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Rockford Fosgate M400-4D
Rockford Fosgate M400-4D
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Old 5th August 2017, 04:31 PM   #1
josesony68 is offline josesony68  Spain
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Default 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There are also some components that have been replaced by other dubious features ...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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Old 12th August 2017, 04:42 PM   #2
josesony68 is offline josesony68  Spain
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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?
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Old 13th August 2017, 12:59 AM   #3
ian33 is offline ian33
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What about the - 12 for the pre-amplifier is it present?

If you have a scope check for oscillation on the output FETs
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Old 13th August 2017, 06:33 PM   #4
josesony68 is offline josesony68  Spain
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Thanks for answering, ian
-12v on the preamplifier board are present
In the audio output FETS (IRF842) there is no oscillation
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Old 14th August 2017, 03:25 AM   #5
ian33 is offline ian33
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I have an amp like this on the bench which is repaired already.The output FETs are IRFB4227

If you want to clarify any part number let me know.
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Old 15th August 2017, 01:38 PM   #6
josesony68 is offline josesony68  Spain
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Yes, the output FETs are IRFB4227, I had not looked at him correctly.

If I need to know anything, I'll let you know.

Thanks
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Old 9th October 2017, 09:28 PM   #7
josesony68 is offline josesony68  Spain
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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.
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Old 9th October 2017, 10:23 PM   #8
MarioRestucci is online now MarioRestucci  Italy
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Quote:
Originally Posted by josesony68 View Post
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.
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Old 10th October 2017, 01:24 PM   #9
josesony68 is offline josesony68  Spain
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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.
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Old 10th October 2017, 01:42 PM   #10
MarioRestucci is online now MarioRestucci  Italy
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Quote:
Originally Posted by josesony68 View Post
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)
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