I posted the following info in quotes on another website with little response so far. I am posting here as well looking for help.
"I recently worked on a 2215b that had 1 blown channel. I checked all other components on the channel, which tested fine. Replaced the outputs that were blown, set the bias, checked the power and distortion with a scope. Play tested for a couple of days and all was good.
It came back to me two weeks later with the same blown output. Tested everything out of circuit again, and everything but the blown output tested fine.
I haven't run into this issue before but my initial thoughts are that the owner is either driving a 15 wpc (actually tested at 18wpc) into clipping, or there is something breaking down under load.
Any advice to prevent a third blown output would be appreciated."
"I recently worked on a 2215b that had 1 blown channel. I checked all other components on the channel, which tested fine. Replaced the outputs that were blown, set the bias, checked the power and distortion with a scope. Play tested for a couple of days and all was good.
It came back to me two weeks later with the same blown output. Tested everything out of circuit again, and everything but the blown output tested fine.
I haven't run into this issue before but my initial thoughts are that the owner is either driving a 15 wpc (actually tested at 18wpc) into clipping, or there is something breaking down under load.
Any advice to prevent a third blown output would be appreciated."
It is odd that it took a couple months for this to happen. How long did you test it for and was it under load? I would think even some oscillation would present itself with adequate testing. Are the replacement parts original for the amp or equivalents?
If it did test out perfect for two days I would suspect some user error. I would ask what speakers the person is using and how they are wiring them. Maybe the speaker wires crossed twice?
If it did test out perfect for two days I would suspect some user error. I would ask what speakers the person is using and how they are wiring them. Maybe the speaker wires crossed twice?
Recommended by many to replace transistors one stage prior to the failure. Shorted output transistors usually damage the driver stage, and although the parts test OK, they fail shortly afterwards.
2215B has a AC-coupled output ? I would also check the electrolytics, perhaps things oscillate or DC offset is too much.
The customer might have a shorted speaker, if he likes to party.
2215B has a AC-coupled output ? I would also check the electrolytics, perhaps things oscillate or DC offset is too much.
The customer might have a shorted speaker, if he likes to party.
Attachments
This amp will clip harmlessly.
I would say it has no short-protection. (The lamp-limiter in H713 Base is lame and crude.)
I would be thinking an intermittent short in his speaker wires. A hair-strand flapping around, or cable pinched under furniture. Maybe works OK until the dog lies against it, or maybe he didn't use it the two weeks.
I would say it has no short-protection. (The lamp-limiter in H713 Base is lame and crude.)
I would be thinking an intermittent short in his speaker wires. A hair-strand flapping around, or cable pinched under furniture. Maybe works OK until the dog lies against it, or maybe he didn't use it the two weeks.
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