PL 400 series 1 XPL910 questions

Q

quirkaudio

New Around These Parts
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Jan 11, 2021
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Hi
I have a PL400 series 1 with XPL 910 outputs, two of which appear to be fried. I have purchased an installed the White Oak Cap replacements and purchased, and not yet installed, the watts abundant speaker protection.

I understand that one needs to replace all the transistors in one channel , so is there a suitable substitute ( these are darlington transistors),- both the fried were on the same channel, and all drivers transistors (RCA) test OK.

alternatively if I install the white oak PL14 replacement board and the white oak backplane board, what outputs can I install?

I used to have one of these back in the day, but this is the first one I have worked on- and my first post here

Thanks in advance for any and all assistance

btw the amp has a "diane" sticker under the PL14 board- what is this?

Peter
 
Except for the RCA410 drivers in the bottom row, replace all those original transistors with MJ21196G output devices. 12 of them.

The originals are junk Peter.
 
Dianne is the lady who wired your amp. There is a Phase Linear Christmas Card photo somewhere on this site with a photo of the "crew" and identifying names. Can someone post a link as I have looked many times and can't find it again. Perhaps Dianne is in the photo. Linda and many others are.
 
George S. said:
Dianne is the lady who wired your amp. There is a Phase Linear Christmas Card photo somewhere on this site with a photo of the "crew" and identifying names. Can someone post a link as I have looked many times and can't find it again. Perhaps Dianne is in the photo. Linda and many others are.
Click to expand...

Even if we gut the amp to bare chassis, we keep the original sticker in it. It's a way to honor the person who originally brought the amp to life.
 
Diane sticker will remain untouched.

I have opted to put the WO PL14 board in and will post some photo's when done
Thanks agian
 
I have the White Oak board and the MJ21196G transistors, should I wire the WO PL14 board for qausicomp or fully comp?

thanks
 
Hi- So I have assembled the board and installed it into the PL400, with all the output and TO3 driver transistors removed. I then, following the instructions provided, set the board up for testing, removing the cables as described by white oak, inserting the bridges, and the two 47ohm resistors per channel. They suggest bringing it up on a variac (I have a Sencore PR57), and state that pin 6 on the board should be 0 volts or a few mv (less than 15).

When I did this (probably did not get to more that AC 20v or so on the variac, I was getting 3v-4v DC on pin 6- which seems very wrong!
This suggests that pin6 (the output) is seeing the rail voltage- which is a very good way to create magic smoke.

I think I must be doing something not clever- any thoughts?
 
Until the front end reaches a certain voltage, around 60 volts, it will not turn.on....do you have a dim bulb tester in line too?
 
Thanks @laatsch55 - I did wonder, I generally just use the sencore, and watch the amperage- which is a very good indication of if there is a problem.

So perhaps set up for ~ 60v AC and then measure pin 6?
 
Yep, but remember a variac will not limit current....watch the voltage on pin 6. Do you have a DC protect board in there??
 
Not as yet- I am planning to install the speaker protection board after the white oak tests OK. However there are no output transistors or driver transistors fitted as yet.

So if I use the variac and bring it up form zero, I should expect the voltage on pin 6 to rise and then as the devices conduct fall back towards zero?

Thanks again for your help

Peter
 
I've also seen the front end come into regulation as low as 40 volts..
 
I have run the unit at 60v (0 on pin 6 both channels) and then at 120v (0v on the right and 15.17v on the left).
Checking the diodes/transistors for correct positioning and all look OK

I am thinking Q7 or Q8 as the likely culprits?
 
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