Yamaha B2 driver board diagnosis

TR124 should be TTA and TR123 should be TTC.According to Hoyle..
 
Verify the R164 and R166 (47Ω emitter resistors) are still serviceable.
 
Checked again. All good.

Installation is right (even checked continuity with surrounding circuitry per schematic). Transistors pass all DMM diode tests.
 
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Side note : how are those Troels Gravesen Xover's working? Make a big difference?
 
I love the crossovers! They were a noticeable improvement over the stock crossovers, particularly in bass. They are hooked up to my other B2. :)

So, it's been a long day. And I forgot to install the bridge CB before taking the measurements - so +/- 60V were absent.

Here are the real values:

TR118: E= -81.5V; C= -0.8V; B= -82V

TR120: E=-47.6V; C= -81.5V; B= -48.2V
 
TR118: E= -81.5V; C= -0.8V; B= -82V
Check R148 (1.5KΩ ) and R150 (470Ω) The emitter voltage of TR118 is a little lower than the base. Probably needs to be .6 volts higher than the base.For the transistor TR118 to switch on.
 
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