The Smoked 400

[laatsch55]

Triple zeros accross both, Q7, Q10 not near as hot..

 

[laatsch55]

No change through full range of adjustment..

 

[laatsch55]

Excuse me, brain dead. Monitoring 9L, 9R, range was 1.023 volts to .563 volts...

 

[laatsch55]

PNP acted the same...with the same ranges...

 

[laatsch55]

So the pico saved the bias tranny?

 

[Gepetto]

No the bias tranny is in the high impedance class A section of the amp, driven by Q5 which also survived. Q5 was saved by R76 fusing open.

What were you running for rail fuses Lee? Pennies?

 

[Gepetto]

BTW, those ranges look fine Lee. You are cleared for takeoff. Not sure about the germanium protection transistors. You should reconnect the protection circuit with the 100 ohm resistors in there and ensure that all is still well.

 

[laatsch55]

K...

Fuses were 5 amp. I was not really monitoring heat Joe, I think it was pretty hot when she blew...I was pretty drunk..,.

 

[laatsch55]

9R, PNPR only go to -.012 with protection circuit in..

9L, PNPL are good..

 

[laatsch55]

And the original fuse blow was rather soft, no burn marks, just a separation of the filament..

 

[Bradrock]

"What were you running for rail fuses Lee? Pennies? "
That's funny. The night it blew I was wondering if he had 22lr cases in there.....

 

[laatsch55]

I'll go to 8's in a 700 if it gets intense , but not a 400. And I was running MJ 21193's andf 21194's for outputs, not as good an SOA rating on them...

 

[Gepetto]

9R, PNPR only go to -.012 with protection circuit in..

9L, PNPL are good..

Looks like you need to replace the 1304/5 for that channel Lee. Check for C-E shorts on those transistors.

 

[laatsch55]

OK, I pulled ends of dD9, 10 again and powered back up, have the same readings on 9R, PNPR..-.012, -.014

Also have -4.85 on bias tranny collector, -6.25 on the base and -7.12 on the emitter...yes the decimal point is in the right place..

 

[laatsch55]

All on the right channel Joe..

 

[Gepetto]

OK, I pulled ends of dD9, 10 again and powered back up, have the same readings on 9R, PNPR..-.012, -.014

Also have -4.85 on bias tranny collector, -6.25 on the base and -7.12 on the emitter...yes the decimal point is in the right place..

The bias transistor readings look OK Lee in terms of expected voltage spread. Where the collector voltage is sitting however is not OK. You said in an earlier post above this that 9R was working properly. Now not? Are you sure?

 

[Gepetto]

Have to sign off for the night Lee. We can pick up tomorrow sometime.

 

[laatsch55]

Yes, I'm sure Joe. I pulled D9, D10 on the right channel, then checked 9R, 6R, and PNPR.
This is still on the DBT and variac, rail voltaqge +/- 73 volts.

Will check voltages again..

 

[laatsch55]

Have to sign off for the night Lee. We can pick up tomorrow sometime.

Night Joe, thanks..,

 

[laatsch55]

9R--- -.011
6R-----.011
PNPR- -.011

Bias tranny
Collector -14.58
Base -15.2
Emitter -16.7