Memphis 16-MC5.1400 Amplifier

Goldie89 · 1st October 2020, 08:11 PM

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 it’s 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.

Maxikill97 · 10:42 PM

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.

Goldie89 · 2nd October 2020, 02:54 PM

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.

Perry Babin · 2nd October 2020, 03:00 PM

Post a photo of the class D section.

Goldie89 · 2nd October 2020, 03:07 PM

Best photo I could capture of class D section.

Perry Babin · 2nd October 2020, 03:20 PM

These amps can do strange things.

Was it in the heatsink when you tried to power it up and it drew excessive current?

Goldie89 · 2nd October 2020, 03:22 PM

Yes it did it inside the heat sink and also out of the heatsink.

Perry Babin · 2nd October 2020, 03:55 PM

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)?

Goldie89 · 2nd October 2020, 04:10 PM

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.

Goldie89 · 18th October 2020, 12:23 AM

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?

1st October 2020, 10:37 PM	#2
Maxikill97 diyAudio Member Join Date: Sep 2020	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.

2nd October 2020, 03:00 PM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	Post a photo of the class D section. __________________ Anyone who purchased the repair tutorial, email me (babin_perry@yahoo.com) if you want to download the latest version.

2nd October 2020, 03:20 PM	#6
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	These amps can do strange things. Was it in the heatsink when you tried to power it up and it drew excessive current? __________________ Anyone who purchased the repair tutorial, email me (babin_perry@yahoo.com) if you want to download the latest version.

2nd October 2020, 03:55 PM	#8
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	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)? __________________ Anyone who purchased the repair tutorial, email me (babin_perry@yahoo.com) if you want to download the latest version.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
JBL 1400 pro for OB?	crash999	Multi-Way	6	2nd April 2017 07:10 PM
Help with Memphis 16MC5.1400 amp goes into protect when Vol. UP	Club-SPL.com	Car Audio	3	6th August 2014 05:40 PM
PPI PC 1400	mike49504	Car Audio	1	6th November 2011 03:06 PM
Anyone have any experience with a memphis MCH1300 5 channel amplifier	scotts530	Car Audio	3	12th August 2011 06:15 AM


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

2nd October 2020, 02:54 PM	#3
Goldie89 diyAudio Member Join Date: Jul 2019	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.

2nd October 2020, 03:22 PM	#7
Goldie89 diyAudio Member Join Date: Jul 2019	Yes it did it inside the heat sink and also out of the heatsink.

2nd October 2020, 04:10 PM	#9
Goldie89 diyAudio Member Join Date: Jul 2019	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.

18th October 2020, 12:23 AM	#10
Goldie89 diyAudio Member Join Date: Jul 2019	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?

New To Site?	Need Help?
Register to Participate Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read