Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
|
|||
|
|||
Yamaha Blown Amp help nearly solved -see schematic -
During a heavy right speaker load the amp blows taking the speaker down with
it. A service technician confirms a blown amp but unable to diagnose further without a schematic. So here it is. http://autotails.tripod.com/yamaha.htm Follow the orange line in this schematic and as you approach Q105 the problem begins. This sorta predriver and everything after it measures off its normal reading by 5,000%. It's remarkable that the output (main) transistor isn't dead since I'd had it tested outside and even put new ones in it's place and still measure 5,000% of normal. The problem began when the speaker output measured: Left channel 28V Right channel 28V Center channel 0V Surround channel 0V The system will shut down after two seconds, cannot bypass See this link for the areas marked in green (similar to above schematic) are the blown areas. Everything else around it measures normal. Also will find more diagnostic details, http://autotails.tripod.com/zoom.htm Website maintained by a coworker. Receiver is a Dolby pro logic RX-V480 70w/channel x3 channel plus two op-amp surround channels with a separate power supply. |
#2
|
|||
|
|||
Yamaha Blown Amp help nearly solved -see schematic -
Q111 was replaced this morning, still won't work. Q111 was replaced the same
time as Q109, Q129C, and Q129A. Measuremwnts were taken and I was shocked to see that the were still the same as before. (Thinking Q111, Q109 drives the output transistors (Q129A, Q129C, replacing them would solve something) Thanks for the suggestions. -W I suspect at least Q111 to be defective. If the voltage difference between B-E is much higher 0.7 it is. Good chance that Q129A is also shorted between B-E so it is perhaps better to replace all of them. During a heavy right speaker load the amp blows taking the speaker down with it. A service technician confirms a blown amp but unable to diagnose further without a schematic. So here it is. http://autotails.tripod.com/yamaha.htm Follow the orange line in this schematic and as you approach Q105 the problem begins. This sorta predriver and everything after it measures off its normal reading by 5,000%. It's remarkable that the output (main) transistor isn't dead since I'd had it tested outside and even put new ones in it's place and still measure 5,000% of normal. The problem began when the speaker output measured: Left channel 28V Right channel 28V Center channel 0V Surround channel 0V The system will shut down after two seconds, cannot bypass See this link for the areas marked in green (similar to above schematic) are the blown areas. Everything else around it measures normal. Also will find more diagnostic details, http://autotails.tripod.com/zoom.htm Website maintained by a coworker. Receiver is a Dolby pro logic RX-V480 70w/channel x3 channel plus two op-amp surround channels with a separate power supply. |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Schematic drawing and PCB design software | Electronics | |||
Viewsonic 1564 (15") monitor schematic wanted | Electronics Repair | |||
newbie - blown yamaha power amplifier | Electronics Repair | |||
Yamaha G100-412 schematic needed... | Electronics Repair |