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New Tubes -> Valve Jr Question


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Hello and sorry to bug again,

 

I bought a new set of tubes for my Epihpone Valve Jr Special. I got one preamp and one poweramp, not knowing that i needed two preamp tubes (Tung-Sol 12ax7's). So i have two questions.

 

1) Can I just order another one and not worry about having matched pairs? (Heard it only really effects how long they last) and

 

2) How do i replace the tubes? It looks like i will have to take the "head" out of the amp somehow. Any help or diagrams would be awesome.

 

Thanks!

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Replace V1. That's where the bulk of tone generation is done.

 

I've never seen a Spcl, but replacing tubes is the same on all amps. Gently pull down on the old tube, after removing whatever tube restraint or hold down is in place. You may have to carefully wiggle it from side to side a bit as you pull. When it's out, don't turn it. Pull it straight down, and look at the pinout. That's how it will have to go back in. If you mis-align the new tube and force it in, you'll bend the pins and probably destroy the tube. You may have to turn the amp upside down and use a flashlight to peek at the socket, to make sure you get the new tube aligned correctly.

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Okay the valve special is similar to the valve junior in that it’s a 5 watt SE amp, but it appears to have 2 12ax7 pre-amp tubes and one EL84 power tube.

 

So the tubes do not need to be in matched pairs, that is only when you are running an amp in a push-pull configuration and then you’d have more than 5watts.

 

Buy another tube and plug it in…

The back cover is held on by 8 screws you’ll need to remove them to access the tubes.

Then follow M-Theory’s directions…

Remember which tube came out of which socket.

Do this with the power turned off.

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I think you're talking about the Valve Special (no junior in there). If so' date=' you'll get heaps of tone (and gain) back if you bypass the DSP section.

 

 

 

[/quote']

 

 

How do I bypass the DSp Section?

 

Are you saying even with the dsp turned off I can get better tone by "bypassing" it?

 

Thanks for the input everybody. I understand the general concept , just there is an odd casing around the preamp tubes and I didn't want to break anything.

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... there is an odd casing around the preamp tubes and I didn't want to break anything.

 

The "odd casing" around the VJr. preamp tube is a metal canister with a spring inside that puts pressure on the tube to keep it firmly in the socket. It is removed by gripping it and applying just enough pressure to turn it in the chassis until the two little lugs on the cannister align with the chassis slots. Then as you allow the spring pressure to push the cannister out of the chassis it will fully expose the tube.

 

If it looks like the same kind of casing on the special' date=' then it probably is removed the same way. [/i']

 

Remove/replace the tube per m-theory's instructions. (I change when the amp/tube is cold and wear rubber gloves: some say gloves keep body oils off the glass tube and may extend tube life. Who knows if true, but I figure it can't hurt.)

 

Hit every BLUE NOTE baaaby..., I'm going to play on:-"

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(I change when the amp/tube is cold and wear rubber gloves: some say gloves keep body oils off the glass tube and may extend tube life. Who knows if true' date=' but I figure it can't hurt.)

[/quote']

 

The theory goes that the oils help to create an uneven temperature gradient by adding a heat sink and possibly evaporative cooling, allowing the tube to cool unevenly and crack. I've yet to see this, and it doesn't make sense because of how heat flows (cold water splattered on light bulb and turn on, the water heats and then evaporates; heat light bulb up and splash it with cold water, it cracks and blows). But there you have it anyway.

 

I tend to remove power and grab the tubes by hand. Others mimicking this might find difficulty getting fingerprinted; it hasn't hurt me but I can't recommend this. Let the damn things cool, they're friggin' hot.

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How do I bypass the DSp Section?

 

Are you saying even with the dsp turned off I can get better tone by "bypassing" it?

 

At least with my Standard, it made a huge, alarming, difference. My first thought was 'why would they do it that way?' And, no, turning off the DSP just turns off the DSP, it doesn't bypass it. You will lose the reverb as well, not the greatest, but I felt it was definately useable.

 

Before I give you instructions how to bypass the DSP (its easy, solder a wire from point A to point B), I want to check the schematic on the Special to make sure it's the same.

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OK, looking at the schematic, you want a jumper from the wiper (middle tab) of the volume pot (VR6). Not the Gain pot.. The other side of the jumper goes to one side of C6. I've provided a link to the schematic for you to look at to help you determine the correct side of C6. It's very obvious how this is done once you see the schematic.

 

You might not be able to get to the middle tab on the pot very easily. If not, then find C13, then figure from the schematic which side you need to solder it to.

 

 

Click this.........

Valve Special Schematic

 

(Sorry, but you'll need to signup at www.ppwatt.com to access the schematic - its free)

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