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Old 12th August 2004, 12:56 AM   #1
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Location: So. Cal
Unhappy Amp failure .. .

My amp is acting up ...

First things first, the amp is wired properly. This problem just started one day, and had no previous oddities ...

When turned on, the amp plays beautifully, for a very short period of time. The amp then shuts off. It seems to shut off as soon as the amp warms up a little, and will not turn back on for more than a second or so, unless I have given the amp plenty of time to cool down. This is very odd, as the amp is not really getting hot. This all started after leaving my system at a high level, for a long period of time, on a very hot day. ..

I suspect that the overheat-shutoff circuit has been damaged. Any ideas as to how I can fix this? Or possibly a diagram that would depict which components make up this circuit, so that I can test the components? Maybe a kind prayer for my poor amp? . .. Any suggestions/directions would be greatly appreciated ..

Thanks!
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Old 12th August 2004, 01:14 AM   #2
clayton is offline clayton  United States
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What kind of amp is it? Also what do you have connected to it and how is it configured.
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Old 12th August 2004, 05:15 PM   #3
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My current setup (I know, it's pathetic):

HU - stock
Line Converter (tapped into rear speakers) - adjustable (don't recall the brand)
Amp - Jensen XA2125
Subs - (2) Pioneer TS-W34C (4 ohms each) wired in stereo mode
Enclosure - qLogic QLH-12D100 (too small, I know)
Power Cables - 8 gauge
Speaker Cables - 14 gauge (maybe 16, I don't recall)

The gain is set to just above half.
The bass boost is set to ~14db, but kept at around 30% via the remote dial.
The LP filter is on, set to around 90Hz.
Etc ...

Any thoughts on this?
Thanx!
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Old 13th August 2004, 12:22 AM   #4
sss is offline sss  Israel
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i dont think that the overheat protection circuit is damaged , maybe its the current protection kicks in

i think maybe one of the channels got a broken transistor so the amp shuts down .check if all the channels are working before it shuts down .
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Old 13th August 2004, 12:40 AM   #5
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I haven't put the meter on it to verify that both channels are functioning, but it sounds as if they are; there does not seem to be a difference in the sound since this issue began. It very well could be one of the transistors, I just didn't realize that it would function at all if one were damaged. I guess I'll just have to start testing the individual components.
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Old 13th August 2004, 01:13 AM   #6
clayton is offline clayton  United States
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It is possible that one of your subs is bad. ohm out both subs to make sure they are at 4ohms. That would be the first thing I would check. Than do what sss has stated.
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Old 13th August 2004, 01:31 AM   #7
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They metered in at 3.3 ohms each. A buddy of mine has these same subs, so I will meter his to see how they compare. Thanks for the suggestion.
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Old 13th August 2004, 04:05 PM   #8
maylar is offline maylar  United States
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Check the Emitter (or Source, if MOSFET) resistors in the amp. Usually low values like .2 or .47 ohms. Lots of designs use these in the current limit sense circuit. If one of them is burned open or high value it could make the amp shut down prematurely.
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Old 13th August 2004, 08:15 PM   #9
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Thank you for that info. I will test those resistors, replace them if necessary, and let you guys know what I find. Thanks again, much appreciated.
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Old 17th August 2004, 04:38 AM   #10
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Well Maylar, it looks like you may have found the problem . .. I've got 2 resistors that are supposed to be .2 ohms; both of which are reading 5 ohms of resistance. I will replace these (hopefully tomorrow), and hopefully have a working amp. Thanks again for your help. I'll keep you guys posted ...
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