Leaving Preamp Sleeves Off

[Archlute75]

Hey All,

I just got my Mk V head a few weeks back, and am loving it. Absolutely the best amp I've ever owned, and is even better in a live mix.

My question is this - is there any drawback to leaving the preamp sleeves of the tubes in V1-3? I retubed from stock, and that V1 is a ******* to get back on. In fact, the main reason I've left it off is that is actually shattered the top of the Tung Sol 12ax7 I had in there (thankfully, had a spare). The springs in those covers are so dang tight, and I even made sure that the tube tip was centered within the spring. I ended up leaving off the V2-3 slots as well, since they were equally tight, and I didn't want to bust any more tubes.

My old Crate used sleeves, but my Blackstar did not (and those were hanging upside down, like the Mk V). Are they just to keep the tubes from shaking loose, or are there other reasons as well? If not, I'll just leave them off, and save a hassle.

 

[bandit2013]

It should not hurt to leave the shields off. However, I tried this as well and had some noisy tubes, they went quiet with pressure on them.

The long shield, not needed. I basically damage mine trying to install it with the Chass in the shell. (I have the MKV Head). The length of the shield is way too long. Just use one of the short one's.

Not too long ago, I bought 7 replacements from the Mesa store since I now have two amps that use the same shields. I tossed the long one and found it much easier to install the short (standard length) shield. Tube rolling, best to pull the amp chassis out and place on top of cab (up side down). Remove all of the shields and roll away with preamp tubes. Once you get it the way you want too, return the shields, and put the chassis back into the shell. Note: not necessary to have the reverb tank connected. Much harder to get that back into the shell once removed, so if you need to have that in the tube roll the trick to getting it back in is simple: use q-tips with one end removed to stack up the spacer and grommet, place the tank over top and pull the q-tip out when you are installing the screw, do it one at a time, easy.

 

[Archlute75]

It should not hurt to leave the shields off. However, I tried this as well and had some noisy tubes, they went quiet with pressure on them.

The long shield, not needed. I basically damage mine trying to install it with the Chass in the shell. (I have the MKV Head). The length of the shield is way too long. Just use one of the short one's.

Not too long ago, I bought 7 replacements from the Mesa store since I now have two amps that use the same shields. I tossed the long one and found it much easier to install the short (standard length) shield. Tube rolling, best to pull the amp chassis out and place on top of cab (up side down). Remove all of the shields and roll away with preamp tubes. Once you get it the way you want too, return the shields, and put the chassis back into the shell. Note: not necessary to have the reverb tank connected. Much harder to get that back into the shell once removed, so if you need to have that in the tube roll the trick to getting it back in is simple: use q-tips with one end removed to stack up the spacer and grommet, place the tank over top and pull the q-tip out when you are installing the screw, do it one at a time, easy.

Okay. Thanks. One problem I had though, maybe because I'm a Mesa noob, or maybe because they've begun to add things to the design of the head, but after I took out the four long screws I was still unable to get the chassis out. It looked like there was a screw pole with a foot on both ends putting pressure between the frame and one of the transformers to hold it in place, but when I tried to loosed the nut (tedious process) it looked like the screw actually went all the way into the frame and that there was no way to remove it. That was a real headache, and I've had to work all the tubes by reaching inside to do it by feel, having bent a few tube pins in the process. If there is a simple process for removing that pressure pole, please let me know, as it has completely grounded the process.

 

[bandit2013]

Well, the head as well as the combo have a transformer support post.

Best to leave the 4 top bolts in place. Keep the tube shield in place to protect the power tubes and Rectifier tube which would be the one that would get damage if you slip.

Loosen the nut on the post. I use an open box wrench to loosen the nut, bring it up about half inch from the bottom. Then you need to use a smaller box wrench to drop the support. Once you get it loose, use your fingers to rotate it so it can drop down. 1/4 inch should be fine. Then you can remove the 4 support screws to remove the amp from the chassis. I had the same issue when I first tried to remove the chassis but then realized the support post on the transformer. If you fear you will damage the power tubes, you can remove them first, just do not install the rectifier tube in the wrong place or it will cause damage to the amp. Rectifier tube is closest to the power chord, check the tube chart on the amp plate or your manual for proper tube placement. Once you get the support loosened up, and removal of the 4 mounting screws, you will have to disconnect the reverb before you can remove the chassis completely out. The white wire is the hardest to remove, I usually carefully pry it off with a small flat blade screw driver. The cable with the molded plug is easy to remove. Remember orientation of the reverb connections. Molded plug is towards the front, and the uncovered RCA jack is towards the rear. It won't take long to realize you connected them backwards as it will squeal and sound terrible.

I normally start with the amp on the floor, front of amp facing down to loosen the mushroom support post. Then I rotate the amp so it is standing in the proper orientation to remove the 4 mounting screws. Remove the front two screws first then start with left side and remove the right side last. While removing the right screw, hold on to the amp chassis with the left hand. This is to prevent the chassis from dropping suddenly It will not drop very far as it will rest on the two side beams of the chassis. Removing the chassis, hold it by both transformers. Do not place your fingers into the amp chassis as the power supply capacitors may hold a high voltage charge. Also do not attempt to pull the chassis out after you had it operating since it will be very hot. Once you do the tube roll of the preamp tubes, let the amp cool down before attempting to reinstall the chassis. You may want to screw in the mushroom support slightly to get more clearance to install the amp chassis. When you get the amp part way into the shell, reconnect the reverb cables. Getting the amp back in is probably trickier than its removal but as long as you take your time, check for binding from the grill or flap of tolex around the opening of the front as this may impede installation. Installing the support bolts, start with the right side rear but do not screw down tight, keep it loose, next start with the right front scew, keep it loose. and do the left side, Always start the screws by hand to prevent cross threading. Once you get the mounting screws tight, you can adjust the mushroom support (do not over tighten this support as it will push against the transformer and bottom of the shell, you want it snug and then tighten the bolt. Once you get used to removal and installation you will find it takes less time than trying to get the tubes in and shields back while the chassis is still in its shell. I can remove tubes either way. If I am tuning for a specific change in power tubes, I usually remove the chassis. That way I can change tubes without having to wait for the power tubes to cool down. Best to turn off the amp when swapping preamp tubes. I usually keep the amp chassis out after tuning, and return a few hours later and recheck the tone (ear fatigue can result in well it sounds great now, but when you come back to it later does it sound the same?).

 

[Archlute75]

Thanks for that thorough reply!

So it sounds like I was almost there, but got stumped at the second nut (which I didn't actually notice). Man, it almost sounds like it would be more simple just to remove the power tubes and do it from the inside, unless you were wanting to avoid cool down times.

 

[bandit2013]

It may be... I tried doing just that, but for starters I have big hands and had difficulty getting to V1. If I just want to change one tube I will do it the hard way. However, with the chassis removed, preamp tubes are easy to install when you can see how they go in. Plus with the amp out, doing a tube roll takes less time. I would rather leave the power tubes in place than to remove them every time I need to swap preamp tubes. I can pull the amp out and reinstall it in less time that it takes me to get the shields back on without removing the chassis. I would not recommend it to most if they never took an amp apart. The Mark V is much easier to remove the chassis from the shell than the RA100. Actually getting the RA100 back into its position is a trick in itself. I found it unnecessary to remove the chassis of the RA100 simply because you only have to pull two power tubes to access the preamp tubes, and nothing is hidden behind the power transformer or output transformer either.

Either way you look at it, you have to be careful in what you are doing regardless if you remove the chassis or not.

As for the long shield, use it on v5 and put the short one on V1. You will find the shorter shield much easier to install once you know where the tube is.

 

[dino2sf]

Here is a mod I did on my Mark V Head. It makes changing tubes effortless. It was simple to do and I dont understand why they dont come this way to begin with.

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

 

[Archlute75]

Here is a mod I did on my Mark V Head. It makes changing tubes effortless. It was simple to do and I dont understand why they dont come this way to begin with.

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

Thanks for posting that. I may try it in the future, but just purchased the amp last month, so the idea of cutting into the most expensive head I've ever owned is currently too much to contemplate :shock:

Looks good though. And, yes, the Mark V noob that I am, the first thing I did was to pull off the faceplate thinking I was clever....

 

[bandit2013]

Guess what, if you could remove the reverb tank, it would be easy. well, you have to get the amp out of its shell first.

Still debating I would do the mod myself, thought about it. Sure would make tube rolling a bit easier since they are right there in front. Well I don't roll the preamp that much anymore since I found what works for me.