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PostPosted: Mon Apr 02, 2018 3:57 pm 
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Mark I

Joined: Mon Dec 08, 2014 2:00 am
Posts: 22
I need to know what caps resistors or whatsoever needed to mod my mark IIII blue STRIPE to the III++.

Thank you all and appreciated.


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PostPosted: Mon Apr 02, 2018 4:51 pm 
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Mark I

Joined: Thu Feb 22, 2018 11:37 pm
Posts: 25
Recently went through this whole process with some help from some of the other members here and a call to Mike B, and hiring a local hifi repair guy to do the solder work [no local amp guys and he did a fine job]. Here's a Red Stripe schematic I added IIC+ and Blue Stripe values to. C26 is apparently something to do with the 5 band EQ, it isn't shown in any of these schematics.

Image

There are a few other component differences when you compare the IIC+ and the III schematics depending on which ones you consult. C. I used this as a reference to compare IIC+ values:

https://www.electronicspoint.com/attach ... -png.30194

And this:

https://drive.google.com/file/d/1Cqtmpp ... MgYQ5GaQP/

These two IIC+ schematics differ in some respects; C506 is at 100nf rather than 47nf on the second schematic. Also the resistor coming from the cathode of V2 is 1.5k rather than 1k in this. C203 is at 22uf in the pdf schematic but 15uf in the drawn schematic. The drawn schematic's values matched those of the Blue Stripe and from memory (which may be wrong) were the same on my Blue Stripe so I chose to leave them as they were. Everything else on my Mark III+ was replaced with the IIC+ values in metal film resistors from the first schematic I posted. This has smoothed the sound somewhat and changed the character of the gain, however as I said in the thread I posted yesterday, the amp still has the grainy character of the Mark III. As I said in that thread, keeping the pull shift disengaged gives a considerably closer sound to a IIC+. I can't see any component values in the pull shift circuit that differ between the III and the IIC+ however there must be a reason for this difference, I've heard it in other demos of Mike B-done Mark III+ amps, or I'd be tempted to put it down to my use of metal film rather than carbon film or carbon comp resistors. It may be that the component differences shown in the above IIC+ schematics are responsible, but I'm also sceptical about that.

There may be other differences in the schematics that I'm not aware of, or it could be something to do with the R1 channel, or something else entirely. I've heard that pcb layout can affect the tone but I'd rather eliminate every other variable as that's not something that can be changed. Interestingly, when I've tried the Mark III mode on a Triaxis it has the same tonal character difference when compared to the IIC+ model. With the III+ mod this character is still there, although less pronounced. If this difference can be modelled on a Triaxis which definitely has a different pcb layout to a Mark IIC+ it stands to reason that it must be due to something else.

I also heavily recommend recapping the filter caps, I haven't replaced the bias caps so I can't speak for how that would affect the tone but before they were replaced the harmonic content and sustain were limp and uninspiring. Much better now. You'll also want to get your head around some terminology if you're not familiar with cathode, grid, etc. There are some good guides online.


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PostPosted: Wed Apr 04, 2018 7:17 am 
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Mark I

Joined: Wed Jan 31, 2018 8:32 am
Posts: 47
Quote:
I need to know what caps resistors or whatsoever needed to mod my mark III blue STRIPE to the III++.

Thank you all and appreciated.


Basically nobody knows or is willing to give out that information at the moment. Sorry. Even modding a III to a III+ is hazy at best. Send it to Mike B for authentic modding. If it's gain you're after though the III Blue Stripe already has more than a III++. All I can tell you from what I've been told is that a III+ turns it into Red Stripe specs with some other minor additions/differences. Then the ++ adds some extra gain onto it. It still won't sound like a IIC+ or ++ though if that's what you're after but comes as close as possible. Why it can't be the same though is also a mystery!

My friend has a III++ done by Mike B but he's reluctant to let me trace it. Until that happens or someone else traces one we won't know. I also don't want to take business away from Mesa if you live in the US but in Europe and elsewhere it's a lot harder to ship amps to Petaluma!

Also the value of the amp may be harmed if you mod it unofficially. Just a word of warning.

So if you're in the US ship it to Mesa. If elsewhere, mod at your own risk using the IIC+ schematics with the results lions has reported.

Quote:
the amp still has the grainy character of the Mark III. As I said in that thread, keeping the pull shift disengaged gives a considerably closer sound to a IIC+. I can't see any component values in the pull shift circuit that differ between the III and the IIC+ however there must be a reason for this difference, I've heard it in other demos of Mike B-done Mark III+ amps, or I'd be tempted to put it down to my use of metal film rather than carbon film or carbon comp resistors. It may be that the component differences shown in the above IIC+ schematics are responsible, but I'm also sceptical about that.


I have purely metal film in my III Black Stripe preamp and don't get this issue as far as I'm aware. Sounds different to any other III I've played - a lot cleaner and brighter. There are also IIC+s that are metal film with no problems. I think it probably comes down to mine having the early transformers, but I cannot be sure.

You can see differences here schematic wise if interested:

https://mega.nz/#F!nYZ1QSIa!JX33ZSGgtDz6R2BBxOWA6Q

Hope that helps,

Jon


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PostPosted: Tue Apr 17, 2018 4:26 am 
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Mark I

Joined: Wed Jan 31, 2018 8:32 am
Posts: 47
Cool so I've done some more research on the ++ and finished tracing my Black Stripe and also done a Board Layout for easier modding. Some things I can gather:

1. The board layout for the different III stripes is the same. Some will have components added or removed or have different component values.
2. The ++ mod is VERY interesting history wise and is basically already incorporated into the III . More on that later.

Firstly, schematics and board view for the III:

PDF LINK TO III BOARD LAYOUT: https://drive.google.com/open?id=1CTJOj ... 0_XyNOSSJ6
PDF LINK TO III SCHEMATIC: https://drive.google.com/open?id=1Hwhcz ... 9XKAcg0aeT

Then schematics for a IIC+ (as close as we'll get until someone verifies with a IIC+)

PDF LINK TO II+ SCHEMATIC https://drive.google.com/open?id=1ljGYj ... HIuMjGJ34C

From these we can work out what's going on with the ++ and C26

Quote:
I need to know what caps resistors or whatsoever needed to mod my mark III blue STRIPE to the III++.


OK, so basically there are two versions of the ++ mod:

Version 1. Version 1. Replacing the 3.3M resistor with a 2.2M OR adding an additional 2.2M and 20pF over the existing ones (unsure which of these if used). The second seems to be confirmed by Boogiebabies who is basically THE guy when it comes to the IIC+ apart from Mike B:: http://forum.grailtone.com/viewtopic.ph ... 15#p437196 and is similar to darkbluemurder's assumptions in this forum https://forum.grailtone.com/viewtopic.p ... 15#p505040

Most likely the second of these was used and incorporated into the III as R133 and C28, although their values ended up as 3.3M and 250pF in the III. Plus for some reason they go to ground before R105 and C47 instead of after??

OR

Version 2. 0.47uf or 10uF cathode cap on V2a (unsure which but it's most likely a 10uF from researching.). This was done to 12 Factory C++s as a switchable ON/OFF version controlled by the Middle Pot having a Push/Pull. Version 2 on the C++ was incorporated as part of the R2 channel in the Mark III but ended up as 0.47uF in the III: http://forum.grailtone.com/viewtopic.ph ... 15#p469289

However, a III+ is a III that's been modded to IIC+ specs as close as possible as Mike B. I don't think he does everything because of the amount of work involved. Just some stuff on the preamp and lead circuits I would imagine and the presence cap C516. Then either of the mods is done above to make it a III++. I imagine the first of these is done to a III, and this has already been done on a Blue Stripe hence why it has a lot more gain compared to other IIIs.

See the schematics and compare this for details.

Quote:
C26 is apparently something to do with the 5 band EQ


Finally solved this mystery as well and has been confirmed by this post with pics of a green stripe https://forum.grailtone.com/viewtopic.p ... 10#p507127

It seems on the Green Stripe C26 is removed for some reason. You can check with the board layout to see if that's present on the blue stripe or not.

The EQ section of the IIC+ is different as you'll see in the schematics. I'm in the process of doing a full III Black Stripe to IIC+ conversion (I'm going to leave R106 as 3.3M and do V2 of the ++ mod because I can then have a switchable ON/OFF ++ via the R2 channel, balanced by the R2 volume mod). I'm talking EVERYTHING I can. Just as an experiment (will probably put a lot of things back after unless I'm blown away).

I'll let you know how it sounds.


Last edited by jrb32 on Thu Apr 19, 2018 7:05 am, edited 1 time in total.

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PostPosted: Tue Apr 17, 2018 6:47 am 
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Mark III

Joined: Sat Apr 20, 2013 4:29 am
Posts: 360
Is this mod related to this one done by this guy?

https://www.youtube.com/watch?v=MB0F9jSA6eU

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MESA BOOGIE MARK III BLUE STRIPE proud owner
https://www.youtube.com/watch?v=qqZz5rHHIIk
https://www.youtube.com/watch?v=VBXj8AJ108Y
https://www.youtube.com/watch?v=1gejXLj8W-Q
https://www.youtube.com/watch?v=6Eptmr_XaRQ


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PostPosted: Tue Apr 17, 2018 7:21 am 
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Mark I

Joined: Wed Jan 31, 2018 8:32 am
Posts: 47
Quote:
Is this mod related to this one done by this guy?


Kind of! He's basically changed C21 and C50 and corresponding resistors in the lead circuit so his Blue Stripe lead circuit is very similar to a IIC+

Ideally, you'd also want to change R153 to 475K and the unnamed ceramic disc off V3A from 500pf to 1000pf in the lead circuit.

That, plus having a 2.2M resistor already on R106 and with the blue stripe preamp being almost identical to a IIC++ already is probably the simplest way to get a III++ on a blue stripe :)

The list of things done are:
A…To quieten the amp, I changed all 4 of the big blue 220UF and 3 smaller darker blue 30UF capacitors.

Not sure changing the filter caps would quieten it unless originals were seriously faulty but definitely worth doing if they've not been changed in decades

B…In location R-119, I changed the 680ohm 1 watt resistor to a 680 ohm 2 watt resistor as advised by Mike B. from Mesa. This was simply to handle the heat better.

Yeah this is a factory recommended mod to stop you getting a hole burned in the pcb board!

C…Changed C21 to 250pf and R243 to 220K. This is for the “quasi” C+ mod.


As mentioned above

D…Changed C50 to 1000pf and R212 to 100K. This is to make the amp more like the original tone of the no stripe/black stripe. Solid bottom, great mids and singing highs.

As mentioned above. This is actually more to get it like a IIC+ in lead mode. The Black Stripe actually has a few other differences in the lead section.

I'd also recommend replacing C516 from a 0.01uF to a 0.0047uF for similar presence control as the IIC+

Anything more than that and you're looking at a load more work to get everything IIC+/++ spec which I don't think Mike B does.

I know lions and charleonthronez did this and some more work though and still have some amp issues. I think this is down to a fault rather than a design but I could be wrong. This is especially with the Treble Shift pulled and it sounding really harsh and grainy. Until my III is back together I can't test this fully to see if I have something similar. We should all have basically the same PCB though so should affect ALL IIIs if it's a design thing rather than fault with that particular amp.

There's still that weird bit in loylo's Red Stripe schematic where LDR6 is connected to the Treble Shift AND R2 which is mega weird? Can anyone confirm this with their Red or later amp? Maybe there was a slight PCB revision.

Thanks,

Jon


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PostPosted: Tue Apr 17, 2018 9:21 am 
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Mark III

Joined: Sat Apr 20, 2013 4:29 am
Posts: 360
Wow Jon!! Thx for taking the time to answer in so detailed way! Cheers! Well, I live in Athens Greece and should I decide to go with the mod, I need to order the parts mentioned from the mesa boogie and have my technician do the work!

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MESA BOOGIE MARK III BLUE STRIPE proud owner
https://www.youtube.com/watch?v=qqZz5rHHIIk
https://www.youtube.com/watch?v=VBXj8AJ108Y
https://www.youtube.com/watch?v=1gejXLj8W-Q
https://www.youtube.com/watch?v=6Eptmr_XaRQ


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PostPosted: Tue Apr 17, 2018 10:54 am 
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Mark I

Joined: Wed Jan 31, 2018 8:32 am
Posts: 47
No problem! For reference this is the amount of work required for to do a full III to IIC+ conversion on a Black Stripe! I see why Mesa don't offer this. I might also permanently wire in R105 and C47 to ground and remove R126 to see what happens!

Image

Thanks and good luck! Definitely recommend the easier version listed about. Plus these are for a Black Stripe so for a Blue you'd need to trace and double check everything first. Just do the easy mod :)

Jon


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PostPosted: Tue Apr 17, 2018 12:12 pm 
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Mark III

Joined: Sat Apr 20, 2013 4:29 am
Posts: 360
jrb32 wrote:
No problem! For reference this is the amount of work required for to do a full III to IIC+ conversion on a Black Stripe! I see why Mesa don't offer this. I might also permanently wire in R105 and C47 to ground and remove R126 to see what happens!

Image

Thanks and good luck! Definitely recommend the easier version listed about. Plus these are for a Black Stripe so for a Blue you'd need to trace and double check everything first. Just do the easy mod :)

Jon

Much obliged!!!

_________________
MESA BOOGIE MARK III BLUE STRIPE proud owner
https://www.youtube.com/watch?v=qqZz5rHHIIk
https://www.youtube.com/watch?v=VBXj8AJ108Y
https://www.youtube.com/watch?v=1gejXLj8W-Q
https://www.youtube.com/watch?v=6Eptmr_XaRQ


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PostPosted: Wed Apr 18, 2018 3:18 pm 
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Mark I

Joined: Thu Feb 22, 2018 11:37 pm
Posts: 25
I don't think the grainyness is a fault. What it sounds like to me is the way it affects the voicing of the gain structure pre-distortion. Treble shift lets more low end/low mids through. When I have it activated I get great saturation but there's a low mid kind of sound that the IIC+ doesn't have and the III doesn't have with it not pulled. It translates as less tightness and attack.

My III+ still needs a few component swaps in the preamp section, but the overall character is much nicer. It just gets a bit mushier on typical settings than a IIC+. Im hoping eliminating the III's weird R1 mode circuitry will alleviate this. If not I'll be lowering the C30 value to 500pf or removing it. But I'm hoping this is the product of some other components I haven't swapped out.

Jon I've got a few questions about some parts I'll fire at you soon. I think r126 was one of them.


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PostPosted: Thu Apr 19, 2018 8:14 am 
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Mark I

Joined: Wed Jan 31, 2018 8:32 am
Posts: 47
Quote:
Jon I've got a few questions about some parts I'll fire at you soon. I think r126 was one of them


No worries I'll answer best I can! R126 seems to be activated only on R2 mode. It would have the effect of turning the middle pot range from 0K-10K to 20K-30K instead. Not sure why this is done - I would imagine some kind of shaping of the R2 sound but seems unnecessary. Could probably just replace with bus wire instead.

Any others fire away either on here or PM me.

Quote:
"I don't think the grainyness is a fault. What it sounds like to me is the way it affects the voicing of the gain structure pre-distortion. Treble shift lets more low end/low mids through. When I have it activated I get great saturation but there's a low mid kind of sound that the IIC+ doesn't have and the III doesn't have with it not pulled. It translates as less tightness and attack."


You could again run some bus wire around R128 temporarily (bypassing it) to engage Treble Shift all the time and see if the graininess is still there. That way it bypasses all the LDR switching and engages it all the time both on R1 and Lead (by design it only has any effect on the Lead Channel). If the graininess disappears you know the issue is with the LDR supply/switching. If not, then it's inherent in the amp for some reason (this would be very odd IMO!). If it's still there most like cause would be to do with the tone stack in V1A which so I would look at replacing the tone stack capacitors first then trying quieter valves in V1. All treble shift does is bridge R128 having the effect of C29 and C22 becoming a 500pF capacitor. The design is the same as a IIC+ for the Treble Shift as in the III:

https://forum.grailtone.com/viewtopic.php?f=3&t=1543


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