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-   -   MHD750/1 going into protect... (http://www.wakeworld.com/forum/showthread.php?t=779111)

Matt 05-03-2010 5:02 AM

MHD750/1 going into protect...
I have 5 MHD amps in my boat, 2 750/1 and 3 600/4, when I turnn up the volume over half, ALL 5 amps shut off the green lights blink 5 times and come back on, once they come on the 3 600/4 amps play and the 750/1 amps do nothing, the green lights are on..

600/4 play 8 ws 650s & pair pro 485

750/1 play 2 10w7

I have 4guage wire going to each amp from a distribution black

The RCAs feed thru one another, come off the 420

Voltage never drops below 12 volts

e_in_tn 05-04-2010 6:19 PM

I think Your 420 is set up to output too much voltage.(it is an awesome line driver) Sounds like it is clipping the input on th amps, especially if all are doing it. I found this in the manual of the HD amps
input sections:
No. of Inputs: One Stereo Pair, sums to mono
Input Type: Differential-balanced with RCA jack inputs
Input Range: Switchable from 200mV - 2V RMS (Low)
to 800mV - 8V RMS (High)

Check the switch and make sure it is set to high and if that doesn't do it put voltmeter on rca end with it set to AC voltage and make sure it is not over 8 volts. If it is then will need to adjust the gains on the 420.

Also check wetsounds site for the 420 manual that explains the process of setting the output. It is an excellent article.

Just another thought are you using a relay on the remote turn on wires? If not I have seen that many amps draw too much current from headunit and when you turn it up the head unit can't supply enough voltage to keep the amps on. I think this is the easiest thing to test, put a jumper between the 12V+ and remote of one amp after disconnecting the remote lead form the head unit. If it plays when you turn up the volume the integrate a relay to handle the load of all the amps turn on amperage.

Hope this helps, seems like the two most likely causes. From the Led blinking green, the amps are shutting off and restarting. Not sure why the 750's are staying off unless the are just muting longer before coming back on?

Matt 05-04-2010 6:41 PM

I had a bad 750/1, the wires going into the amp, (quick connect was shorting out @ high power...) I got it going now... Sounds great, And I turned the amps to high power input... That helped alot...

e_in_tn 05-04-2010 7:12 PM

cool glad u got it fixed
helped a buddy put 2 in his x30 last year and remebered they were very input sensitive. He did blow one up though, I think one of the subs it was running shorted and fried it though. were running 2 dvc rockford in a very efficient ported enclosure and i think the crown royal got a hold of the sub volume! the other was flawless running pair of NVS towers 4 10" midbass and 2 horns (dont remember what they are called?)

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