Teal
New Head-Fier
- Joined
- Jan 1, 2009
- Posts
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I recently built a Mini^3 amp and I tested it and it passed all the tests and worked wonderfully.
I then went to work on the case (A real pain) and noticed that the battery wouldn't fit in the case because of the contacts, so I desoldered them, cut away a portion, resoldered them back and connected the battery. When I went to see if it fits in the case, I didn't trim the leads at the bottom and the battery contacts shorted out on the case, and the blue LED lighted up.
Worried, I went through the initial check again. This battery is old and even though I recharged it, it gives out very little current. I measured the quiscent current at 15 mA. Then I switched it to a new 9 V that I did all my previous checks and listening tests with (it's too big to fit in the case). I measured the quiescent current at ~100 mA, and before the battery/case work it was at 25 mA (the proper amount).
I also found the DC offset on output ground and one of the channels to be ~0 and ~3 mV on the other. It was all 2-4 mV before.
When I tried a brief listening test (with a cheap pair of dollar store headphones), only the right channel was working. Also U5 started to noticeably heat up. Nothing heated up when I did the hour+ listening test the day before.
I have no idea what's wrong, but I feel I may have destroyed one of the op-amps. I don't however see how shorting out the battery terminals (all other leads were trimmed) could cause this. I checked every lead of the opamps for a short and there were none (a few had ~150 Ohms). When I tried to use wall power, I noticed U5 began to heat up (too hot to touch), so I didn't try any listening tests on it.
If anyone has experienced this problem and could shed some light, that would be greatly appreciated. Replacing one of these SMD opamps on a populated board is going to be nigh impossible, so I want to know if anything else could cause this before attempting that (in which case I'd lose the other opamp too).
I then went to work on the case (A real pain) and noticed that the battery wouldn't fit in the case because of the contacts, so I desoldered them, cut away a portion, resoldered them back and connected the battery. When I went to see if it fits in the case, I didn't trim the leads at the bottom and the battery contacts shorted out on the case, and the blue LED lighted up.
Worried, I went through the initial check again. This battery is old and even though I recharged it, it gives out very little current. I measured the quiscent current at 15 mA. Then I switched it to a new 9 V that I did all my previous checks and listening tests with (it's too big to fit in the case). I measured the quiescent current at ~100 mA, and before the battery/case work it was at 25 mA (the proper amount).
I also found the DC offset on output ground and one of the channels to be ~0 and ~3 mV on the other. It was all 2-4 mV before.
When I tried a brief listening test (with a cheap pair of dollar store headphones), only the right channel was working. Also U5 started to noticeably heat up. Nothing heated up when I did the hour+ listening test the day before.
I have no idea what's wrong, but I feel I may have destroyed one of the op-amps. I don't however see how shorting out the battery terminals (all other leads were trimmed) could cause this. I checked every lead of the opamps for a short and there were none (a few had ~150 Ohms). When I tried to use wall power, I noticed U5 began to heat up (too hot to touch), so I didn't try any listening tests on it.
If anyone has experienced this problem and could shed some light, that would be greatly appreciated. Replacing one of these SMD opamps on a populated board is going to be nigh impossible, so I want to know if anything else could cause this before attempting that (in which case I'd lose the other opamp too).
