Are power tubes supposed to glow blue....?

I removed the chassis of my Mark IV from the combo today to take a look at the tubes. One of my power tubes is rattling, so I'm pretty sure that has to get replaced, but what made me wonder a bit is that when I went out of stand by mode, all the power tubes had this blueish glow inside. The orange parts were still orange, but that blue was weird, because it was in most of the tube.

These tubes are pretty new by the way.

Yes, it is typical for Russian and some Chinese to have a blue glow like you described. As long as you are not getting "Fire Cracker" sounds or it sounds like loud radio static when you switch from standby to on, all is well.

fishyfishfish said:

Yes, it is typical for Russian and some Chinese to have a blue glow like you described. As long as you are not getting "Fire Cracker" sounds or it sounds like loud radio static when you switch from standby to on, all is well.

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Actually, there is a slight crackle... But the tube actually rattles after going out of standby mode. I already wrote TubeDepot about it, seeing as I just got the tubes like 3 weeks ago! I also get some weird staticky crap when playing sometimes. A good whack on the amp fixes it until I start playing again though.

Get the tubes replaced. I think the Depot has a good return policy and it shouldn't be a problem. Pop the old set in and see if that clears it up.

fishyfishfish said:

Get the tubes replaced. I think the Depot has a good return policy and it shouldn't be a problem. Pop the old set in and see if that clears it up.

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The old set was original I believe... From 91... So these are the replacements for the humming tubes with burn marks on the inside


I know they have a 90 day warranty, so I already contacted them. I'll see what their reply is tomorrow.

Blue glow in power tubes is normal and not just "typical" of any particular brand or place of origin.I have many different NOS tubes that have the blue glow.Has nothing to do with your rattle or crackle sounds,that is an unrelated condition.

fishyfishfish said:

Get the tubes replaced. I think the Depot has a good return policy and it shouldn't be a problem. Pop the old set in and see if that clears it up.

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I got a very friendly reply today telling me that they'll exchange the defective tube or both from the set. The guy that replied happened to be a fellow Mark IV owner!

stokes said:

Blue glow in power tubes is normal and not just "typical" of any particular brand or place of origin.I have many different NOS tubes that have the blue glow.Has nothing to do with your rattle or crackle sounds,that is an unrelated condition.

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Thanks! You really have been offering a lot of information lately. I'm glad the blue glow isn't bad, because to be honest it looks pretty badass.