Switch MK4 from combo to head

[rollyfoster]

I'd like to switch my Mark IV from a combo into a head. Is this a hard process (i.e. something I could do myself)? Is there a good place to look for shells? I'd rather use a boogie one than have one custom made.

 

[Scott K]

It shouldn't be hard. You can buy a head from Mesa for $247 with the fan installed. All you'd have to do then is unscrew the chassis and screw it into the head shell. Your best bet is to buy a black tolex shell, the hardwoods cost over $800.

 

[Russ]

It is pretty simple really...

Try to follow this if it makes any sense...

The following instructions are for a short chassis amp. Be sure your amp is off and that it has cooled down. Then unplug it and disconnect the fooswitch and set it aside. You must of course remove your speaker cable from the output of the amp. Also disconnect your reverb and fan from the amp. Once you have disconnected the cabling then invert your combo on a folded towel on a table. Slide the cabinet towards the edge (must be a solid stable table). Then once you expose two of the mounting screws on one end, remove the mounting screws. Spin the amp around and repeat. Once your screws have been removed simply slide the chassis out of the cabinet. Be careful it is heavier than it looks.

*** DO NOT LET YOUR FINGERS SLIP INTO THE INSIDE OF THE AMP.***
(You might get a shock that would kill you dead instantly.)

I would suggest that you slide it out onto the table or another towel on the table. Remove your grille from the combo cabinet to access your speaker mounting screws. Remove them. Carefully remove your speaker. Remove the fan by removing the screws holding the mounting brackets to the sides of the cabinet. There should be a bag on the bottom held by a nylon strap. Remove one of the screws holding the bag down. Then pick up the bag and slide the reverb tank out. Install your reverb tank into the head cabinet. You will need the rubber mounting grommets and t-nuts for the head cabinet to mount the reverb tank. If you do not have these you can get them at any hardware store. The fan goes in the back of the front panel blowing up towards your preamp tubes just over your reverb tank. There isn't much space so keep it as close as you can to the top of the reverb tank. Without it touching but still allowing what will seem like very little air space maybe a 1/4 of an inch. You may have to reconfigure your mounts to do this. Once you have installed the reverb tank and fan, invert the head cabinet like your combo cabinet was on the folded towel. Get your chassis close to the cabinet. Install your reverb wiring. Your fan power should be long enough to connect to the chassis also so connect that as well. Slide the chassis into the cabinet still inverted. Be careful that your fan doesn not hit your preamp tubes. It may rest on them once you have the chassis in temporarily but try not to disturb the preamp tubes. Place one screw through your chassis strap or finish washer and align the screw to the chassis through one of the mounting holes and into the chassis. Do not fully tighten it. Then align the other screw on the same side. Do not tighten it all the way either. Spin the amp around and repeat the alignment process. Once you have all four screws in the amp tighten the two on the same end that you just installed. Then spin it around again and tighten the other two. Once you have tightened the chassis mounting screws carefully flip the amp over on to its feet. Do a quick check to make sure that all your tubes are still well seated. Install your footswitch. Plug your speaker cable into the proper output jack and into the speaker. Check your power and standby switches to ensure that you have not moved them. Put them in the proper position for standby and off if they have been disturbed. Plug the amp in. Plug your guitar in. Turn the power on. Wait for the tubes to heat and then come out of standby. You should be able to play at this point.

If you have the medium chassis you will have to contend with the floating FU-3 footswitch mount. Otherwise the same instructions will apply with exception to when you must deal with the mount.

 

[rollyfoster]

whoa...can i get shocked even if it's not plugged in?!?!?! I think I've decided to nix this route and sell my 2 X 12 to fund a sweet new speaker for the combo instead.

Thanks for the info, though. I didn't realize a shell would cost so much and that I might face death attempting the switch :shock:


Now I just need to unload my cab and figure out what speaker to put in the combo. Tone Tubby, perhaps? Any suggestions?

 

[Russ]

You can usually find cabinets on E-bay once in a while or look in the classifieds here, Gear Page, Recycler, Craig's List, or wherever. They shouldn't cost you more than $100 used even in mint condition. Some will even come with the reverb tank already installed and maybe even the fan too. If you need the chassis straps, do not hesitate to order from Mesa. They cost about $6. The finish washers can be found at your local hardware store for a couple bucks. The T-nuts are a couple bucks at a hardware store too. The rubber grommets should be about 3/8" tall then compressed to about 1/4". If you were in a head migrating to a combo you would have to either get an extension cord or a new fan with a cord long enough to reach if your fan's power cord wasn't long enough. If you go with a used cabinet chances are you will find the old holes for your fan mounting screws. Older Mark series head cabinets work too but do not have the footswitch mounts. You can order those from Mesa for about $25 but you have to carve a little wood from the back of the side panels to be able to use them. It is not uncommon to find combo cabinets for sale. Many sell them. It is a good way to recoup the cost of the head cabinet swap. You should be able to get the same amount back for your combo cabinet as you spent on the head cabinet. You may even get a little more. The rackmounts are the hotter ticket. These sell like hotcakes. Though you will need at least a 4 space rack to put your amp in if you choose to ever go that route. Those sell for anywhere from $50 to $100 used depending upon condition. Look around. You might get lucky and find a real deal on your amp's new home.

I would suggest getting a used cabinet or rackmount because Mesa's prices on new cabinets of any sort or rackmounts are a little high like the amp are prices new especially if you go for a custom covering or grille cloth.

 

[Russ]

Yeah, if you get shocked by a cap that discharges to you as ground you can get hit with serious voltage. This is why the insides of your amp are inside there and not exposed. Some manufacturers will put warnings on their amps including the serious risk of shock causing serious injury and/or death. Look at your Mark IV, there may be a warning somewhere (on the transformer?). People have died getting shocked before while trying to service an amp. I would just use extreme caution. It really is nothing to scare you off provided you can be careful. There is a good sized lip that runs around the chassis (about 1/2") that you can get a grip on. Just do not go beyond the lip. The amp weighs a lot for its size. I usually hold onto it by its sides using the lip as a place to place my fingertips and putting the meat of my thumbs over the exposed cover on the sides next to the transformers. As long as you do not start poking around inside the internal electrical parts there is nothing to be afraid of. Just do not sweat too much (like a rainstorm) or you might also cause your electrocution by means of the sweat acting as a conductor. I use the towels to serve as a soft medium upon which to rest the amp so that I can still get my fingertips under it when I go to pick it back up. Just do not spill your drink on it while you are working on your amp. When you go to pick your amp back up it may bunch up underneath and act as a conductor and cause you to get shocked too if it gets wet.

 

[Russ]

Hold onto the 2x12. You can add another dimension to your sound if you use it with the combo speaker.

 

[Monsta-Tone]

I used a Weber Thames speaker in my Mark IV, it sounded incredible.

I have long since sold the amp, but the Thames resides in my DC-5 now.

I've A/B'd this speaker against many Mojotones (which are great speakers too!), Celestions, & Mesa/Celestion Black Shadow speakers. It had them all beat, hands down, in my opinion.

www.tedweber.com

 

[rollyfoster]

Hold onto the 2x12. You can add another dimension to your sound if you use it with the combo speaker.

I'd love to keep it, but I really don't have much use for it right now since I live in a 3rd story apt. and don't have a designated practice spot, either. Carrying the amp itself is a chore! I'd benefit a lot more from a different speaker in the combo right now.