Hello, can someone help me with repairing old yamaha?🤔 I would like to repair this amplifier to learn a Little about electronics but i dont know how to start. When i buy it it has broken transistor 2SC1815 and smoked resistor 1.5k ohm and i replace them and try to power on through lamp and it started then i pluged fuse and the resistor started to burn. I discontcted power source from the main board and measured the voltage on the 2 big capacitors and it was + and - 58,6v
Can someone help me what i need to check more to find what coused burning of the resistor.
I am adding the schematic and the picture where the parts was damaged.
There is no magic or fancy solution here
All discrete boards require testing each component per si
It seems you do have a dead short
A common "fit all" solution is to power the board
with a variac.. raising it enough to not burn...
But enough (via CC/CV control) to hot spot the dead short culprit
Today thermal cameras are handy..
10y ago we just put some vapor like fluid or alcohol
your finger sometimes...
Paul
and BTW.. there is a SERVICE MANUAL for this class
which in time was quite complex to diagnose.
It helps a lot with proper check points...
Paul
Ok thank you for targeting me to resolve the problem.👌
I dont find any hot spots but i started to desolidering end transistors and all at the end are shortcircut and even other transistors at this channel so i think it is not worth to buy all of the transistors.