Kevin's "I Want a Phase Linear 700 B White Oaked" thread

[laatsch55]

Forgot to post the pics. Distortion readings were excellent.

Movement of the bias pots had no effecty. DC offset adjustment pots had excellent resolution and range. This has an 0171 board.

 

[soundude]

Lee sounds like the bias transistors are passing control voltage, or pots my be screwy...take a resistance reading across the pots then at the wiper. Check transistors for shorts...don't have the schematic isn't there zeners in the circuit?

 

[Gepetto]

Yes the pots that Phase used were cheap carbon types that failed often with age. I have replaced 2 of them on 3 amps I own prior to total White Oak board transplant.

But that is not the cause of 20V appearing there. The transistor has to be open collector to emitter in order for that to occur. That could be either a bad transistor or a broken wire to the transistor (or something else in the related circuits).

 

[laatsch55]

Why the good distortion specs????

 

[Gepetto]

Hard to say Lee because the amp is not in front of me but would guess that you are developing some serious static heat... If you have 20V in the normal measuring location (R38 10 ohms) then the 10 ohm resistor would be dissipating 40W!! And the B-E of the upper predriver is likely open.

Are you sure of your readings?

 

[laatsch55]

Oh yes, after seeing that I double checked.

 

[laatsch55]

On the pl0171 boards Bias is not measured there . It's taken from the positive side of C11 and a positive speaker post.

 

[laatsch55]

The previous owner also put a soft start circuit in it. Works damn good too. No lights dim during turn on.It utilises a relay, couple big resistors and some things I can't see yet.

 

[Skratch]

Lee, with a soft start will the front end come up fast enough?

 

[laatsch55]

Oh yeah, just a half second delay, and current seems to lag voltage.

 

[laatsch55]

DONE!!!!!!!!!!!!!!!!!!!!!!!!

Shpongle as we type this!!!!!!!

God Particle


This one turned out as good as it sounds. Clean inside, out and sonically!!!

Jer, Scott, the 47 K seems to make a difference. A few numbers in the same decimal place, but when idling, there is a big difference.


Whadda ya think of the new knobs???????

This is also the first time I've left the ground wire from the RCA ground plane to the star ground----OFF. Shield and ground soldered at the RCA'S AND only the signal and ground at the board input.

 

[laatsch55]

I think I heard something on "The Last Days of Gravity". The intro to track 3, in the background is that a waterfall or someone wadding up some papers??

 

[soundude]

Congradulations Lee, the amp looks awesome. When you heard the shuffling papers were you direct?
When I build a amp there is nothing between the input and the gain stage, I don't even use a coupling cap, I hear alot of things that you normally would hear, like Diane Krall, can hear her breathing and humming during the piano solo's. Don't have the pots in the line to dirty up the sound..the only true pot I would use is a wire wound, more direct than a carbon...
Also with sacrificing watts I will go direct to the amp from the cd player, just make sure your player has a volume control or gain control built in...
Going to try the led tape around the VU meters, will post pics when done....

 

[laatsch55]

Yep, I was in in direct mode. Straight to the board. Looking forward to seeing the lights. Just gotta solve sourcing some meters now. On this one the distortion readings were exactly the same through the pots as not, haven't listened through the pots yet.

 

[soundude]

Lee, in a ealier post I put in some meter suppiers that had very close to the PL meters, just need to change backing..

 

[ksrigg]

The amp looks fabulous.
Brilliant job. This one was a complete rebuild...looks like..with new resistors and everything...a brand new amp..

Wonder where Kevin is? He should see this beauty...and if you are hearing things you've never heard before on some CD's, it really is something special. Every one of these you rebuild gets better and better. Unreal...with the new analyzer it's scary what you are able to do...

 

[soundude]

Lee, those are the knobs from Antique Electronics?
They look like the originals.....nice.

 

[kevin]

Kevin is always here !!!!!

 

[soundude]

I don't know Kev, Lee's bulletproofing this amp, ur going to have to learn to tame this beast!!!
I've been beating the piss outta this thing hitting with everything...Have a small muffin fan just drifting air on this thing and is just luke warm....[attachment=0:32uk4ht5]Picture 029.jpg[/attachment:32uk4ht5]

 

[ksrigg]

I'd love to know the temperature on one of these babies after running at 0 db for a couple of hours..They don't get nearly as hot as the original ones did...

Odd thing though.....out of the four 400's there is one that gets hotter than the others...wonder what the reason might be? It is certainly warmer than the others, but still not hot...could be the speakers I have it working with...maybe a little more resistant load?

I know, I need to get a digital laser thermometer and objectify my observation...

Kevin will have a blast with the amp. I've already emailed him a link to the planar tweeters we used in the Linus Array. They have gone up in cost from $30.00 to $76.00 in the few years since we built them. I'm assuming the Dayton ones are still a YAG product...The two planars in the center of the line are name brand (HiVi, I THINK)....and I don't know how much these cost now...I think they were over $100.00 when we bought them...I'll bet they are over $20.00 each now, if they are still available..