I recapped my M-65 and have a few questions.

[Sparkplug]

The zener diode then serves what purpose?

Provides a near constant voltage for R109, R110, and therefore near constant current through both for IC101, 102, reducing distortion. C100 gets rid of the noise generated by the Zener diode.

so what dual FETs?

JFETs in IC101 and IC102 as was pointed out above.

 

[FriedChicken]

(differential amp).The amplifier front ends.

So these are the very important ones; from the schematic the first transistors that receive the audio signal...... C100 doesn't sit in the signal path, and only needs to be fancy insofar as that it can supply delicious juicy voltage.

This really isn't the amplifier to learn how amplifiers work....

IC101 only has 3 prongs on the diagram and looks like a normal transistor? Or does the striped line around the transistor pair indicate it is one IC... So C100 provides the clean voltage for the initial amplification of everything... This isn't the amp to learn on.

 

[avionic]

IC101 only has 3 prongs

It has 7 pins.

2SK389 GR,BL



Pin 4 the substrate is not electrically used.

 

[Sparkplug]

This really isn't the amplifier to learn how amplifiers work....

You can say that again …

 

[avionic]

This really isn't the amplifier to learn how amplifiers work....

Once you get it figure out. Then all Yamaha amplifiers get a little easier to T-shoot.

 

[FriedChicken]

It has 7 pins.

2SK389 GR,BL

View attachment 3759979

Pin 4 the substrate is not electrically used.

No, I mean:



So the dotted line encompasses the full transistor?

 

[avionic]

So the dotted line encompasses the full transistor?

Encompasses the dual JFET. Which illustrates 6 connections.

 

[FriedChicken]

Once you get it figure out. Then all Yamaha amplifiers get a little easier to T-shoot.

I'm not looking so much for how to troubleshoot yamaha amplifiers, but rather want to get a handle on how all audio amplifiers work.
It's been a while since I've acquainted myself with Mr. Kirchhoff and Mr. Thévenin

 

[Soundscape]

but rather want to get a handle on how all audio amplifiers work.

Mr. Chicken...Think of the M-60 as a KFC-60. A machine that's fed with 2 chicken wings in the front, and produces 2 buckets of chicken out the rear.
But it seems they shorted you 2 thighs on the left side bucket after the recap? Probably just meter board anomaly. Maybe turn the right channel down 1 leg to compensate, or a small breast.

 

[avionic]

Mr. Chicken...Think of the M-60 as a KFC-60. A machine that's fed with 2 chicken wings in the front, and produces 2 buckets of chicken out the rear.
But it seems they shorted you 2 thighs on the left side bucket after the recap? Probably just meter board anomaly. Maybe turn the right channel down 1 leg to compensate, or a small breast.

Popeyes?

 

[FriedChicken]

Mr. Chicken...Think of the M-60 as a KFC-60. A machine that's fed with 2 chicken wings in the front, and produces 2 buckets of chicken out the rear.
But it seems they shorted you 2 thighs on the left side bucket after the recap? Probably just meter board anomaly. Maybe turn the right channel down 1 leg to compensate, or a small breast.

I mean to say I need to brush up on my old electrical engineering skills and sort it out, including all the math. Current is j!