Red Plateing question

[Mooncusser]

Hi guys,

I have a simple question for you.....
It is about red plateing. The reason I ask is because I have never seen it.
As I understand it, normal tube operation will allow you to see a nice healthy glow in the tube, accompanied by a slight blue hue as well.
Logic tells me that red plateing is when the actual plates begin to glow red, which is a bad sign of a series of problems, no?

Thanks on the help with me understanding this....
All the best,
Mass

[Blue Strat]

You're right. If you've ever seen a piece of metal in a fire get so hot that it glows red, that's what redplating looks like.

[da-boogieman]

Hi Mass,

I know you hang out here and at Metro amp but you may have missed the picture of red-plating in the thread.

See justonwu thread:
http://www.thegearpage.net/board/showthread.php?t=193340

There is a good jpg of red-plating there if you can wade through the pages!

[John Phillips]

I'm sure justonwo won't mind us using his very good pic...

http://www.the-byline.com/misc/Misc%20005%20small.JPG

This is red-plating, seen in a darkened room.

If you can see it in daylight, you're really in trouble...

The 'ribs showing' effect is very typical in pentodes, it's caused by the suppressor grid wires protecting the plate slightly.

[justonwo]

Sadly, I'm famous around here now for red plating. I still think it should be called orange plating though. Red comes at a higher, and more fatal temperature. :-(

[Mooncusser]

Thats exactly what I thought and as a 14 year plumber/pipe fitter/gas fitter/ OB Tech, I could probably write several compilations on metal in different states of heat.....:D

Even though that was probably an overly simple question.....thanks guys for helping me there.
All the best,
Mass

[Chris Scott]

Sadly, I'm famous around here now for red plating. I still think it should be called orange plating though. Red comes at a higher, and more fatal temperature. :-(

justonwo-

I wouldn't say sadly!! (although it's easy for me to say) I'm here to tell ya that the thread you started turned into one of the absolute best I've EVER read. John, Mike, and others contributed so much usable info, and I think you should be commended for such a thorough presentation of the data you collected- that was a hell of a ride!!

I hope your build is working better--
Chris

[justonwo]

Thanks, Chris. It's good to hear that the information has been so useful to others. But the thanks should really be directed at John Phillips, Randall Aiken, and others who were so generous with their time and feedback. I owe you guys a big debt of gratitude.

[LesPaulMan]

Yeah, that was a great thread.

I actually found the thread as I have a Marshall clone that is redplating at 3/4 volume. 448 Volts biased to about 32.8 = about 60% dissipation. I'm going to reduce it to about 50% and prey that it goes away. (As I don't want to lug around my variac either.) LOL

[justonwo]

Yeah, that was a great thread.

I actually found the thread as I have a Marshall clone that is redplating at 3/4 volume. 448 Volts biased to about 32.8 = about 60% dissipation. I'm going to reduce it to about 50% and prey that it goes away. (As I don't want to lug around my variac either.) LOL

Did you build it or buy it? What brand tubes are you using?

[LesPaulMan]

I bought the amp. The tubes are mid 90's Svetlana's with very little use on them. It's a pretty sturdy tube, but doesn't like full volume operation on this amp. I actually tried some new JJ KT-77's and didn't get any redplating. Problem is that I like the sound of the 34's better.

[justonwo]

Mid 90s Svets are the same as the SEDs that I tried, and those red plated pretty badly. You can try JJs. My experience is that they help significantly. Apparently, EH 6CA7s do really well, too, perhaps better than the JJs.