# Are my tubes red plating?



## JimiGuy7 (Jan 10, 2008)

Hi all, just have a question about the state of my new power tubes. I recently replaced the tubes in my super and am just wondering if they look okay to your eyes. I own a bias probe and I biased the amp, so it is set at the correct setting and the amp sounds great and is'nt making any odd noises. They seem to look like they are glowing orange to me, I don't see the normal red I find in pictures of red hot tubes. It doesn't seem to be running too hot so I think it is running properly. I am just curious as to what you think as I have never seen a tube red plate with my own eyes. Sorry about the picures, but it is the best I could do and the do seem to represent the colour of the center plate (if that is what it is called LOL). 

http://i718.photobucket.com/albums/ww184/JimiGuy7/DSCF0171_zps3f7efda1.jpg

http://i718.photobucket.com/albums/ww184/JimiGuy7/DSCF0174_zps6613228f.jpg

http://i718.photobucket.com/albums/ww184/JimiGuy7/DSCF0170_zps71e9719f.jpg


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## WCGill (Mar 27, 2009)

I don't see any red-plating. If the grey metal of the plate, which is the dominant visible structure inside the glass, starts to glow cherry red, then you have a problem. Do a google search and look at the images that come up, worth a thousand or so words.


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## zdogma (Mar 21, 2006)

Here's a pic:

http://s948.photobucket.com/user/aluevano2299/media/2011-04-15_12-25-14_753.jpg.html

I've had it happen a couple of times and it usually pretty dramatic.


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## JimiGuy7 (Jan 10, 2008)

Sweet, I thought so. I changed the bias balance to a bias adjust, and just wanted to be sure everything looks okay. I went out last night though, and noticed a small amount of hum that sounds a bit like 60 cycle, even though I am using HB's. I am wondering where that could possibly be coming from. Anyone have any ideas?


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## guitarman2 (Aug 25, 2006)

Definitely not redplating. I'm having an issue with my amp right now where one tube is redplating. I think I have a blown Plate stopper resistor that happenned when the tube in that socket shorted.


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## jb welder (Sep 14, 2010)

JimiGuy7 said:


> Sweet, I thought so. I changed the bias balance to a bias adjust, and just wanted to be sure everything looks okay. I went out last night though, and noticed a small amount of hum that sounds a bit like 60 cycle


 Is this a silverface that had the bias balance which is used to null out the hum? If so, that may be where the hum is coming from. Ideally, you want bias adjust _and_ balance. You can buy matched tubes, but the circuit is not necessarily matched.
Try swapping the output tubes around and see if it has any effect on the hum.


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## dtsaudio (Apr 15, 2009)

> Plate stopper resistor


That's a Grid Stopper.



> sounds a bit like 60 cycle


Was the hum there before you changed output tubes? Also did you change the bias trimmer at the same time as replacing the output tubes?

- - - Updated - - -

jb beat me to it. It's possible that the output tubes are not balanced. When that happens any hum present does not cancel completely in the output transfomer and you get an audible hum.


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