Mark goes at it again... just bought a PL700/II!

MarkWComer

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Minimum order on SilPads is...
7,200?​
Minimum order on the bridge rectifier was 1,000.
(Digi-Key)
 
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MarkWComer

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Control board built:

And an arrogant putz ragging me about the zero ohm resistor (see the comments here):
 
laatsch55

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Mark, did Joe explain the reasoning behind the zero ohm resistor? In this application it acts as a fusible link. And it works...with a catastrophic failure in the output stage it prevents additional (some) damage to the driver board. I've had it happen...
 
MarkWComer

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laatsch55 said:
Mark, did Joe explain the reasoning behind the zero ohm resistor? In this application it acts as a fusible link. And it works...with a catastrophic failure in the output stage it prevents additional (some) damage to the driver board. I've had it happen...
Click to expand...
No, Joe didn’t explain, but after looking at the change history about reducing the load on one of the voltage regulators I figured it out. Yeah, the pompous ass was correct about the fuse thing, having a weak point to direct failure to a specific point. Maybe a picofuse isn’t available for the certain amperage/voltage necessary to direct that failure to that specific area- don’t know, but one thing for sure is that Joe has the cerebral horespower to design the circuit and I DO NOT! I’m convinced that he knows what he’s doing.

I thought the .33Ω (previously .22Ω) emitter resistors were damn close to not being a resistor at all and thought to myself that they were close to being moot, so to see something with an even lower value just hit my brain sideways!

Wow- the things I’ve learned from you guys over the last few years...
 
oldphaser

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MarkWComer said:
I thought the .33Ω (previously .22Ω) emitter resistors were damn close to not being a resistor at all and thought to myself that they were close to being moot, so to see something with an even lower value just hit my brain sideways!
Click to expand...
When you get a chance, in order to gain a better understanding of the purpose of an emitter resistor, perform a search on the internet for "emitter degeneration".

Ed
 
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MarkWComer said:
No, Joe didn’t explain, but after looking at the change history about reducing the load on one of the voltage regulators I figured it out. Yeah, the pompous ass was correct about the fuse thing, having a weak point to direct failure to a specific point. Maybe a picofuse isn’t available for the certain amperage/voltage necessary to direct that failure to that specific area- don’t know, but one thing for sure is that Joe has the cerebral horespower to design the circuit and I DO NOT! I’m convinced that he knows what he’s doing.

I thought the .33Ω (previously .22Ω) emitter resistors were damn close to not being a resistor at all and thought to myself that they were close to being moot, so to see something with an even lower value just hit my brain sideways!

Wow- the things I’ve learned from you guys over the last few years...
Click to expand...
You are a funny guy Mark. I enjoy your videos a lot, I remember the first one I viewed was when I was traveling in Taipei a long time ago.

Maybe we should discuss the tempco on that zero ohm resistor in addition to the tolerance :)
 
MarkWComer

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oldphaser said:
When you get a chance, in order to gain a better understanding of the purpose of an emitter resistor, perform a search on the internet for "emitter degeneration".

Ed
Click to expand...
Well, well! New connections in my synapses are always welcome!

Gain will be different from device to device, gain decreases slightly but bandwidth is smoother. A little negative feedback goes a long way. Above my understanding by a mile, but I understand the basic concept.

Thanks!

Oh- thanks for the link to the PL Lynnwood page, too!
 
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MarkWComer

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A little update...
Ordered the rectifier, snubber caps, and PNP/NPNs from Mouser today. Sil-Pads are backordered.
After hemming and hawing, decided NOT to use the existing NPNs already on the 700- don't know what abuse they've been subjected to, don't wanna take the chance on them.
 
MarkWComer

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Hey- a little question- thermal compound on the TO-5s? Should I think about that? The transistors on the back of this unit have a lot on them from whomever upgraded/repaired it last time. Didn't do that on the 400.

Is ONE SilPad per transistor OK?
 
MarkWComer

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I did put a dab of thermal compound on the TO-220s on the driver board...
 
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