MJ21196G buy anybody?

If anybody doesnt want to use NEC outputs I'll swap 2 XPL909's for each NEC that hasn't shorted. I'm not sure what weak output means, but the malfunction is likely not the output transistors.

I also don't believe in replacing bridge rectifiers that haven't failed. I may have seen one 25 amp bridge rectifier fail. Several that endured foil wrapped around the fuses. Perry can probably justify it for what he's selling, but it doesn't improve reliability.
 
mlucitt said:
Working to upgrade these amplifiers is a slippery slope. You upgrade the ten output transistors to keep them from failing, but think, hey - I'll just replace them all so the amp can 'breathe' a little better and you find out that the best way to exploit the new capability of your higher gain outputs is to install a new WOA Control board. Then you find yourself in WIIT (while I'm in there...) mode, so you upgrade the bulk capacitors and the ancient bridge rectifier. Then you decide, hey I'm already 90% there, so let's install the Backplane Boards. And now you have a WOPL, as Perry would say.
I would change out the 2SD555 devices, but not because they are ticking time bombs. Who cares, you only need the transformer and the heat sinks; everything else is available to you. I would change them because the ON Semi MJ21195G/MJ21196G output transistors are just so much better. Then you can also get rid of the mica and grease, and install the Bergquist Sil-Pads that make changing the transistors so much easier.
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I’d be glad to get on the wagon here then and reach out to anyone who’d like to offer the MJ’s or at least a good place they get them from. Sorry I derailed the OP a bit. I’d also like to obtain those sil-pads too. I am leaning in the direction of starting on the PL400 My father has. It’s completely kaput. Blows rail fuses. I figure start small and work my way up. He likes the 400 so much more (why I have no idea). So anything that WO does not offer. New RCA’s, bridge rectifier, snubber caps; you know, the tiny little things that anyone who upgrades to a WO also does “while they’re in there”. Might as well go Full Monty for him. :)
 
There is a thread over in WOPL Building that has a shitload of part numbers listed... You COULD look there
 
Gepetto said:
You only need the transformer and meters, everything else is available to you including the heat sinks.
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Well heck. You know I never even noticed the Transistors and Sil pads were a line item on the WO parts list before? But there they are. Now I know where I’m sourcing them from. Then again five years ago was the last time I actually ordered something more than a light board. Back then there were no backplane boards, or chasis’ or heat sinks or face plates etc. It’s so amazing how far the upgrades have come in just that window. I await the day WO starts doing their own transformer windings and making their own meters! At that point.....you can iust BUY the amp as a whole. Maybe open up a WO factory and start building direct to consumer? Hah I kid of course but that’s not too far off considering it’s all pretty much there?

Looking forward to your boards to arrive today. My brother brought over his two 700B’s since he wants the same thing done to HIS. Sitting on the fireplace there currently waiting. He said now I have enough amps to power A stadium event. I told him well not just yet. But with these new boards; it’ll be one heck of a “Light Show”. :cool:

3F9E9DA5-D828-4032-BAF6-A061EA47F4C6.jpeg
 
wattsabundant said:
If anybody doesnt want to use NEC outputs I'll swap 2 XPL909's for each NEC that hasn't shorted. I'm not sure what weak output means, but the malfunction is likely not the output transistors.

I also don't believe in replacing bridge rectifiers that haven't failed. I may have seen one 25 amp bridge rectifier fail. Several that endured foil wrapped around the fuses. Perry can probably justify it for what he's selling, but it doesn't improve reliability.
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Don, a new rectifier is $4.00

If the rest of the amp is new, why wouldn't you replace it?
 
Phase Linear Phanatic said:
Well heck. You know I never even noticed the Transistors and Sil pads were a line item on the WO parts list before? But there they are. Now I know where I’m sourcing them from. Then again five years ago was the last time I actually ordered something more than a light board. Back then there were no backplane boards, or chasis’ or heat sinks or face plates etc. It’s so amazing how far the upgrades have come in just that window. I await the day WO starts doing their own transformer windings and making their own meters! At that point.....you can iust BUY the amp as a whole. Maybe open up a WO factory and start building direct to consumer? Hah I kid of course but that’s not too far off considering it’s all pretty much there?

Looking forward to your boards to arrive today. My brother brought over his two 700B’s since he wants the same thing done to HIS. Sitting on the fireplace there currently waiting. He said now I have enough amps to power A stadium event. I told him well not just yet. But with these new boards; it’ll be one heck of a “Light Show”. :cool:

View attachment 45685
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Just keep watching David...
 
it's 40 years old, and a new one is $4 woooopieeeeee bad or not, if you were building a new engine for a customers car, would you keep the 50 year old cam EVEN if it was in spec???? Not me. My customer would fire me for being a cheese weenie
 
WOPL Sniffer said:
it's 40 years old, and a new one is $4 woooopieeeeee bad or not, if you were building a new engine for a customers car, would you keep the 50 year old cam EVEN if it was in spec???? Not me. My customer would fire me for being a cheese weenie
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“Cheese Weenie”. Okay; that’s the funniest thing I’ve read in a while. In this particular case, I’m afraid I have to agree with Perry. I bought a pack of 4 from Mouser along with snubber caps yeeeeears ago when I was upgrading my 700B while changing out the bulk caps. It was so cost effective I figured why not? I was tearing everything else out? I’d aiken it to going to have your car detailed, and having the exterior waxed, the interior polished, but leaving the floor matts unvacummed and dirty. Just while you are in there, why not? But that’s just ME. If i’m paying hundreds for new boards, I’m paying $4 for a rectifier. It costs me More to have a burger and fries for lunch. And in the end; I don’t even get to keep that...........It’s the principal...
 
Phase Linear Phanatic said:
By the way; while on that subject.........seriously educate me here. 39000uF? How do these actually FIT in a 700? I have yet to see anyone HERE talk about using caps like these?
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Size is the limiting factor. When you consider that you cannot go below 100VDC, you look for the highest MFD rating that will fit. Back in 1970, about 9,800 MFD was the highest rating that would fit in the space provided. Today, with modern materials and manufacturing technology, you can have 15,000 MFD and a plus up in voltage to 160 VDC that fits in the same space.
Don't forget they added this warning in 1979:
1979 Capacitor.jpg
 
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