Mark III and possibly other boogies Reverb Hum Fix!!!

[dgr888]

This fix will reduce the hum in the Mark 3 and possibly other models of the Mark series. It seems the problem is the reverb tank simply needs to be turned around so the input with the shielded cable is the farthest away from the power transformer. When you turn up the volume knob on the reverb up after you do this there you will notice almost no power transformer induced hum into your reverb. Grounding the rca jack on the cable that has no shield actually induces more hum in the tank through the chassis ground. So don't. If this hasn't been posted before it should have been picked up by the folks at "MESA ENGINEERING" long ago....Also MESA'S ONE WIRE FIX DOES NOT WORK!!!!
Also DO NOT CHANGE where the cables go. The reverb input is a shielded cable and the output is a single wire. So do not reverse the cables OR use a shielded one for the single wired one as you will still have hum issues..One might be a little short but it should still work..
Just reverse the tank with the cables in the same place....
dgr888

 

[dgr888]

Also let me know how this works out for ya'll and make sure you guys try it on all your Boogies to see if it works on the other models...Thanks

 

[dgr888]

Any one try this reverb hum fix???? Let me know....

 

[>Photi G<]

My amp was like this from the time I bought it. The Reverb is dead silent (as in no hum, which is a good thing), so it works! Thanks for the tip!

 

[jpdennis]

I will check when I get off work. Thanks for the tip.

Dennis

 

[Shawnee]

Wow. Great tip!

 

[dgr888]

Thanks for taking the time to try this out and giving your feedback. I know how frustrating it can be listening to the noise the reverb in these amps make. It also is a shame after paying top dollars for these they have no clue and have sent these out for years like this. You would think something simple as this they would have corrected long ago. Maybe they will read this post and finally figure out the mystery of the noise in their reverb!!!!!!!!!!!!! I have 2 Mark 3's each from different years and both had this same problem. Either they have no quality control or ?????? So if you have reverb hum in your Boogie no matter what model here is your fix!!!!!

 

[RussB]

Here's the reverb fix, it's the 220k (IIRC) resistor from the jack to the resistor on the board (it's sitting parallel to the red wire)

 

[dgr888]

No need to replace ANY components on the board unless you want more depth to the reverb....Or adding a wire between the rca plugs.....The hum in the reverb is caused by the power transformer because the input of the reverb tank is too close. The simple fix is to turn the tank around so the input transformer does not pick up the hum created by the power trans. The folks at Boogie have said in some posts here that the hum is just the way it is in their amps. Wrong... They put the tanks in backwards from the factory and turning it around makes them quiet.

 

[phyrexia]

So you are saying as a blanket statement that EVERY mesa/boogie amp with reverb hum can be fixed by swapping the tank?

I am just clarifying.

 

[dgr888]

Phyrexia
My first post on this states it works on Mark 3's and possibly other older mark series amps that have buzz/hum problem in the reverb. Most of these were made in the 70's,80'&90's. As far as other models that may have this problem it might work all you have to do is try it. I've asked in my posts for replies to see if any other amp models were corrected by doing this.
If they didn't notice the tanks were backwards from the 70's,80's and 90's there might even be newer models with the same issues and we won't know until there are more responses. So try it and let us know!!!!!!

 

[Restless Rocks]

I'm just finishing restoration of a Mark IIb short head and the original reverb pan is already mounted with the output side opposite the pwr trans. Mesa also had the forsight to put those metal plates over the open side of the pan. This one actually has a second 4"x4" metal plate over the output side so as to double sheild the output pickup coil. I have yet to have a Mark w/reverb come into the shop with humming problems in the reverb.

John

 

[dgr888]

Mesa provided the extra plate to help shield the hum in the heads and might have even turned the tank around because the tank is much closer to the power trans. EVERY combo I have had come in has had the hum problems because they were installed with the reverb input transformer directly under the power transformer. They did not have any "foresight" to getting it right in their combos and left quite a few leave their factory. Needless to say I have been fixing these since '89'......

 

[dgr888]

530 views and still counting so a lot of you must have some noise issues. Let the rest of the members know that this works and also on what other models it might work. Thanks for the support.....

 

[dgr888]

bump

 

[gts]

bump

?? bump? Is there something for sale here? :lol:

Also MESA'S ONE WIRE FIX DOES NOT WORK!!!!

Pretty sure Mesa's one wire fix was not created to reduce the hum you are referring to,
it was meant to fix amps who's reverb had stopped working due to loss of a ground contact.

Mesa provided the extra plate to help shield the hum in the heads and might have even turned the tank around because the tank is much closer to the power trans. <snip>

You say "might have even turned the tank around because the tank is much closer to the power trans" but imho it was not done for this reason. It was done because of the headshells design, where the tank is dropped through an opening in the bottom of the shell (springs now facing up). This allowed more room inside the shell so they didn't have to build a taller headshell (to accommodate the full tank's height). But you may be on to something as well.

Based on how you say reverb tanks were installed in combo cabs, be it accidental or not, flipping it over when putting it in a head reverses the position of the input and output jacks.
This is because Mesa used the same tank in combos as well as heads. Once again this could have been an accidental cure to the problem you cite as the 9AB2A1B tanks were meant to be installed with the springs facing down. The next question: Did the tank designed to have the spring facing up (9AB2A1A) have the input and the output in the same position as the 9AB2A1B. Meaning, when placed next to each other in there default installation positions, are the input and output jacks on both tanks on the same side as the other. If so I'd say the flipping of the 9AB2A1B when installing it in headshell was an accidental "cure" to the hum problem you state exists. And if a 9AB2A1A tank is used in a headshell the hum problem will exist.
That being said I recently acquired a 9AB2A1A and will see if the jacks are on the same said as the 9AB2A1B and if so will see what happens when installing it in a head (will try installing in both a Mark III and a Mark II)

 

[dgr888]

Gts, Thanks for your info on this as I am not as familiar with how the reverb tanks are oriented in the head shells. I am asking board members to try this as I have been doing this fix in combo's for a long time and know it works when there is a hum problem that is persistent even when the reverb control is all the way down. I have had guys bring me their combo's for other work and while I repaired the amp also showed them what happened when we turned the tank around. A lot of theses were Mark 1's 2's and 3's and the owners had these since the day they were new and thought the hum issue was just the way it was and nothing could be done. So let us know what you find out with the heads and other models you come across.
Thanks dgr888

 

[mark2boogie]

dgr888,

You can have a look to this, if you like :
http://forum.grailtone.com/viewtopic.php?f=27&t=54614&start=30
Where I explain how I cured the numerous (factory stock) hum problems of my MKIIA, including the reverb.

A+!

 

[dgr888]

Mark2boogie,
Thanks for the link to your post as it is very informative and others that look at this should check it out. I can't tell you exactly how many of these amps I have done but I know I made a lot of Boogie owners happy. It is a shame to spend 1500-2000 and to have these type of issues. Think before you build and get the bugs out before they sell them is how it should be........

 

[mark2boogie]

Mark2boogie,
Thanks for the link to your post as it is very informative and others that look at this should check it out. I can't tell you exactly how many of these amps I have done but I know I made a lot of Boogie owners happy. It is a shame to spend 1500-2000 and to have these type of issues. Think before you build and get the bugs out before they sell them is how it should be........

Well... Somewhere, I agree ! I think that about the MKIIA, in the late 70's, MESA was kind of "pioneering" and "growing fast" in the meantime, so it may be an apology, or at least an explanation to these obvious factory misconceptions. But yes, as a part-time tube amp builder and repairman, I completely subscribe to what you wrote above...

If not already done, have a look to the 1st series of MARSHALL Class 5 combo : it's an excellent sounding amp for blues playing, very convincing, but this amp is GRRRRRRRRRRR DZZZZZZZZZZZZZ all-around-innard-vibrations ridden !!! Many obvious and serious mechanical misconceptions, nothing else, make it sound like a squadron of jigsaws...

A+!