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I took a chance and grabbed a broken Acoustic BN6210 amp (class D, 600W, 2x10 neo speaker combo) from a local pawn shop yesterday. I figured there was a chance the speakers weren't blown and it was really cheap. There were a couple minor issues to get it powered up and deal with distorted signal to the headphones, but even after that the output was really low and would cut out. Tried an external speaker cab and it worked great. The internal speakers had measured a reasonable 3.7 ohms at the plug, but opened it up to have a look. This is what I found.
So there is a 10" Onkyo 50W speaker (8 ohm) and a Polk Audio 8" speaker (4 ohm). The 8" was fit into the 10" hole using a smashed out 10" basket and a plastic bucket lid. Speakers were connected with the quick connect terminals from smashed out speakers. Why they bothered with the quick connects (which they soldered to the home audio speakers) is beyond me. Obviously the class D amp was shutting down because of the messed up load. I can only guess the quick connects had enough DC resistance to give me the reading I got on my DMM. I have started to appreciate a well designed class D module (and still hate poorly done ones). Replaced the speakers with a couple of 8 ohm 10" high power bass/pro audio speakers I had and it is working fine. I'm wondering if someone bought the amp, took the original speakers, then returned it to the pawn shop and said it was broken. I know this shop has had that stuff happen before.
So there is a 10" Onkyo 50W speaker (8 ohm) and a Polk Audio 8" speaker (4 ohm). The 8" was fit into the 10" hole using a smashed out 10" basket and a plastic bucket lid. Speakers were connected with the quick connect terminals from smashed out speakers. Why they bothered with the quick connects (which they soldered to the home audio speakers) is beyond me. Obviously the class D amp was shutting down because of the messed up load. I can only guess the quick connects had enough DC resistance to give me the reading I got on my DMM. I have started to appreciate a well designed class D module (and still hate poorly done ones). Replaced the speakers with a couple of 8 ohm 10" high power bass/pro audio speakers I had and it is working fine. I'm wondering if someone bought the amp, took the original speakers, then returned it to the pawn shop and said it was broken. I know this shop has had that stuff happen before.
I doubt they would do the cobbling just from a liability standpoint, as this is a part of a chain of shops. I have gotten to know the manager a bit and he sold me this amp for less than 1/10th of their original asking price. Being Class D I was basically thinking there was a good chance it wasn't repairable (in a cost effective manner). Sometimes I win the pawn shop roulette. 
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