The Phase Linear 400 Guinea Pig

[laatsch55]

You should be able to open the 2 connect points to the cap screws to prove that Lee.

Gotcha.

 

[Gepetto]

The star point ground from the boards.

No the single white wire connection from the star point bus bar between the caps to the upper standoff stud on the Left Backplane board. Removing the nut and taking off this wire will totally separate chassis ground from DC ground.

Makes it easy to check for shorted components, like bad mica insulators and the like.

 

[laatsch55]

Nice trick, infinite on all collectors, base and emitters.

 

[laatsch55]

DC screws of caps disconnected, I have -78, and + 78 through the DBT. Not the rectifier.

 

[Gepetto]

Nice trick, infinite on all collectors, base and emitters.

We aim to please Lee

 

[laatsch55]

Reconnected caps, left rail fuses out, bright bulb....

 

[laatsch55]

Broight it up all the way without rail fuses, bulb went way bright long after the caps were charged, then went dim immediately. Stuck rail fuses back in. Offset -11, -13. Damned if I know, both q7's cool, piece of .010 solder finally melted?

 

[Gepetto]

Broight it up all the way without rail fuses, bulb went way bright long after the caps were charged, then went dim immediately. Stuck rail fuses back in. Offset -11, -13. Damned if I know, both q7's cool, piece of .010 solder finally melted?

I would watch those caps if they did that Lee. That is suspicious. Have you done a leak check on them?

Do you have your +/- 20V at the regulator outputs? R73 for +20, R74 for -20

 

[laatsch55]

I'll ck that Joe..

 

[laatsch55]

+ 20.23, -20.32

 

[laatsch55]

Left Q7 getting pretty hot.

 

[orange]

If you've lost faith in the Spec 2 I will gladly love it and care for it the rest of my life...

I thought not. Resting my case

 

[Northwinds]

aaarrrrrgggghhhh

 

[laatsch55]

After a short listening test last night which was rudely interrupted by a DC protect activation, I now have 147 minus DC volts on the speaker outs. This I have never seen. Considering you start out with 80.

 

[Northwinds]

Figure it out yet?

 

[kevin]

I'd say you could bet your ass he has !!!!! LOL !!!

 

[laatsch55]

Took an afterlunch nap. I'm on it now.

 

[laatsch55]

When you're taking measurements with ground referenced at the bias + test point point things get weird. With DBT in line and ground referenced at the correct point I still have plus 71 volts DC on the rails..and the speaker outs.

 

[laatsch55]

B- pico fuse bad, sloppy B- FUSE HOLDER!!! CREATING UNBALANCED OPERATION AND NO MINUS VOLTAGE SO + VOLTAGE BEING PASSED TO SPEAKER OUTS.

Fuse holder had been used to AGC fuses, AGX were sloppy.

Resetting bias now . A cool -11mv and -13 mv offset.

 

[laatsch55]

It's ALIVE!!!!!!!!!!!!!!!!!!!!!



The Pig lives!!!



The Pig in-situ-----damn these amps are tight and quiet!