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PostPosted: Tue Jan 02, 2018 4:56 pm 
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Mark II

Joined: Wed Dec 23, 2015 9:50 am
Posts: 108
I would like to ad some more gain to my Purple Stripe Mark iii as well as get the R2 mod.

What mods could I have my amp guy do that would add a little more gain and possibly improve an already awesome tone?

I searched for a topic and couldn't find anything specific for the Purple Stripes. So, I thought I'd ask. If there is one please feel free to post a link.

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JP-2C
1985 Mark iii Simul Class Black Dot w/Red Stripe upgrade
1987 Mark iii Coliseum Purple Stripe
1987 Red Stripe Combo
Mark IVb
Rocket 4Forty
JP2C (#2)


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PostPosted: Sat Jan 06, 2018 2:27 pm 
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Mark II

Joined: Wed Nov 13, 2013 7:53 am
Posts: 79
The R2 mod will let you dial in a better rhythm tone mix and to crank the input more to get more grit. A useful mod.

I use an MXR Microamp to boost R2. Goes from warm to blazing. Best solder free mod is a nice clean boost.

My Purple Stripe also has a mod to increase the reverb depth and to cure a slight noise that the purple stripes can have when using reverb. Mesa sent me a sheet of mods when I asked.


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PostPosted: Mon Jan 08, 2018 9:21 am 
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Mark II

Joined: Fri Jul 28, 2006 5:58 pm
Posts: 104
Location: Europe
In an earlier thread I described what I did to my 60 watt purple stripe Mk III. These changes were:

- replaced the 0.01uf cap in the feedback section that is parallel to the 56k resistor with a 0.005uf
- replaced the 0.002uf plate bypass cap on V3b (the second lead gain stage) with a 0.001uf
- fixed the reverb glitch (that is what is also mentioned in the post above)
- replaced V4 (the reverb tube) with a 12AT7
- replaced the speaker with an Eminence Legend MOD (preferred it over both the C-90 and the EVM).

Other than that I replaced the electrolytic caps in the power supply but since I used the same values as stock that is not a mod but maintenance.

Cheers Stephan


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PostPosted: Mon Jan 08, 2018 4:05 pm 
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Mark II

Joined: Wed Dec 23, 2015 9:50 am
Posts: 108
Thank you both for your replies.

darkbluemurder
I actually copied yours onto a Word Doc and am handing it to the Tech. thank you so much for all of that info!

Promethean
Thank you as well. I actually asked Mesa for a Mod sheet and they said no...lol
Sucks to be me sometimes.


Well, I am about to head out to the Tech's Shop. Thank you for your help!

_________________
JP-2C
1985 Mark iii Simul Class Black Dot w/Red Stripe upgrade
1987 Mark iii Coliseum Purple Stripe
1987 Red Stripe Combo
Mark IVb
Rocket 4Forty
JP2C (#2)


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PostPosted: Tue Jan 09, 2018 7:45 am 
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Mark II

Joined: Fri Jul 28, 2006 5:58 pm
Posts: 104
Location: Europe
The reverb glitch fix is a 120k resistor from the red wire of the reverb transformer to ground. I have no idea why this works but it does.

The reverb increase mod is a 3.3k resistor that is inserted. Most of the posts I have read say it should be attached to the return jack connection but I have seen one drawing where it was attached to the send jack. You could also decrease the 1.5 meg resistor going into the reverb with a 470k (that is in the Mark IV or in the Lonestar - the Lonestar has a 250pf cap with a switch in parallel to the 470k - this is the warm/bright reverb switch). Going from a 1.5 meg to a 470k would drive the reverb harder. I can only guess that Mesa received wishes to make the reverb more Fendery so that's where the reverb evolved in later models.

I considered the reverb increase mod but dropped it since I am no big reverb guy anyway (personal preference). A little reverb for ambience is all I need, and the stock Mark III circuit provides that.

Cheers Stephan


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