AmpClones.com Mesa Boogie Mark IIC+ Help total newb

[WesPalladini]

Hello.

My dream amp (right now) is a mesa boogie mark IIC+. I was tired of constantly getting out bid on e bay for one, then waiting months for another to appear. If I won and wanted to send it to Mike B at mesa for a mod/upgrade it is even harder because he said if it comes from the states they can only ship it out once they upgrade it to someone in the states, (I live in Canada). So that means I would have to get it shipped to me then ship it to Mike then him ship it back, such a mess. So I decided to give a shot at making one.

I ordered the chasis and the PCB from MARK 2C+ Chassis + Complete PCB set - $155.00 : AMPCLONES.COM, Tube guitar amplifier PCB boards, chassis, transformers and DIY kits
It came with 3 boards, and 6 pages of schematics. FML this is not as easy as lego, nor as safe.

1) So I thought my first step should be to take a picture of each PCB, start writing down every component I need to buy and how many and open the picture up in paint and scratch off that component as I go.
2) So I am trying to match the boards with the schematics, I believe I have found the board and schematics that are responsible for the Graphics EQ but have some questions:

I noticed it says 60Hz on the schematic but the equalizer on the boogie is 80Hz (Small issue for the most part, I think)
RV8 to RV12, does RV mean Variable Resistor (Pot)?, if so why do they call it RV instead of VR?
are all of those pots supposed to be 50k Ohms?
How do you call a pot like this that is not round but supposed to be vertical, and where can I buy some?
Is the pot supposed to fit between position 1 and 2 after the 470 and 1k resistors or in each pair of spots labelled 3?
How do those 3 holes at the bottom left of the board match up with the schematic?

Any help would be EXTREMELY appreciated, I think I am in over my head and will need a lot of walking through this, I thought amp clones would have included a lot more detailed instructions.

THANKS!!!

[überfuzz]

Lets see, capacitors and coils affects the resistance in a circuit. The resistance varys over different frequencys. So the eq has coil+cap connection to get a frequency band. The 5 controls are there so that you can vary how much of the frequency band will get through to the next stage.

The eq-controls, you posted a picture. Isn't that your picture..? The 5 controls seems to be mounted already.

By the way. I like your spirit - jump in the deep end! Just don't underestimate the voltages you're going to mess around with.

Edit. I just had an other look on your picture. The switch is to stop the signal to ground dump. In other words, a switch that works as an on/off to the eq.

[g1]

Have you contacted them and asked if there is more info/instructions available? That should be your first step.
Yes you are in way over your head. Not impossible but it's going to take a LOT of time and money. Have you priced out transformers? I don't think there will be much room in there, you will need something very close in size or exact replacements if you don't want to redrill the chassis mounting holes. You should look into transformers before you go much further.
Once it's all built, the routing of the wires (lead dress) will be critical. It may take a long time to work out wiring issues.
Sorry to sound scary, but you need a realistic idea of what you are up against.

1) So I thought my first step should be to take a picture of each PCB, start writing down every component I need to buy and how many and open the picture up in paint and scratch off that component as I go.

This will be the easy part. Again suggest you do more research first so you don't end up with a bunch of stuffed pcb's you can't find/afford hardware for. Also, the schematic does not show wattage for the resistors or voltage ratings for the capacitors. You won't be able to get the right parts without that info.

2) So I am trying to match the boards with the schematics, I believe I have found the board and schematics that are responsible for the Graphics EQ but have some questions:
I noticed it says 60Hz on the schematic but the equalizer on the boogie is 80Hz (Small issue for the most part, I think)

Small issue, maybe even a typo on their schematic. Does the chassis you have say 60 or 80? Is that their schematic? Get the proper mesa schematic and check if that circuit is the same.

RV8 to RV12, does RV mean Variable Resistor (Pot)?, if so why do they call it RV instead of VR?

Maybe that's how they do it in Russia?

are all of those pots supposed to be 50k Ohms?

Yes, the frequency depends on the cap and the coil, as uberfuzz stated

How do you call a pot like this that is not round but supposed to be vertical, and where can I buy some?

They are called slide potentiometers. You will have to find parts suppliers (mouser, digikey etc). Prepare to spend a lot of time looking for parts. Google is your friend.

Is the pot supposed to fit between position 1 and 2 after the 470 and 1k resistors or in each pair of spots labelled 3?

The slide pots will have 2 legs at one end that go in 1 & 2, the other end will have a leg that fits in #3. The middle hole #3 is probably optional.

How do those 3 holes at the bottom left of the board match up with the schematic?

The schematic is showing a bit more than the eq board. Some of the parts on that schematic (LDR5 and the upper half of schematic) are probably on the main board. One hole goes to pin 3 of LDR5, one hole to the ? you drew lower left, one hole the the ? you drew at Q3.

[WesPalladini]

Lets see, capacitors and coils affects the resistance in a circuit. The resistance varys over different frequencys. So the eq has coil+cap connection to get a frequency band. The 5 controls are there so that you can vary how much of the frequency band will get through to the next stage.

The eq-controls, you posted a picture. Isn't that your picture..? The 5 controls seems to be mounted already.

By the way. I like your spirit - jump in the deep end! Just don't underestimate the voltages you're going to mess around with.

Edit. I just had an other look on your picture. The switch is to stop the signal to ground dump. In other words, a switch that works as an on/off to the eq.

No the controls are not mounted yet, I just google searched an image of the Mark IIC+ then cropped the graphics EQ part and pasted it in this picture to give people a better idea of what I am talking about.

Yes high voltage stuff is what I am worried about, any tips on staying safe?

[überfuzz]

Safety... Well I guess the best thing to do are some google searches.
In short

• Always one hand on the back while you're got the amp fired up.
• Make sure you know how to drain the filter caps on your amp and why you need to do it. (They hold juice even if the amp is turned of or un plugged.))
• Measure from ground to point. A simple subtraction is safer than point to point measurements.
• Always triple check every thing. (Might save other things than your life.) ;-)

Edit, no point in reanswering questions answered by g-one.

[tedmich]

you'll really need an accurate "Bill of Materials" (BOM) to build this up, as the PCB is designed with very specific parts, ie the spacing of the lead pins on the linear pot will only work with the pot it was designed for. Did they send a BOM? You can even build up a BOM at Mouser if you register and then buy parts as you can afford them.

Putting parts on the PCB is a no brainer, just be sure that orientation is observed for EL caps (+/-) and any transistors LDRs etc as there is only one right way to mount them. Lead dress/running wires between the PCBs is where it can all go south for a high gain amp, take your time and totally mimic some of the beautiful build's documented at sloclone and the sloclone/smashguitars commercial sites.
Soldano SLO100 Log


If ampclones has an online build guide/photo diary this would be PERFECT, even if its in russian its the pictures you'll need to copy.

Nothing bad can happen except:

-electrocute/kill yourself, burn down house
-very noisy amp which drives you nuts

[WesPalladini]

Thank you for your comments so far.

I have e mailed them to see if they have a BOM or a picture journal. Also I am still waiting for the chasis and I just got my new soldering iron !

I am just thinking that there must be a good book/text book that I should purchase to teach myself more about this field. Any suggestions?

It would be cool if there were a few dedicated people to help guide me through this, I would post videos/pictures to make a journal for future builders.

-WP

[tedmich]

the build guide I posted is a good study, and there are MANY online, for intros to tubes
try here:
Technical books online
(the Crowhurst books are great)


For guitar amps try Merlin's web site,
How to design valve guitar amplifiers
some of it is down ;(

[diagrammatiks]

keep in mind that the mark IIc+ is a bit more complicated then the slo.

well a lot more complicated actually.

that being said the parts themselves should be all available on mouser or something like it.

The inductors for the eq and the slide pots are probably going to be the most expensive.

Other then that take a look at some MarksII's to get an idea of what you are getting into.

[überfuzz]

Are you absolute sure you'll pull this off..? I'm not a pro builder, more like average, this scheme seems kind of gnarly.

This forum has more than a "few dedicated people" eager to help. So if you think you can land this jumbo jet by instructions. Go for it dude! My first build was a Twin Reverb and I loved every bit of it. Eh now I love playing/listening to it.

Keep us nerds updated. :-)

[big_teee]

Are you absolute sure you'll pull this off..? I'm not a pro builder, more like average, this scheme seems kind of gnarly.

This forum has more than a "few dedicated people" eager to help. So if you think you can land this jumbo jet by instructions. Go for it dude! My first build was a Twin Reverb and I loved every bit of it. Eh now I love playing/listening to it.

Keep us nerds updated. :-)

Hi, and best of Luck:
I'm a 40 year Communication Tech, and I just built from scratch my JCM800 2204 Marshall Clone.
It was plenty tough for me, Your Project is way over my Head.
If I were You, I would put that thing in the closet.
Build some lesser Kits, and get the skill and confidence up.
That way you could learn some practical amp experience, with the transformers, and Cap discharging Procedures.
Don't mean to scare or discourage you, but looks like a Heavy chore for Sure.
Good Luck,
Terry

[Corona Blue]

The switch is to stop the signal to ground dump. In other words, a switch that works as an on/off to the eq.

This is correct. But there is more. The original switch for the EQ was a 3 position switch that was setup this way:

UP = EQ on

MID: IF channel = "Rhythm" THEN off. ELSE, on.

Down = EQ off

So the lead channel switch also closed the circuit for the EQ when the EQ switch was in the MID position. This is where I leave mine most of the time, although with some guitars, I will switch the Graphic out completely.

As if that wasn't enough, there was also an auxiliary footswitch box available to switch the reverb or the graphic in or out. On the originals, there was a stereo phone jack up under the chassis pan, just to the right of the speaker (looking from the back). It's a pain in the butt to reach around all the tubes to plug it in, but it is great to be able to control these features with the footswitch.

Mine is a December of 1983 Mk II C Simul (Reverb, EV12L, hardwood combo) that was upgraded to a C+ a few months later by the Mesa techs. I ordered and picked it up directly from the factory as I lived in the SF Bay Area at that time.

I agree with what Big_Tee says... it's a huge undertaking to build one of these for a first amp build. Finding transformers that will operate and sound like the originals will be very challenging as well. The OT's on these amps were designed to run specifically around the performance parameters of the Sylvania STR-415 power tubes. You can use other tubes, and some will sound pretty good. But the unique character of these amps was, in my experience, largely found in that combination of the OT and the 415's. I pass that along just as anecdotal info.

There must be other builders who have built this kit before. What kind of information are you getting from them about things like proper trannies and inductors?

[soundguruman]

Well, the design is very complicated and it's not for a beginner. You will probably wind up taking it to a tech and spending a lot of money to make it work.

[broken flyer]

Hi, i have a mesa mark III and i was going to copy the eq and untilize it in a different amp. If you'r having trouble finding inducers take a look at futurlec. I haven't personally had any expierience ordering from them but i have heard that they'r a little slow if your in a hurry but they should be reliable at least as far as i know.

[WesPalladini]

Thank you

Just wanted to say thank you to everyone who has posted so far. I am going to post the schematics they gave me so you can all see. And respond to all your comments later today just had a lot of school due for university in the past few weeks.