Retubing

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legionserial

legionserial

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Ok. I need to retube my Peavey 6505, but I know vry little about this kind of thing. So was hoping for a bit of advice.

Basically, to start, am I right in thinking I just need to buy 5 of these...and 4 of these? Or is it not as simple as that?

Cheers :)
 
The Peavey 6505 requires 6 input tubes (12AX7) and 4 output tubes (6L6). Wow, that's quite a few tubes. Yes, just go plug them in.
 
Isn't there more to it, like matching..biasing and all that?
 
Whoops, I thought that amp was self biasing, but it's apparently a fixed bias design, which means you'll need to have an amp tech set it up optimally. It's not a major job, perhaps 30 to 45 mins of the tech's time.

I'd get a trim pot installed first time round, which will cost some more, but will allow you to do it yourself next time. For this, you will need a multimeter - or even easier, a meter that plugs into the power tube sockets themselves (on top of which you plug in the tubes). Saves you opening up the amp to measure voltages - I bet that's what the amp tech uses.

If you like the way the amp sounds after the amp tech's tweak, use your own meter to make a note of the meter readings and next time round, set to the same (using the trim pot) when you change out the tubes.

By the way. input tubes need far less changing than output tubes.

This guy is good for tubes, advice apparently: http://dougstubes.com/
 
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Matching - you're right. Matched tubes never hurt, and any decent tube dealer will see you right. Not essential though.
 
Call Bob at EuroTubes. He'll set you up with a proper kit. http://www.eurotubes.com/

Bottom line, ...input, drivers and inverters and rectifiers don't need bias attention. Just plug them in and go. The final output tubes require bias adjustment. Purchase the output tubes in matched pairs, quads, octets, what ever because the bias adjustment in MOST amps doesn't permit for individual tube adjust.
 
punkin said:
Call Bob at EuroTubes. He'll set you up with a proper kit. http://www.eurotubes.com/

Bottom line, ...input, drivers and inverters and rectifiers don't need bias attention. Just plug them in and go. The final output tubes require bias adjustment. Purchase the output tubes in matched pairs, quads, octets, what ever because the bias adjustment in MOST amps doesn't permit for individual tube adjust.
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I'll second this !

Those guy's at EuroTubes are great and very informative.
If your amp is the same as a 5150 (mine btw) you might want a ballanced pre amp tube in the invertor section (Bob will explain).
For the Output tubes, a matched quad will be what you want.

I had to modify my 5150 (not sure if your 6505 is the exact same) in order to create an adjustable bias circuit.
I also had to build a current checker in order to check the bias current as I was making adjustments.


Whatever you do:

Don't touch the tubes with your fingers !

And, don't even think of opening your amp up unless you are thoroughly familiar with capacitance and how to discharge it, that could kill you.



Good Luck !
 
RocknRollOver said:
Whatever you do:

Don't touch the tubes with your fingers !
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Why not? Halogen lamps you should not touch with your fingers because they are made from quartz glass which is sensitive to acids and oils on your skin (or so I'm told) and touching them can lead to premature failure of the lamp. Tubes are just plain glass.

Unless you mean when the tubes are hot you will get burned.
 
ggunn said:
Why not? Halogen lamps you should not touch with your fingers because they are made from quartz glass which is sensitive to acids and oils on your skin (or so I'm told) and touching them can lead to premature failure of the lamp. Tubes are just plain glass.

Unless you mean when the tubes are hot you will get burned.
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Good Point.
I always understood it to be good practice to keep the oils from your hands off of the tubes as much as possible to help prevent uneven heat build up in spots.
But they really don't get near as hot as something like a halogen lamp so some prints probably won't kill it.
I'm sure I'm just on the cautious side.
 
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Thanks guys.
So would it be a good idea to maybe put on some latex gloves to do it or something just to be safe?

As for discharging capitance....the amp hasn't been plugged in for months, I'm not sure it would make any difference, but am I right in thinking that flipping the power switch on while it's unplugged will discharge them?....Sorry if that's a dumb question. I've never been too much of an expert with electronics.
 
Discharge the cap properly, dont take the risk.

And why are you wanting to put on latex gloves? It doesnt matter if you touch the tubes as they dont get anywhere near that hot. The halogen light thing is because they get so hot that oils from your skin can cause it to heat uneavenly and crack the glass/quartz. With tubes, this doesnt matter.

Also, seeing you dont really seem to know what your doing, take your amp to a tech to get it setup properly, and ask to be shown how to bias the amp properly. Thats if its a fixed bias. If it is a set bias, then take it to a tech to get pots put in so you can make it a fixed bias, so you can adjust the amp to get the most out of it with different tubes.

While biasing isnt hard, its not something you want to mess up :)

But this is probably just the bass player inside me, because our amps tend to have more tubes, and they are also usually more expensive, so its a mistake not worth making :p
 
Just noticed your in the UK, where abouts? I could put you in contact with a damned good tech if you wanted
 
West Sussex. I'm actually looking for a good amp tech. I can't find one withour travelling across to Guildford, which is a little out of the way when the amp is so bastard heavy and I don't have a car.
 
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legionserial said:
Thanks guys.
So would it be a good idea to maybe put on some latex gloves to do it or something just to be safe?

As for discharging capitance....the amp hasn't been plugged in for months, I'm not sure it would make any difference, but am I right in thinking that flipping the power switch on while it's unplugged will discharge them?....Sorry if that's a dumb question. I've never been too much of an expert with electronics.
Click to expand...

It won't hurt to keep your skin oil off of the tube, it could be likewise the other way around but I'm cautious and it's just my opinion.
I use a clean rag or maybe a clean jersy glove or possibly the tissue paper that comes with them when i'm messin with tubes.

Capacitors store energy, therefore it is possible to receive a serious (even life threatining) shock after the amp has been unplugged.
After a few months it's not likely to harm you but because of the above being true, you should stay on the safe side and discharge them properly, always.

With that being said, I agree with Will_R in that you shouldn't mess with your amp on your own right now except to change the tubes.
If your really interested, find a good tech that won't mind teaching you while he works on your amp.
Then, you can see if that's (bias circuit) something you ever want to dive into. :)
 
Peavey's are hard...like them. Even better,...their Wolfies!!! :D
 
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