What could be the best fix, replacing all those parts (drivers etc.) or just trying to rebias it? I had no time to check the bias up to now, but I must order most of the parts anyway. better then to buy the Ampeg Micro CL or even better the Micro VR then the BA115HP. It cost much more then the regular version but with 1x15W no way it will be much loader then the 100W version. The BA115HP version with claimed 220W seem like a 'bad' investment. I just got a BA-115HP with the same symptoms, it oscillates like crazy, absolutely LOUD, so i had to turn it off immediately. Here in Norway the BA115 100W is a real good deal. I was after insurance by replacing them)Īnd U3B (5532) is the driver for the drivers, so it must be sound.Hi JazzBass, (most of the original parts checked out o/k with a meter. I replaced the drivers, the outputs, all four zeners, and (do not forget these) the two 47 ohm gate resistors. When I went to change the bias lower, the outputs blew (no load). I had one of these on the bench awhile back. I would not "turn" anything without a proper measurement.
I may be wrong but I think turning the bias pot "clockwise" increases the bias. The bias measurement is made by going across R61, with a 5mv setting. So, I am replacing all the parts again, all outputs, all diodes, thermistor, drivers, the bias transistor.Īnything else I need to do before testing it? I built a current limiter so I can hopefully avoid burning up any more parts. Also, the thermistor on the input is charred and cracked, so I replaced it. I pulled the outputs and the fuse stayed on, but R35 was burning up. So, I changed the same parts again, turned the bias all the way clockwise (down), changed out the diodes (6,7,8,9), and powered up. I know now not to mess with the bias control without measuring (thanks Enzo)! The amp worked and had a little bit of distortion, so I turned the bias pot down a tiny bit, which made it play clean for about 4-5 seconds before the amp blew.
Ampeg ba115 drivers#
I'm starting a dedicated thread for this, instead of tagging onto the other one.īasically the amp had a bad hum/popping crackling going on and I changed the drivers and outputs.
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