Is my Mark a IIa or a IIb? how to work pedals/reverb?

[asmith9509]

Greetings all... Mesa Mark newb here... just picked it up today. It has been sitting in a closet for 15 years and is absolutely flawless! Was taken to the amp tech a few months ago and refurbed; it sounds absolutely unreal. I am trying to determine if it is a IIa or a IIb. When I called MB customer service and gave them the serial number, they said IIa but the amp does not seem consistent with that. Here are the stats:
- serial number 5059, DOM 4/16/1980
- walnut (?) cab with wicker front
- 100/60 watt switch on back
- 5 band EQ on front
- input and footswitch jacks on front
- volume 1, T/M/B, master 1, lead drive, and lead master knobs on front
- reverb, presence, and slave level dials on back
- effects looo, pre-out jack on back, return jack underneath
- switch underneath to go between fetron and 12ax7; 12ax7 currently installed.

I also have some questions about how to operate it.
- it came with two little metal footswitch boxes; neither are marked very well. One has a switch and an LED with no marking; the other has two switches and marking that I can't read. Do I plug them into the front switch jack? Mono or stereo cables? What do they actually control?
- if this is indeed a IIb, can I use the effects return with a volume pedal to do the gain trick?
- when I turn the reverb dial up, I get increased noise but no actual reverb. Do I need the footpedal to work the reverb? If not, could something be broken?

Thanks in advance for your help. Sorry about the newb questions- I am really psyched about this amp and want to get it rocking!

 

[Nomad]

Not sure about which amp is which, not up on all the different Mark II's.

I believe your footswitch with the LED is for chanel switching that should plug into the front of the amp and I believe the other is for Reverb on/off which should plug into the back underside of the chasis. It's either for the Verb or a GEQ.


Be patient and someone who knows the facts for sure will chime in. This place gets a little slow sometimes but I'd rather hang here as anywhere.

 

[carlosasi]

It is a Mark IIA if it has the Fetron. Very, very nice amp.

Footswitch plugged into the front with standard equipment cable, not speaker cable and it controls the switch between rhythm and lead mode. The second footswitch might control reverb and eq and would plug into the jack underneath the chassis in the rear. Not sure about the reverb problem. Tube or loose cable might be a quick fix. What did the tech say?

Good luck and welcome.

 

[Harry the Horder]

If you check my post you will see all the hassle I've had sorting mine out.
The Pedal with the Led plugs into the front and switches the Lead channel in that is controlled by the two pots on the right expect a loud POP when you do this. The other plugs into the chassis underneath you will find two inputs sometimes three.
Looking in from the back the first on the left is for power/pre out the next one controls Reverb/EQ ( EQ switch on front must be in the on position for this to work and sometimes there is an extra input to the right mine is an RCA socket and is for the gain boost or mid boost.
I think the gain trick you are on a\bout is done by plugging a volume peal into the right socket for power/pre amp out but not sure so check first.The Reverb should be permanently on if the footpedal is not plugged in it seems they suffer with a bad connection at times on that grey moulded plug so might be worth checking if no other faults are found.

 

[asmith9509]

Thanks to all for your help. After checking many different sources, it appears that I do in fact have a Mark II (or IIa, as you please). The fact that it has the master drive and lead master knobs threw me for a loop; according to the Boogie files, they weren't introduced until the IIb. After further examination, I actually don't have the effects loop either; I misunderstood the Slave Out to be an effects send.
This is a completely awesome amp. I know some don't compare them as favorably to the IIc's, but it is the best amp I've had by a pretty far stretch. I absolutely love the tones I can get from it, and the power is just overwhelming.
I figured out the rhythm/lead footswitch problem; when I opened the switch there was a cracked solder joint. Fixed the joint, switch works perfectly! Will take some tweaking to get the levels right, but I'm very happy I got it working.
Turns out the other footswitch (with two switches) controls the reverb and the gain boost. I didn't have a stereo cable until this afternoon, so I will try this pedal tonight.
The reverb is still not working; I tried jiggling the grey/yellow RCA cables to no avail; may try spraying some Caig De-Oxit on the jacks this weekend. I may also try taking out the reverb tank this weekend and cleaning it out; the amp was full of decomposed green foam from the road case, I'm wondering if it may have gotten in the tank. I also have a fresh 12AT7 on order to try. Any other suggestions to get the reverb working (short of sending it back to M/B) would be appreciated. I am an engineer and have built tube amps before, so I know my way around a soldering iron.
Next project after that may be to build a custom footpedal that controls all three functions from one place. These dinky little project-box pedals are pretty hokey, and the switching is pretty simple. I'll have to look for some three-conductor shielded cable.
Thanks again for the posts to help me get this work of art back to it's former glory!

 

[Harry the Horder]

Hi me again,
When I tried jiggling the grey RCA cable nothing seemed to happen but I took the bull by the horn and changed the plug, that cured it. It might be worth plugging the tank into another amp using the current wiring so testing connections and then move on to the PCB it's possible someone has wired the reverb down to earth to leave it permanantly switched off.
If you look at the point the wire from the reverb pot joins the circuit you'll see a .003pf disc cap and a wire should go from there to the ring connection of the pedal socket when this is switched it shunts it down to earth .make sure to DRAIN the CAPS before going in there.Harry

 

[DreamTone7]

After checking many different sources, it appears that I do in fact have a Mark II (or IIa, as you please). The fact that it has the master drive and lead master knobs threw me for a loop; according to the Boogie files, they weren't introduced until the IIb.

I have one of the earliest IIAs (made in '78) and it does have the Master and Lead Master knobs on it...as well as a factory installed adjustable bias (something rarely found on Boogies). I had the amp serviced by Mike Bendinelli who confirmed all of this, so the Boogie files you're referring to are in error.

 

[igfraso]

Hi DreamTone7,
can you tell us in what month of 1978 your MarkIIA was manufactured?
Also, what serial number is it? The last digit is not meaningful (i.e. 306X).

Thank you in advance