Putting together a Mark III Guide

Pre Recto days. Boogie modified Fenders, Mark I-IV, Dual Calibers, etc

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jrb32
Mark III
Posts: 194
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Re: Putting together a Mark III Guide

Post by jrb32 » Wed Jan 16, 2019 5:11 am


jrb32
Mark III
Posts: 194
Joined: Wed Jan 31, 2018 8:32 am

Re: Putting together a Mark III Guide

Post by jrb32 » Wed Jan 16, 2019 5:12 am


jrb32
Mark III
Posts: 194
Joined: Wed Jan 31, 2018 8:32 am

Re: Putting together a Mark III Guide

Post by jrb32 » Wed Jan 16, 2019 5:14 am

I've probably made a few errors as some component values I've made an educated guess on, especially the 1KV disc caps, but should pretty much be complete otherwise :)

Hope that helps someone out there!

Jon

JD
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Re: Putting together a Mark III Guide

Post by JD » Wed Jan 16, 2019 1:39 pm

Great Work Jon
Mesa Boogie Mark 3++ RGX 60W
Axe fx 2
Mesa Boogie Quad Preamp with C+ Mod

Fleflo
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Re: Putting together a Mark III Guide

Post by Fleflo » Thu Jan 17, 2019 2:48 am

Superb! :) :)
Mesa/Boogie Mark V
Mesa/Boogie Triaxis
Mesa/Boogie 2:90
Mesa/Boogie Quad
Mesa/Boogie 2:90
Mesa/boogie Mark III Green stripe

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HighWattGuitars
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Re: Putting together a Mark III Guide

Post by HighWattGuitars » Thu Jan 17, 2019 5:44 am

Thanks for all the work that you put into this. You've created a very useful set of reference material.
current:
MkIVa (2nd of 2)
MkIII black
MkIII purple
MkIII red
MkIII blue
Quad a
Quad b
50 Caliber (EL84)
Mk Series 4x12 (4)
previous:
MkII Series 300 Imbuya
Son of the Original Boogie
MkIVa (1st of 2)

jrb32
Mark III
Posts: 194
Joined: Wed Jan 31, 2018 8:32 am

Re: Putting together a Mark III Guide

Post by jrb32 » Thu Jan 17, 2019 11:36 am

Thanks! To sum up in a general way schematic wise:

Black - Essentially the original schematic based off the incorrect IIC+ schematic with R130 and R126 for R2 channel. C214 added in later for R2 channel.
Purple - A black stripe with basically a IIC+ lead circuit minus a few slight component value changes. But then C26 removed to make it less like a IIC+ in the EQ section... very underlooked amp. Easiest to + mod in my opinion.
Red - A purple stripe but some weird preamp values going on. Lead circuit now almost identical to IIC+. R2 channel changed to remove R126. In its place sticks in an automatic treble shift to be enabled when in R2 mode via an additional LDR.
Blue - 2.2M for R106. Crazy gain lead channel that was completely overhauled. Same R2 channel as Red. Power section finally has 0.0047uF presence cap and 1.5K presence control resistor (same as IIC+)
Green - same as a blue but has 3.3M for R106. Outer simul power valves wired in pentode.

s-fresh
Mark III
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Re: Putting together a Mark III Guide

Post by s-fresh » Thu Jan 17, 2019 12:32 pm

Really impressive work. Not sure what I will ever do with this information having Mike and Mesa in my backyard, but still awesome to have on file for when he eventually retires.

jrb32
Mark III
Posts: 194
Joined: Wed Jan 31, 2018 8:32 am

Re: Putting together a Mark III Guide

Post by jrb32 » Thu Jan 24, 2019 9:58 am

Really impressive work. Not sure what I will ever do with this information having Mike and Mesa in my backyard, but still awesome to have on file for when he eventually retires.
Exactly I'm not sure what will happen with regard to III+ mods or even IIC+ maintenance or C upgrades after Mike B retires. Plus it's nice to document these old amps as much as possible :) I'm sure Mesa have all information on file it just depends if they choose to continue doing the work with another person in place. I would imagine they will still do repair and maintenance but probably stop the + mods on the C and III.

Moving onward as a guide, there is a Reverb mod/fix done at the factory. If this was done there will be a big R written on the back. This essentially adds a 120K 2W resistor from R116 to ground. I'm not 100% sure on the reason for this but it's supposed to sort an issue with the reverb distorting or causing interference. Personally I have also found you can get a popping noise on the speaker sometimes causing interference without this 120K resistor in place. The fix hasn't got anything to do with increasing reverb strength and, in my experience, it does change the overall tone of the amp and I wasn't a fan.

Some people say you can sort this reverb issue by moving the reverb tank around 180 degrees so the reverb tank plugs are no longer under the power transformer. I ended up removing this 120K resistor and made the voltage rail going to R116 from C to B on the schematics. I did this with running wire off the B rail 30uF cap to R116 with one leg of R116 lifted off the board going to this wire and this got rid of the popping or distorting issue and for all and made the reverb all so sweet. This B rail is how it's done in the C+. I'd recommend upping R116 to a 2W resistor though in this scenario.

xdg999
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Re: Putting together a Mark III Guide

Post by xdg999 » Thu Jan 24, 2019 10:48 am

Mike B. can’t retire until he mods my Studio Preamp and Mark lll HRG!
c+ x 14, III+ x 5, D-180, Studio Preamp, 50/50, Mark V 25,1994 Rev G Dual Rec x 2, Mini Rec and lots of Mesa cabs.

How many guitars and amps do you really need!

diancarlo81
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Re: Putting together a Mark III Guide

Post by diancarlo81 » Mon Feb 04, 2019 11:12 pm

Hoping a guide for III+ (schematic)... Thanks!

lovetoboogie
Mark II
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Re: Putting together a Mark III Guide

Post by lovetoboogie » Tue Feb 05, 2019 10:38 am

Outstanding work and effort my friend. This will really be useful to help keep Mark III's up and running. And more importantly to respect their differences when doing service work. Quite impressed!

jrb32
Mark III
Posts: 194
Joined: Wed Jan 31, 2018 8:32 am

Re: Putting together a Mark III Guide

Post by jrb32 » Wed Feb 06, 2019 7:50 am

diancarlo81 wrote:
Mon Feb 04, 2019 11:12 pm
Hoping a guide for III+ (schematic)... Thanks!
viewtopic.php?f=27&t=74714&start=60#p521928

Just compare the two schematics!

jrb32
Mark III
Posts: 194
Joined: Wed Jan 31, 2018 8:32 am

Re: Putting together a Mark III Guide

Post by jrb32 » Wed Feb 06, 2019 7:52 am

lovetoboogie wrote:
Tue Feb 05, 2019 10:38 am
Outstanding work and effort my friend. This will really be useful to help keep Mark III's up and running. And more importantly to respect their differences when doing service work. Quite impressed!
No problem! Ideally I'd like to do this with all the early Mk series at some point but that is budget depending... one day I'll own them all maybe! :lol:

truongbilico
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Re: Putting together a Mark III Guide

Post by truongbilico » Mon Sep 09, 2019 2:08 am

This is just great!
I´m looking forward to see this.
truongbilico.

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