Preamp tubes will affect your overall sound quite a bit.
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I'm not a big fan of Electro harmonics tubes, but they'll work as well as any others. If the tubes seem to be glowing too brightly, which I really don't think will be a problem, you can have them biased down to reduce the voltage. If it sounds good then you should be fine. Replace the power tubes first and have a listen after playing for about 10-15 minutes. I've replaced stock marshall and medium rated groove tubes with Svetlanas with no problem. There's not enough difference in the tube rating to present a problem to the head so don't worry about damage to your amp. Either way, Once they're in listen to how they sound, and check to see if the glow pattern is the same(do they glow aout as brightly as your old power tubes) when the tube is on and the amp has been running for about 10 minutes. Svetlanas are good tubes, and are usually a medium rated tube. I'd rather change tubes than guitar strings. You'll find changing tubes is a peice of cake. I've probably given you way more information than you need but you say you've never done it, and it's always good to be informed. I do my own biasing, which saves me time and money, but again if you use a mid rated power tube or original peavey power tubes you shouldn't need biasing of any kind. If you do take it in for biasing, again keep in mind that it's only the power amp section they need to bias so if the amp is fine in all other respects there's no need for them to do any other repairs or modifications.Īct informed and state that you simply want a bias for the power tubes and that's it.Īlthough biasing isn't expensive I've seen shops that find the biasing to be perfect but will still charge you for a bias because they had to open the amp. When reinstalling the tubes use the same motion, or a side to side motion to reinsert the tubes, this time pushing down.
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Again just line them up before you insert the tube and then rock it into place. Just line up the new tube so the tab matches the notch and it'll fit in easily.ġ2ax7's don't have that base, but you'll notice that there's a wider gap between 2 of the pins, which corresponds to a wider gap in the tube socket. You'll notice a center post with a tab on it that lines up with a notch at the base on the 5150's tube socket. When you remove a power tube look at the bottom of the tube. Tubes fit snugly in the sockets so there's no electrical arcing from the tube pin within the socket so you want to keep that snug fit, and rolling it out in a circular motion is the best way to do that. Grip the tube near the base and use a gentle circular rocking motion as you lift the tube out of the socket so you don't damage the tube socket or pins. To remove both the preamp and power tubes, first unplug the amp and make sure the tubes are cool. Since almost all the 5150 distortion is in the preamp section with the 12ax7's, until the amp's volume is way up, a medium rated power tube is fine, which is what your 5150 originally came with. With preamp tubes you can replace one or two at a time. If you're just replacing one or 2 tubes power tubes then biasing is a good idea because you want an even signal through the tubes and just by looking you can't tell which tube is the worst of the batch.
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A power tube considered soft will break up earlier, while a hard tube will have to be pushed with more volume before it distorts.Īlthough it costs more, it's alway a good idea to replace all the power tubes at the same time with a matched quad of 6L6s. If you're going with another manufacturer and you're not sure of the rating then a bias might be a good idea.Īgain, you can check with the manufacturer and see how their tube is rated for hardness. If the new tubes fall into that category you should be fine. If you're using groove tubes or a different manufacturer then it might need biasing.ĥ150 amps are biased to take a medium tube (a rating of 4-6 if it's a groove tube)
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If you use a replacement set of peavey 6L6 tubes then it's a straight exchange and done. If you're replacing the large 6L6 power tubes then it might need biasing, depending on the tubes you use. You can simply replace them as the preamp section is self biasing and will "adapt" to the new 12ax7 tubes, regardless of the manufacturer. If you're just replacing the preamp tubes (small 12ax7's) then don't worry about it. There's no reason to make contact with them while changing tubes. The will not discharge into the tube sockets so don't even worry about the capacitiors. Thers' enough voltage in a power capacitor to kill you and then some. As a matter of fact that's an extremely dangerous thing to do if you don't know what you're doing. If you're just changing tubes there's no need to drain the capacitors.