Kenny Nelson's WOPL 400 conversion.

Lee is apparently getting close to making it live again Mark. He can rebuild it :-) he has the technology!
 
That oscillation was what happened with the 410's I originally pulled out of my 700 series I. Replaced with the MJ15024's.

Haven't seen what the best combo is for a 400 yet (anyone? Joe.. Lee Mark?), but I may be getting one soon to rebuild. Got the WO stuff lined up, but haven't heard a peep back from Don yet???:sad4:
 
Lee has something going on her Jer that needs to be fixed so you should not judge what to use by this particular case (yet).
 
Agreed, Lee has some technology (that awesome ATS-1 among others). This is the newer one:
 

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Gepetto said:
Lee has something going on her Jer that needs to be fixed so you should not judge what to use by this particular case (yet).
Click to expand...

Nah, was just asking in general since I've yet to get parts for it. With R2's blowin' I'd say there's some multiple issues going on there - how DO you get that much current back up through the ground especially in both channels without.... hmmmm...

If the oscillation's hitting all the way up to the rails, then feeding back via the +/- 20 regulated via C23, that could be of enough amplitude, no? That's also perhaps assuming there is NOT a good ground via 5L/5R - which could cause BOTH symptoms. Was BOTH 5L AND 5R verified to be properly grounded??? AND.. has that been verified with both unfused +/- rails disconnected PLUS the rail fuses pulled??

Just a theory... that and the suggestion of mica's going south with this post back a few pages (just another way of saying the same thing... )

http://forums.phxaudiotape.com/show...elson-s-WOPL-400-conversion?p=60814#post60814
 
I learned long ago Jer to let the data come in first before forming an opinion. When you have been around as long as I, I have seen just about every wierd condition come up that you would not expect to see.

I figured Lee was putting in the 2.7M ohm resistors, not the 2.7 ohm ones. Just kidding Lee.
 
I figure you need on the order of 430 mA flowing through each R2 to blow open a 2.7 ohm 1/4W resistor. And there are 2 of them in parallel which would put the current up around 0.85A to do this, at least for the first resistor. The second blows more easily after the first one ruptures.

I am thinking more an external equipment ground loop than internal to the amp.

Rule #1
Check your test equipment setup first.
Rule #2
Refer to rule #1
 
Ok back at it. With the first 21194 replaced we have the weird sinewave, fixin to pull it and put in the next one.
 
Lee did you strip both the bottom and top back to the RCA410's? If you are putting only one MJ21194 in, which position are you installing it in?
 
Ok, second used 21194 in the first output socket from the driver looks way good to 5 watts, then it gets a little shaky, like maybe a low level oscillation, although can't feel it or hear it. Gonna go with another used 21194 as the second output. hang on...
 
Third used 21194 in the 2nd output socket caused it to go funky at 15 mv input.
 
I suppose the bottom half shopuld have the same number of outputs eh??
 
laatsch55 said:
I suppose the bottom half shopuld have the same number of outputs eh??
Click to expand...

Yes Lee, that strip down to the predriver trick does not work when you start adding outputs assymetrically.


It seems you may have some compromised devices however based on the significant differences you are seeing.
 
With new 21194's in the Q13,Q14 sockets, nice and solid to 30 watts. Second pair going in.
 
Lee
You might find that the compromised MJ21194s turn up leaky at higher voltage. You will need a high voltage lab power supply to test for that.
 
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