Hello everybody. I'm new to the forum, so thanks in advance if anyone can offer some help with this question.
I am approaching the need to re-tube one of my amp heads. The amp is a 5150 II biased to 37 mA in the poweramp section. When I change the tubes, will I have to re-bias or does this not change from tube to tube based on how much that specific tube is drawing?
Thanks again!
I am approaching the need to re-tube one of my amp heads. The amp is a 5150 II biased to 37 mA in the poweramp section. When I change the tubes, will I have to re-bias or does this not change from tube to tube based on how much that specific tube is drawing?
Thanks again!
Hello everybody. I'm new to the forum, so thanks in advance if anyone can offer some help with this question.
I am approaching the need to re-tube one of my amp heads. The amp is a 5150 II biased to 37 mA in the poweramp section. When I change the tubes, will I have to re-bias or does this not change from tube to tube based on how much that specific tube is drawing?
Thanks again!
First does the amplifier have fixed or cathode bias?
Second, what type are the output valves?
Paul
What or who is 5150 II ?
My point is that not everybody here is a bass amp tech. A schematic would help greatly, too
No problem. It is a Peavey 5150 II 120w guitar amp head. I'll try to dig up a schematic from Peavey.
A 5150 is a common Peavy guitar tube amp. Aka 6505 Plus.
You should be able to find the manual online, see what Peavy recommends.
You will have to check your new tubes too be certain, after you put them in. That is the point which you will adjust between performance vs tube life.
Your new tubes might sound better a little below or above 37mA depending on what you get. Experiment a little to taste.
Modern guitar store tubes may not like to be biased hot whereas some vintage NOS tubes might let you run a little hotter without too much compromise to longevity.
You should be able to find the manual online, see what Peavy recommends.
You will have to check your new tubes too be certain, after you put them in. That is the point which you will adjust between performance vs tube life.
Your new tubes might sound better a little below or above 37mA depending on what you get. Experiment a little to taste.
Modern guitar store tubes may not like to be biased hot whereas some vintage NOS tubes might let you run a little hotter without too much compromise to longevity.
What or who is 5150 II ?
My point is that not everybody here is a bass amp tech. A schematic would help greatly, too
http://www.blueguitar.org/new/schem/peavey/5150evh.pdf
the power amp section is page 3 I believe.
Right, but like I said it is modded to allow adjustment on the bias as they come biased very cold stock. This was done by an amp tech of the previous owner, not by myself, so unfortunately I dont have those specific schematics. But in general, if my tubes are a fixed bias of 37mA, and I used the same tubes to replace the 6L6's currently in there, would I have to adjust the bias again when the new tubes are installed? Its basically the difference between taking it in to have someone pop new tubes in for me at substantial cost, or just removing them and replacing them myself?
I think you didn't mention that it's been modded. Does the mod have any means to check current at each tube (for example a low-Ohm resistor on pin 8 to ground) ?
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doh! you are correct, i ommitted that part. honestly, I do not know the answer to that question. I know the bias on 5150II/6505+ is adjustable stock, but not as hot as some like it. the mod basically makes it so you can bias hotter.
yikes, the more the experts ask, the more I know that I dont know..its sounding like I may just want to take it in.
I have no physical means of proving the mA draw, just the information that was provided by the seller.
Thanks anyway guys.
Not cheap. For labor, probably in the neighborhood of $100-150 USD, then figure about $40 per tube.
I had assumed, perhaps prematurely, that since the bias was already set, if I just needed a new set up power tubes, would I be able to just pop out the old set, pop in the new, and then power up without having to re-bias anything, assuming that I was able to procure identical manufacturer/model. Its sounding like there are a bunch of other factors to consider.
150$ !!! I want to immigrate!
Seriously, you sure can pop in a new set. Espexially if they re the same make, nothing can go too wrong. Just buy them matched, and don't lose your sleep anout that.
Do some homework, too, seems it will really pay off
Tales From The Tone Lounge:Biased Opinions
Seriously, you sure can pop in a new set. Espexially if they re the same make, nothing can go too wrong. Just buy them matched, and don't lose your sleep anout that.
Do some homework, too, seems it will really pay off
Tales From The Tone Lounge:Biased Opinions
wow, thanks! that link had a lot of great info, most of which I will have to read after work it seems. cheers!
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