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

MarkWComer

Veteran and General Yakker
Joined
Nov 1, 2014
Messages
3,198
Location
Gaston, SC
Tagline
Victim of the record bug since age five
#61
Minimum order on SilPads is...
7,200?
Minimum order on the bridge rectifier was 1,000.
(Digi-Key)
 
Last edited:

MarkWComer

Veteran and General Yakker
Joined
Nov 1, 2014
Messages
3,198
Location
Gaston, SC
Tagline
Victim of the record bug since age five
#68
Control board built:

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

laatsch55

Administrator,
Staff member
Joined
Jan 14, 2011
Messages
74,124
Location
Gillette, Wyo.
Tagline
Halfbiass...Electron Herder and Backass Woof
#70
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

Veteran and General Yakker
Joined
Nov 1, 2014
Messages
3,198
Location
Gaston, SC
Tagline
Victim of the record bug since age five
#73
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...
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

Chief Journeyman
Joined
Sep 8, 2012
Messages
845
#74
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!
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
 

Gepetto

Administrator
Staff member
Joined
May 15, 2011
Messages
13,473
Location
Sterling, MA
Tagline
Old 'Arn Enthusiast
#75
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...
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

Veteran and General Yakker
Joined
Nov 1, 2014
Messages
3,198
Location
Gaston, SC
Tagline
Victim of the record bug since age five
#76
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
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!
 
Last edited:

MarkWComer

Veteran and General Yakker
Joined
Nov 1, 2014
Messages
3,198
Location
Gaston, SC
Tagline
Victim of the record bug since age five
#77
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

Veteran and General Yakker
Joined
Nov 1, 2014
Messages
3,198
Location
Gaston, SC
Tagline
Victim of the record bug since age five
#78
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

Veteran and General Yakker
Joined
Nov 1, 2014
Messages
3,198
Location
Gaston, SC
Tagline
Victim of the record bug since age five
#80
I did put a dab of thermal compound on the TO-220s on the driver board...
 
Top