Mark IIC+ - Guide for Dummies

[Boogiebabies]

Thanks to George Stergiou Jr. again, and again, and again.

 

[decker]

Noob questions :

1/ What exactly makes the IIC+ so famous (OK, Metallica, Petrucci use them...) ? Does the power section of the IIC+ have something special to do with this ? For example, if I have the transformer replaced (because the original one is dead), will it kill the sound of the IIC+ ?

2/ Moreover, the distorsion of the IIC+ comes from the preamp and the power amp section is rather clean, that's it ?

Thanks.

 

[kippiejr]

It just a circuit, it just happened to be the best sounding circuit there is.. :lol: O yeah' and the ability to run El34's and 6L6's at the same time might have something to do with it!!! :shock:If you have the simul-class model.

 

[xldh44]

Well, well, well... wow! Today is my first day on this site and the first post I came across was this one. Obviously I'm very late to the party, having had my Boogie for over thirty years but no matter, I'm here now. Boogiebabies, thank you!!! This is sooo helpful!

I have a 60W MK 2c+, no reverb, no eq, cream tolex and a Black Shadow 12" speaker. Through earlier studies and research I determined I had one of the early IIc+'s with a serial# of 1242x. Imagine my surprise when I realized that that info I found years ago was authored by Boogiebabies. Handwritten on the chassis are intitials that I can't make out but looks like an "M" or a "W" with a circle around the letter and a clear date of 3/84. Other hand written markings I found are, MB + on each side of the power cord (I did a loop test anyway... passed yayyyy!) 12ax7 writtten underneath four small sockets and a large S 46. I have pics of this for what that is worth. And I think this is enough said... except I'm pleased to have found this forum and eager and certain that I'll get a lot more of what I know is "a lot to learn."

Special thanks again to Boogiebabies and to all of you, I read every single post in response to BB's post. : ) Very cool!

 

[dodger916]

Noob questions :

1/ What exactly makes the IIC+ so famous (OK, Metallica, Petrucci use them...) ? Does the power section of the IIC+ have something special to do with this ? For example, if I have the transformer replaced (because the original one is dead), will it kill the sound of the IIC+ ?

2/ Moreover, the distorsion of the IIC+ comes from the preamp and the power amp section is rather clean, that's it ?

Thanks.

Yes, the magic is in the preamp, although the Simul output does add a great flavor. This is the Mesa formula for most of their amps (i.e., cascading preamp gain), and their output sections are typically biased pretty cold/clean (although that can be modified too).

The C+ preamp is a wonderful thing, and though Mesa's efforts to replicate it come extrememly close in sound, it's the feel of the Mark IIs that really make it for me. Just prepare to play them loud to get them to really sing. Although great tones can be found at lower volumes, IMO, it's at higher volumes that they really bare their soul.

 

[Road Hat]

As posted by Boogiebabies, ""A “+” also refers to any amplifier upgraded below 12,500 that has been verified either by the loop test or visual circuit identification. If your amp was upgraded in the early 90’s to the present, Mesa will have an RA, or Return Authorization verifying the upgrade. Mike B. has a very good catalogue of the amps he upgraded, but please call customer service with the serial number first and let the guy earn a living."

Per Mesa, my '81 IIB underwent the mod in '92, including volume pots. It a 60-watt SRGX, and there's a "+" marked into the top corner of the chassis nearest the pilot light. I didn't want to bug Mesa again, so does anyone know what circuit board I should look for on my poorman's c+ as compared to the stock IIb? I checked the Idiot's Guide and also tried Search, but I didn't see a spec for a 60-watt SRGX.

Thanks

Edit/Question: Would the '+' sign indicate it would be designated as a Mk IIB+?

 

[dodger916]

As posted by Boogiebabies, ""A “+” also refers to any amplifier upgraded below 12,500 that has been verified either by the loop test or visual circuit identification. If your amp was upgraded in the early 90’s to the present, Mesa will have an RA, or Return Authorization verifying the upgrade. Mike B. has a very good catalogue of the amps he upgraded, but please call customer service with the serial number first and let the guy earn a living."

Per Mesa, my '81 IIB underwent the mod in '92, including volume pots. It a 60-watt SRGX, and there's a "+" marked into the top corner of the chassis nearest the pilot light. I didn't want to bug Mesa again, so does anyone know what circuit board I should look for on my poorman's c+ as compared to the stock IIb? I checked the Idiot's Guide and also tried Search, but I didn't see a spec for a 60-watt SRGX.

Thanks

Edit/Question: Would the '+' sign indicate it would be designated as a Mk IIB+?

Copied from Page 1:

"The Circuit Boards –

Preamp – SP11A – Early 60/100 non Reverb.

SP-11A – Simul-60-100 watt non-reverb
RP-11A Simul-100 and 60 Watt Reverb

The SP-11A, RP-10 and RP-11A were designed for the MK IIC. Their use was continued with the IIC+, Hence, the ability to upgrade from IIC to IC+."

Look for those codes on the preamp board. Be very careful when removing the chassis; deadly voltages can be stored in those large capacitors.

 

[gts]

What's with all the "–" showing up in this thread?

Whatever that symbol is it seems to be replacing / or getting substituted for actual numbers.
Very weird.

 

[mxr2000]

What's with all the "–" showing up in this thread?

Whatever that symbol is it seems to be replacing / or getting substituted for actual numbers.
Very weird.

Agree... Is possible to upgrade this amazing thread??? OP post barely can be read!!

 

[IronSean]

What's with all the "–" showing up in this thread?

Whatever that symbol is it seems to be replacing / or getting substituted for actual numbers.
Very weird.

My best guess is they ported the posts from forum systems at some point, and some special characters got encoded weirdly. Someone might have to go into the original post and edit a bunch of them back. Maybe the forum database is using ISO-8859-1/Windows-1252/CP-1252 encoding instead of the UTF-8 it should be, so special characters like ’ are being stored weirdly.

 

[gts]

What's with all the "–" showing up in this thread?

Whatever that symbol is it seems to be replacing / or getting substituted for actual numbers.
Very weird.

My best guess is they ported the posts from forum systems at some point, and some special characters got encoded weirdly. Someone might have to go into the original post and edit a bunch of them back. Maybe the forum database is using ISO-8859-1/Windows-1252/CP-1252 encoding instead of the UTF-8 it should be, so special characters like ’ are being stored weirdly.

Nice Sean. Good info!
I did some research and found some similar info.
It seems like commas and/or periods are being formatted weirdly.

Here's a copy of the original text pasted from a "txt" file.
Let's see if the formatting is still whacked.
-----------------------------------------------

The IIC+ Guide


The Chassis Codes –

SR – Sixty Watt -Reverb
SRG- Sixty Watt- Reverb- Graphic
HR – 100 Watt-Reverb
HRG- 100 Watt- Reverb-Graphic
HRGX- 100 Watt-Reverb-Graphic-Export
DR – Simul-Class - Reverb
DRG- Simul-EQ-Reverb
DRGX- Simul-EQ-Reverb-Export
K - Coliseum / Series 300

You could get a standard 60 or 100 watt with no graphic or reverb so there are possible S, D and H only chassis codes. Any amp could have an export power transformer, so an X is possible as well. For example, SX, DX and HX.

A 15” could be added to the chassis code designating a long chassis.

The Number after chassis code –

This is the week of production.

Example – A DRG 6 is a Simul-EQ-Reverb from production week six.

For Reference – The DRG 6 was finished in 6/84.
Estimated start of production is early to mid April 1984, or about two months prior to final tech date.

The Options –


The cabinet and chassis could be ordered as a standard head, standard 1x12 Combo, 1X15 Combo, 15” Head and all could be
tolex, hardwood, but only combos have the SUS-4 Shock Mount option. They could be ordered with the “Boogie” logo or the “Mesa Boogie” logo. The “Mesa Boogie” logo appeared primarily on the long chassis heads, but you could have requested on an any amp.

A ridiculous option known as the 300 series was also available.
The 180 Watt, Six 6L6 powered behemoth could be ordered with all the classic options and had a half power switch. Almost all had a limiter circuit to reduce the ouput volume of these 180 Boogie watts. From time to time, one can see a Simul-Class 300 150W series running two EL-34’s in the center sockets and four 6L6GC’s in the outer four sockets.


The “+”-

The plus is dedicated to IIC’s after the 12,500 production.
There have been documented +’s as low as 12337, mainly in some prototype, nearly stock or customized circuits. In recent months I have witnessed two IIC I’s. These are IIC’s that almost made it to a plus, but had “Pull Deep” faceplates and a stock IIC circuit with the RP11A circuit board. These were very interesting times at Mesa. A customer could have chosen a C or a C+, hence, the “I” looks like the initial swipe of a +, but never got the other horizontal swipe so do your loop tests. I could imagine Mesa having to call on all outstanding IIC orders and asking if they wanted the upgrade. In the C+ transistion around 12,3XX/124XX
a “yes” meant a plus and a “no” could be the “I”. In my opinion, the earliest orders for a IIC+ were made in late November and December of 1983. The earliest IIC+ found to date was a 12,33X dated 2/84.

A “+” also refers to any amplifier upgraded below 12,500 that has been verified either by the loop test or visual circuit identification. If your amp was upgraded in the early 90’s to the present, Mesa will have an RA, or Return Authorization verifying the upgrade. Mike B. has a very good catalogue of the amps he upgraded, but please call customer service with the serial number first and let the guy earn a living. The amp may have the 100 or the 105 PT. For those seeking originality, the 105 would be the production transformer. In some opinion’s, and depending on playing style the 100 may be a better fit and offers a smoother tone than the 105. It’s really up to personal preference for tone or originality. Now, if Mesa found two 100’s On a shelf in stock room during the C+ production, they would use them, so never put it past Mesa to be frugal. Some also infer that the Export, or X101 is the most suitable transformer for the C+. Again, it is up to your personal preference. Another view of Mesa’s frugal nature is it took half a year to finally get “Pull Deep” face plates for the 15” models. These 15” chassis +’s have been left to doubt, rumor and speculation as to the amps authenticity. A simple serial number should dispel any questions. If it’s above 12,500, 15” wide and sounds awesome, you should not have to question the “Gain Boost” face plate not being a +.



The Quest –

Sometime in late winter 1983 Randall Smith was attending the Musik Messe in Germany to represent Mesa/Boogie products in the European market. During his absence, Mike Bendinelli and Doug West decided to modify the IIC.
A few weeks of R&D turned out to be a significant step in the evolution of the high gain tube amp. Although the original modifications proved to be a move in the right direction, I am sure that the tone obsessed duo would not be satisfied until they nailed it. The final design did not go into production until about February 1984. In essence, the C+ circuit was born sometime in January of 1984. This circuit has the tendency for extreme gain and brightness. When asking Mike B. why the IIC+ was so bright he kindly replied, “That was Doug West, he kept saying make it brighter”. Doug was obviously looking to shred without the assistance of a boost pedal and got what he wanted. The moral of the story is why the cats away the techs will play. Obviously Randall was impressed with the results and gave the green light for the change in circuit design and production. I also must admit that the 100 PT was probably being phased out. Many 105’s date to late 1983. The X101’s could date back to 1982. Another oddity is that Mesa was going to the “Pull Deep” face plates as well. The 1983 Christmas card shows the IIC with a “Pull Deep” face plate. It makes more sense as it adds a minimum of gain and a wall of bottom end. Knowing Mesa’s frugal nature, they probably sat boxed until they ran out of the previous plates.

The rest is history.


The Tech –

Below the power cord are the famous initials MB, for Mike Bendinelli. No, he did not build every amp, he did the vast majority of final inspections and Burn ins. If you look at the circuit boards they have the initials of the person who populated each individual board. If you’re lucky enough to have a final inspection tag, you we get the initials of everyone who built your amp. Any C+ could have the initials MB, PC, SDG, BN, CD, RH, LB, PG and RCS, yes the man himself. Doug West, or DW is most commonly found as the final play tester on the hang tags that came with the amp.

To dispel a myth, Mike B. was not the only person to perform the final Inspection of the IIC+ amps. A very small number of them are signed “RCS”. Yes, that it Randall C. Smith. Who do you think covered for Mike when he had to take an off site tech visit to Prince on the Purple Rain Tour in late 1984? Also, Mike had vacations, but he has mentioned coming back to piles of amps so the initials RCS are pretty much an Alien sighting on the back of the IIC+, but they do exist. I have only found three with Smith's initials.
An 11/84 RCS IIC+ with Simul-EQ and Reverb was sold on E-Bay in April, 2007 and July, 2008.

The Face Plates –

The stock face plate should say “Pull Deep” over the Master volume. If it says “Gain Boost” it is the IIC face plate and you should do the loop test regardless of the “+” marked status if the serial number does not fit the sequence. The exceptions would be a 15” chassis above 12,500. Mesa used the remaining 15” IIC face plates before rotating to the “Pull Deep” stock. Late IIC non-eq amps used the beginning "Pull Deep" plates.

Note: Pull Deep Face Plates Appear in the 1983 Christmas Card.

Long chassis face plates can have a Full PWR / 1/2 PWR switch on the front. The only way to determine what effect the power drop will be is if you know your amp is a 60/100 or Simul-Class. Some C+'s did not come with a Simul-Class sticker. The identity can be found by looking at the output transformer part number. For the 300 Series, it will drop the center two of the six 6L6's for the 180 Watt and 2 outer sockets on Simul-Class models.

The early “Pull Deep” plates had a dark gray EQ face and the EQ toggle order is –

Top – Auto
Middle – Out
Bottom – In

The Later Plates had light gray EQ face, which scratched much easier. The change in toggle order is probably by customer request or a change in the availability of the switch.

The EQ toggle order is –

Top- Auto
Middle - In
Bottom – Out

The EQ face was later changed back to the darker gray face with the same toggle functions.


The Loop Test –

1) Plug your guitar into the Effects Return jack
2) Switch to lead mode
3) Turn the Lead Drive and Gain controls with a note ringing.
4) If they have NO effect on the volume and sound you have a+.




The Circuit Boards –

Preamp – SP11A – Early 60/100 non Reverb.

SP-11A – Simul-60-100 watt non-reverb
RP-11A Simul-100 and 60 Watt Reverb

The SP-11A, RP-10 and RP-11A were designed for the MK IIC. Their use was continued with the IIC+, Hence, the ability to upgrade from IIC to IC+.

Power Amp – PWR- 7-C1 Simul-Class and 100
PWR -7D – 60 watt.

Filter Cap – PS-1C
Coliseum - PS-2C

Limit Circuit - DR-1A
Limit uses a 12AT7 and 6FQ7/6CG7 tube for PI and Limiter.

Upgrade Info:

The RP-10A is based in the style of the IIB with LDR's for switching instead of the one relay. The RP-11A is the circuit board that was
redesigned for the IIC with a much different layout. It was also later the board used in the IIC+ with many component changes and
a different circuit layout. From what I could find out about the RP-10A, it was the early production IIC PCB. It was changed somewhere in the mid range
to the RP-11 in mid to late 1983. Hence, both boards have 1983 copyrights. The reason the RP-10 can be upgraded is the five LDR's. The rest of the
circuit Mike B. just does his magic on.

This info does not pertain to non-reverb models of the IIC or IIC+. The "R" in RP-10 or 11 is for reverb.
The SP-11A would be the pcb for these amps from IIC revision one and two.

The Soup –

The components used in the manufacture of the IIC+ vary widely from start to finish. From resistors to capacitors you will see changes in size, color and type of construction. Some have metal film resistors in certain amps, while others have carbon film. Dale metal film resistors were mostly used on the V1. The coupling caps could be Sprague 715P, 225P, Mallory Orange Drops and all could be used in any section of the preamp. The cathode caps are generally black Mallory’s and in certain areas of the circuit, a military specification hermetically sealed silver cap was most often used on the .22 Pull Bright, Graphic EQ, V1A Pull Shift circuit and the 3.3uf cap for the V4B reverb cathode. Substitutions are common so you may see all of the above replaced with the same value in the black Mallory or even an ITT case. The pot tolerances are all over the map. After July or August of 1984 Mesa had to use a 22K series resistor with the Master Volume pot as CTS switched production from the USA to Taiwan. These early Taiwanese pots would have your Master Volume pumping out the volume of 5 at a setting of 2. From this point on, the series resistor stayed and is still in use on the MK IV today. So if you think all IIC+’s will sound the same, think again. Some will be louder with the Volume 1 and Lead Drive set to 7 and others may need to go to a Master of 3 and Lead Master of 8 or 9. The same is accurate for the EQ settings. One of the most consistent components is the graphic EQ. It’s surprising that when you set them all flat, it basically sounds exactly like having the EQ out. A special debt of gratitude goes to Richard Ray who always told us to use our ears and not the numbers on the knobs.

Update:

The dark brown preamp resistors that look like 1/4 watt are 1/2 watt Beyschlag.
After August 1984 the 120pf cap from the grid to the cathode on V2B was removed. This is the effects loop signal, lead master and reverb output
from V2A.


The Schumacher Transformers –

The digits 606 are Schumacher’s EIA manufacturer code.

The digits after are the last number of the production year, example, 3 is 1983. The next two digits are the week of productions, example, 42 is the 42’nd week of 1983. It’s not the Fibonacci Sequence, trust me. EIA 606-342.

60W OT - T60-152019
Simul Output - SC-152019B – Simul-Class
180W - SD 190555 Coliseum

60W PT - 00-162310 - 448V
60W Export - PT: X62-162318 - 448V
Early 100 - 100-162318 - 448V
Simul/60-100 Power - 105-162318 -483V+
- X101-162318 – Export - 448-460V
180W - 0180322 Coliseum - 500V+

Some early IIC+’s may have leftover 100 power transformers.


The Serial Numbers –

12,500 to 14,400 are pretty much unquestionable. 14,400 to 15,000 in my opinion have early black dot MK III’s in the serial number sequence, or were never even used. There has been visual proof that a 15,000 does exist ( BWK aka Ian Dickey), but IIC +’s between 14,400 and 15,000 just never seem to surface. Anything from 12,300 to 12,499 is a certain possibility, but the loop test is your only way of knowing without pulling the chassis to view the circuit board. Even then, if you do not know what you’re looking for it will be hard to tell.
A recent MK III Black Dot surfaced with a serial of 15113 from 5/14/85. It had a DR 13 chassis code which may put the start of the MK III production to 2 or 3 of 1985 which would coincide with the last of the IIC+ production, but it may dispel the 12,500 to 15,000 serial number sequence. With a IIC+ in the 1406X range from 2/85, the C+ may not have even made it to 14,400. If it did, it may have been randomly sequenced in with the early MK III production. An inference to the actual monthly production from 12,500 from April 1984 to 137XX from October 1984 averages 200 units per month for the six month period. From late 137XX in November 1984 to 1406X in February 1985 the average drops to around 121 per month. With the MK III looming Mesa was definitely phasing out the C+ as orders for the III were being generated and amps being built as early as March 1985. Any C+ after March 1985 would have possibly been an attempt to use up the remaining stock and finally push production to the MK III full blast. Even if the IIC+ production was in full effect at an average 121 per month, the sequence would be about 14,370 to 14,400 as an inference. With new MK III orders and fewer MK II orders, the production slowed on average 79 amps less per month, thus reducing the amount of upper range IIC+ serial numbers. The final peek into the model change was the use of the 105-162318 power transformer on the first 150 or so MK III’s. When they were gone, the much smaller unit we know today was assimilated into production.


The End of an Era-

Asking why Mesa quickly went to the MK III is like asking why the earth spins. The circuitry and board design on the MK III was Mesa’s leap from the MK I style circuit boards and labor intensive manufacturing. It would have happened eventually. RCS is an amazing engineer, but an astute business man as well. As the PCB market moved forward with newer, cheaper techniques, so did Mesa. The extra savings may have been necessary to the companies long term survival as the orders increased the labor cost increased while the pricing stayed consistent. Saving an extra $ 300 per amp in production cost and still producing a bullet proof design was an outstanding achievement and allowed Mesa to move forward with future designs. Obviously, the stripes were a constant evolution to fine tune the III to player’s desires. With input from the chief designer, play tester and the brilliance from the Chief Technician the core team managed to sell around 13,000 plus units. With the three modes, we had our first glimpse of the future MK IV. The IV has lasted longer and sold more than any previous MK design. It may get to the point where it will pass them all combined unless the rumored MK V makes its debut soon and the IV is put to pasture.


Best Regards,

Edward P. Morgan
©10/2007

The Mark II-C FOOTSWITCHING SERIES- Pricing September 1984


Mark II-C Combo Amplifier with 12” Black Shadow Speaker

Standard 60 Watts, Vinyl Cabinet, Specify Black or Cream.
Slip Cover, SUS-4 Shock Mount & Lead/Rhythm Footswitch Set - $ 750
(Mark IIC 1X12 as above but without speaker $ 720 )

Performance Options Each Extra

Hundred Watt Chassis with Fan & 100/600 Watt Switch ………… $ 150
Simul-Class with Fan & Switch ( Add to 100 Watt Option) ……. $ 25
Reverb ……………………………………………………………… $ 150
Graphic Equalizer ………………………………………………….. $ 150
Electro Voice EVM 12” Speaker …………………………………... $ 70
Export Switch & Transformer (For All World Operation) ……….. $ 50

Cabinet Options Each Extra

Hardwood Cabinet with Wicker Grille …………………………….. $ 175
Hardshell Road Case with wheels, Black ……………………………$ 180

Mark II-C Amplifier Head, Top Only

Standard 60 Watts, Vinyl Cabinet, Specify Black or Cream.
Slip Cover, Lead/Rhythm Footswitch Set - …………………………$ 700
(18 ¾” wide, fits well visually on 1X12, 2X12 & 4X10 Cabinets)

Performance Options Each Extra

Hundred Watt Chassis with Fan & 100/600 Watt Switch ………… $ 150
Simul-Class with Fan & Switch ( Add to 100 Watt Option) ……. $ 25
Reverb ……………………………………………………………… $ 150
Graphic Equalizer ………………………………………………….. $ 150
Export Switch & Transformer (For All World Operation) ……….. $ 50

Cabinet Options Each Extra

23” wide cabinet – For Hundred or Simul ONLY (Black or Cream) $ 25
(Not available in Sixty – Fits well visually on 2X12, 4X10 & 4X12’s)
Hardwood Cabinet with Wicker Cane Grille (Either Widths) …… $ 155
Hardshell Road Case without wheels, Black (narrow chassis) ……. $ 115
Hardshell Road Case without wheels, Black (wide chassis) ………. $ 130


THE COLISEUM SERIES 300

Coliseum Series 300, 180 Watts, 6 Power Tubes, Half Power Switch,
Vinyl Cabinet, 23” Wide only (specify Black or Cream) & Slip Cover,
(Can be wired for 117 or 230 volt operation.)

Mark II-C Type Series 300 Amplifer Head, includes Footswitch… $ 1000
Reverb ………………………………………………………………$ 150
Graphic Equalizer …………………………………………………..$ 150

Cabinet Options Each Extra

Hardwood Cabinet with Wicker Grille ……………………………..$ 155
Hardshell Road Case without wheels, Black……………………….. $ 130


1X15 COMBO AMPLIFIER SERIES

Combo Amplifier with 15” EVM Speaker, Hundred Watt chassis with
Half Power Switch & Fan, Vinyl Cabinet (Specify Black or Cream),
Removable Casters & Slip Cover. Not Available in 60 Watt Model.

Mark II-C Type HundredWatt 1X15 w/EVM 15-4, Incl. Footswitch $ 1005
Simul-Class with Fan & Switch ………………………………….. $ 25
Series 300 Power Section ……………………………………………$ 150
Reverb ……………………………………………………………….$ 150
Graphic Equalizer ………………………………………………….. $ 150
Export Switch & Transformer (For All World Operation) ……….., $ 50


Cabinet Options Each Extra

Hardwood Cabinet with Wicker Grille …………………………….. $ 175
Hardshell Road Case with wheels, Black…………………………... $ 185



Mesa Engineering Price List – SEPTEMBER 1984



A gracious thank you goes out to Ian Dickey, Richard Ray, John Kamaly, George Stergiou Jr., Todd Duane, Joey B., Mike Bendinelli and to the hundreds of C+ owners that allowed me to invade their privacy.

Last edited by Boogiebabies on Tue Nov 03, 2009 11:46 am, edited 18 times in total.

 

[IronSean]

That looks much better. I'd guess it's not the current forum system, but instead just happened when the forum upgraded/moved from one database or system to another at some point, and they didn't agree on character encoding.

 

[bgh]

Guys,

I was able to edit a lot of the formatting characters and change them to what it looks like they should have been. If you see any mistakes, please let me know (so I can correct them).





Mark IIC+ - Guide for Dummies

Not sure what happened to BB's original post but here is a copy:
---------------------------------------

The IIC+ Guide


The Chassis Codes -

SR - Sixty Watt -Reverb
SRG- Sixty Watt- Reverb- Graphic
HR - 100 Watt-Reverb
HRG- 100 Watt- Reverb-Graphic
HRGX- 100 Watt-Reverb-Graphic-Export
DR - Simul-Class - Reverb
DRG- Simul-EQ-Reverb
DRGX- Simul-EQ-Reverb-Export
K - Coliseum / Series 300

You could get a standard 60 or 100 watt with no graphic or reverb so there are possible S, D and H only chassis codes. Any amp could have an export power transformer, so an X is possible as well. For example, SX, DX and HX.

A 15” could be added to the chassis code designating a long chassis.

The Number after chassis code -

This is the week of production.

Example - A DRG 6 is a Simul-EQ-Reverb from production week six.

For Reference - The DRG 6 was finished in 6/84.
Estimated start of production is early to mid April 1984, or about two months prior to final tech date.

The Options -


The cabinet and chassis could be ordered as a standard head, standard 1x12 Combo, 1X15 Combo, 15” Head and all could be
tolex, hardwood, but only combos have the SUS-4 Shock Mount option. They could be ordered with the “Boogie” logo or the “Mesa Boogie” logo. The “Mesa Boogie” logo appeared primarily on the long chassis heads, but you could have requested on an any amp.

A ridiculous option known as the 300 series was also available.
The 180 Watt, Six 6L6 powered behemoth could be ordered with all the classic options and had a half power switch. Almost all had a limiter circuit to reduce the ouput volume of these 180 Boogie watts. From time to time, one can see a Simul-Class 300 150W series running two EL-34’s in the center sockets and four 6L6GC’s in the outer four sockets.


The “+”-

The plus is dedicated to IIC’s after the 12,500 production.
There have been documented +’s as low as 12337, mainly in some prototype, nearly stock or customized circuits. In recent months I have witnessed two IIC I’s. These are IIC’s that almost made it to a plus, but had “Pull Deep” faceplates and a stock IIC circuit with the RP11A circuit board. These were very interesting times at Mesa. A customer could have chosen a C or a C+, hence, the “I” looks like the initial swipe of a +, but never got the other horizontal swipe so do your loop tests. I could imagine Mesa having to call on all outstanding IIC orders and asking if they wanted the upgrade. In the C+ transistion around 12,3XX/124XX
a “yes” meant a plus and a “no” could be the “I”. In my opinion, the earliest orders for a IIC+ were made in late November and December of 1983. The earliest IIC+ found to date was a 12,33X dated 2/84.

A “+” also refers to any amplifier upgraded below 12,500 that has been verified either by the loop test or visual circuit identification. If your amp was upgraded in the early 90’s to the present, Mesa will have an RA, or Return Authorization verifying the upgrade. Mike B. has a very good catalogue of the amps he upgraded, but please call customer service with the serial number first and let the guy earn a living. The amp may have the 100 or the 105 PT. For those seeking originality, the 105 would be the production transformer. In some opinion’s, and depending on playing style the 100 may be a better fit and offers a smoother tone than the 105. It’s really up to personal preference for tone or originality. Now, if Mesa found two 100’s On a shelf in stock room during the C+ production, they would use them, so never put it past Mesa to be frugal. Some also infer that the Export, or X101 is the most suitable transformer for the C+. Again, it is up to your personal preference. Another view of Mesa’s frugal nature is it took half a year to finally get “Pull Deep” face plates for the 15” models. These 15” chassis +’s have been left to doubt, rumor and speculation as to the amps authenticity. A simple serial number should dispel any questions. If it’s above 12,500, 15” wide and sounds awesome, you should not have to question the “Gain Boost “ face plate not being a +.



The Quest -

Sometime in late winter 1983 Randall Smith was attending the Musik Messe in Germany to represent Mesa/Boogie products in the European market. During his absence, Mike Bendinelli and Doug West decided to modify the IIC.
A few weeks of R&D turned out to be a significant step in the evolution of the high gain tube amp. Although the original modifications proved to be a move in the right direction, I am sure that the tone obsessed duo would not be satisfied until they nailed it. The final design did not go into production until about February 1984. In essence, the C+ circuit was born sometime in January of 1984. This circuit has the tendency for extreme gain and brightness. When asking Mike B. why the IIC+ was so bright he kindly replied, “That was Doug West, he kept saying make it brighter”. Doug was obviously looking to shred without the assistance of a boost pedal and got what he wanted. The moral of the story is why the cats away the techs will play. Obviously Randall was impressed with the results and gave the green light for the change in circuit design and production. I also must admit that the 100 PT was probably being phased out. Many 105’s date to late 1983. The X101’s could date back to 1982. Another oddity is that Mesa was going to the “Pull Deep” face plates as well. The 1983 Christmas card shows the IIC with a “Pull Deep” face plate. It makes more sense as it adds a minimum of gain and a wall of bottom end. Knowing Mesa’s frugal nature, they probably sat boxed until they ran out of the previous plates.

The rest is history.


The Tech -

Below the power cord are the famous initials MB, for Mike Bendinelli. No, he did not build every amp, he did the vast majority of final inspections and Burn ins. If you look at the circuit boards they have the initials of the person who populated each individual board. If you’re lucky enough to have a final inspection tag, you we get the initials of everyone who built your amp. Any C+ could have the initials MB, PC, SDG, BN, CD, RH, LB, PG and RCS, yes the man himself. Doug West, or DW is most commonly found as the final play tester on the hang tags that came with the amp.

To dispel a myth, Mike B. was not the only person to perform the final Inspection of the IIC+ amps. A very small number of them are signed “RCS”. Yes, that it Randall C. Smith. Who do you think covered for Mike when he had to take an off site tech visit to Prince on the Purple Rain Tour in late 1984? Also, Mike had vacations, but he has mentioned coming back to piles of amps so the initials RCS are pretty much an Alien sighting on the back of the IIC+, but they do exist. I have only found three with Smith's initials.
An 11/84 RCS IIC+ with Simul-EQ and Reverb was sold on E-Bay in April, 2007 and July, 2008.

The Face Plates -

The stock face plate should say “Pull Deep” over the Master volume. If it says “Gain Boost” it is the IIC face plate and you should do the loop test regardless of the “+” marked status if the serial number does not fit the sequence. The exceptions would be a 15” chassis above 12,500. Mesa used the remaining 15” IIC face plates before rotating to the “Pull Deep” stock. Late IIC non-eq amps used the beginning "Pull Deep" plates.

Note: Pull Deep Face Plates Appear in the 1983 Christmas Card.

Long chassis face plates can have a Full PWR / 1/2 PWR switch on the front. The only way to determine what effect the power drop will be is if you know your amp is a 60/100 or Simul-Class. Some C+'s did not come with a Simul-Class sticker. The identity can be found by looking at the output transformer part number. For the 300 Series, it will drop the center two of the six 6L6's for the 180 Watt and 2 outer sockets on Simul-Class models.

The early “Pull Deep” plates had a dark gray EQ face and the EQ toggle order is -

Top - Auto
Middle - Out
Bottom - In

The Later Plates had light gray EQ face, which scratched much easier. The change in toggle order is probably by customer request or a change in the availability of the switch.

The EQ toggle order is -

Top- Auto
Middle - In
Bottom - Out

The EQ face was later changed back to the darker gray face with the same toggle functions.


The Loop Test -

1) Plug your guitar into the Effects Return jack
2) Switch to lead mode
3) Turn the Lead Drive and Gain controls with a note ringing.
4) If they have NO effect on the volume and sound you have a+.




The Circuit Boards -

Preamp - SP11A - Early 60/100 non Reverb.

SP-11A - Simul-60-100 watt non-reverb
RP-11A Simul-100 and 60 Watt Reverb

The SP-11A, RP-10 and RP-11A were designed for the MK IIC. Their use was continued with the IIC+, Hence, the ability to upgrade from IIC to IC+.

Power Amp - PWR- 7-C1 Simul-Class and 100
PWR -7D - 60 watt.

Filter Cap - PS-1C
Coliseum - PS-2C

Limit Circuit - DR-1A
Limit uses a 12AT7 and 6FQ7/6CG7 tube for PI and Limiter.

Upgrade Info:

The RP-10A is based in the style of the IIB with LDR's for switching instead of the one relay. The RP-11A is the circuit board that was
redesigned for the IIC with a much different layout. It was also later the board used in the IIC+ with many component changes and
a different circuit layout. From what I could find out about the RP-10A, it was the early production IIC PCB. It was changed somewhere in the mid range
to the RP-11 in mid to late 1983. Hence, both boards have 1983 copyrights. The reason the RP-10 can be upgraded is the five LDR's. The rest of the
circuit Mike B. just does his magic on.

This info does not pertain to non-reverb models of the IIC or IIC+. The "R" in RP-10 or 11 is for reverb.
The SP-11A would be the pcb for these amps from IIC revision one and two.

The Soup -

The components used in the manufacture of the IIC+ vary widely from start to finish. From resistors to capacitors you will see changes in size, color and type of construction. Some have metal film resistors in certain amps, while others have carbon film. Dale metal film resistors were mostly used on the V1. The coupling caps could be Sprague 715P, 225P, Mallory Orange Drops and all could be used in any section of the preamp. The cathode caps are generally black Mallory’s and in certain areas of the circuit, a military specification hermetically sealed silver cap was most often used on the .22 Pull Bright, Graphic EQ, V1A Pull Shift circuit and the 3.3uf cap for the V4B reverb cathode. Substitutions are common so you may see all of the above replaced with the same value in the black Mallory or even an ITT case. The pot tolerances are all over the map. After July or August of 1984 Mesa had to use a 22K series resistor with the Master Volume pot as CTS switched production from the USA to Taiwan. These early Taiwanese pots would have your Master Volume pumping out the volume of 5 at a setting of 2. From this point on, the series resistor stayed and is still in use on the MK IV today. So if you think all IIC+’s will sound the same, think again. Some will be louder with the Volume 1 and Lead Drive set to 7 and others may need to go to a Master of 3 and Lead Master of 8 or 9. The same is accurate for the EQ settings. One of the most consistent components is the graphic EQ. It’s surprising that when you set them all flat, it basically sounds exactly like having the EQ out. A special debt of gratitude goes to Richard Ray who always told us to use our ears and not the numbers on the knobs.

Update:

The dark brown preamp resistors that look like 1/4 watt are 1/2 watt Beyschlag.
After August 1984 the 120pf cap from the grid to the cathode on V2B was removed. This is the effects loop signal, lead master and reverb output
from V2A.


The Schumacher Transformers -

The digits 606 are Schumacher’s EIA manufacturer code.

The digits after are the last number of the production year, example, 3 is 1983. The next two digits are the week of productions, example, 42 is the 42’nd week of 1983. It’s not the Fibonacci Sequence, trust me. EIA 606-342.

60W OT - T60-152019
Simul Output - SC-152019B - Simul-Class
180W - SD 190555 Coliseum

60W PT - 00-162310 - 448V
60W Export - PT: X62-162318 - 448V
Early 100 - 100-162318 - 448V
Simul/60-100 Power - 105-162318 -483V+
- X101-162318 - Export - 448-460V
180W - 0180322 Coliseum - 500V+

Some early IIC+’s may have leftover 100 power transformers.


The Serial Numbers -

12,500 to 14,400 are pretty much unquestionable. 14,400 to 15,000 in my opinion have early black dot MK III’s in the serial number sequence, or were never even used. There has been visual proof that a 15,000 does exist ( BWK aka Ian Dickey), but IIC +’s between 14,400 and 15,000 just never seem to surface. Anything from 12,300 to 12,499 is a certain possibility, but the loop test is your only way of knowing without pulling the chassis to view the circuit board. Even then, if you do not know what you’re looking for it will be hard to tell.
A recent MK III Black Dot surfaced with a serial of 15113 from 5/14/85. It had a DR 13 chassis code which may put the start of the MK III production to 2 or 3 of 1985 which would coincide with the last of the IIC+ production, but it may dispel the 12,500 to 15,000 serial number sequence. With a IIC+ in the 1406X range from 2/85, the C+ may not have even made it to 14,400. If it did, it may have been randomly sequenced in with the early MK III production. An inference to the actual monthly production from 12,500 from April 1984 to 137XX from October 1984 averages 200 units per month for the six month period. From late 137XX in November 1984 to 1406X in February 1985 the average drops to around 121 per month. With the MK III looming Mesa was definitely phasing out the C+ as orders for the III were being generated and amps being built as early as March 1985. Any C+ after March 1985 would have possibly been an attempt to use up the remaining stock and finally push production to the MK III full blast. Even if the IIC+ production was in full effect at an average 121 per month, the sequence would be about 14,370 to 14,400 as an inference. With new MK III orders and fewer MK II orders, the production slowed on average 79 amps less per month, thus reducing the amount of upper range IIC+ serial numbers. The final peek into the model change was the use of the 105-162318 power transformer on the first 150 or so MK III’s. When they were gone, the much smaller unit we know today was assimilated into production.


The End of an Era-

Asking why Mesa quickly went to the MK III is like asking why the earth spins. The circuitry and board design on the MK III was Mesa’s leap from the MK I style circuit boards and labor intensive manufacturing. It would have happened eventually. RCS is an amazing engineer, but an astute business man as well. As the PCB market moved forward with newer, cheaper techniques, so did Mesa. The extra savings may have been necessary to the companies long term survival as the orders increased the labor cost increased while the pricing stayed consistent. Saving an extra $ 300 per amp in production cost and still producing a bullet proof design was an outstanding achievement and allowed Mesa to move forward with future designs. Obviously, the stripes were a constant evolution to fine tune the III to player’s desires. With input from the chief designer, play tester and the brilliance from the Chief Technician the core team managed to sell around 13,000 plus units. With the three modes, we had our first glimpse of the future MK IV. The IV has lasted longer and sold more than any previous MK design. It may get to the point where it will pass them all combined unless the rumored MK V makes its debut soon and the IV is put to pasture.


Best Regards,

Edward P. Morgan
©10/2007

The Mark II-C FOOTSWITCHING SERIES- Pricing September 1984


Mark II-C Combo Amplifier with 12” Black Shadow Speaker

Standard 60 Watts, Vinyl Cabinet, Specify Black or Cream.
Slip Cover, SUS-4 Shock Mount & Lead/Rhythm Footswitch Set - $ 750
(Mark IIC 1X12 as above but without speaker $ 720 )

Performance Options Each Extra

Hundred Watt Chassis with Fan & 100/600 Watt Switch ........ $ 150
Simul-Class with Fan & Switch ( Add to 100 Watt Option) ..... $ 25
Reverb ................................................ $ 150
Graphic Equalizer ........................................ $ 150
Electro Voice EVM 12” Speaker ............................. $ 70
Export Switch & Transformer (For All World Operation) ........ $ 50

Cabinet Options Each Extra

Hardwood Cabinet with Wicker Grille ........................ $ 175
Hardshell Road Case with wheels, Black ......................$ 180

Mark II-C Amplifier Head, Top Only

Standard 60 Watts, Vinyl Cabinet, Specify Black or Cream.
Slip Cover, Lead/Rhythm Footswitch Set - ....................$ 700
(18 ¾” wide, fits well visually on 1X12, 2X12 & 4X10 Cabinets)

Performance Options Each Extra

Hundred Watt Chassis with Fan & 100/600 Watt Switch ........ $ 150
Simul-Class with Fan & Switch ( Add to 100 Watt Option) ..... $ 25
Reverb ................................................ $ 150
Graphic Equalizer ........................................ $ 150
Export Switch & Transformer (For All World Operation) ........ $ 50

Cabinet Options Each Extra

23” wide cabinet - For Hundred or Simul ONLY (Black or Cream) $ 25
(Not available in Sixty - Fits well visually on 2X12, 4X10 & 4X12’s)
Hardwood Cabinet with Wicker Cane Grille (Either Widths) .... $ 155
Hardshell Road Case without wheels, Black (narrow chassis) ..... $ 115
Hardshell Road Case without wheels, Black (wide chassis) ....... $ 130


THE COLISEUM SERIES 300

Coliseum Series 300, 180 Watts, 6 Power Tubes, Half Power Switch,
Vinyl Cabinet, 23” Wide only (specify Black or Cream) & Slip Cover,
(Can be wired for 117 or 230 volt operation.)

Mark II-C Type Series 300 Amplifer Head, includes Footswitch.. $ 1000
Reverb ................................................$ 150
Graphic Equalizer ........................................$ 150

Cabinet Options Each Extra

Hardwood Cabinet with Wicker Grille ........................$ 155
Hardshell Road Case without wheels, Black.................... $ 130


1X15 COMBO AMPLIFIER SERIES

Combo Amplifier with 15” EVM Speaker, Hundred Watt chassis with
Half Power Switch & Fan, Vinyl Cabinet (Specify Black or Cream),
Removable Casters & Slip Cover. Not Available in 60 Watt Model.

Mark II-C Type HundredWatt 1X15 w/EVM 15-4, Incl. Footswitch $ 1005
Simul-Class with Fan & Switch ............................ $ 25
Series 300 Power Section ..................................$ 150
Reverb .................................................$ 150
Graphic Equalizer ........................................ $ 150
Export Switch & Transformer (For All World Operation) ........, $ 50


Cabinet Options Each Extra

Hardwood Cabinet with Wicker Grille ........................ $ 175
Hardshell Road Case with wheels, Black....................... $ 185



Mesa Engineering Price List - SEPTEMBER 1984



A gracious thank you goes out to Ian Dickey, Richard Ray, John Kamaly, George Stergiou Jr., Todd Duane, Joey B., Mike Bendinelli and to the hundreds of C+ owners that allowed me to invade their privacy.

 

[bgh]

Ok, Weird results. Yesterday, the post from gks (from July 1) was coming out all messed up in my browser. That is what I copied from when I re-posted. When I viewed it and copied it to my editor, all of the odd characters were present.

But today, I am able to read their post okay. Everything is coming out fine. No funny characters are being displayed.

Sorry for sticking my nose into this thread. I honestly was not trying to butt in. I thought the control characters were present, and simply wanted to try to help.

My apologies for adding a repeat of what gks had already so graciously provided.

 

[liquidchris]

If I understand correctly, it is possible to have a mark IIC with a serial number above 12500 and "pull deep" face which is not a "+". Especially those without EQ?

Thanks

 

[Wyzard]

Some early-ish just-above 12500s with Pull Deep, and that should have been marked as plusses, were shipped without a "+" or even a vertical line on them. I have personally owned one and seen another.

Unless you're prepared to assume that some people were in the habit of buying them and rubbing the + out... anything is possible, after all. I've never yet seen one of the unmodded ones above 12500, however. I'm not saying they don't exist - I'm just saying that even the best researched lore on this is prone to hearsay and definitive statements unsupported by personal experience: so be appropriately aware.

People were asked in the early stages which they wanted -plus or not - and I guess some may have chosen not to have what they may have thought of as "just a modification for gain fanatics".

The factory records aren't IMO totally 100 per cent reliable as to which s/n's are factory + and which are what Mike Bendinelli has sometimes described as "Minuses."

The loop test should be your friend in all cases.

 

[liquidchris]

Thanks for your response Wyzard!

 

[tbguitar55]

I just found this thread yesterday, and have re-formatted the OP's info to make it easier to read. Please proof-read and send me suggestions on how to improve it for everyone:

http://defendublog.com/wp-content/uploads/2018/02/Mark-IIC-For-Dummies.pdf

http://defendublog.com/wp-content/uploads/2018/02/Mark-IIC-For-Dummies.pdf

 

[jrb32]

I've been analysing the history and development boards used for the IIC+ in massive detail and have a theory but it doesn't fit with the narrative exactly about winter '83. It seems like it should have been a good few months earlier maybe summer '83 when Doug West and Mike B were experimenting.

Basically if you look at the RP-10 and SP-10 boards which were designed for the early IICs it takes a load of modding to get these to IIC+ spec. By the time the RP-11 and SP-11 boards come along, also designed for the IIC, the IIC versions of these (and these are rare but I've managed to get some detailed pics of some) already have treble shift enabled only on lead mode and the power section already put to IIC+ spec. V2A and V2B are already swapped around, the EQ values have been updated and the entire layout is designed in such a way to make the + upgrade far far easier. Most of the work is already done. It's like they were designed to give the customer a choice and then if the + mod was requested during production it allowed a far easier conversion than the RP-10 or SP-10. The RP-11A boards for the IIC started to be put in around September/October '83 meaning if they had been designed with the easier + upgrade in mind, this would have been done earlier in the summer to get a new PCB drawn up and manufactured in time. It's also only the RP-11s or SP-11s which are the referred as the 'factory C+s' as their + upgrade was done from the RP-11 during the production line rather than afterwards.

So either the RP-11 was developing the IIC already into the features eventually found on the IIC+ during '83, or that these boards were designed with the + mod in mind. I think the latter is far more likely because circuit wise apart from a weird pull bright on the lead circuit, the RP-10 and RP-11 preamp sections are identical including FX loop placement and reverb placement. The main changes happen in the EQ and Power Section which are already set up ready for the IIC+ upgrade ready to go. It just makes logical sense! Why else would you redesign the entire PCB preamp board and give it identical circuitry to what was before but with a different layout?

My history is probably wrong as it's 36 years ago but it makes sense. Either way great amps and you can see the final factory switchable IIC+/++ develop into the III in a similar way. Look at the circuit - it all just makes sense!

 

[Danny2c+]

So I have a 1989 mkIII blue stripe and from some information I found on this site I found out it has a 2c+ Simulcass output transformer in it. Anyone else here have one like this as well, & have you been able to compare it to an actual 100watt 2c+?