I recently managed to blow the left output channels on a pair of 3BST amplifiers (most likely due to inadvertently touching the ends of the speaker cable together while under power. Face, meet palm...). Both internal and external fuses blew on the left channels, along with a number of output transistors. After talking briefly with Bryston tech support, I consolidated the two working channel modules into one functional amp and set about repairing the others. I've managed to replace all the transistors on the bad channels, put the respective channel modules back in their proper amps, re-bias the transistors, and adjust the DC offset down to somewhere under <1mV. Amp #1 seems to be working fine and, if anything, sounds as good as, or better than it did before. Amp #2 appears to give correct bias and offset readings, powers on normally, and initially gave a rather feeble output signal on one channel and then quietly crackled into silence over the course of maybe 20-30 seconds, and now refuses to produce any output whatsoever. I put a cheap oscilloscope on the outputs and, as expected, it's a lifeless, flat line. It's rather odd that both outputs are non-functional, since one was working before when installed in the other amp. So perhaps something beyond the channel modules is bad.
At this point, I'm hitting the limits of my diagnostic skills, and am running out of ideas. Can anyone suggest what I might check next to get a better idea of what might be going on here? A month ago I barely knew which end of a multimeter to point at a circuit, and now I'm reading technical whitepapers on class AB amps. I'm not experienced, but I'm a quick study...
At this point, I'm hitting the limits of my diagnostic skills, and am running out of ideas. Can anyone suggest what I might check next to get a better idea of what might be going on here? A month ago I barely knew which end of a multimeter to point at a circuit, and now I'm reading technical whitepapers on class AB amps. I'm not experienced, but I'm a quick study...
i imagine the two amplifiers were still covered under the 20 year warranty.
before you opened them up and took them apart.
i hope the person you spoke to at bryston made the warranty coverage clear to you. if they didn't you might want to talk with someone higher up at bryston (james tanner perhaps) about getting both amplifiers repaired and updated. for free
before you opened them up and took them apart.
i hope the person you spoke to at bryston made the warranty coverage clear to you. if they didn't you might want to talk with someone higher up at bryston (james tanner perhaps) about getting both amplifiers repaired and updated. for free
Hi, I have the same amp. I was wondering if you were able to fix it?
Perhaps there is something wrong in the input board?
This thread might be of interest to you 4BSST clone thread
Also, with my amp, it has always lightly popped when powered on and off. Was it the case with yours? I’ll have to check DC offset at output.
Mine is presently at Bryston for some repair... Something broke on the power board and didn’t feel like repairing it myself. They charge hourly workbench + parts for repairs. It might still be worth it for you if you are in North America. They are not too heavy so shipping fees will not be outreageous.
Perhaps there is something wrong in the input board?
This thread might be of interest to you 4BSST clone thread
Also, with my amp, it has always lightly popped when powered on and off. Was it the case with yours? I’ll have to check DC offset at output.
Mine is presently at Bryston for some repair... Something broke on the power board and didn’t feel like repairing it myself. They charge hourly workbench + parts for repairs. It might still be worth it for you if you are in North America. They are not too heavy so shipping fees will not be outreageous.