Road King - diode/fan upgrade?

[FoxMustang]

I've been looking to buy my first tube amp, and naturally the Road King has caught my eye In reading through countless online reviews and auctions, I'll occassionally find a mention of a "diode/fan upgrade" done on older Road Kings. I search the board here and Googled around some but couldn't find any more info on exactly what this is. So what is it? When did this upgrade become standard production, and how can I tell if an amp does/does not have this upgrade?

 

[Erik]

FoxMustang,

If memory serves correctly, the first 500 or so heads didn't have the fans. There were a few other "upgrades" Mesa included later...one happens to be a different Pentode/Triode switch. I found out about the latter the hard way when I blew mine. No big deal, I brought it to an authorized tech and had my amp back within 36 hours. I'm not sure what serial numbers have the new Pentode/Triode switch. If you get an "old" Road King, take it to an authorized tech...they can do the upgrade (at no cost to you) in a flash.