tube springs buzzing

[gatorbrit]

I've got an annoying problem. I have a crate v50 amp. When I play a note on the 9th fret, 5th string on my guitar the little springs that hold the power tubes in place vibrate and buzz. Playing pretty much anywhere else doesn't cause this.

Anyone have any suggestions as to how I can fix this..

Thanks

Rich

[SemiHollow]

I believe if you look on ebay, you can find some rubber tube rings that go around the tube and can help dampen the springs as well.

[gatorbrit]

Wouldn't rubber get too hot?

[Spudman***]

Wouldn't rubber get too hot?

Nope. It's a special silicon rubber that wont melt.

FWIW - try taking the springs off and playing it a bit. It might be the internals of the tube that is actually rattling. What model Vintage Club do you have? Year?

[Tone2TheBone]

Take them off. You're welcome.

[SemiHollow]

Like spudman said, the rattling could also be a microphonic tube

[gatorbrit]

Like spudman said, the rattling could also be a microphonic tube

Thanks for the suggestions. My amp is a crate v50 with two GT 6L6 power tubes and 3 12AX7 WB preamp tubes. I got the amp used, but was told that the tubes were pretty new (they are not original).

I took off the springs off the power tubes as I thought that was what was buzzing, but the buzz is still there. But it is sort of hard to tell exactly where the buzzing is coming from.

So, I cranked up the gain then I lightly tapped on the preamp tubes with a chopstick and got a chiming noise out of one of them - almost a clean feedback note. I am guessing that this preamp tube is microphonic.

This is my first tube amp (always had line6 amps before) and my first tube issue. I am perfectly capable of swapping out a tube but I don't know anything about biasing etc.

Assuming that I should replace the preamp tubes, what should be my course of action? Do it myself, or is this something my local guitar shop should do for me? Also is the amp playable, or will it do permanent damage to keep using it?

Thanks

Rich

[Spudman***]

I have a mid 90s VC5212 and they have a tendency to bias drift over time. I suggest, if you feel comfortable, biasing yourself because you'll save a ton of cash in the long run and be able to keep your amph in tip top shape.

There is complete biasing instructions at Eurotubes.com and you can get the proper tool on Ebay for not much money.

That said, if you just replace the preamp tubes then you don't need to check the bias. It's only when changing the power tubes that you check the bias, and for piece of mind and better performance of course.

[otaypanky***]

My hunch is that it's the power tubes that give that little rattle. If you're going to stay with tube amps you better learn to live with it. You are the only one that will notice it unless it's really pronounced. Playing out or in a band situation it would be hard to detect except for a very quiet passage. A new pair of 6L6's may well be the same. It's pretty common with 6V6, 6L6, and rectifier tubes, and it happens with different brands of tubes too. I had a 5E3 with a new Sovtek 5Y3GT that rattled so badly that playing through a different amp that was 10 feet away rattled it.
Tapping on a 12AX7 can give you a sound. That's pretty normal too. A bad pre amp tube usually shows itself as a whine or feedback type of sound, or maybe the reverb stops working, things like that. That annoying little rattle is not likely to be caused by one.

[jim p]

The preamp tubes are cathode biased by a resistor so they are self biasing so they are a plug in item. The power tubes in the amp are grid biased and they do need the bias voltage adjusted if replaced. On the preamp tubes you could try swapping the tube locations to see if that has an effect on your problem. If you e-mail or call Crate they will send you schematics for the amp that may help and would be good to have anyway. Crate has 10 ohm resistors in series with the cathodes of the power tubes so if the power tubes are replaced you can check the bias current by the voltage drop across them not all amps have these. On the 12AX7 tubes in the amp V4 is the phase splitter, V1 is used for the input stage and overdrive V2 is later gain stages in the amp. All three tubes are used in either mode clean or overdrive.
One problem on the Crate V50 it has a switch mode power supply that has failed on people which may be due to high current draw on the high voltage power supply and Crate had no ability to repair the power supply. To play it safe on the V50 I gave to my son I increased the value of the screen grid resistor R68 to a 2k and reduced the fuse F1 to a 300mA fuse, so hopefully the fuse will blow and the power supply will be OK if a power tube fails.

[gatorbrit]

Thanks for all the great advice and input. I think I'll leave it alone as for now and see if the sound changes. As was pointed out, it might just be a rattle that I have to live with - which isn't too bad really. At least now I know much more about the inner workings of the thing.

Thanks again.

Rich

[gatorbrit]

An update: I got some tube rings from Eurotubes for the two 6L6s and they have helped the buzzing a whole lot.

Thanks for the advice.

[Ch0jin]

....One problem on the Crate V50 it has a switch mode power supply...

Wow thats interesting. I suppose it makes perfect sense though, you can generate massive voltages without the use of heavy and expensive transformers, so it'd probably cut costs and definitely save weight. Given that these type of power supplies also tend to lend themselves to high voltage low current applications, like say, a tube amp, I'm surprised more vendors don't do it.

As you said though, they can be tricky to repair. I always hated fixing switch mode power supplies in equipment. You think you've found all the components that died, then you turn it on and BLAM, everything you replaced is toast again. Then there's the ones that whistle under load. troubleshooting those is a female dog.



Fortunately all my amps have old school tranny/rectifier/filter PSU's

[NWBasser]

An update: I got some tube rings from Eurotubes for the two 6L6s and they have helped the buzzing a whole lot.

Thanks for the advice.

You went to the right place. Bob rocks!