Mark IV: replacing just the outer tubes?

[BoogieBomb]

So I was putting in the power tubes in my Mark IV, and broke the plastic key on one of the outer 6L6's. Is it possible to just get another matched pair of tubes and replace the outer two? I believe the mark IV can run different tubes on the outer ones, so is it possible to get a matched pair just for the outer two?

Thanks in advance,
BB

 

[tony777]

There's no problem running different tubes in the outer sockets.
The MKIV is designed to do that, ie EL34 in the outer sockets, and 6L6 in the inner sockets.

Anyway, if the tube itself is not broken, but only the plastic part of the socket it should be able to work with no problem, you only have to be dead sure that you insert it correctly.

 

[BoogieBomb]

Exactly what I thought! So, even another set of 6L6's will work fine, from what I gather, they are two different circuit, correct?

 

[MrMarkIII]

Exactly what I thought! So, even another set of 6L6's will work fine, from what I gather, they are two different circuit, correct?

Yes. Any other matched pair of 6L6s that are designed for Mesa use will work. If you are buying tubes from anyone other than Mesa, be sure to tell them which amplifier you have.

If they are Mesa tubes, and the broken pin tube is a "blue", for example, you could replace it with a single "blue" from your spares.
All Mesa tubes of the same color should match each other.

But if you're buying new tubes, most likely you're going to get a pair that have been matched. This pair can go in either the inner or the outer sockets. Be sure to tell the seller which amp you are buying the tubes for.

 

[BoogieBomb]

Wonderful.

For now, I think I can use the other 6L6 and see which way the pins are oriented in the socket, so I can still plug in that tube with the damaged base, does that make sense?

 

[MrMarkIII]

Where's the broken pin?
You can superglue it back in place.
If you re-use the tube with the missing key, mark the outside of the base visible to you when the tube is installed so you know how to match up the pins. Don't use masking tape as it will dry out from the heat and be very difficult to remove.

 

[BoogieBomb]

Not broken pin, just the keyed part. It got stuck in the socket and it broke into a few pieces when I removed it

Also, I want to settle a discussion I was having with a friend. I know other push pull amps you can remove the outer or inner tubes and cut the power in half, because they are working in parallel, but I believe this is not possible on the Mark IV, am I correct?

 

[MrMarkIII]

"Broken pin" and "keyed part" are the same thing.
There's no need to remove tubes, silly. When you flip the Simul-Class switch to Class A, the output power is cut from 85 to 25 watts.
The manual is available at the Mesa website. It makes good reading.
Questions are answered, secrets are revealed, mysteries solved.
Now go study... this will all be on the final.

 

[BoogieBomb]

"Broken pin" and "keyed part" are the same thing.
There's no need to remove tubes, silly. When you flip the Simul-Class switch to Class A, the output power is cut from 85 to 25 watts.
The manual is available at the Mesa website. It makes good reading.
Questions are answered, secrets are revealed, mysteries solved.
Now go study... this will all be on the final.

Sorry, when you say "pin" I think of the metal pins of a tube.

I wasn't asking about the removal of tubes to bring the wattage down. I was curious if it was just possible to even do so. I currently just used my spare quad to retube another amp, and am going to get another set and a spare set today, but just wondering if it was possible to do so.

I'm well aware of the manual, thanks, I just wanted to verify that the outer sockets had the flexibility I thought they did.

cheers,
BB