PL400 Backplane Rev B

[FredR]

Spent most of the long July 4th weekend doing another 400 conversion, this one using Joe's new Rev B backplane with the cool new socket cups. Congratulations to Joe on doing it yet again. Rev B is just outstanding. Fred.

 

[laatsch55]

Rev "B" is only on a 400 so far..

 

[laatsch55]

Fred, you need to review the assembly notes again. Blue wire #3 needs to be relocated to unfused B- just above Pad #3 and to the right.....

 

[laatsch55]

I see you like a 6-32 Allen heads on the voltage regulators too!

 

[FredR]

Fred, you need to review the assembly notes again. Blue wire #3 needs to be relocated to unfused B- just above Pad #3 and to the right.....

Joe fixed that issue with Rev B.

 

[FredR]

This conversion was particularly special since I'm the original owner and we have a lot of history together. See attachments. Being she's extra-special I converted her from a 4 fin to and 8 fin cause she deserved it.

 

[Gepetto]

Very nice work Fred! Congrats
I wonder if mine will be Rev.B too...?

So you want your amp shipped back as a PL400. Ok we have that confirmed

 

[Gepetto]

Fred, you need to review the assembly notes again. Blue wire #3 needs to be relocated to unfused B- just above Pad #3 and to the right.....

Nope, Fred has it right...R6 takes care of that now.

 

[FredR]

Full disclosure: Can't take credit for the control board. Purchase those assembled from Joe. Need to cut project time down as I'm pushing the edge of the WAF right now.

 

[Gepetto]

Hi Joe,
what is the list of improvements in Rev B vs A?

Here are the Release Notes Przem...

View attachment Release notes for PL400_Backplane_RevB PCB.pdf

 

[FredR]

Thank you Joe,
i undersdand that from the improved components perspective, Lee may already put them onto Rev.B blackplane PCB for the PL 700 model? Have to ask him....
Anyway great job!
I installed your driver board Rev.C to my friend 700 II Amp. and the result was stunning. I think that sound was more positively impacted by the driver PCB than by the output stage PCB. Would you agree?

Hi Przem. My experience is limited to the 400 backplane, but knowing both amps I can say that without doubt the PL400 and PL700 backplanes are radically different designs. The PL400 stacks the TO-3s 4 high and the PL700 stacks them 6 high. Also, Joe developed the PL700 backplane quite a while after the first PL400 backplane so I expect that some of the improvements he put into the PL400 Rev B are actually already in the PL700 Rev A. There is no PL700 Rev B that I am aware of. Hope that helps. Fred.

 

[Northwinds]

I would love to convert Sally to a 8 finner but she never gets that hot, even when I have the meters buried. What I would love to figure out is how to adjust the meters so they have a more accurate range. When I bury the needles, it certainly does not sound like 500w because it so clean sounding and I still have more volume knob to go. I think it's because they are calibrated for 200w per channel and I have at least 50w per channel more right?

 

[FredR]

I would love to convert Sally to a 8 finner but she never gets that hot, even when I have the meters buried. What I would love to figure out is how to adjust the meters so they have a more accurate range. When I bury the needles, it certainly does not sound like 500w because it so clean sounding and I still have more volume knob to go. I think it's because they are calibrated for 200w per channel and I have at least 50w per channel more right?

If you have Joe's light board installed it has jumpers to adjust the meter sensitivity.

 

[Gepetto]

Thank you Joe,
i undersdand that from the improved components perspective, Lee may already put them onto Rev.B blackplane PCB for the PL 700 model? Have to ask him....
Anyway great job!
I installed your driver board Rev.C to my friend 700 II Amp. and the result was stunning. I think that sound was more positively impacted by the driver PCB than by the output stage PCB. Would you agree?

Hi Przem

The PL700B backplane kit includes all the component upgrades (Dale resistors) that are in the PL400 Backplane RevB kit so you will definitely get the benefit of those. I informally upgraded these components on the PL400 RevA backplane boards near the end of the RevA kit run as the Dale components became available and were qualified. The socket cups are the only item not currently in the PL700 Kit.

The White Oak Audio standard philosophy is to continuously find, qualify and include the highest quality components and design techniques into the products. Everyone appreciates high quality, especially in vintage amplifier gear that we are trying to keep living on...

 

[laatsch55]

Nope, Fred has it right...R6 takes care of that now.

Suppose I outta assemble one before I lip off eh??