JL Audio AMP MHD750.1 Turns on! Power goes from GREEN TO RED

superjoey01 · 23rd April 2012, 04:14 PM

Hi my name is Joey i have here is a JL AUDIO AMP MHD 750.1 The was working it was pushing one 15 cerin vega now it blew the sub and i installed new subs kicker L7 only to find out that the amp wasn't working. So when i pulled the amp off the amp rack i turn on the key and found that the power led light was going back and forth from GREEN TO RED, was wondering what to check for thank you

J.R.Freeman · 5th May 2012, 03:57 PM

Hey Joey,

It sounds like the amp is going into a protection mode. When the subwoofer it was driving died, it may have taken part of the amp with it. It may have damaged the output stage.

Unfortunately these types of things are very hard to debug just on the forum with only text. The good news is if the amp is alive enough to power up, figure something is funny, and go into protection mode it can probably be repaired. But you might want to take it to a local repair shop.

Jim

nigelwright7557 · 5th May 2012, 11:27 PM

First stop is checking the output transistors.
Could be the class d chip went with them tho.

MOER · 6th May 2012, 06:38 AM

There are no output transistors Nigel, they are MOSFETs.

These amplifiers are extremely complex and unless you have a lot of experience with class D amplifiers I suggest you send it to someone who knows these amplifiers. This amplifier employs the single cycle technology which is one of the most complex circuits I have worked on.

The power supply is also complex and they use a separate switcher for the front end whose frequency is clocked to the main PWM chip

Steve Mantz
Zed Audio

superjoey01 · 11th July 2012, 07:12 PM

hi Moer if i send the amp too u can u fix it for me and how much? please i love this amp

23rd April 2012, 04:14 PM	#1
superjoey01 diyAudio Member Join Date: Jul 2011	JL Audio AMP MHD750.1 Turns on! Power goes from GREEN TO RED Hi my name is Joey i have here is a JL AUDIO AMP MHD 750.1 The was working it was pushing one 15 cerin vega now it blew the sub and i installed new subs kicker L7 only to find out that the amp wasn't working. So when i pulled the amp off the amp rack i turn on the key and found that the power led light was going back and forth from GREEN TO RED, was wondering what to check for thank you

5th May 2012, 11:27 PM	#3
nigelwright7557 diyAudio Member Join Date: Apr 2008 Location: Carlisle, England	First stop is checking the output transistors. Could be the class d chip went with them tho. __________________ http://www.murtonpikesystems.co.uk PCBCAD50 pcb design software.

6th May 2012, 06:38 AM	#4
MOER diyAudio Member Join Date: Aug 2003 Location: SIMI VALLEY CA	HD750 There are no output transistors Nigel, they are MOSFETs. These amplifiers are extremely complex and unless you have a lot of experience with class D amplifiers I suggest you send it to someone who knows these amplifiers. This amplifier employs the single cycle technology which is one of the most complex circuits I have worked on. The power supply is also complex and they use a separate switcher for the front end whose frequency is clocked to the main PWM chip Steve Mantz Zed Audio

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5th May 2012, 03:57 PM	#2
J.R.Freeman diyAudio Member Join Date: Aug 2008	Hey Joey, It sounds like the amp is going into a protection mode. When the subwoofer it was driving died, it may have taken part of the amp with it. It may have damaged the output stage. Unfortunately these types of things are very hard to debug just on the forum with only text. The good news is if the amp is alive enough to power up, figure something is funny, and go into protection mode it can probably be repaired. But you might want to take it to a local repair shop. Jim

11th July 2012, 07:12 PM	#5
superjoey01 diyAudio Member Join Date: Jul 2011	hi Moer if i send the amp too u can u fix it for me and how much? please i love this amp

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