Mark IIB Problems...Suggestions?

Hi. I've got a 1980 Mark IIB. EVM12L. Great sound. I've got three issues that I'm looking for help with. One of them's probably not fixable, but I figure I'll throw it out there, anyway:

1) When I'm in Lead mode, the reverb begins to cut out as I dial down the amount of distortion in the Lead Drive pot. Volume 1 is at "8", so there's plenty of break up there, if I want it. The cut becomes really noticeable when the pot's at 6 or below. It's bothersome when I switch from the clean channel, as the loss of reverb's pretty noticeable. I've been getting around that by using a RealTube pedal for the subtle overdrive (reverb stays constant) and the Boogie Lead drive at 8 for the heavier stuff, which keeps the reverb constant there.

2) I've got the stereo footswitch for EQ and Gain (wish it was the treble pull out pot and not the gain...anyone know if I can do that?). Sometimes I get an annoying *POP* when I switch into the EQ. Sometimes not. I'd love to get rid of that.

3) Along the same lines, I get a pop when I switch in and out of lead mode. This doesn't seem fixable, though...so I make sure I blunt the strings before making that change, which gets rid of the pop. Be nice if someone knew a different fix for that.

I had a mod done to the lead drive which kicks it up a couple of notches. I love both channels.

Thanks for your time, people.

Bob

gitapik said:

Hi. I've got a 1980 Mark IIB. EVM12L. Great sound. I've got three issues that I'm looking for help with. One of them's probably not fixable, but I figure I'll throw it out there, anyway:

1) When I'm in Lead mode, the reverb begins to cut out as I dial down the amount of distortion in the Lead Drive pot. Volume 1 is at "8", so there's plenty of break up there, if I want it. The cut becomes really noticeable when the pot's at 6 or below. It's bothersome when I switch from the clean channel, as the loss of reverb's pretty noticeable. I've been getting around that by using a RealTube pedal for the subtle overdrive (reverb stays constant) and the Boogie Lead drive at 8 for the heavier stuff, which keeps the reverb constant there.

Click to expand...

First of all, you do realize that the "rhythm channel" does effect the drive on the lead channel. Just want to make sure you are aware how to set these amps because I've seen guitar player that just bought a used Mark IIB don't really know how to use them. They don't read the manual and they don't realize that they have to "juggle" the three volumes (yes, there's actually 4).

As for the reverb, the Mark II, IIB reverb and effect loop should be upgraded. This is a standard modification done by MESA's head chief technician Mike Benedelli. This will great improve the performance of your reverb.

gitapik said:

2) I've got the stereo footswitch for EQ and Gain (wish it was the treble pull out pot and not the gain...anyone know if I can do that?). Sometimes I get an annoying *POP* when I switch into the EQ. Sometimes not. I'd love to get rid of that.

Click to expand...

It possible to do that modification of the treble pull but that's medium modification done by amp technician. He'll probably discourage you from doing this modification anyway.

gitapik said:

3) Along the same lines, I get a pop when I switch in and out of lead mode. This doesn't seem fixable, though...so I make sure I blunt the strings before making that change, which gets rid of the pop. Be nice if someone knew a different fix for that.

Click to expand...

This amp runs on relay so there will be some pop sound. Also your footswitch are old and a bit faulty which cause this loud pop. Those footswitch buttons should be replace. I''ve replaced all of mine dual (gain & EQ) and the channel switching and the pop was not as noticeable.

Hope this help. Yes, Mark IIB is one of my favorite MESA.

RR said:

gitapik said:

Hi. I've got a 1980 Mark IIB. EVM12L. Great sound. I've got three issues that I'm looking for help with. One of them's probably not fixable, but I figure I'll throw it out there, anyway:

1) When I'm in Lead mode, the reverb begins to cut out as I dial down the amount of distortion in the Lead Drive pot. Volume 1 is at "8", so there's plenty of break up there, if I want it. The cut becomes really noticeable when the pot's at 6 or below. It's bothersome when I switch from the clean channel, as the loss of reverb's pretty noticeable. I've been getting around that by using a RealTube pedal for the subtle overdrive (reverb stays constant) and the Boogie Lead drive at 8 for the heavier stuff, which keeps the reverb constant there.

Click to expand...

First of all, you do realize that the "rhythm channel" does effect the drive on the lead channel. Just want to make sure you are aware how to set these amps because I've seen guitar player that just bought a used Mark IIB don't really know how to use them. They don't read the manual and they don't realize that they have to "juggle" the three volumes (yes, there's actually 4).

Click to expand...

Great to meet another Mark IIB admirer. Your point about the different channels is well taken. I've had this amp for a while and have gotten them down. Blows me away how many different tones I can get. I think a lot of people give up on the Mark Series because it's easy to lose patience. I know it took me some time...

As for the reverb, the Mark II, IIB reverb and effect loop should be upgraded. This is a standard modification done by MESA's head chief technician Mike Benedelli. This will great improve the performance of your reverb.

Click to expand...

Thanks for the tip. Mike's great. He definitely knows these amps. I'll ask my techie here about it. If he can't do it, I'll send it out. Costs $$$ to ship from NY to CA.

gitapik said:

2) I've got the stereo footswitch for EQ and Gain (wish it was the treble pull out pot and not the gain...anyone know if I can do that?). Sometimes I get an annoying *POP* when I switch into the EQ. Sometimes not. I'd love to get rid of that.

Click to expand...

It possible to do that modification of the treble pull but that's medium modification done by amp technician. He'll probably discourage you from doing this modification anyway.

Click to expand...

Yeah...that was just a flyer, but thanks for addressing it. I just like that midrange boost a lot more than the Gain boost that's provided. It's easy enough to just walk over and pull it out or in, though.

gitapik said:

3) Along the same lines, I get a pop when I switch in and out of lead mode. This doesn't seem fixable, though...so I make sure I blunt the strings before making that change, which gets rid of the pop. Be nice if someone knew a different fix for that.

Click to expand...

This amp runs on relay so there will be some pop sound. Also your footswitch are old and a bit faulty which cause this loud pop. Those footswitch buttons should be replace. I''ve replaced all of mine dual (gain & EQ) and the channel switching and the pop was not as noticeable.

Click to expand...

I do have the original boxes. What did you replace them with?

Hope this help. Yes, Mark IIB is one of my favorite MESA.

Click to expand...

Click to expand...

Very much so, thanks! Much appreciated. Happy New Year!