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Memphis 16-MC5.1400 Amplifier
Memphis 16-MC5.1400 Amplifier
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Old 1st October 2020, 08:11 PM   #1
Goldie89 is offline Goldie89
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Default Memphis 16-MC5.1400 Amplifier

I got this amp and it was stuck in protection, replaced some outputs on the A/B portion of the amp and amp is no longer in protect. However, now the amp is maxing out my 30 amp power supply even though itís not in protect. I removed the rectifiers for the class D section and amp draws less than a amp of current and produces clean audio on the A/B section. I checked the mosfets for class D no shorts removed driver card and found no faulty components on the board. Pictured below is the drive signal for the gates of the outputs. I wiggled the output indicators and nothing changed as far as current draw. Not sure where the issue is.
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Old 1st October 2020, 10:37 PM   #2
Maxikill97 is offline Maxikill97  Netherlands
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Hi,


If you removed the rectifiers and the current pull is less than one amp, the problem is on the output section for sure, if it pulls 30a with the rectifiers installed.


Your oscilloscope pwm signal to the gate of the fets does not look very clean.
What is the drive signal which is coming from your pwm chip?
Can you post a photo?
Are you 100% sure your fets are okay? 30a is a lot for not having any shorts on the fets.

Last edited by Maxikill97; 1st October 2020 at 10:42 PM.
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Old 2nd October 2020, 02:54 PM   #3
Goldie89 is offline Goldie89
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I need a schematic or somebody who has repaired one of these before to explain how the class D section of the board works. Specifically how the pwm is generated. It’s very similar to the 3S boards but is slightly different. The photo is of the signal to the output driver pads.
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Old 2nd October 2020, 03:00 PM   #4
Perry Babin is offline Perry Babin  United States
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Post a photo of the class D section.
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Old 2nd October 2020, 03:07 PM   #5
Goldie89 is offline Goldie89
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Best photo I could capture of class D section.
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Old 2nd October 2020, 03:20 PM   #6
Perry Babin is offline Perry Babin  United States
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These amps can do strange things.

Was it in the heatsink when you tried to power it up and it drew excessive current?
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Old 2nd October 2020, 03:22 PM   #7
Goldie89 is offline Goldie89
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Yes it did it inside the heat sink and also out of the heatsink.
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Old 2nd October 2020, 03:55 PM   #8
Perry Babin is offline Perry Babin  United States
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Try applying remote then removing it and immediately reapplying it (rectifiers in the circuit).

Will it power up after the class D rail caps have charged (by repeated application of remote)?
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Old 2nd October 2020, 04:10 PM   #9
Goldie89 is offline Goldie89
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Yes it will charge up but when rails get to 18 volts it starts drawing excessive current with rectifiers and outputs in it also creates a ugly square wave on the gates of the outputs. With outputs out it gets 60 volts on rails.
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Old 18th October 2020, 12:23 AM   #10
Goldie89 is offline Goldie89
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Perry,

I noticed when I connect the base of q4a to pin 1 of u4 for a second after remote engaged and remove the amp will play audio and behave like it should. But as soon as the rail caps discharge it does it again. Are you aware of a solution for this?
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