AmpClones.com Mesa Boogie Mark IIC+ Help total newb

[Edward Unfred]

Help with Mark II-C+ Channel switching.

Hello my name is Edward and I own a 1984 Mark II-C+ 100 watt unit with EQ and Reverb. My amp has worked wonderfully for the past six months flawlessly and I am quite happy with it. Last night though I came to find out that I am unable to switch between either of the channels. In other words the lead channel no longer works properly. I have tried the obvious tube scenerio, foot switch, and also the pull lead parameter and nothing works. Im thinking that it is internal then. The schematics on the web are all hand drawn as well all know which creates a major issue for those of us who live on very tight budgets. If anyone has an idea or a resource that would or could be helpful I would greatly appreciate it. Thank you for your time.
Edward

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!!!

[tedmich]

Bummer on the switching issue, these amps are a real pain to work on due to the compressed rats nest layout favored by Mesa. Your issue may be due to a problem with the optoisolators shown on page 5 of the pdf schematic I linked to on the first page of this thread. https://drive.google.com/file/d/0Bx4...it?usp=sharing
They are getting hard to find, too, their data sheet is here http://www.farnell.com/datasheets/87223.pdf

I wonder if Wes ever got his kit thing working...

[Edward Unfred]

Thank you very very much. For some reason I was not able to download the pdf files so I could save them. Is there a way you could send them to via email at unfred.edward@aol.com? I will need some time to look them over and then come back to you with questions.
Edward

Bummer on the switching issue, these amps are a real pain to work on due to the compressed rats nest layout favored by Mesa. Your issue may be due to a problem with the optoisolators shown on page 5 of the pdf schematic I linked to on the first page of this thread. https://drive.google.com/file/d/0Bx4...it?usp=sharing
They are getting hard to find, too, their data sheet is here http://www.farnell.com/datasheets/87223.pdf

I wonder if Wes ever got his kit thing working...

[g1]

For some reason I was not able to download the pdf files so I could save them.

In the upper left corner where it says "mesa.pdf" click on file, then click on download.
https://drive.google.com/file/d/0Bx4...it?usp=sharing

[Corona Blue]

Be sure to replace the 470uf/16 volt cap in the half-wave regulated supply rail. The cap can fail and smoke the resistor or the 1N2006 rectifier diode.



This little power supply section is tagged onto the back corner of the RP11A preamp board, so you will have to loosen and swing-away the main power supply board which occludes that corner of the preamp board. It is regulated by a 15v zener diode and the rail will make around 13.5 volts without the footswitch box. With the box in line, you should see 12.2v to 12.5v.



The original schematic seems to call out for a 1W 680 ohm resistor. 1W seems to be a bit close to the edge, but may have been done intentionally to allow the resisitor to be the sacrificial compoonent as there is no fuse in the line. For this reason, I would stick with a carbon composition resistor.

I replaced the old 470u cap with one of these, because of their long service life and high temp rating...

MAL211835471E3 Vishay / BC Components | Mouser





As stated above by Tedmich... this is a tight space to bring a soldering iron into... With the graphic wires traversing the pre-amp board, you really have to be careful... take precautions to protect wiring from accidental contact.

Also... the RP11A board has the solder pads ON TOP the board for easy access to the components, BUT be careful not to over-extend the electrodes of replaced components through the board as they can touch or even arc to the chassis!! Easy mistake to make, and could have very ugly consequences.

Hope this helps.

[edge59]

What happened to the Amp clone site, I cannot get any info on it, wanted to get a IIC+ kit...

Thanks
Ed