Replacing the fan in a Mark IV combo

[ThatDamnSG]

My Mark IV (small body combo) didn't have the cooling fan in it when I got it (used). Can anyone recommend a replacement fan for this amp? Also, how exactly is it mounted in the amp? I have seen there's a power outlet for a fan up in one corner of the chassis, but how are the fans mounted in there? Any help...pics even, would be greatly appreciated. Thanks.

 

[zebpedersen]

It's screwed on in two or three places. You'll need to get the speaker out of the combo to remove/install it. Possibly the reverb tank also. There is one screw on the 'half-back' (wood at the bottom of the cab on the back), and either one or two on the side of the cabinet on the inside. You need to have frontal access to the inside of the cabinet to remove it , as you can't remove the back panel because the fan is screwed to it. Thus, the speaker must be removed.

 

[ThatDamnSG]

Cool, thanks for the info. So I'm understanding correctly that its mounted in the corner where the half back and side of the cabinet meet then. Now I just need to find the right fan.

 

[zebpedersen]

Yeah basically. Should be two screw holes in the side of the cab and one on the half-back. See if you can find Globe Motors - you need a 110v fan no matter what locale you are in, as the (input?) transformer already changes the voltage from whatever it is in your country to 110v.

 

[tbguitar55]

The fans are pretty standard (Howard) Box fans - try getting one from an Electronics outlet. It mounts under the right rear (under the simul_class switch area). They used three L brackets - which you can get from Mesa. And yes, it plugs in next to the trannie up and under the chassis. I'll take some shots of my Mark 1 and email you if you'd like.


More specifics:

The fan should sit just above the reverb tank near the bottom of the cabinet leaving enough room for air to circulate - maybe a finger width. Air will be pulled from under and pushed out the top towards the power tubes. On most back covers, Mesa used a lip (cleat) - I mount two of the L brackets under this lip. I then secure the fan to the side of the cabinet with the remaining L bracket.

I usually take the speaker out and do most of the placement from the front side - this makes it a lot easier. The fan should sit just under the right cabinet side cleat so that when you remove the back cover, it slides right out - it's a tight fit for sure, but makes for the best overall placement. Using three L brackets also provides the best stability. With this method, you simply(?) remove the right side screw, then the back panel screws and can slide the entire assembly out if needed.

Right Rear corner view:

Right cab side view:

L-Bracket view: (attached to rear panel - this cab has no cleat, but Mk IV should?)

-tb

 

[ThatDamnSG]

Thanks for all the info guys....and the pics tbguitar55. Very helpful. I can't seem to find those Howard specific fans anywhere...managed to get a model number, but I'm not sure they even make them anymore.

 

[av8or3]

Try Globe Motors....