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Amplifier voltage trouble shooting

 

New member
Username: Lowz24

Post Number: 6
Registered: Jul-06
just wondering if someone can tell me approximately how much voltage my multimeter should be reading at the speaker terminals & rca jacks....any help would be appreciated. i have the power ,ground & remote lead hooked up to it, i just want to be sure on the readings b4 i go & fry something. i just got this amp off ebay


thanks
 

Gold Member
Username: Illuminator

USA

Post Number: 4054
Registered: Apr-05
You'd be better off with an oscilloscope...multimeter won't tell you much.
 

Platinum Member
Username: Glasswolf

Wisteria, Lane USA

Post Number: 11537
Registered: Dec-03
RCA inputs won't show anything, as the voltage comes from the head unit, not the amp.
without a signal input, the speaker leads from the amp won't register anything either.
to read an AC signal from an amplifier with a DMM, your DMM has to be able to read "true RMS" or AC voltage specifically.
Most of the cheap basic meters do not.
 

Gold Member
Username: Illuminator

USA

Post Number: 4058
Registered: Apr-05
And, honestly, it would be kind of pointles...the best way to test an amp is to just hook it up haha.
 

New member
Username: Lowz24

Post Number: 7
Registered: Jul-06
ya...thanks everyone for your input.

And, honestly, it would be kind of pointles...the best way to test an amp is to just hook it up haha.

ya i did hook it up & only 3 of 4 channels would work for me, then next thing i know its smoking(ahh the fresh smell of burnt electronic equip.:-) so i open it up & find a burnt trace(soldered a jumper wire in its place).
then i noticed one of the 1000uf caps is bulged on top so i replace it & the identical one next to it(might as well,the amps old!). now i want to hook it back up but im trying to be cautious bout it.
 

New member
Username: Lowz24

Post Number: 8
Registered: Jul-06
ok so i hooked it up little while ago & all 4 channels apparently work, buuuuttt...for some reason when i put my hand on the amp heatsink the sound cut out(like it muted)& suddenly some smoke was coming from my headunit & rca wires had gotten hot all the way from the amp to the head unit. the head unit is ok after all that & i hooked up a speaker to all 4 channels one at a time & for some reason the sound cut out every time i touched the amp. of course i would cut power to the stereo after every time the sound muted on me as i didnt want to burn something up permanently. i just hope my headunit wont malfunction on me now.dont know if i trust it now that i saw & smelled smoke coming from it.
 

Gold Member
Username: Illuminator

USA

Post Number: 4074
Registered: Apr-05
You'd probably get better help from this forum for your problem: http://www.diyaudio.com/forums/forumdisplay.php?s=&forumid=38
 

Silver Member
Username: Van_man

Boston South, MA

Post Number: 800
Registered: Mar-06
Well, Interesting problem. Sounds like a bad amp. Anyway, You should have 4-5 volts on the rca leads from the HU. Depends on what model it is. Make sure the ground wire is good by checking ohms reading through it. Readings should be near zero. If Your rca were getting hot, then sounds like amp was grounding thru them instead of the amps ground. Recheck ground path in amp where you repaired it. Use a continuity tester to verify ground terminal on amp does not connect with the rcas input terminals. Like stated above, you would need to hook up the rcas, rem, power and ground to test the WRMS of the speaker terminal.
Example: if the amp was a 100 X 1
The feed voltage was 14.4 and amp draw was around 7 amps, then you would read @ 100 volts ac on the meter. Anything above 70 would be close depending on the amp. Also by touching the amp, you may have acted like a ground. So to reiterate, recheck your grounds. run a known good temp ground to help diagnose. Good luck.
 

Gold Member
Username: Illuminator

USA

Post Number: 4103
Registered: Apr-05
Looks like your question has been answered, 'jdp'

Perry Babin, owner of bcae1.com, responded and it looks like he hit it right on.
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