Chassis removal... Mark IIC head

[zodiac272]

Hey everybody,

I need to remove the chassis to have a look and replace the tubes in my mark head. I know I can change the output tube without taking it apart, but the preamp tubes, all shielded look mor difficult. Does anybody have any tips on how to do this? I'm guessing to unplug the reverb tank, fan, and remove the screws. Should I stand the amp on the end with the big ass transformer so it doesn't fall onto the tubes? Or put wooden blocks to prop the chassis up so it doesn't crush the tubes... But I can also remove the tubes first. Anybody think this can be done one handed? I can't use my right hand yet... Recovering from surgery. I just got it and was told it was working fine (it's not right now... Nothing from the cabinet) but will need new tubes immediately, so I'm thinking it will be fine. I'm rambling so I'll shut up... Lol
Anyway, thanks for any help

Scott

 

[MrMarkIII]

Get someone to add a pair of helping hands. I wouldn't attempt this with a recently repaired hand. You are only asking for it.

 

[zodiac272]

I'm thinking about asking a friend, or going into a shop. I just retubed my 2:90, so that gave me confidence to do more. But either way, I was still looking for input as to the best way to disassemble #5. I'm gonna send it to Mesa anyway to get modded. I have a lot of time on my hands these days so I wanted to learn a bit.

Thanks...
Scott

 

[cremona]

All done looking at/ and from the rear of the amp.

1. Unplug the amp.
2. remove power tubes:
3 unplug fan located under the chassis to the left of the power tranny. It can be hard to reach as it's in a very small space. (This is if it has a fan).
4. unplug the reverb cables from underneath the chassis
5. remove all four mounting screws
6. put one hand under the power tranny, the other under the output tranny, slide chassis back and out of the cab.

+ 1

Thats have i do it as well, OT the stock mesa head cabinet is actually really solid build , there runs a big heavy constucted middel wood that combined with the amps dimensions create a very good protectiv shell.

I droped my simula sat 85 markIV stock head shell unto the ground from about 1 meters height into the asfalt, all there happent was that the tolex cracked in on side and there was a very small displacment of one of the wood sides,nothing at the core, i used the right glue in there and gave it a slight knock with a rubber hammer let it dry, and its like new , and the amp was 100% intact, now if it had been a marshall it had disintegrated onto the ground , ofcause :lol:

 

[DaveP]

You could just turn the amp upsidedown on a padded bench and slide it off the edge a bit remove the screws on both sides and grab the transformers and pick it up a little and slide it out. (remove the fan cord and reverb cables as was stated).
Put it back in the same way, you can see where the holes line up looking from the bottom up.
That's how I do it.

 

[zodiac272]

Thanks!

I got it out last night... I figured I would lay it upside down with the screws over the edge, undo, then repeat on the opposite end. I then was able to slide it out of it's shell. I took the fan out and cleaned it up, took the front off the head shell, and cleaned it and the shell. There are two "L" shaped metal brackets, that look like they will support the chassis when the screws are loosened. BTW, It has the RP-11A board in it. I took some pics i'll post when i figure that out.

I noticed that there appears to be a couple resistors cut off of the big capacitor board. I replaced all the tubes and still nothing! So i tried to check continuity with a DMM, and there seem to be a couple resistors not working, but who knows. The guy who sold it to me said it was working fine but needed tubes. I told him it wasn't working, and he offered to take it back or help with repairs. either way i'm not too worried. It's probably nothing much to fix... as long as the transformers are fine.

I spoke with Mike B. from boogie (duh) and he would be happy to do the upgrade for $400 plus about $150 to boogie to clean it and change the caps. He said that the amp just missed being a factory IIC+ by about a month! but he said i should feel lucky to at least have a IIC, since when its upgraded, it's basically the same animal.

thanks again for the great insight.

scott