The Smoked 400

laatsch55 said:
Out of circuit , same result. Should I reattach the free end of R76 before applying power w3ith new Q7?

For some reason didn't check C-E in circuit, just B-C, B-E and reverse polarity...jeez..
Click to expand...

Yes reattach R76 and try the 22 ohm setup again.

Yeah I figured you might have just measured the junctions and not the C-E. Common oversight. That poor transistor was sucking all the base current from the output transistors when the upper side shorted out. It could not win.
 
Showing acceptable offset on the outputs and relay click.
 
2nd row in..
 

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And are you still just on the 22 ohms? what is the voltage across each 22 ohm resistor? Try going up to ~100 ohms now on each of the test resistors.
 
Protection circuitys are still disabled. .000 bias. Voltage accross 22 ohm resistors coming up..
 
Is this the experimental amp you have had for testing?
 
laatsch55 said:
Protection circuitys are still disabled. .000 bias. Voltage accross 22 ohm resistors coming up..
Click to expand...

The voltage across the 22 ohm resistors is currently the bias Lee. You should see 0 at the real bias resistors as you noted.
 
Ground reference at Star ground
9L---+.648vdc
6L-- -.017vdc
LPNP -.647vdc

9R--- +.595vdc
6R--- -.012vdc
RPNP- -.625vdc
 
She actually won it in an amp lottery we used to have around here...
 
laatsch55 said:
Ground reference at Star ground
9L---+.648vdc
6L-- -.017vdc
LPNP -.647vdc

9R--- +.595vdc
6R--- -.012vdc
RPNP- -.625vdc
Click to expand...

Excellent Lee. If those 9 and PNP (L/R) respond to adjustment of the bias pot then it looks like you are ready to hook things back up again.
 
Go to 100 and then the heat should go down on the 2 transistors which will give you more time to work with it.
 
We have heat on all 4 pre drivers now. Hang on I'll get some 100's in there. How much response are we lookin for??
 
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