V1 Tube replacement. Removing Chassis

[paulg2uk]

Hey guys,

Had to replace the V1 position in my mark v yesterday. Had a little bit of a problem putting the shield back and let's just say I broke a couple of preamp tubes in the process. Every time I try and put the shield on top it breaks the end of the tube off. What a pain to try and get the shield back on.

Any tips for getting the chassis off? I can see the 4 screws on the top but there us a nut holding the transformer to the base of amp which will need to come off to get the chassis out?

Also any recommendations to try in the V1 position apart from the stock mesa tubes?

Many Thanks

Paul

 

[pivot]

I had the same problem. Broke the tip off of 2 SPAX tubes cost me allot of money. Remove all of the power tubes and turn the head on its side when replacing V1. Its a beast but once you do it a couple of times its not that bad. Get a SPAX preamp tube or stick to stock. so many tube rollers out there but in my experience Mesa put those tubes in for a reason because the sound bad ass

 

[cradlefish]

I've had a minor stall in that problem but i didn't break any tubes. I would suggest like Pivots advice to remove at least two of the power tubes nearest to v1...and try to be careful not to angle the tube shield off the center. If you can use two hands, the better.

 

[paulg2uk]

Thanks for the advice guys. I can get the V1 tube in its just getting the cover back on. I emailed the guys at mesa and they said it's not necessary to put the cover back on but it can block out some of the noise coming from the transformer. I tried it last night without and I never noticed any noise what so ever.

I think I might try an SPAX in the V1 position and stock in the rest. Or even a Tun-sol in V1.

 

[daverose]

Not even sure how you managed to get at the tube without taking it out of the chassis.

That little nut on the transformer is not actually attached to it, it's just pressing against it to provide some stability. If you loosen it a bit it will come away from the transformer. Take the 4 screws out of the top and it should just slide out the back, without too much effort, giving easy access to all the tubes. I usually have more trouble getting it back in and getting the screw holes lined up. I assume you are using the head, not the combo?

Good Luck

 

[Authorized Boogie]

Removing the chassis from a head cab is pretty straightforward - but if its a combo, here are some instructions that should help:

Instructions for removing MKV combo chassis*

Remove the Grille.
Loosen the bottom transformer brace nut with a 1/2" wrench by moving the wrench to the right.
Loosen the top transformer brace nut with a 11/32" wrench by moving the wrench to the left.
Remove all cables from the chassis...Power Cable, Reverb Cables and Speaker Cable.
While holding the chassis in place loosen the top four phillips head screws and remove them completely.
Lastly, slide the chassis out of the backside of the cabinet.

*For chassis installation reverse these instructions.

 

[paulg2uk]

Removing the chassis from a head cab is pretty straightforward - but if its a combo, here are some instructions that should help:

Instructions for removing MKV combo chassis*

Remove the Grille.
Loosen the bottom transformer brace nut with a 1/2" wrench by moving the wrench to the right.
Loosen the top transformer brace nut with a 11/32" wrench by moving the wrench to the left.
Remove all cables from the chassis...Power Cable, Reverb Cables and Speaker Cable.
While holding the chassis in place loosen the top four phillips head screws and remove them completely.
Lastly, slide the chassis out of the backside of the cabinet.

*For chassis installation reverse these instructions.

Thanks for the info guys I have a head version of the mark v. I've been in contact with Tien and he told me what to do. I was just interested to see if anyone had managed to do it on the forum.

 

[K-Roll]

in addition to the previous posts, I'd suggest removing the amp handle, too just purely because the screws are quite long and pierce through the chassis and come out on the other side which sometimes causes the inner cables to get stuck mainly when you pull the amp back inside the chassis.


usually what I do is when I pull the amp back in is that I turn it upside down, it's easier to move inch by inch and fit inside the chassis

 

[bandit2013]

I found an easy way to replace the preamp tubes especially V1 without having to pull the chassis out of the shell.

place the head on the floor to covered table (face and control knobs down on floor or table)
Remove power tube protector and power tubes (you can leave the Rectifier tube in its socket).

Special note: Forget about the extra long tube cover, it adds no additional protection. If you look close enough at it, it is just an aluminum tube glued onto the end of the regular tube shields. Due to its ridiculous length, use it on one of the tubes you can actually see and have better access too, say V5. Replace your tube in V1 and use the short shield from V5 or get another from Mesa Store (they are inexpensive). I can change all of my preamp tubes without removing the amp chassis from the shell in about 5 minutes of time. My hands are big and I found it very difficult to re-install the long V1 shield. You are better off with using one of the short ones since there is plenty of room to get it in there and twist into place without damaging the preamp tube.

 

[dino2sf]

Here's what I did. Solved all the problems. I can change ALL tubes in a couple minutes now

http://forum.grailtone.com/viewtopic.php?f=33&t=63388

 

[mesa metal]

Removing the chassis from a head cab is pretty straightforward - but if its a combo, here are some instructions that should help:

Instructions for removing MKV combo chassis*

Remove the Grille.
Loosen the bottom transformer brace nut with a 1/2" wrench by moving the wrench to the right.
Loosen the top transformer brace nut with a 11/32" wrench by moving the wrench to the left.
Remove all cables from the chassis...Power Cable, Reverb Cables and Speaker Cable.
While holding the chassis in place loosen the top four phillips head screws and remove them completely.
Lastly, slide the chassis out of the backside of the cabinet.

*For chassis installation reverse these instructions.

thanks for that tip..with many tube rolls under my belt with the mkv i can actually do it without seeing the socket in V1..
however i just leave all the metal protectors off..so far no problems with my sound..

 

[bandit2013]

Doing a tube roll in a combo would be cumbersome at best. That is why I am happy I opted for the head since I already had the 412 cab to go with it. If and when I change power tubes, and if the tone is not the way I prefer, I will remove the Chassis from the shell and place it on top of the 412. Sometimes I pull the reverb tank too.

Trick for Head users for installing reverb tank: Use Q-tips with one end cut off. Push the Q-tip through the bottom into the T-nuts. Place the nylon and silicone bushings onto the Q-tips. Carefully place the tank over the assembly. Install one screw at a time. The Q-tips will hold the bushings in place while you install each screw (removing the Q-tip while you insert the screw at the same time.)

If I did not mention it earlier, the extra long shield will cause more issues when trying to install it especially if your amp is a head unit. The short shields work better on V1 and install is easy without damaging the shield or preamp tube. The extra long shield can be used on V5 or anywhere, best to replace it with a short one. Mesa does sell them on their store web site.
With the head, there is not much room between the reverb tank and the chassis to install the long shield. With the combo, there probably is not in the way. However, I found the short shields easier to install since you can feel the spring loop and tip of the preamp tube. If I do not remove the chassis to do a tube roll, it is easier to remove and install the 12ax7 with the amp upside down. (that is assuming you have not done the cut out on the front of the shell. Something I may consider to do later on but have been able to manage without doing so.)

 

[diddlydan]

Just finished changing the V1 tube myself.Had to remove the chassis.Pig of a job first time.Should be handy nuf from now on as I know what to do now.

 

[bandit2013]

One you get familiar with changing V1 in the Mark V, an easy trick to do is to swap the long tube shield for a short one. It only has an extension on it so you can find it. However trying to get it back on the tube while the chassis is in the shell of the Head can be very difficult. It is much easier to install the short shield than it is the tall one. Before converting my Mark V to a combo amp, I damaged the nubs on the long shield so I had to buy new ones. Mesa does not sell the long or extended tube shield. I found the standard short ones to be ideal with this amp anyway.