changing tubes

[Digital Reason]

Hey ya'll just a quick question here.

I have a peavy 5150 head and a Crate Blue Voodoo head.

Does ANYONE know how to change the tubes in either of these heads, I have heard that you have to change 2 at a time BUT the question is which 2 to change. (each head has 4 tubes)
1 and 2
1 and 4
2 and 3
2 and 4
Or does it make a difference?????

well you get the picture, I have had these heads for a while and never have I had to change the tubes, anyone done this before????

Any help would be great, thanx in advance

Jeff
Saunavation Audio Productions

 

[Emeric]

Look in your manual, or look on the crate and peavy website.

You will have preamp tubes, and power tubes. I suppose it would make sense to do these in pairs. But, often they are not pairs. Sometimes 4 tubes for the amp section and 2 for the preamp etc. It's possible your looking at 4 power tubes, and preamp tubes are not visible. You need two know the specs.

It's quite easy to change them, just find out what the tube is.

This info can be found either in the amp manual, the manufacturer website, or by opening the amp up and pulling the tubes out and reading the numbers.

Depending on the amp, often re-calibration is required. Depends on the amp as to whether it is necessary and how difficult it is.

 

[M.Brane]

If the amps get played at band volume levels on a regular basis you should replace ALL the output tubes (the large ones) about once a year. Always replace the driver tube (small tube usually closest to the outputs) when replcing power tubes. Preamp tubes (small ones) can last for years at low gain levels. If you drive the amp hard for distortion count on replacing preamp tubes once a year as well. I really don't recommend replacing just two of the outputs as the amp will become unbalanced and sound bad or worse

I would stick with OEM tubes if possible to avoid potential bias problems. Most amp makers get their tubes from the same factories as the specialty tube companies. Make sure you watch your new output tubes for a while when you fire 'em up. If the big metal plates inside the tube begin to glow red TURN IT OFF! You'll have to have the amp biased. Preamp tubes are self-biasing.

If you can get a copy of "The Tube Amp Book" by Aspen Pittman of Groove Tubes there's lots of good "how to" info in there. You also might want to read this: http://www.mesaboogie.com/US/Smith/biasadjust.html

Don't forget that tube amps can have 500 volts in the caps even when uplugged. Not a problem when changing tubes but something to be aware of. Don't go poking around in the sockets or inside the amp chassis unless you know what your doing.

Good luck!