afroaudio
Active Member
Hi gents,
I have an AU555 that I have recapped. Also replaced 2SC458s and flying saucers as well as output transistors (MJ21194G) trim pots and most resistors on main amp board. All thanks to others here that have gone before me and documented the process
After solving another problem with the preamp I now have a working amp which sounds great...Bias has been adjusted but not clipping (no scope)
My problem now is my replacement driver transistors are heating up very quickly as soon as signal is put into the amp. The flying saucers were replaced with NEC 2SA1220A and KSC2690A. After a minute or two I can smell that something is getting very hot and traced the heat to those driver transistors, (can barely touch them)
Can anyone point me to where I should look for faults here? I am probably going to take the amp to a tech tomorrow but thought I would ask here also.
555 main board by bregtje_lush, on Flickr
I have an AU555 that I have recapped. Also replaced 2SC458s and flying saucers as well as output transistors (MJ21194G) trim pots and most resistors on main amp board. All thanks to others here that have gone before me and documented the process
After solving another problem with the preamp I now have a working amp which sounds great...Bias has been adjusted but not clipping (no scope)
My problem now is my replacement driver transistors are heating up very quickly as soon as signal is put into the amp. The flying saucers were replaced with NEC 2SA1220A and KSC2690A. After a minute or two I can smell that something is getting very hot and traced the heat to those driver transistors, (can barely touch them)
Can anyone point me to where I should look for faults here? I am probably going to take the amp to a tech tomorrow but thought I would ask here also.
555 main board by bregtje_lush, on Flickr
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