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How do I check my driver?

post #1 of 8
10/4/12 at 8:56pm
Thread Starter 
My A7-350 went out a couple of months ago and I sent the module in the amp to Daveds50 and had it fixed, but it is still not working. He said that I should check my driver with a multimeter to see if it is bad. I looked up a video on how to do this, but I could not find any one doing this to a driver with dual voice coils. Can anyone explain the process on how to do this.

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post #2 of 8
10/4/12 at 9:40pm
Quote:
Originally Posted by ozziedog View Post

My A7-350 went out a couple of months ago and I sent the module in the amp to Daveds50 and had it fixed, but it is still not working. He said that I should check my driver with a multimeter to see if it is bad. I looked up a video on how to do this, but I could not find any one doing this to a driver with dual voice coils. Can anyone explain the process on how to do this.
Thanks

Check each voice coil independently.
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post #3 of 8
10/6/12 at 10:28pm
Thread Starter 
So, it read 0 on the multimeter. That means it is blown right? Is this worth fixing or should I be looking at other options?
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post #4 of 8
10/6/12 at 10:55pm
If the resistance of the voice coil is ~0 that means the voice coil is fine. The voice coil is just a loop of wire and has low resistance.

I've never tried it but I remember hearing people tapping the leads to a 9 volt battery for a second to see if the cone moves in or out. If it moves, it works and the amp is broken.
Edited by Bushi - 10/7/12 at 11:24pm
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post #5 of 8
10/7/12 at 7:01pm
Thread Starter 
I thought a 0 meant the voice coil was shorted.
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post #6 of 8
10/7/12 at 7:03pm
Quote:
Originally Posted by ozziedog View Post

I thought a 0 meant the voice coil was shorted.
It does. You should measure a few ohms of resistance with a multimeter.

Just measure each coil separately. It's easier. Remove any wires from the driver before measuring.
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post #7 of 8
10/7/12 at 9:16pm
A working driver has the impedance of the coil slightly lower than the rating impedance of the driver. Example: An 8 ohms driver would read around 6 ohms on a multimeter.

But a blown coil has zero impedance or an infinite reading.
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post #8 of 8
10/7/12 at 11:28pm
Yeah I don't know what I was thinking when I posted that. Still the 9 volt test will work.

The two failure modes of the voice coil I imagine would be the insulation melting/stripped off and causing the coil to be shorted to ~0 resistance or the coil wire being totally trashed that it has very high impedance or totally severed and infinite impedance.
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