What is this power tube issue?

  • Thread starter Thread starter Mr. Willy
  • Start date Start date
The Sovtek labelled wafer bottom tube pictured next to the big black bottom is a REBRANDED real military tube. Forget the bottoms, look at the plates. Notice the wafer bottom has silver printing. These are the old ones, same as the 6P3S-E in the eBay link I sent you. They are night and day better than the others. Go check out some HiFi forums, they are compared to Mullard EL-34’s in those circles.
 
Nigel said:
The Sovtek labelled wafer bottom tube pictured next to the big black bottom is a REBRANDED real military tube. Forget the bottoms, look at the plates. Notice the wafer bottom has silver printing. These are the old ones, same as the 6P3S-E in the eBay link I sent you. They are night and day better than the others. Go check out some HiFi forums, they are compared to Mullard EL-34’s in those circles.
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I don’t doubt that those are killer in certain applications. They may be better than the ‘other’ wafer Sovteks. I’ll have to check my stash. But, tubes that kill in multiple amp circuits (Winged C, GE, Sylvania) may only sound ok in others. The Naylor I had was ok with Winged C 6L6 but killed with the black label Sovteks. Each amp does different things, at this point I can say with certainty that old Marshalls love Winged C, Siemens and vintage Mullard 34s. SLOs love cheap Sovtek wafer bottom 5881s. So do Naylors. I’ll have to look into the silver label 5881s.
 
Racerxrated said:
I don’t doubt that those are killer in certain applications. They may be better than the ‘other’ wafer Sovteks. I’ll have to check my stash. But, tubes that kill in multiple amp circuits (Winged C, GE, Sylvania) may only sound ok in others. The Naylor I had was ok with Winged C 6L6 but killed with the black label Sovteks. Each amp does different things, at this point I can say with certainty that old Marshalls love Winged C, Siemens and vintage Mullard 34s. SLOs love cheap Sovtek wafer bottom 5881s. So do Naylors. I’ll have to look into the silver label 5881s.
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The cheap black letter Sovteks are just lower value/cheaper knock-offs of the real deal. I’ve had both, and can say without hesitation that the new ones are trash compared to the old glory. 🗑

You will rediscover the joy of your amp and come here singing praises in Russian, friend. That much I can tell you!
 
Nigel said:
The cheap black letter Sovteks are just lower value/cheaper knock-offs of the real deal. I’ve had both, and can say without hesitation that the new ones are trash compared to the old glory. 🗑

You will rediscover the joy of your amp and come here singing praises in Russian, friend. That much I can tell you!
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This is a new one. I hadn’t heard this before; all I know is the lower priced Sovtek 5881s happen to sound best AND handle high plate voltages of SLOs, Coliseums etc. so they are a nice inexpensive choice for 6L6 amps. I’ll have to look in to picking up a quad or two.
 
Mr. Willy said:
I’m not sure when or if the sockets have been cleaned. It’s a ‘92.
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Didn't you mention you're in the southeast? Lot's of humidity, right?
Definitely not the best for metal to metal contacts.
 
Nigel said:
Forget the bottoms, look at the plates.
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Any significance to the differences here?

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Don't spray Deoxit inside your amp.
That stuff promotes conductivity and doesn't really evaporate which can have disastrous effects.
If need be spray "contact cleaner" on tube pins then gently work the tube in & out of the socket.
Deoxit will also fry the wiper of a pot that has that shit inside while soldering the back of the pot.
Done it.
 
Corroded switching contacts on effects loop jacks can cause cutting in and out noises where the volume drops and gets all trebly-sounding, like a cheap AM radio.

You can test this by plugging a cable in the loop, if it stops, you need to clean the effects loop switching contacts or replace the jack.
 
Thanks for all the responses. I’m thinking now based on comments that it’s use + simple tube failure.
I did gig and rehearse this quad pretty regularly between 2016-2018. I never played anywhere where the sweat just dripped, but we did play several gigs at a bar on the lake in the spring and summer that would open the windows and a huge patio door.
The head is pretty clean. I try to take care of my equipment. I did have the caps replaced around 2016-2017 by Curt Granger.
Aside from all that, what is happening with the tube when it glows blue like that?
 
Tubes glowing blue is not a sign of anything in my experience...all my Mesa STR 415s (Sylvania 6L6GC) glow blueish in my Coliseum. No static or any sound related issues. That's just what they do when they are cooking. It's when they are red...houston we have a problem.
 
Racerxrated said:
Tubes glowing blue is not a sign of anything in my experience...all my Mesa STR 415s (Sylvania 6L6GC) glow blueish in my Coliseum. No static or any sound related issues. That's just what they do when they are cooking. It's when they are red...houston we have a problem.
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I’m not even sure that’s the problem. It’s kinda weird, though, that that one tube is really glowing blue when the others are not. It seems like it shouldn’t. Not sure. Really hope a tube swap fixes the issue. Never ever had a problem with this amp.
 
Mr. Willy said:
I’m not even sure that’s the problem. It’s kinda weird, though, that that one tube is really glowing blue when the others are not. It seems like it shouldn’t. Not sure. Really hope a tube swap fixes the issue. Never ever had a problem with this amp.
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Hey, stupid question: You noted which position/tube in the amp is glowing blue.

Have you tried swapping the tubes around to see if it's either the same tube or the
same tube socket position that glows? Quckly scanned the thread again and didn't see it.
 
Donnie B. said:
Hey, stupid question: You noted which position/tube in the amp is glowing blue.

Have you tried swapping the tubes around to see if it's either the same tube or the
same tube socket position that glows? Quckly scanned the thread again and didn't see it.
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That's a good question....rotate the tubes and check it out.
 
Donnie B. said:
Hey, stupid question: You noted which position/tube in the amp is glowing blue.

Have you tried swapping the tubes around to see if it's either the same tube or the
same tube socket position that glows? Quckly scanned the thread again and didn't see it.
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No, I haven’t. Good suggestion. I’ll do that soon as I get a chance. Probably this weekend.
 
Mr. Willy said:
Thanks for all the responses. I’m thinking now based on comments that it’s use + simple tube failure.
I did gig and rehearse this quad pretty regularly between 2016-2018. I never played anywhere where the sweat just dripped, but we did play several gigs at a bar on the lake in the spring and summer that would open the windows and a huge patio door.
The head is pretty clean. I try to take care of my equipment. I did have the caps replaced around 2016-2017 by Curt Granger.
Aside from all that, what is happening with the tube when it glows blue like that?
Click to expand...
What causes blue glow in vacuum tubes?
Sometimes you may notice a blue hazy glow inside your amp tube. This glow is rarely a sign of a defect and is fairly common especially in modern power tubes. This type of glow is called Fluorescence. This phenomenon is due to electron bombardment of the glass taking place within the tube.Aug 15, 2013
 
RedPlated said:
That’s a very common symptom of a bad power tube. They will crackle and pop when going bad.
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What he said and losing power is also a symptom of a bad power tube. Volume may fluctuate. Dirty tube sockets or corrosion on the tube pins can cause a bad connection also.
 
Deoxit is fine. It's the application you have to get right. Pull the tube, spray only the tube pins (the tube pins, not the socket), dont drench. Insert the tube, done.

If the sockets are really nasty, use crc contact cleaner, blast it directly in the socket, flood the hell out of it. It evaporates in seconds, and leaves 0 film. Of course you want the chassis to be pulled so the cleaner can run out. Do not use the CRC in pots.
 
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