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VB- 2 Tubes Red plating

Right_Butterscotch64

Right_Butterscotch64

Oct 18, 2012
1,763
442
#1
So today I plugged in my VB-2 and noticed two of my El34s were glowing red on the metal plates after a minute or so of playing.

Lets say my tubes are like this:

1 2 3 4 5 6

4 and 5 are red plating

So I was wondering do I need to replace just these two power tubes? Or get a whole new set? My research has led me to think that I should just replace the ones that are red plating.

Just a little background on my tubes, they usually run really hot even at low low volumes. I'm guessing this sped up the appearance of a red plate and has something to do with the Bias not being set a certain way.

I'm not an amp expert, but I don't think I can just buy a matched pair of El34s and throw them in there and expect optimal results? Seems a little too simple. Do you guys think its tech time to see about the bias?
Should I buy a new matched Sextet?

I Pm'ed Bobby about this as well but I just thought I'd get as much info as possible before I start spending any money.


Edit: I also noticed my tone coming from the amplifier sounds a little Brittler/Harsher than normal. Very bright...
 
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#2
The manual says to have it biased by a tech and use a matched sextet of EL34's. Now how important it is to have them all match identically and replace all 6 every time one goes out, I don't know, since I don't know how it biases. Like the SVT biases its power tubes in triplet sets, so if one goes down, at most you have to replace three. I don't know if Bobby came up with something similar for the VB2 or not. Best to wait and see what he says.
 
#5
Check this out...this thread happened to pop up today and it had a pertinent reply from Bobby:

1) Can I replace the broken tube by trying to get a "close enough" match, and 2) if not, can I pull another tube and run 4 tubes until I can save for a re-tube?
1. If you order the tube from us, you can get a matching one. Just give the sales person the matching number. I'm sure there are other places to do the same thing. You won't have to re-bias if you do that.
 
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#6
Thats what I figured the #s on my tubes were for. Ill give peavey a call when I get the chance.

EDIT: Yep, almost all the power tubes read

1315
PC-52
TC-3500

With the exception of one that was
1322
PC-54
TC-3550

Not too sure what the #s mean, but I'm sure Peavey does :thumbsup:
 
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#8
Right_Butterscotch64 said:
My main concern is that if I replace the tubes, won't my amp just eat the next pair and cause them to red plate as well?
Click to expand...
Not if your tubes went because they became defective. Tubes do wear out ;) and they don't wear out at the same time even if they're matched. You could swap your tubes around and see if the red plating stays with the socket or follows the tubes around as a quick check to see if there's something wrong in the amp itself. But if you move them to different sockets and they red plate in their new locations, then it's the tubes.
 
#9
+1 with what Jimmy has told you Jelling, In would get a pair at the same spec as the rest and see what happens, I had a pair of Winged C KT88 that drifted out of bias setting and began to red plate after about a year, I got replacements to the same quiescent current settings, popped them in and they checked out fine for bias without any adjustment.
Always check your bias after you change tubes anyway.
 
#11
Dropped it off at the Tech. Found a local amplifier builder/repair shop called SteamBoat ampworks. Guy was nice and seemed to know what he was talking about and agreed with what Bobby told me was probably wrong with the amp. I guess I'll find out in a couple of days. :thumbsup:
 
#13
Well bad news, I take the amp home from the shop and plug it in. It seems normal until I start turning up the volume, now I start getting this really bad distortion that just sounds like speaker farts. But my speakers are fine (ampeg 810e). Also whenever I adjust the resonance and presence knobs to a certain degree it adds this fizzy distortion to my signal. It just sounds bad whenever its turned up now. This is extremely upsetting especially since it is a pretty long drive to this amplifier repair guy.
 
#17
Well I take it in and it works like a charm, get it home and its just fart city. I really don't think its my speakers, you can hear the flabby distortion coming out of all 8. I tried a different instrument cable but it did nothing. Playing with the resonance and presence is what really gets it sounding bad.
 

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