Complete Mark III Schematic

Mark I's, II's, III's and the almight IV

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McBarry
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Re: Complete Mark III Schematic

Post by McBarry » Wed Jul 20, 2011 7:35 am

Hi Chip, I'll let George answer to original traces, but I can advise thus:
There IS a junction at FX jacks - 2 black wires - one from rev pot, other from board, the Musicparts and Mesa schematics are hard to follow here. Here's a pic of the FX jacks showing red incoming wire from board and the 2 black wire.
Image
Reverb IS before the FX loop, but again, both the Musicparts and Mesa schematics are little hard to follow, and my physical board is hard to follow there courtesy of a birds nest of LDR's, orange drops and underside tracks.

Now, my V1p9 is definitely positive, thus the LV bridge is drawn wrong polarity on Musicparts, Mesa and likely George's diagrams.

Chip, is your electro after this bridge 1000uf or 3300uf per the diagrams??

And yeah, I welcome good critiquing - it can only benefit all of us i reckon..
Keep the observations coming..
Dave
Mk I,export,GEQ,cream
Mk IIA,exp,rev,cream
Mk IIB,exp,rev, tweed
Mk IIB,exp, rev,GEQ,simul, black
Mk III head,rev,GEQ,cream
Mesa Studio 22+, fan
Kitty Hawk M1 head
Fender 75, exp, 1973,15".
Fender 6G6A Bandmaster 1962
Fender AA763 Bandmaster 1964

>Photi G<
Mark III
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Re: Complete Mark III Schematic

Post by >Photi G< » Wed Jul 20, 2011 11:14 pm

chipaudette wrote:Also,

On the bottom half of your latest page (page 3), the traces are a bit confusing to me. Could you recheck your drawings in the following areas:

1) Relay 1B: You've shown nothing powering the coil. Also, you've shown M+ being attached to the signal pathway, both of which are connected to ground. I'm not sure that you meant to do that.

2) Signal to FX Send: at the junction right after the 3.32K resistor, there's a junction. Is that supposed to be a junction, or is the wire to the send supposed to jump over the wire from the reverb. I don't know what's right here. If it does jump, then the reverb signal goes around the Effects Loop (by connecting only at the "Return")...so it probably does connect here.

3) Reverb vs FX Loop: This schematic says that the reverb is before the effects loop, which is weird. Usually, the FX loop is before the reverb so that your signal is effected first and then reverb is applied. I have seen this in other Mark III schematics, so it could very well be true for the Mark III. I'm just asking for your confirmation.

Thanks again for the hardwork. These are intended very much as friendly questions.

Chip
Good questions, chip, let me clear them up for you.

My reference amp is a Blue Stripe, McBarry's is a Red. He simply borrowed my drawings, and pasted his voltages on it, that's all.

1.) There is no power being shown to Relay 1B because it is the second half of Relay 1A. They are a DPDT switch actuated by a single coil, since they are a single component much like 2 OP Amps in a TL272 chip, or two triodes in a 12AX7. I felt it was redundant to redraw the coil supply, much like it is redundant to redraw the power/ground of a dual OP Amp, or the heaters of a dual triode.

2.) There is a junction at the FX send. All overlapping traces on my drawings are represented by a semicircle "jumping" over the trace underneath it.

3.) The reverb is in parallel with the dry signal before the FX loop. A divider network feeds a low level signal from V2A to V4A, and passes a padded dry signal along side of it, straight to the FX send. V4B outputs a wet signal then blended with the dry before the FX send. This is a design error in the Mark III, which causes weak reverb, and sometimes, distortion in the FX loop. The blend was fixed on the Mark IV and later models, but the Reverb was always Pre-FX.

chipaudette
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Re: Complete Mark III Schematic

Post by chipaudette » Thu Jul 21, 2011 6:05 am

McBarry:
Chip, is your electro after this bridge 1000uf or 3300uf per the diagrams??
I actually don't have a Mark III. I have an older Mark. I'm just a guy who's really interested in the circuit changes over the years I like to mod my own amps, so this kind of comparative study helps me understand what changes can make what kind of sound.

Chip

chipaudette
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Re: Complete Mark III Schematic

Post by chipaudette » Thu Jul 21, 2011 6:12 am

>Photi G<:

Thanks for the detailed reply. I appreciate it.

With respect to Relay 1B, with the relay in the position shown in the schematic, it shows M+ as being routed (through the relay) directly to ground. I don't know what M+ is (I don't have the full schematic), but it is drawn as if it were a voltage rail. One doesn't usually just send a voltage rail to ground. Is this really what happens? If so, where is M+ coming from?

Thanks. I love circuit talk.

Chip

McBarry
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Re: Complete Mark III Schematic

Post by McBarry » Thu Jul 21, 2011 7:05 am

Cool Chip,
which Mark do you have?
George, and anyone else,please can U have a look and tell me what value capacitor U have after the low voltage bridge - 1000uf/16v or 3300uf/16v?
Its on the preamp board and it's the single big electro next to the 3x 30uf/500v caps..
Dave
Mk I,export,GEQ,cream
Mk IIA,exp,rev,cream
Mk IIB,exp,rev, tweed
Mk IIB,exp, rev,GEQ,simul, black
Mk III head,rev,GEQ,cream
Mesa Studio 22+, fan
Kitty Hawk M1 head
Fender 75, exp, 1973,15".
Fender 6G6A Bandmaster 1962
Fender AA763 Bandmaster 1964

chipaudette
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Re: Complete Mark III Schematic

Post by chipaudette » Thu Jul 21, 2011 12:01 pm

McBarry
which Mark do you have?
I have a Mark IIC that has been upgraded by MikeB at Boogie to a IIC+. It's a 60/100, not a Simul-Class. It does have Reverb and GEQ, though. It's pretty rockin', but I actually find myself playing my (heavily modified) Fender Deluxe Reverb Reissue more often. Weird.

Chip

>Photi G<
Mark III
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Re: Complete Mark III Schematic

Post by >Photi G< » Thu Jul 21, 2011 5:07 pm

chipaudette wrote:>Photi G<:

Thanks for the detailed reply. I appreciate it.

With respect to Relay 1B, with the relay in the position shown in the schematic, it shows M+ as being routed (through the relay) directly to ground. I don't know what M+ is (I don't have the full schematic), but it is drawn as if it were a voltage rail. One doesn't usually just send a voltage rail to ground. Is this really what happens? If so, where is M+ coming from?

Thanks. I love circuit talk.

Chip
Haha, as do I. :lol:

M+ is one of the voltage rails coming off the switching matrix. If you notice the tone stack, there are two LDR's in parallel that bypass the 10meg resistor thus engaging the Treble Shift function. M+ is the voltage that is fed to the second of the two LDR's. In Rhythm 1 mode (which is shown in the schematic), M+ is shorted to ground, thus disabling the LDR and engaging the treble shift control. When in Rhythm 2 Mode, the relay changes positions, lifting the ground on an R/C system feeding V2B, and M+. This disables the Treble Shift function during R2 operation, which gives R2 its darker sound. The other LDR is tied to the Lead switching matrix, so it is active only in the Lead mode.

MikeDD
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Re: Complete Mark III Schematic

Post by MikeDD » Wed Dec 14, 2011 9:42 am

As many others have said, your a saint for doing the hard work to develope a correct schematic for the Mark III. That said, I've done all I can to get to the link, including paying the $$. Can't find the info anywhere using every trick in my bag.

Can anyone provide the schematic in any format? e-mail is mike.darnell@hydrite.com

Thanks for the help.

McBarry
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Re: Complete Mark III Schematic

Post by McBarry » Tue Dec 27, 2011 1:47 pm

G'day,
tried PM but can't, so I'll send U my schematics which are correct for my particular amp soon as I get home in the morning.
regs, Dave
Mk I,export,GEQ,cream
Mk IIA,exp,rev,cream
Mk IIB,exp,rev, tweed
Mk IIB,exp, rev,GEQ,simul, black
Mk III head,rev,GEQ,cream
Mesa Studio 22+, fan
Kitty Hawk M1 head
Fender 75, exp, 1973,15".
Fender 6G6A Bandmaster 1962
Fender AA763 Bandmaster 1964

>Photi G<
Mark III
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Re: Complete Mark III Schematic

Post by >Photi G< » Sun Jan 15, 2012 1:51 am

Oh, god, it's been too long. I haven't been active on the forum lately due to tons of things going on IRL, but I thought I'd drop by. I noticed that the file sharing site I've been using for the schems has been shut down :oops: , so if anyone has any ideas for a new host, I'm all ears. In the meantime, I'll entertain any requests for the files via email-just pm me. Any other requests/feedback are/is appreciated as always.

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jpdennis
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Re: Complete Mark III Schematic

Post by jpdennis » Sun Jan 15, 2012 9:28 am

>Photi G<

So are there schematics labeled for the various stripe colors now?

Dennis
Mark III no mark w Randy's initials & some IIc+ parts
50 Caliber (6BQ5) 4xEL84
Heartbreaker
Fender 75
Acoustic 165

1970 LPGT
1981 The Strat
1983 GZ-300
1983 (Elite Neck)/2001 FrankenStrat
1990 Firebird
more guitars, so little characters

McBarry
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Re: Complete Mark III Schematic

Post by McBarry » Tue Jan 31, 2012 12:32 pm

As mentioned by Photi, his original is a blue strip, so that should be a great starting block.
The voltages I've done are for my red strip, and from memory I think I corrected a few different component values and placements.
I'm happy to email folks if the file sharing is down - get me direct at:
mcbarry@grapevine.com.au - I don't get on here as often as I'd like.

I'm hoping also to get correct circuits for my Mk IIA and my two IIB's. Importantly, EACH have a different preampboard. But don't hold you're breath - I'm aiming 6 months at the current rate...LOL
Dave
Mk I,export,GEQ,cream
Mk IIA,exp,rev,cream
Mk IIB,exp,rev, tweed
Mk IIB,exp, rev,GEQ,simul, black
Mk III head,rev,GEQ,cream
Mesa Studio 22+, fan
Kitty Hawk M1 head
Fender 75, exp, 1973,15".
Fender 6G6A Bandmaster 1962
Fender AA763 Bandmaster 1964

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GoranS
Mark II
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Re: Complete Mark III Schematic

Post by GoranS » Mon Feb 27, 2017 1:14 pm

Hi everyone!
Old thread I know, but since being able to buy a Mark III blue stripe 60W the schematics is of great interest of mine.
Unfortunately only two of five pages are available at the moment at photobucket and the rest of the links does not work.
Would anybody be so kind and repost the schematics again??

Thanks in advance
/Goran S
Amps: Express 5:50, Peavey Classic 30 with Mercury Magnetics upgrades
Guitars: A couple of Strats, A Tele, Gibson Nighthawk, Squier Jazz Bass and some others...

tonyelbatal
Bottle Rocket
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Re: Complete Mark III Schematic

Post by tonyelbatal » Fri Jun 23, 2017 2:23 pm

GoranS wrote:Hi everyone!
Old thread I know, but since being able to buy a Mark III blue stripe 60W the schematics is of great interest of mine.
Unfortunately only two of five pages are available at the moment at photobucket and the rest of the links does not work.
Would anybody be so kind and repost the schematics again??

Thanks in advance
/Goran S
Hello!

Did you manage to get the schematics? I didn't see any response hence why I'm asking. I'm looking to mod my newly acquired Mark III Blue Stripe.

Thank you!
Tony

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