Alpine MRP-F300 amp is dead, need help with repair

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#27
The resistance had very weird readings. It started off less than 100 then increased more and more and then showed a 1 to the very left of my dmm. I tried higher ranges but this time I had absolutely no readings at all. It would just show a 1 to the left. I measured all of the 4 non bridged terminals. They are the 4 center ones in the pictures. No power should be applied correct?
 
#29
My dmm shows just a 1 when i connect ground to any speaker wire coming from my speakers. And the input is not shielded because they are line level inputs from the radio HU. I am using the factory HU so there is no RCA out from it. There is no way that the speaker wires are shorting to ground. All my connections are clearly visible and there is no visible connection that can be continuous to ground. If that were the case my amp and/or speakers would have been fried long before now.

On a side note, my speakers are connected to crossovers before it gets connected to the amp. Could the crossovers be at fault? And what would you think was the likely reason the amp got fried?

Thanks Perry.
 
#31
I tried using a different electrical tester to check for continuity. I checked the speaker terminals against ground and it showed no continuity. That's what I should be looking for right? I checked the amp terminals again with the same tester and it shows continuity between all terminals between ground and the B+. I'm getting conflicting results. How else can I check this. I am using an electricians tester and a cheap dmm.
 
#33
I think I am confusing myself. There should not be continuity between the speaker terminals and ground. Meaning I should see infinite resistance. Which I do so that's good. And the amp terminals should not be continuous to B+ meaning I should see infinite resistance, which I do so that's good. So I guess I'm in the clear?

And if for some reason the speaker words come on contact with a 12 v power source, would the amp get fried right away or would it be a slow death so to speak? Thanks again perry.
 
#34
I think most of the confusion is over the definition of continuity. Continuity is not simply shorted or open. You can have continuity through the filament of a light bulb but it's not a short. Various meters will have different thresholds where they show continuity. The problem is, you don't generally know what that threshold it.

On resistance, you'll get various reading but the behavior of the meter readings will help tell you what you have. For example, if you touch the meter probes across the B+ and ground terminals (with no connection to a power source), the meter will have a reading that will change for a while and then stop at some point. If you were using the meter on continuity and touched the probes across the B+ and ground terminals it may show continuity and lead you to believe that there was a short. On resistance mode, you'd see that the readings were changing and you'd realize that there was no problem.

I don't understand the second question.
 
#36
On some amps, the amp would be immediately damaged if any speaker wire came in contact with a 12v power source like the main battery supply wire. Other amps would pass the voltage to the head unit which would likely burn the RCA shield ground or burn the RCA cables along their entire length. This especially applies to the speaker wires connected to the non-bridging speaker terminals.

If the 12v source contacted the speaker wires connected to the bridging terminals of the amp, there may be damage but the damage would likely be limited to the amp's internal components (particularly the output transistors).
 
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