New (to me) Mark2C+ gut shots!

[Elpelotero]

Here are some pics (and even a vid for those really into it (BB)) of my mark2c+ (IIC+). It looks and sounds amazing. It has it all except for an EQ, which I can use a pedal or rack for. It's a 1x12 combo with an eminence speaker similar to an EV, which may be changed in the future even though it sounds great now. It's in great condition. no rust.

Let me know what it's got!

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http://www.dotphoto.com/Go.asp?l=pelotero&P=&AID=4268175&Pres=Y

VID http://www.youtube.com/watch?v=3Dt4kuu5TTw

 

[Boogiebabies]

Miguel,


It's the real deal. It has the .001/1000pf bright reduction mod. You need to see if there is a 100K resistor from the Volume 1 pot to the Treble pot instead of a buss wire. This is a gain reduction mod as well. Check to see if the 3.3M resistor has a 20pf or a 10 pf cap across it. It's in the middle of the preamp.
The preamp and power amp board are correct C+ boards and of course, all the transformers check out. The only items to note is the odd re-cap on the power section. It has definately had a re-cap, but that black cap does not make sense as the rest look like current/more recent Mesa United Chemi-Con caps. I would call Mesa with the serial number and see if they did the work un a RA/repair authorization. The bias caps have been changed as well, so if everything works and it sounds killer you should have a clean bill of health. If you want some idea of how old the caps are, they usually have the year and week they were produced. An example would be 9525 which would be the 25th week of 1995.

Someone was nice enough to count your power tube pins for you too !!!
The power tube sockets have been replaced. Mesa used a brown phenolic which were prone to getting loose from the crimps and breaking the connectors as you had to wiggle for 10 minutes to get 1 tube out. As you wiggled, the connections soldered to the power board would snap. I have been work on a week 6 DRG with those old sockets, but there is a way to fix them rather than replace all four. It looks like a pretty decent job.

Enjoy your Simul !!!!

 

[Boogiebabies]

What a video !!!!

Who was feeding the chickens ?

 

[Elpelotero]

What a video !!!!

Who was feeding the chickens ?

lmao! apparently my digital camera makes clicking noises when recording. the house was silent when i was recording so i don't know how that noise came in.

 

[Elpelotero]

Miguel,


It's the real deal. It has the .001/1000pf bright reduction mod. You need to see if there is a 100K resistor from the Volume 1 pot to the Treble pot instead of a buss wire. This is a gain reduction mod as well. Check to see if the 3.3M resistor has a 20pf or a 10 pf cap across it. It's in the middle of the preamp.
The preamp and power amp board are correct C+ boards and of course, all the transformers check out. The only items to note is the odd re-cap on the power section. It has definately had a re-cap, but that black cap does not make sense as the rest look like current/more recent Mesa United Chemi-Con caps. I would call Mesa with the serial number and see if they did the work un a RA/repair authorization. The bias caps have been changed as well, so if everything works and it sounds killer you should have a clean bill of health. If you want some idea of how old the caps are, they usually have the year and week they were produced. An example would be 9525 which would be the 25th week of 1995.

Someone was nice enough to count your power tube pins for you too !!!
The power tube sockets have been replaced. Mesa used a brown phenolic which were prone to getting loose from the crimps and breaking the connectors as you had to wiggle for 10 minutes to get 1 tube out. As you wiggled, the connections soldered to the power board would snap. I have been work on a week 6 DRG with those old sockets, but there is a way to fix them rather than replace all four. It looks like a pretty decent job.

Enjoy your Simul !!!!

Thanks for the diagnosis. The previous owner told me he had the amp re-capped a short while before deciding to sell it, so that's where all those caps come from. I'll look into the other things you noted about the gain and mods. As for the power tube sockets, that's one of the first things I noticed. I simply assumed they were the kind Mesa used back then, but I guess you know otherwise. They are so SOLID! they feel like rocks. changing tubes is a breeze. thanks once again. I'll see what else I can find out.

 

[Boogiebabies]

Look for the 100K resistor between the Volume 1 pot and the Treble pot.
All those mods reduce gain !!! All the mods combine to make it less agressive and smoother. You may not mind it so much using an EQ with more bands to tweak. I am so used to the sound of a stock C+ that I am very unaccustomed to having to redial all the knobs.

 

[Elpelotero]

on the volume1 to treble pot, i see a buss wire (i googled it. it's a thick silvery wire connecting the pots right?). however, on the volume pot itself--not connected to the treble pot--i see a faint orange cap, very very small like the diameter of a pencil, that says MP 101K 1KV. Note again, it goes from the top of the pot to the black plastic bottom.

as for the 3.3M resistor and 10 or 20pf cap, (again after googling-don't you just love that thing) i found a small red pill-like looking thing with green, orange, and yellowish stripes (i presume this to be the resistor). right next to it is a cap that says "10K 1KV S2L". this is the only cap i see around the board with the number 10 and it sits in the middle of the board.

the fat black cap says "A 105degrees Celsius". the bottom part i cannot see since it is soldered down, but i can vaguely make out the numbers 220uf 350V. the blue cap next to is is a Chemi-Core as you said. the other 3 big blue ones are Sprague Atom TVA 1907 30UF 500V.

the bright recution mod I assume is why I can run the treble so high right? like up to 7, 8, 9...removing this mod would allow me to have the same amount of treble/attack at lower numbers such as 5,6,7--i can only presume. i would definitely love more gain. where is this mod on the board?

so doc, what do these things mean? thanks.

the previous owner was a blues guy. he even had fender tubes in there, so i would not be surprised if he did some mods to reduce the gain and bring out the clean more.

 

[Boogiebabies]

on the volume1 to treble pot, i see a buss wire (i googled it. it's a thick silvery wire connecting the pots right?). however, on the volume pot itself--not connected to the treble pot--i see a faint orange cap, very very small like the diameter of a pencil, that says MP 101K 1KV. Note again, it goes from the top of the pot to the black plastic bottom.


Good on the 100K. The 101K cap is the Volume 1 Pull Bright.
It's totally correct.


as for the 3.3M resistor and 10 or 20pf cap, (again after googling-don't you just love that thing) i found a small red pill-like looking thing with green, orange, and yellowish stripes (i presume this to be the resistor). right next to it is a cap that says "10K 1KV S2L". this is the only cap i see around the board with the number 10 and it sits in the middle of the board.

This means you have the 10K/10pf bright reduction mod for the clean channel. For Simul's it should be 20pf.

the fat black cap says "A 105degrees Celsius". the bottom part i cannot see since it is soldered down, but i can vaguely make out the numbers 220uf 350V. the blue cap next to is is a Chemi-Core as you said. the other 3 big blue ones are Sprague Atom TVA 1907 30UF 500V.

The caps look good and are the right spec, but the black one makes no sense.

the bright recution mod I assume is why I can run the treble so high right? like up to 7, 8, 9...removing this mod would allow me to have the same amount of treble/attack at lower numbers such as 5,6,7--i can only presume. i would definitely love more gain. where is this mod on the board?

Correct, without them you will get a great treble range between 5 and 7.

so doc, what do these things mean? thanks.

the previous owner was a blues guy. he even had fender tubes in there, so i would not be surprised if he did some mods to reduce the gain and bring out the clean more.

Even with these mods, it is nowhere near a blues amp per se, but they do round the tone out a lot more. You can tell this by running the gain higher and compensating with running the treble so high. You would be amazed at what a good blues tone you can get running your gain lower and using different setting. It can go over the top with using the Pull Deep. The other day I tried my new Xotic BB preamp through the clean channel and it was just ripping and dripping heavy blues. In the lead mode It pushed it over the top using it as a clean boost to get into crazy amounts of contollable gain.

 

[Boogiebabies]

On the right between the third and fourth preamp tube sockets there is an orange drop cap facing toward the back of the chassis. Just to the right you will see two ceramic caps glued to it. The bright cap is the one connected to the 270K resistor towards the edge of the circuit board. It's soldered in paralell with the 270K to cust highs. To try it without this cap all you have to do is remove one leg of the cap by de-soldering it. even if you like it without it I generally leave it glued to the cap and cover the leg with shrink tube.

The 10pf would have to be totally replaced as it is 100 percent imperative that that there is a cap across the 3.3M. This is for the clean channel and the 20pf will brighten the amp, but it will also push a bit more sizzle to the lead channel as all of the tubes are involved in the lead circuit.

 

[Elpelotero]

you are THE man! thanks for all the help and specificity!

i guess i got some work to do before i put her back into the combo. do you suggest i replace the black cap with one similar to the ones next to it?

 

[Boogiebabies]

If it's the right value and it works, I would leave it.

 

[#2121313]

Miguel,


It's the real deal. It has the .001/1000pf bright reduction mod. You need to see if there is a 100K resistor from the Volume 1 pot to the Treble pot instead of a buss wire. This is a gain reduction mod as well. Check to see if the 3.3M resistor has a 20pf or a 10 pf cap across it. It's in the middle of the preamp.
The preamp and power amp board are correct C+ boards and of course, all the transformers check out. The only items to note is the odd re-cap on the power section. It has definately had a re-cap, but that black cap does not make sense as the rest look like current/more recent Mesa United Chemi-Con caps. I would call Mesa with the serial number and see if they did the work un a RA/repair authorization. The bias caps have been changed as well, so if everything works and it sounds killer you should have a clean bill of health. If you want some idea of how old the caps are, they usually have the year and week they were produced. An example would be 9525 which would be the 25th week of 1995.

Someone was nice enough to count your power tube pins for you too !!!
The power tube sockets have been replaced. Mesa used a brown phenolic which were prone to getting loose from the crimps and breaking the connectors as you had to wiggle for 10 minutes to get 1 tube out. As you wiggled, the connections soldered to the power board would snap. I have been work on a week 6 DRG with those old sockets, but there is a way to fix them rather than replace all four. It looks like a pretty decent job.

Enjoy your Simul !!!!

Hey - so if I look at my pic here it appears I do indeed have a 100K Resistor going from Vol1 to Treble, does that mean this is reducing gain (at least to some degree)? And secondly, can I simply replace this 100K Resistor with a solid wire and be good to go and expend a gain increase?

I show pics with arrows of my amps circuit below, its an '83 Mark IIC++

Thanks so much.

 

[#2121313]

On the right between the third and fourth preamp tube sockets there is an orange drop cap facing toward the back of the chassis. Just to the right you will see two ceramic caps glued to it. The bright cap is the one connected to the 270K resistor towards the edge of the circuit board. It's soldered in paralell with the 270K to cust highs. To try it without this cap all you have to do is remove one leg of the cap by de-soldering it. even if you like it without it I generally leave it glued to the cap and cover the leg with shrink tube.

The 10pf would have to be totally replaced as it is 100 percent imperative that that there is a cap across the 3.3M. This is for the clean channel and the 20pf will brighten the amp, but it will also push a bit more sizzle to the lead channel as all of the tubes are involved in the lead circuit.

Second question for you, does it look like I have the Brightness Mod? This amp lacks brightness and if I understand your post above it looks like I would need to clip one of the legs of the 2 orange caps, but I am uncertain which leg to clip and also not sure if there's anything else I need to do in addition or is it just this one leg?

For me, I love bright amps, so if it becomes 'heinously bright' as previously mentioned I am perfectly fine with that. I also understand the point about tweaking the Presence knob and Pulling Vol1 but for me I prefer the amp to be super bright and just turn things down as needed vs up. Just sorta in line with my other amps and how I achieve my personal tone so rather remove the brightness mod if indeed its in my circuit.

Thanks again!



photo upload sites

 

[JD]

You can replace resistor with solid wire try it and see you can always put it back.
Clipping the small caps you have pointed arrow towards will reduce brightness again.
That should be really bright as is and have plenty of gain I am thinking of either component failure or tubes.
Have you got a clean channel or is it semi dirty as it looks like you have the C++ Mod done which you will lose the clean channel.
Also you have the RP10 board which is for amps that have reverb but I see you dont have reverb.

Has the problem occurred recently or since you've had it
What are your settings

 

[#2121313]

You can replace resistor with solid wire try it and see you can always put it back.
Clipping the small caps you have pointed arrow towards will reduce brightness again.
That should be really bright as is and have plenty of gain I am thinking of either component failure or tubes.
Have you got a clean channel or is it semi dirty as it looks like you have the C++ Mod done which you will lose the clean channel.
Also you have the RP10 board which is for amps that have reverb but I see you dont have reverb.

Has the problem occurred recently or since you've had it
What are your settings

Thanks so much for the reply.

I had the Reverb uninstalled by Mike B, I just never used it and wanted to keep things simple and also not have to waste an additional tube in my circuit. He wired it as per a stock non-Reverb C+ but yes kept the board (also the In/Out jacks are there too but out of the circuit).

I will try removing that resistor later and see, I noticed my Mark III which is very bright and has tons of Gain has a solid wire between Vol1 and Treble.

I have all brand new Mesa tubes in Power and Pre so no tube issues. Also Mike went through the amp in 2019 and all was well, I just haven’t played it much over the last year since I got it back, but 99% there isn’t a fault because he just had it on his bench and since then I’ve played it at home about <10 hours worth.

Settings are:

Vol 1 - 9
Treble - 7 (pulled)
Bass - 0
Middle - 2
Master 1 - 2.5 (pulled)
Lead Drive - 5 (pulled)
Lead Master - 4
Presence - 4 (3 and under it gets so dark which is why I think it has a bright reduction in it)

I’m also having to use a Boss SD-1 upfront with Level and stone maxed and Drive off. With the pedal it’s perfect, right there with Master of Puppets. Without the pedal it’s lacking that tight, bright grainy sound.

The reason I thought that I needed to clip one of the orange caps is because of you read Boogiebabies reply above that I quoted he describes that exact section and suggests clipping the one leg as it reads in his post that as it is now it’s reducing brightness.

I’m just looking to do away with the SD-1 and I’m fairly sure the amp isn’t as bright as some C+’s, from my experience of owning a few over the years.

Thanks again!

 

[JD]

Fair enough, I have the same board RP-10 in my amp and it is plenty bright with heaps of gain, Might pay to give Mike a call or email

 

[#2121313]

Thanks! Just sent over an email with some pics. We’ll see what happens will wait before I make any changes myself.

If anyone sees anything in my circuit that is worth mentioning as far as brightness goes please let me know.

There also seems to be a slight hum I’ve noticed which is not present in my Mark III. Like when I’m not even playing. Amp
In standby mode slight hum. Not crazy but enough to notice it’s there since the Mark III doesn’t have it. Curious about that also.

 

[#2121313]

You can replace resistor with solid wire try it and see you can always put it back.
Clipping the small caps you have pointed arrow towards will reduce brightness again.
That should be really bright as is and have plenty of gain I am thinking of either component failure or tubes.
Have you got a clean channel or is it semi dirty as it looks like you have the C++ Mod done which you will lose the clean channel.
Also you have the RP10 board which is for amps that have reverb but I see you dont have reverb.

Has the problem occurred recently or since you've had it
What are your settings

Okay so I removed the resistor and replaced it with a wire. That definitely helped. So previously it was like I was plugging into a Low Gain Jack and now it’s like plugging into a High Gain Jack. Sorta like a Marshall JCM800 has the two jacks. Which makes sense from what I understand on how resistors work.

I noticed another resistor going from me Presence knob (center lug) to the circuit board. My Mark III again (which is very bright to my liking) has a solid wire vs resistor.

Any thoughts on if this will brighten my amp up natural to how a IIC+ typically is (referring to those ‘heinously bright’ ones), or is this resistor key as far as preserving the C+ tone we all know and love.

Looks to be a 1K resistor (my presence is on the back) can see in the pics previously posted.

 

[JD]

The resistor on the presence pot should stay. They are on all C+'s should be 1.5k
The Mark 3 will have it also but it will be on the circuit board it will also be 1.5k or 3.3k depending on what stripe Mk3 you have

 

[#2121313]

The resistor on the presence knob should stay. They are on all C+'s should be 1.5k
The Mark 3 will have it also but it will be on the circuit board it will also be 1.5k or 3.3k depending on what stripe Mk3 you have

Okay perfect thanks for that info!

Do you see anything else in the circuit that could attribute to reducing brightness?