Sutton's Phase Linear, White Oak 500

[mlucitt]

I like how that DC protect board looks like it was designed to fit right in that space. Nicely done.

 

[laatsch55]

It was designed to fit right in there. It was made to bolt right to the existing speaker posts. It also has provisions for the Zoebel network as those have to go when this is added. The Z network is built into the protect board. It's actually pretty ingenious. the 700 board is the same basic idea. Bolts to the speaker posts. Don Imlay (wattsabundant) builds them.

 

[laatsch55]

Anita is getting new outputs tonight. On-Semi- MJ 15024's for drivers, MJ-21194's as outputs. The bottom pic is a very big no-no. Some one has used the same device for a driver as well as an output, not only that but has mixed different devices in the same channel. And used an inferior device to boot-the 15022.

 

[laatsch55]

BTW Sutton, the left, negative rail driver was shorted. I take it this was a non-worker??

 

[laatsch55]

And the left positive rail driver was also shorted.

 

[laatsch55]

Outputs in. I hate those chintzy standoffs PL used, so in goes a set of 1/4 inch hex, with stainless allen heads holding them to the chassis.

 

[laatsch55]

The 150 ohm resistor soldered to the emitter and base of the aforementioned shorted driver. This resistor measures wayyyyy out of spec and appears to have been hot enough to start taking the coating off. I would hazard a guess the 2 failures are related!! How's that for going out on a limb!!??

 

[laatsch55]

The toasty looking resistor measured 3.2 MEGOHMS, the other 151.2. Beins both drivers were shorted, both resistors got replaced.

 

[laatsch55]

Board is in, time to test.

 

[laatsch55]

Brought it up on the DBT and variac and no bias on the left channel. What got the drivers and resistors I am assuming got the bias tranny (Q6). R&R'd the Q6 and everything is fine on the left now. .330-.360 Volts DC on each channel with the bias pots dead center, cool how ya made that work out Joe!! 2.3MV-DC offset on the left channel, 14.2 MV DC offset on the right channel.
Power supply transformer neither hot nor cold, straight up average at 79.7 Volts DC on the positive, and -79.6 on the negative.

Load test tomorrow evening.

 

[Gibsonian]

Do the new boards have pots for adjustment of the dc offset as the original boards have?

 

[mlucitt]

Isn't it funny how those toasted parts jump out at you when the amp doesn't quite work the way it is supposed to???

It looks like you are almost finished with a VERY nice 400.

Mark

 

[laatsch55]

Do the new boards have pots for adjustment of the dc offset as the original boards have?

No Scott they do not. The White Oak board was designed to replace the 14a/b, Pl 020 boards which of course did not have any DC offset adjustment.

 

[laatsch55]

Isn't it funny how those toasted parts jump out at you when the amp doesn't quite work the way it is supposed to???

It looks like you are almost finished with a VERY nice 400.

Mark

Yeah, "Anita" will be a sweetie.

 

[laatsch55]

Unloaded sine waves look excellent, clipping was symmetrical.

 

[laatsch55]

Loaded waveforms, both channels with 8 ohm loads, both driven. AC input-120.8 volts

 

[laatsch55]

One last bias setting then on the speaks it goes.

 

[Elite-ist]

Lee: have you noticed I seem to chime in just as you are about to audio test your latest project? I wish I was there. Paging through the documented work you have done on Sutton's Phase Linear amplifier makes me appreciate electronic technicians for their expertise in working on these old pieces.

Salut!

Nando.

 

[laatsch55]

Thank You ever so much Nando, I hope one of these days you can stop by so i can give you one of those smiles, knowing what is about to hit you...........................................

 

[Elite-ist]

I would probably surprise you with my vigor to be slammed with sound pressure levels you have been so accustomed to since you have become slightly hearing-impaired.

Scenario #1: I exclaim, "Is that it?" as you slightly tilt your head forward to peer out through the top of your eye glasses at me.

Nando.