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Discussion Starter #1
I was looking at the back of my Peavey Delta Blues last night and noticed that out of the 3 12AX7's and the 4 EL84's one of the 12AX7's and one of the EL84's weren't glowing very much compared to the others.

Can anyone tell me if that's normal? Is this an indication that I need to replace the tubes?

As for sound, it's relatively new to me. The amp is probably 5 - 10 years old and it looks like the tubes have been replaced at least once.

Thanks!!
 

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You can't tell how good a tube is by whether it glows the same as the others, there are lots of things that determine the glow of a tube.
 

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I was looking at the back of my Peavey Delta Blues last night and noticed that out of the 3 12AX7's and the 4 EL84's one of the 12AX7's and one of the EL84's weren't glowing very much compared to the others.

Can anyone tell me if that's normal? Is this an indication that I need to replace the tubes?

As for sound, it's relatively new to me. The amp is probably 5 - 10 years old and it looks like the tubes have been replaced at least once.

Thanks!!
+1 on what Ripper said!

You should know that preamp tubes (the little ones) are voltage amplifiers and do not wear like output tubes, that have to pass honking gobs of current.

This means that 12AX7s and such can last for years and years. I have pulled some 40 or more years old that are still working fine. They can go microphonic and get vibration sensitive or like the glorified light bulbs they actually are they can just burn out but they rarely seem to get weak with age.

Output tubes are a different story, especially modern ones which often don't last like they used to years ago. EL84s in amps like Peavey can really be worked hard. Often the plate voltages are higher than they should be to squeeze out a bit more power. Air flow around the tubes may be poor (a fan is ALWAYS a good idea!) and the short story is that a year or two of steady use may be enough to wear them out.

You may also notice rattles or noises coming from such output tubes. The elements inside are spaced apart by mica wafers. Too much heat and stress can loosen things and the elements can vibrate at certain notes, from acoustic energy from the speaker shaking the tube. This vibration can affect the current flowing in the tube and the noise gets amplified right out to the speakers. Combos see this problem far more often than separate heads and cabinets, for obvious reasons.

Differences in filament brightness, a bit of a blue glow or pretty well anything you can see with your eyes tells you llittle or nothing about the shape of the tube. Glowing orange or red hot spots on the outside plate (the outermost grey or black sleeve which is the only element you can see since it wraps around all the others) are a different matter - they're bad news! The bias is off and the tube is being asked to flog itself to an early death.

You need a good tube tester to tell you if the tube is still handling power well. Such testers can't tell you if the tube is vibration sensitive or noisy. You need human ears for that.

I've had so many customers who tell me they just came from a music store and they had been advised to buy from them a complete set of new tubes to fix a problem. Usually the problem is still there because it had nothing to do with tubes at all, that's why they ended up coming to me. Meanwhile they've been charged up to $200 on a full set for a larger amp and I'm asking "Maybe the output tubes were getting old and weak but did they actually test them? And why did they replace all the preamp tubes? There was likely nothing wrong with them!" Then I ask "Did they at least give you back your old tubes to use as spares? I can test them for you and save you some money."

Of course the answer is always that the store kept the tubes.

The best and shortest answer I can give you is this:

IF THE AMP SOUNDS FINE LEAVE THINGS ALONE!
:smile:

In the words of Kurt Cobain: "Just play the damn thing!"

:rockon2::food-smiley-004:
 

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Discussion Starter #4
LOL! I can't STOP playing the damn! It's a great amp for the money. Best $400 I've ever spent.

Thanks for the tips Ripper and Wild Bill. I will pack up my tinkering tools and break out one of my guitars instead. :rockon:
 

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i've replaced the 6L6's in my traynor because the tone was obviously getting worse

i agree with "if it sounds good, dont touch it"
 

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This seems to be a big debate subject. I know people who never replace tubes. Myself I replace power tubes all the time. I find my Marshall 18 watt gets a little "squishy", thats when I replace the power tubes. I've always been told to replace the preamp and retifier while I'm at it but always suspected they didnt need changing.

Would love to hear some amp techs chime in honestly.
 

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The whole replace your preamp tubes at the same time was thought up by tube salesmen. I've seen preamp tubes that were 30 or more years old that were still functioning perferctly in the amps they came in. Preamp tubes don't wear out the same way that power tubes tend to. I've got a garnet amp here of my own that was made in 69. The preamp tubes are all original in it with the Garnet logo screened on them. They function perfect and still test a-okay on a tube tester. I got this amp off the original owner and I know that it got used alot, so they still aren't good because they were never used.

With rectifier tubes it's also been my experience they either work or they don't. They tend to last a long time as well.

Preamp tube obviously can go bad or microphonic but it's the power tubes in an amp that really take the abuse. I've also seen amps where folks thought that their power tubes were going bad, that was really that the bias had drifted off and just need resetting. It's not always the tubes that are at fault.
 
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