking the black probe of the multimeter in B-, and red probe of the multimeter in the central pin of a FET (for example, the first one to the left of the board) of audio output, I observe 25V and taking reading to the FET that is next to him I observe 48,8V.
These measurements are observed by each pair of FETS, ie looking at the board and watching the eight output FETS, if one has 25V the next has 48.8V the next 25V, the next 48.8V and so all
 
-B and +B (with black probe on Pin 2 of irs2092s ) are identical and symmetric, have a very small variation.

I was saying:
Taking the black probe of the multimeter in B-, and red probe of the multimeter in the central pin of a FET (for example, the first one to the left of the board) of audio output, I observe 25V and taking reading to the FET that is next to him I observe 48,8V.
These measurements are observed by each pair of FETS, ie looking at the board and watching the eight output FETS, if one has 25V the next has 48.8V the next 25V, the next 48.8V and so all
Measuring the voltage between drain of fets and -b is wrong.
If you want, can measure +b and -b like this:
- black probe on pin2 of IRS2092S
- red probe on leg 2 of hi-side fet (now you must see +b= 48v)
- red probe on leg 3 of low-side fet (now you must see -b=-48v)
any little differences (decimal volts) it's not important/relevant.
So, if you have tested and no problems found, your primary problem is the absence of VCC.
Go backwards in the circuit and found the regulator or the part of circuit that provide to create VCC. If u can, share photos here!