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Problem With MA5002VZ


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#1 Audio Assurance

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Posted 05 June 2005 - 11:03 AM

When I power up the amps everything is cool; the amps power on and the ODEP LED clicks on after about 2 seconds and they pass signal like they should.  After about an hour of operation one of the amps ODEP LED's turns off, the signal LEDs go solid green and the amp stops passing signal.  The client had been complaining of this for a while but I had not seen it myself until today.  It was in the middle of a service (this client is a church) so I turned the amps input attenuators all the way down and power cycled the malfunctioning amp.  After coming back on line, the amp worked for about three seconds and then the ODEP lights went back off and the signal LED's went solid green and again no signal being amplified.

It is a very important intall for our company so I hope you guys can help me before I really disapoint the client.

Oh side note; amp is seeing a 2.75 ohm load on both sides.   Its running in stereo mode and is connected to a sense input on a Nexo NX242.  The amp is driving arrays of 6 GEO-S cabs per side.  And of course the one amp that is screwed up is the one responsible for all the HF/MF in the room so when it goes its really freakin obvious.

Thanks for your time and my apologies if this is topic has already been discussed

Adam

#2 DGlass

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Posted 06 June 2005 - 10:50 AM

Have you tried switching the load from one side to the other to see if the problem follows the load or stays with the channel?

How are you determining it is a 2.75-ohm load?
Are you calculating it? Measuring it with am ohm meter? or measuring it with an Impedance Bridge?

Since impedance is a function of frequency the speaker on that side, when heated up could be exhibiting a load that is appearing as a short to the amplifier and the amplifier is going into protection.

If switching the load from one side to the other doesn’t transfer the problem, to the other amp channel, than there could be a week output device on that side of the amp. In this case the amplifier would need to be serviced.

#3 Audio Assurance

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Posted 14 June 2005 - 11:48 AM

Have you tried switching the load from one side to the other to see if the problem follows the load or stays with the channel?

Both sides of the amp go out at the same time.  I swaped in a completely different 5000 and the problem went away.

How are you determining it is a 2.75-ohm load?
Are you calculating it? Measuring it with am ohm meter? or measuring it with an Impedance Bridge?

Calculating it (for what its worth).

#4 DGlass

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Posted 19 June 2005 - 11:55 PM

QUOTE(Audio Assurance @ Jun 14 2005, 11:48 AM)
Have you tried switching the load from one side to the other to see if the problem follows the load or stays with the channel?

Both sides of the amp go out at the same time.  I swaped in a completely different 5000 and the problem went away.

How are you determining it is a 2.75-ohm load?
Are you calculating it? Measuring it with am ohm meter? or measuring it with an Impedance Bridge?

Calculating it (for what its worth).
View Post

You swapped the amp and the issue is no more???? blink.gif  Well that would tell me there is something going on with the amplifier and the amp needs to be looked at. Can't say exactly whats wrong but if the issue doesn't show up in another amp then........ dry.gif