Mark III - Volume Pot Mod - R2, yeap, yet again...

[Drew816]

Ok, I got my long chassis Mark III and there was the channel 'imbalance' between R1, R2 and Lead. So I'd done my research and was ready due to the nice write-ups and postings of other members (along with a few PM's, thanks guys!). Here are the two main posts that I followed and then see my process below:

http://forum.grailtone.com/viewtopic.php?t=15252

http://forum.grailtone.com/viewtopic.php?t=12918

And here's my series of photos and notes; as mentioned before, you essentially replace the R130 with a pot using one spot from the old R130 'lugs' and I used a spot from R131 just because I had more room to solder there and that was it. I left the old R130 there (just snipped and out of the way) and no I wouldn't go on a 'world tour' with my amp as is but it works and makes the ability to balance the 3 Channels perfect, no issues now!

 

[phyrexia]

Nice Post.

I've run my amp hard after the mod and nothing happened. I have confidence in my soldering skills - don't worry too much.

 

[edward]

Yup, it's a simple and very worthwhile mod. It's "invisible" once the mod is done --since I've set it I haven't adjusted it since, but I sure am glad I did it.

Edward

 

[psychodave]

I would put some shrink wrap on the floating resistor 8)

 

[Generic Jeff]

:mrgreen: Another pleased DIY "R2 Mod" Mark 3 owner! Thanks for the info gents! :mrgreen:

 

[Tuna141]

Thanks for taking the time to post. I'm sure your informative post will help a lot of Mark III owners.

Moderators, please "sticky" this info. Thanks.

 

[rvschulz]

i am very timid about doing this to my Mark IIIs ... until now. That is some great camera work, thanks. One question - I want one of those "knobs" like the other knobs - marked 0-10. where can i get one of those ? also, on the pot, i noticed (to me, a goof) that it looks like there are 3 solder points and you chose two - are they marked ? if so, which ones did you select ?

 

[MusicManJP6]

Sounds like a cool and very useful mod!

 

[GIG4FUN]

Sounds like a cool and very useful mod!

absolute necessity with the Mark III amp. A "must do"... I wouldn't own one without it. (gettin' it?)

 

[rvschulz]

called Mesa yesterday afternoon. ordered 2 Mark III volume pots and knobs - i wanted it to look the same. shipped yesterday too, guess i will have something to do next week.

 

[Whoopysnorp]

For whatever reason, R131 is not present on my blue stripe. I assume then it doesn't matter which one of the eyelets I use to attach the lead coming off the pot?

 

[kmanick]

great pics!!
thanks

 

[jhale667]

I want this mod for my Red-Stripe MK III but apparently Mike B. said it can't be done on a short-chassis head....?

 

[frets70]

I purchased a mark III grn stripe from a board member about 5 months ago. This head has the R2 mod, he stated it was performed by Mike B at Boogie.

The weird thing is my reverb (V4) tube socket is gone. Is this what they do at the factory? Or is mine a slightly different mod?

The reverb knob does control R2 master. Only it is not very effective when I run the the Vol 1 above 5 (really needs to be at 7 for optimal tone) So I end up not using R2 by itself.

 

[cthulhu]

I want this mod for my Red-Stripe MK III but apparently Mike B. said it can't be done on a short-chassis head....?

That isn't strictly true if I recall correctly. I had it done on my short chassis, it has the GEQ and Reverb, so I got a stacked pot from here - http://www.has-sound.com/parts.htm

Using this thread http://forum.grailtone.com/viewtopic.php?t=25347&postdays=0&postorder=asc&start=15 as a reference for the tech that did the work and replaced my Presence knob with the stacked pot/knob set.

It works great!

 

[238839]

I want this mod for my Red-Stripe MK III but apparently Mike B. said it can't be done on a short-chassis head....?

I did this mod on my Short Head Mark III with very positive results.

 

[psychodave]

I want this mod for my Red-Stripe MK III but apparently Mike B. said it can't be done on a short-chassis head....?

I have a red stripe short head and it doesn't have a resistor at R131. I tried doing the R2 volume mod, but the amp didn't work correctly and I had to remove it.

Can anyone offer suggestions?

 

[Crowdaddy]

Help!

New member here. I just got my Mark III back from having the mod done. I realize The R1 volume has an effect on the amount of crunch on R2 however, my new R2 volume is also controlling my R1 volume. When the R2 volume is at an acceptable level R1 is not loud enough. They only way I can get R1 loud enough is to turn up the new R2 which makes R1 fine but R2 way too loud. It is almost the opposite of the way it was before the mod.

I am going to have the tech look at at it again. He said he used the info I gave him that I got from this site but something has to be hooked up wrong. Do any of you have any idea what it might be? It looked pretty straight forward and by looking at the pictures I am wondering if he didn't leave that one resistor connected.

Thanks

 

[Crowdaddy]

I realize this topic has been around a while but I really need to get this amp up and running. Any help would be appreciated.

 

[danyeo1]

I want this mod for my Red-Stripe MK III but apparently Mike B. said it can't be done on a short-chassis head....?

I have a red stripe short head and it doesn't have a resistor at R131. I tried doing the R2 volume mod, but the amp didn't work correctly and I had to remove it.

Can anyone offer suggestions?

That's wierd Dave. My Red Stripe short head does have the R131. I'm going to try the mod on mine. I think I can snip the wires off the reverb pot and use it for the R2, or am I wrong?