Testing PreAmp Outputs
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=53846
Printed Date: May 06, 2024 at 5:46 AM
Topic: Testing PreAmp Outputs
Posted By: korruptone
Subject: Testing PreAmp Outputs
Date Posted: April 13, 2005 at 11:30 AM
Wondering how to test the preamp outputs on my Alpine head unit. Im thinking when the negative and positive touched on the amp (fireworks) it shorted out the head unit. No bass since. Thanks much - Eddie
Replies:
Posted By: Jay T
Date Posted: April 13, 2005 at 12:15 PM
if it was fused properly it should have blown the fuse at the battery end. Double check all your fuses at the amp and the fuse on the deck and under the dash. Does the amp turn on at all?
Posted By: korruptone
Date Posted: April 13, 2005 at 2:28 PM
All fuses appear to be fine. The amp powers up but gets no sound. I tested with a brand new amp of my friends and I get the same results. The radio / Cd player still works though.. so i dunno, what do you say? can you stick a DVM in the preamps to test them?? just to see if sound is leaving the head unit. tnx man
Posted By: kgerry
Date Posted: April 13, 2005 at 2:57 PM
you can scope for signal... you may have burned/fused open the audio ground path or may have damaged the pre-out OP amp ( although they tend to be pretty bullet proof)....
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Kevin Gerry
Certified Electronics Technician
MECP First Class Installer
Owner/Installer
Classic Car Audio
since 1979
Posted By: jstruckman
Date Posted: April 13, 2005 at 4:59 PM
Yes you can use a DMM to test for voltage coming from the RCA's of the head unit. Touch the positive test lead to the inside of the RCA and the negative test lead to the outside shield of the RCA, make sure you have your DMM set on AC voltage. It is best to play a test cd that plays a single tone, and then just keep turning the head unit volume up to and watch for voltage to increase.
Jazzy
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Posted By: korruptone
Date Posted: April 14, 2005 at 1:53 PM
Jstruck, did the test.. im pulling .2v at max. Definatly fried the Preamp circuitry. sucks, ima get a new head unit soon though. thanks for the assistance
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