Boogie MKIIB ....... hmmm

[Rob Livesey]

Hi Chaps,

This weekend I bought a hardwood Boogie MKIIB #7069 and I've got some issues with it.......

The amp has me a little puzzled, so I need some advice from those here who have more experience with them. If anyone can help me out I'd very much appreciate it. I'd also like you to look at the amp and determine if it's original or modified in any way, which could explain some things.

I'll list my concerns in order.

1. The reverb is quite weak, even on 10 on the clean channel it's not that present, but when going to the lead channel it then sounds swampy.
2. On the clean channel, it gets louder up to about 4 on the master, but then after that, any further master increases have no effect.
3. The lead channel lacks gain, with the first volume on 7 and the lead drive on 10, there really isn't enough gain for the kind of lead lines I play. Only when adding the boost function can I get close to enough gain.
4. The lead channel is very dark and muddy, I'm struggling to get any crispness out of it. If I eq the lead channel for enough gain and top end, my clean channel is really toppy.

The amp looks original inside, see pics below. The amp is currently running all NOS Phillips 12AX7's in the pre-amp and Sovtek 5881WXT's in the power (I will change these). I have questions too about the ins and out's on the underside of the chassis. There are THREE RCA phono connections underneath the chassis, the reverb tank plugs into two of them, one is un-used? I also have two 1/4" jack sockets under there, one labelled pre-amp and one labelled Boost & Graphic. I had thought that it was supposed to be Reverb & Boost?

Anyway, I hope you can help me guys, I'm digging the clean channel and the added boost with my 335, I just need to get to the bottom of the reverb and the lead channel really, as well as understand what's going on underneath.

Front:

[img666]http://personalpages.manchester.ac.uk/s ... G_2476.JPG[/img]

Back:

[img666]http://personalpages.manchester.ac.uk/s ... G_2478.JPG[/img]

Ins & Outs underneath - The RCA phono on the left is not currently being used:

[img666]http://personalpages.manchester.ac.uk/s ... G_2461.JPG[/img]

Chassis underside:

[img666]http://personalpages.manchester.ac.uk/s ... G_2462.JPG[/img]

Inside:

[img666]http://personalpages.manchester.ac.uk/s ... G_2463.JPG[/img]

Cable from Reverb Tank, NOTE bare blue wire....

[img666]http://personalpages.manchester.ac.uk/s ... G_2472.JPG[/img]

Reverb connected:

[img666]http://personalpages.manchester.ac.uk/s ... G_2474.JPG[/img]

Cheers,
Rob

[LarryN]

That's my favorite Boogie. Very nice. I wasn't crazy about the lead channel; it sounded kind of ratty to me. I don't know if that was just mine or what. It might be worth a mod to that channel. The clean side is just beautiful, IMO. Some Boogies' reverbs were weaker than others, not sure why. Too bad you're not in the U.S. Mike Bendinelli at Boogie could make that thing happen in a big way. It might benefit from a cap job and thorough cleaning. they are very tube sensitive as well. Best of luck sorting it out.

P.S. - I think the extra RCA jack is for switching the tonestack bypass for more gain.

[Structo]

Sorry I haven't had the pleasure of owning one of those.

But are you positive that those two 1/4" are jacks?

Sometimes a bias pot looks like that from the outside.
But that would be obvious when you look into them as you
would see a slotted head.

Here is an owners manual for the Mark IIB.

It sort of like one long run on sentence!

http://www.mesaboogie.com/manuals/Mark%20IIb.pdf

[LarryN]

After a closer look, the left hand RCA jack seems to say "reverb", I guess it's the switch jack? The left hand 1/4" says "boost" and something, so it's probably the tonestack bypass jack.

After reading the manual, I'm totally confused about those jacks. Thanks for the download, Structo.

[Reeltarded]

Turn off the EQ. Do everything to a baseline with the graphic EQ off. Ok, never turn it on again. It woofs, and shrieks, but it's not good for dirt, only clean.

The lead drive should be wailing if the rhythm drive is up. Set everything to 7. 7 is the magic number.

These amps sound grainy, and they lack note separation in the end.

Smerge.

[greenbottle]

You could try the SLO Clone forum. They have a messy Booger section.
They may more detail information on specific Mesa boogie amps.

Alan

Is'nt it a lovely looking cabinet.

[Rob Livesey]

Thanks for the input chaps. I've been away for a few days so not had chance to respond. I'm getting the idea that it's the clean channel on these amps which is where it's at. Not many people use the lead side of the amp and prefer to use a decent pedal.

Apparently Mike Bendenelli still takes these amps back into Boogie for service and mods and he has a few tweaks which he regularly makes to the MKIIB's to help out the reverb and the lead channel. I'm considering doing this, but I'm thousands of miles away, so I need to find a cheap shipper. I was hoping that the tweaks and mods were "out there" but it appears not.

I'll keep you posted.

Rob.

[jspax7]

I had one of the first MkII's. Gigged with it for several years. Nice amp. Mine was a 60 watt, no graphic, EVM speaker.

Mine came with Sylvania 6L6GC's. I ran the first volume at 7, lead drive at 7, Treble at 7, Mid at 5, Bass at 3, master at 1.5 for small clubs. (I didn't care for the pull pots.) Les Paul neck pickup, Santana tones. Not as nice with low output Strat pickups.

The jacks under the amp should be Preamp out / Power amp in. (Passive loop) My reverb was weak too.

You might email Mesa tech support to see if they can help you. That amp should sound very nice.

[FUCHSAUDIO]

Certainly filters will help. They are original and had a 10-15 year lifespan before declining in quality. I like the TAD's as they fit well (small) and work very good. I would speak with Mesa (mike knows the amp well), and perhaps they can guide you.

BTW: The reverb wires are correct. One shielded (output from pan) one input not shielded (it's like an 8 ohm speaker lead). I think they avoided ground loops or saved money (or both) by wiring it like that.

Should be a great amp after proper tweaks are applied.

[ampexplorer]

I have used a mark IIB and the two 1/4 inch jacks are for the preamp out/ power amp in and the other jack is a stereo jack for footswitching the gain boost(bass boost) and the graphic eq. the under chasis rca jack is for footswiching the reverb

[ampexplorer]

also don't give up on the lead chanel. if you want to smooth it out try pushing it with an overdrive pedel like a Fulldrive or ts808. I also liked to hit the lead chanel with a germanium booster i built to give the amp a bit more gain. I also turn the presance control down when the amp is turned up otherwise they can be very harsh sounding any setting below 4 cut highs

[Rob Livesey]

Thanks for the help chaps.

I've had the chassis out again and cleaned all the jacks and sockets etc, I now have a decent reverb ! Just goes to show, a bit of TLC goes a long way.

The clean channel on this amp is absolutely wonderful, input vol on 7, treble 6.5, middle 5, bass 2.5, reverb 3.5, presence 4. Strat or 335, just lushious.

Basically, don't use any of the "pull" features or the graphic. When kept simple I think the clean tone of this amp would be hard to beat. Unless I can get the amp to Mike Bendenelli, I can't see me ever using the lead channel.

Obviously, it still needs the recap before I do any gigs with it, one of the filters is blistered.

If anyone has the details of the "Reverb & Loop Mod" I would appreciate it, in confidence of course.

Cheers,
Rob.

[Rob Livesey]

Certainly filters will help. They are original and had a 10-15 year lifespan before declining in quality. I like the TAD's as they fit well (small) and work very good. I would speak with Mesa (mike knows the amp well), and perhaps they can guide you.

BTW: The reverb wires are correct. One shielded (output from pan) one input not shielded (it's like an 8 ohm speaker lead). I think they avoided ground loops or saved money (or both) by wiring it like that.

Should be a great amp after proper tweaks are applied.

Hi Andy, thanks for the info. When changing the filters in one of these, someone here in the UK has suggested this can be done without removing the board and desoldering/soldering from the top. What do you do?

Would you recommend swapping just the main filters on the seperate board or all the electrolytics in the amp?

Cheers,
Rob.

[butwhatif]

I worked on many of these, and modded some to have the pre and post efx loop circuitry like a Mk III. They still had the single overdrive stage, which worked well. Also, the reverb circuit works much better looped to this circuitry. The reverb shielded wire is the return, unshielded the send.
Also some early IIs had NTC resistors for cathode, which i changed out to real CC resistors.

[FUCHSAUDIO]

Hi Andy, thanks for the info. When changing the filters in one of these, someone here in the UK has suggested this can be done without removing the board and desoldering/soldering from the top. What do you do? Would you recommend swapping just the main filters on the seperate board or all the electrolytics in the amp? Cheers, Rob.

The main filters on the power supply board, can be changed easily. There are two on top and two on bottom, so it's best to lift the board and replace that way. Not tough. Take a couple of pictures, so you know what went where and proper lead connections etc.

The one filter on top of the main audio board can have the leads snipped right at the old cap body, pried up with a screwdriver, and the new cap (usually smaller) can be glued in place and "J-hooked" onto the existing cap leads.

I've never had to remove the main board in these amps very often.

If they have the constant current sources on the cathode of the first tube (that may have been the MK-I's only) , replace with the proper cathode resistor value.

Cleaning the preamp board with an old toothbrush and some flux remover (dry it out with a heat gun) is wise too, especially if the fan has blown lots of gunk into the chassis. Be careful not to get that stuff into the relay(s).

Spray the sockets (from the tube end) with contact cleaner and lubricant too.