basil13
Active Member
Hi All
I have been working on a B1 for too long now and was looking for some help resolving a problem I have encountered during the set up procedure. Additionally, it would help if Yamaha didn't include so many errors in the manual and schematic.
Attached are pictures of the set up starting at step 2-1 of the driver circuit. The output modules are not installed, the thermal sensors are shorted between pins a2 and b2 on both channels (yellow jumpers), the positive sides of both channels are jumpered with a 4.7K resistor at pins a1 and b4 (green and black jumpers). The unit is not in thermal protection or overload.
My problem relates to step 2-6. I can not get the -15 volts required on pins a4 and a3 on the negative side socket (picture 2) or positive side for that matter. Both channels are acting the same except one maxes out at -4 volts and the other at -5 volts after a quarter turn of bias pot VR502.
It is unusual that both channels are behaving the same way so I am wondering if something is connected improperly or if there is something I am missing. I have checked the voltage measurements at all 15 pins of the board socket and they are fine. The pots were pulled from the boards and checked with a meter and track fine.
I have taken all voltages on the transistors and FETS if you require them.
Any help would be appreciated.
Bob
I have been working on a B1 for too long now and was looking for some help resolving a problem I have encountered during the set up procedure. Additionally, it would help if Yamaha didn't include so many errors in the manual and schematic.
Attached are pictures of the set up starting at step 2-1 of the driver circuit. The output modules are not installed, the thermal sensors are shorted between pins a2 and b2 on both channels (yellow jumpers), the positive sides of both channels are jumpered with a 4.7K resistor at pins a1 and b4 (green and black jumpers). The unit is not in thermal protection or overload.
My problem relates to step 2-6. I can not get the -15 volts required on pins a4 and a3 on the negative side socket (picture 2) or positive side for that matter. Both channels are acting the same except one maxes out at -4 volts and the other at -5 volts after a quarter turn of bias pot VR502.
It is unusual that both channels are behaving the same way so I am wondering if something is connected improperly or if there is something I am missing. I have checked the voltage measurements at all 15 pins of the board socket and they are fine. The pots were pulled from the boards and checked with a meter and track fine.
I have taken all voltages on the transistors and FETS if you require them.
Any help would be appreciated.
Bob
