testing speaker inputs with a DMM

[zachzchw 5,000+ posts]

How do you test speaker inputs on an amp with a DMM? What sort of readings would I be looking for?

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[Acidburn 5,000+ posts]

wait, what exactly are you trying to do?

 

[AznRevlAzn 10+ year member]

don;t you mean the output? if you mean setting the gains, theres a tutorial for that here, it's stickied.

 

[Beat_Dominator 5,000+ posts]

He's trying to read the output voltage from his HU maybe?

 

[AznRevlAzn 10+ year member]

well, my guess is that he is trying to find the pre-outs of his reciever or i don;t know. Take a channel, left or right (not the rca's, the actual wires fromt he recievers harness. Connect it to DMM pos to pos and neg to neg. pop in CD 50Hz tone on repeat. Thats all i can really think of.

If i am wrong well **** whata waste of typing lol.

 

[zachzchw 5,000+ posts]

Sorry I wasnt specific.

I hooked up my amp yesterday, sub played fine. So, I start the car, and no more sub //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif . The amp power light still comes on, no fuses blew, no wiring is faulty, the one and only thing that changed was me starting the car. Im thinking the speaker inputs (or maybe they are outputs, the speaker terminals on the amp) are blown.....I thought there was a way to test them with a DMM.

 

[Acidburn 5,000+ posts]

set your DMM to AC volts, put the leads on the speakers outputs of your amp, if it shows any volts, its not blown

 

[zachzchw 5,000+ posts]

set your DMM to AC volts, put the leads on the speakers outputs of your amp, if it shows any volts, its not blown

Cool, thanks Acid. So any voltage at all indicates the outputs are fine?

If they are blown, how hard of a repair is it? Something easy to do, or would I need to send it off to be repaired?

 

[Acidburn 5,000+ posts]

if you're playing music, the voltage should jump around quite a bit

i'd doubt you could repair it yourself

 

[zachzchw 5,000+ posts]

So, since both multimeteres and amps apparently own me, can you elaborate on exactly how I do this?

I put the red lead on the positive speaker output, the black on the negative?

Where, on the multimeter should each plug (red and black) be?

Top hole: 10ADC

Middle: VohmsignmA

Bottom: COM

 

[zachzchw 5,000+ posts]

Bump.......trying to figure this out before dark.... //content.invisioncic.com/y282845/emoticons/naughty.gif.94359f346c0f1259df8038d60b41863e.gif

 

[Acidburn 5,000+ posts]

red lead to Middle Plug and positive speaker output

black lead to Bottom Plug and negative speaker output

 

[JimJ 5,000+ posts]

If it's a blown MOSFET, that should be an easy repair if you can get a replacement part. Involves desoldering the bad one from the PCB, and re-soldering the new one on, making sure to goop lots of heat-conductive goo between the active device and the heatsink.

 

[zachzchw 5,000+ posts]

If it's a blown MOSFET, that should be an easy repair if you can get a replacement part. Involves desoldering the bad one from the PCB, and re-soldering the new one on, making sure to goop lots of heat-conductive goo between the active device and the heatsink.

Any way to tell if this is indeed what it is? I thought a blown mosfet would leave a brown residue on the board.....I dont see anything, but Ive never done any amp repair, so I may be missing something vital.

 

[ruckus]

were your gains all the way up? I had a speaker blow out like that before it just stopped playing. push the cone in a little bit while running and see if it starts jumping.

on a side note when a dmm is AC/DC on 1 setting how the hell do you make it read AC? I cant run on my amp cause it is reading DC voltage to me.