new owner of a 1979 MKIIA

This one is kind of special. I got this yesterday, it's a 1979 Mesa Boogie MKIIA. And it's in almost new condition.
The clean tones and reverb sound great, I will have to figure out how to use the gain side.

Years ago I had a blonde MKIIB 60 watt, so I'm somewhat familiar with the amp.

This one is a 100 watt version, no graphic EQ, has a 60/100 watt switch.
has the upgrade Altec 417-8H 12" speaker.
The only downside is that it's a heavy bugger, but it is compact and I also got an Anvil roadcase with wheels.

I found a copy of the manual online. Apparently a lot of these came with a SS tube substitute called a Fetron in the first preamp position, there is a switch underneath to choose between using the Fetron or a 12AX7. This amp didn't have the Fetron, so I may never know what that sounds like.

Any other MKIIA owners out there?
And if so, have you found a good sounding but much lighter weight speaker that would work in this amp? The Altec sounds great but if I can lighten the amp up I might go that way.

Also there is a jack on the bottom of the chassis for a dual footswitch, so would that be channel switching and reverb on this amp since it doesn't have the graphic EQ?

Welcome to the IIA Club! The jack on the bottom should be for Gain Boost and Reverb; your channel switching jack is the one under the input jack on the front. There is a second jack on the underside of the chassis which is a junction between the preamp and power amp, (which was removed after the Mk II B incarnation) that can be used in a very cool way as a secondary Master Volume... Check this out: https://thegenerationofmusic.wordpress.com/2012/03/17/guitar-how-to-the-mesa-boogie-mark-iiaiib-ultimate-master-volume-pedal-trick/

As far as lighter speakers are concerned, there are several possibilities available depending on what kind of tone you're going after. But, for that classic Santana vibe, you have his speaker of choice. IMHO there is something about the sound of early Mark I and II's with an EV-12L; everyone knows it's not the lightest speaker in the world, but the tones are incredible. Most people think of that sustainy high gain distortion when it comes to Mark Series Boogies, but these amps have incredible clean tones, which when paired with a high wattage speaker makes for some lucious and LOUD sounds with headroom for days.

I have an early Mk II with a 15" JBL and it is a monster; I do have the FETRON plug, but haven't tried it. The reason behind it was because some preamp tubes at the time were prone to microphonics and noise; with today's QC, and better made tubes we don't have to worry about such issues.

Have fun dialing in your tone!

Eminence has some EV like lighter speakers. However, you have the holy grail for this amp.

I have a fetron but choose to use a tube. Couldn't really tell a difference. Maybe you could if you overdrive the front end.

You can use the preamp/power amp junction as an effect loop if you get a C-Lator or Glab pre box. The loop is too hot for most effects, you have to turn down the input and won't have enough gain from most effects to drive the power amp much. The volume pedal trick is cool.

The cleans are very good and you have good range from very clean at input volume about 6 to some dirt add you go past 7, depending on pickups. I find I need to set input volume to about 8 to get really good overdrive. Just have to try various combinations.

If things start sounding bad, smell, odd noises, could be needing a cap job. Likely due if it has never been done. These amps can keep going and going.

Thanks for the input / info. I just got it, so I'm going to feel it out for a while , I may not change anything.
It is dead quiet at idle, the only thing you can hear is the fan. I don't think it was played much in the last 20- 30 years.
I tried a Peavey TRS dual footswitch into the jack on the bottom, it turned the reverb on and off on one side but the other switch didn't do anything that I could tell.
I also tried it into the jack on the front and it worked for the channel switching.
I don't really want to use 2 different footswitches, so I will probably just use the Peavey switch for channel switching and control the reverb manually.
I didn't really care for the pull boost tone, too dark.

I will pull the chassis out at some point and see what everything looks like inside. When I do I'll post some pics here.

I know the MKIIB 60 watt I owned years ago had a great clean tone, a OD / Dist pedal into the clean channel sounded great. Since it has a gain channel I do want to see what I can get out of it, it's there why not use it some?

You already know that there's a balancing act to dialing in the two channels; I prefer to have mine set clean for most things, but every now and then I gotta get my Boogie on, and make it do what it does best.

The Pull Boost is kinda fun for times when I go for the heavier tones; I love being able to get that creamy distortion at moderately low levels. Santana's "Europa" was that pivotal song that made me want to play guitar; having that tone at my disposal is a fantastic thing. You can get enough gain without it, but it does add a nice bit of extra flavor when needed.

Twiddle them knobs!!