The Smoked 400

[Gepetto]

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..

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.

 

[laatsch55]

Showing acceptable offset on the outputs and relay click.

 

[laatsch55]

2nd row in..

 

[laatsch55]

Joe, Q7, Q10 are still getting VERY HOT....

 

[Gepetto]

Joe, Q7, Q10 are still getting VERY HOT....

Did you measure your bias? Are the protection circuits still disabled? D9/10?

 

[Gepetto]

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.

 

[laatsch55]

Protection circuitys are still disabled. .000 bias. Voltage accross 22 ohm resistors coming up..

 

[roccus]

Is this the experimental amp you have had for testing?

 

[Gepetto]

Protection circuitys are still disabled. .000 bias. Voltage accross 22 ohm resistors coming up..

The voltage across the 22 ohm resistors is currently the bias Lee. You should see 0 at the real bias resistors as you noted.

 

[laatsch55]

Ground reference at Star ground
9L---+.648vdc
6L-- -.017vdc
LPNP -.647vdc

9R--- +.595vdc
6R--- -.012vdc
RPNP- -.625vdc

 

[laatsch55]

Is this the experimental amp you have had for testing?

No, that was The Pig.....long gone...

 

[roccus]

No, that was The Pig.....long gone...

ah yes "the pig" I thought you had sold that to a drummer girl here in ME.....

 

[laatsch55]

She actually won it in an amp lottery we used to have around here...

 

[roccus]

She actually won it in an amp lottery we used to have around here...

OK I remember that. thought this might be that amp with the copper fins...

 

[Gepetto]

Ground reference at Star ground
9L---+.648vdc
6L-- -.017vdc
LPNP -.647vdc

9R--- +.595vdc
6R--- -.012vdc
RPNP- -.625vdc

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.

 

[laatsch55]

At 22 ohms or 100 ohms? Still on 22...

 

[Gepetto]

Go to 100 and then the heat should go down on the 2 transistors which will give you more time to work with it.

 

[laatsch55]

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??

 

[Gepetto]

Tenths of a volt Lee

 

[laatsch55]

K..