Hi guys,
I'm new to this forum bit I've post the process elsewhere is anybody is curious to see.
I have change fews part and now just installed new output transistors from ON Semi(new motorola). The problem is the +30.5Vdc and -30.5Vdc from BD901 and 4 mains big caps. When I probe it to the board I have +60Vdc and -2Vdc...
I getting near to clueless about this.. when I pulled out the old output transistors and verify voltage at caps and had the +-30.5Vdc.
Left channels looks alright all over the power amp that I chech yesterday and it was before the replacement transistors. Right channel was now okay and I have to check that with new transistor.
Could the soft-clipping could make that weird voltage?
I've put attached the diagram I have put together from the manual.
Thanks for all the help in advance!!!
I'm new to this forum bit I've post the process elsewhere is anybody is curious to see.
I have change fews part and now just installed new output transistors from ON Semi(new motorola). The problem is the +30.5Vdc and -30.5Vdc from BD901 and 4 mains big caps. When I probe it to the board I have +60Vdc and -2Vdc...
I getting near to clueless about this.. when I pulled out the old output transistors and verify voltage at caps and had the +-30.5Vdc.
Left channels looks alright all over the power amp that I chech yesterday and it was before the replacement transistors. Right channel was now okay and I have to check that with new transistor.
Could the soft-clipping could make that weird voltage?
I've put attached the diagram I have put together from the manual.
Thanks for all the help in advance!!!
Attachments
Looks like the ground connection is floating. Start at the centre tap of the transformer and trace it to the main pcb.
Thanks maudio!!
I found out there was indeed a ground problem, managed to wire tagt correctly. Bias and offset adjusted right on and power on almost everything is perfect.
I have sort of a "chhh" noise at idel.. its not like a "hum" that we are familiar to see with old amp..
Ir follow the volume knob, balance and its really let noisy when "audio muting" pushed but still in the background.
It is in the preamp since there is nothing when link are removed and it start fews seconds after power on.
I found out there was indeed a ground problem, managed to wire tagt correctly. Bias and offset adjusted right on and power on almost everything is perfect.
I have sort of a "chhh" noise at idel.. its not like a "hum" that we are familiar to see with old amp..
Ir follow the volume knob, balance and its really let noisy when "audio muting" pushed but still in the background.
It is in the preamp since there is nothing when link are removed and it start fews seconds after power on.