Mark IV Fan Wiring Question

[GD_NC]

I just picked up a older Mark IV-b combo yesterday for a pretty good price. Overall the amp is great but it has one strange mod that I'm scratching my head over.

The fan has been replaced with a after market fan and the fan's power wire is not wired directly into the chassis. Instead, it has a standard plug on it and you just plug it into the 110v auxiliary outlet on the back of the amp. This set up works fine, but the fan runs anytime the amp is plugged in instead of being controlled by the Amp's power switch. So...

Question 1 - Were any Mk IV's combos made without the fan? Is this a creative add-on or is this just a shoddy replacement job?

Question-2 - Where is the wire supposed to go? Does anybody have a picture or diagram that shows the correct wiring?

Question 3 - If I remember correctly, the fan in the Mark IV-a I had a few years ago only ran when the amp was in full power mode. Is that correct or is my memory suffering from old age?

Thanks!

 

[Tuna141]

The 3-prong AC outlet on the rear of the chassis is just an auxillary outlet (intended to be used to power effects, etc). The fan is supposed to have a 2-prong AC connector, but I don't remember if it is a standard size that will fit a regular 3-prong outlet or not. The fan is supposed to plug into a designated 2-prong AC outlet on the bottom of the chassis. Locate the receptacle and see if the fan plug will fit. If not, you may have to purchase a replacement from Mesa - would be an easy fix.

I'm pretty sure the fan is standard (not optional) on all Mark IV combos.

The fan will run continually when the amp is on, regardless of whether it is in Full Power mode or not.

 

[GD_NC]

Yep, there's the two prong outlet. It's located in a tiny space between the transformer and the case. I would have never seen it (I guess the guy I bought it from didn't see it either!). I plugged the fan in and it works like a champ. Easiest fix I ever did.

Thank you!!!