Phase 400 rebuild

[R1200S]

To give you an idea on a Variac. I snagged a used one off eBay back in April for $89. It was an old Superior Electric, Powerstat 126. Runs 0V to 140V
WITH new brushes and its original paperwork! Shipping was $20 since those things are heavy! I think a new one would be double that price at the very least. Set up an eBay search with the parameters you want and then set it so their system emails you when new Variacs are listed on the site.
I have no experience with all the imported units out there but I have to say that Superior unit is a tank!! Made in the USA baby!
Let me know if you need any help setting up that search.

 

[WOPL Sniffer]

I have gotten by over the years without a Variac. Never thought about it. Is everybody here using them? With a new build (or replacing the guts in an old one) I thought the DBT would suffice for finding any big problems. I know on the older shit you may want to run a variac if the equipment was sitting idle for ages so as not to "shock the system" (old crusty caps go boom)...... JMsHittyOpinion...

 

[laatsch55]

Perry, the optimal combination is running the DBT through the variac with the DUT running through the DBT. A variac will limit voltage BUT NOT current, and with the DBT limiting current, ya got both covered. Some amps such as the Spec 2 have protection circuits that will jack off with a DBT so a variac alone has it's uses...

 

[WOPL Sniffer]

Some say it's overkill, some not. I'm just your average Joe (sorry Joe) and I yield to the guru's.... (still won't run a variac but I yield)....

 

[laatsch55]

Threy also make a great variable DC power supply if a guy gets in a bind...

 

[MarkWComer]

(maybe Mark can steer me in the right direction to build such a test apparatus)?

Building the DBT is here: https://www.youtube.com/watch?v=83WSNeOsFJs Some people make theirs with a ceiling light fixture, but this one just uses a plug-in table lamp.

When ordering the variac, make sure it handles 10A of current or more. I found a cheap-o on ebay but found it wouldn't have handled the load (so then I found another one on ebay...).

Probably order the assembled driver board and add it next and then the transistor updates last.

Watch how you're doing that- the driver boards and the backplane boards can be assembled in two different ways depending on what you're doing with the transistors! As your PL400 came to you, more than likely ALL of the transistors are NPN (this is a quasi-complimentary design). When building the upgrades, you have the choice of staying with the quasi-comp design or going full-complimentary with brand new shiny transistors of higher quality (am I steering you in the right direction?). The full-comp design uses a combination of NPN and PNP transistors and are much quieter than the old automotive transistors that PL installed at the factory.

 

[Dchristie]

Just bought my 2nd PL400 so now all I have to do is wait on the White Oak parts and DC protection relays to arrive. I figured I would go ahead and do both amps at the same time and since I will be messing with one , might as well do the other. So my next question for those who have done the WO PL400 mods, is there a logical procession I should follow as I rebuild the amp as I go from one modification to the next. I know there will be integrity tests that will have to be performed throughout the process so are any of the testing procedures dependent on the completion of one mod prior to the testing of the other or can each mod be worked on independently and then tested and then go on to the next?


Thanks

Dean

 

[MarkWComer]

can each mod be worked on independently and then tested and then go on to the next?

You don't have to do everything all at once. I did the control board and DC protect board first because it's what I had the money for, then the capacitors, and last of all, the backplanes. When I went on to the backplanes I had to modify the control board a little bit because I went to the full comp transistor set.

 

[Dchristie]

Firstly, I am sure this has been reported before, but are the WOPL400 amps pretty consistent regarding the final specifications from amp to amp since all of the critical components have been replaced with much more superior parts?

And secondly, can someone please list what a typical WOPL400 specs out at regarding distortion and power output into various loads ?

And finally, are the amps stable into electrostatic speakers and less than 4 ohm loads?

Thanks

Dean

 

[Northwinds]

Lee or Joe will probably post the specs

Under 4ohm loads is a no no. I suppose Joe could make it work but I am thinking it would require a LOT more heatsink area?

 

[laatsch55]

My bud Stepen in Phoenix ran The Pig on 2 ohms for months. It requires A LOT of cooling , and it had copper heatsinks....

 

[Fishoz]

Firstly, I am sure this has been reported before, but are the WOPL400 amps pretty consistent regarding the final specifications from amp to amp since all of the critical components have been replaced with much more superior parts?

And secondly, can someone please list what a typical WOPL400 specs out at regarding distortion and power output into various loads ?

And finally, are the amps stable into electrostatic speakers and less than 4 ohm loads?

Thanks

Dean

Lee, I'm pretty sure you have my spec book still on file. You have my permission to forward to Dchristie if you wish.

 

[laatsch55]

Firstly, I am sure this has been reported before, but are the WOPL400 amps pretty consistent regarding the final specifications from amp to amp since all of the critical components have been replaced with much more superior parts?

And secondly, can someone please list what a typical WOPL400 specs out at regarding distortion and power output into various loads ?

And finally, are the amps stable into electrostatic speakers and less than 4 ohm loads?

Thanks

Dean

The output power is pretty much dependent on rail voltage and thus transformer secondary voltage.
THD & N will be pretty consistent. Residual noise depends, to a certain extent, on your wire discipline. If wired to Joe's grounding scheme, were talking 200 to 400 MICROVOLTS....

If you plan on pushing difficult speakers hard, go with a 700. And have very good fans moving lots of air...

The amps original SOA limiting circuit has been improved by Joe. They really are (almost) bulletproof. If the SOA limiting circuit is not disabled and you don't mess with the fuse ratings you really can't hurt them. And saying that someone will find a way......that's my job....

 

[laatsch55]

Lee, I'm pretty sure you have my spec book still on file. You have my permission to forward to Dchristie if you wish.

They are also posted in your build thread......like all of em.....

 

[drummergrl]

My bud Stepen in Phoenix ran The Pig on 2 ohms for months. It requires A LOT of cooling , and it had copper heatsinks....

What Pig you talkin' about? I have The Pig. There's another Pig?

 

[laatsch55]

Nope, you have the one and only. He had quite a life before you...

 

[drummergrl]

He had copper heatsinks?

 

[drummergrl]

And I'm confused, I had to wait for you to build The Pig. What incarnation was he in when your friend had him?

 

[laatsch55]

Yep, he had copper heatsinks at one time. I was experimenting with copper heatsinks and how to build them before I built 2 sets for Ed Blackwood. Tony (blaze ES ) has a set on his lottery amp, and my bud Stephen has a set on his 400.

Stephen had the Pig while I was building a 400 for him. It was in the form you have now, minus the copper heatsinks. He lost his copper heatsinks to the last lottery amp a year before you got yours..,


He was the Guinea Pig, he took a lot of abuse.....

 

[laatsch55]

The reason you got the Pig is because I felt bad about how long it was taking, So I threw a facerplate and meters from another amp on im. He spent most his life without a faceplate..