C+ pic gut's.

[Shep]

So i am right now goint over my C+ working what cap's i need to replace.I took some photo's of it's gut.


The power Transformer is a blue printed 240volt 105! voltages are spot on with a 105 running 120volts.so i know that isn't orginal.

So just wondering What else looks like has been done to it.

There are some cut resistors on the power supply board that look abit strange.
?
And i looks like to me the bais resistors have been changed on the outer tubes.(they look different?)


Any info would be cool.


Also i am after some bright reduction mod's.

Thanks Alot Tom.

 

[Boogiebabies]

Tom,

Everything looks dead stock including the bias supply.
Besides the PT, the "Death Cap" was removed because it is illegal in Ozland.

 

[Shep]

Thanks Ed!

 

[Boogiebabies]

Do you want to add the bright reduction mods ?

 

[chipaudette]

I'm intrigued...what are some of the different mods that are done to reduce the brightness?

Thanks,

Chip

 

[Shep]

Do you want to add the bright reduction mods ?

Yeah,Is there anything you would recommend??I will most likely do the mod's after i do the Re cap. The amp is Really needing it. The clean sound is good. but the lead channel is Flabby , grainy and as loose as a goose.

Thanks Ed

Tom.

 

[Boogiebabies]

1. Replace 20pf cap with 10pf cap. 1000C ceramic disc.
2. Add 1000pf/.001 1000V ceramic disc cap in parallel with 270K resistor.

 

[Elpelotero]

Do you want to add the bright reduction mods ?

Yeah,Is there anything you would recommend??I will most likely do the mod's after i do the Re cap. The amp is Really needing it. The clean sound is good. but the lead channel is Flabby , grainy and as loose as a goose.

Thanks Ed

Tom.

How do you set the bass knob? Most folks don't go much past 2-3 and introduce bass via the graphic eq.

 

[Boogiebabies]

Even 3 is high on the bass knob.

 

[JOEY B.]

1. Replace 20pf cap with 10pf cap. 1000C ceramic disc.
2. Add 1000pf/.001 1000V ceramic disc cap in parallel with 270K resistor.

As per this schematic, this is like using a 60 watt or 60/100 watt preamp board in a simulclass amp.

http://www.schematicheaven.com/boogieamps/boogie_mkiic_plus.pdf

 

[Shep]

Thanks Ed,that is a huge help. i am really looking forward to hearing it with the new cap's and the mod's to.


i have to say that my bass settings are mainly on 0 to 1.and even with the EQ off it sounds flabby.


thatnks Alot Again.

 

[Shep]

Hey Ed, Just wondering What sort of tone difference the reduction mod's will do. Eg. Will they Make it more smooth and less agressive? Will they make it muffled?

Just wondering thanks A heap!!

 

[Boogiebabies]

Your preamp should be pretty smooth as it is. It mostly polyester coupling caps.
They are a bit smoother than the polypropylene's. During a conversation with Mike B. I asked why
the use of 225P and 715P caps was so different from amp to amp. It seems that Mesa was constantly toying
with the amp to find out what positions were best to use the smoother 225's and brighter 715's. I don't think I have ever seen two alike
in this respect. Your amp is a tweener between early and middle. The late amps George is referring to are the "Heinous Crunch" ones.
These have mostly Mallory 715P's and a different brand of ceramic disk caps in the lead stage. I don't think Mike was happy with these even when
they were being produced, but I have a late one that has stupid amount of gain, but it was built with two 225P's for the phase inverter so
it is not heinous, but smooth !!! Lastly, the Simul's don't have the same tonal attack as the 60/100's. They seem to sag much more whereas the 60/100
lets it fly a good bit tighter.

The mods at most trim a bit of treble off both channels
and will allow you to use a higher treble setting without feedback in lead mode.
You may find the notes in lead mode to have a bit more touch sensitivity. The best
thing is they are reversible in 30 seconds.

Check the 1K resistor off the B+. If it reads 1K it's good, but I have seen tons of these replaced. If it looses value
it could either cause too much preamp voltage or not enough and would lead to tonal issues.

 

[Shep]

Your preamp should be pretty smooth as it is. It mostly polyester coupling caps.
They are a bit smoother than the polypropylene's. During a conversation with Mike B. I asked why
the use of 225P and 715P caps was so different from amp to amp. It seems that Mesa was constantly toying
with the amp to find out what positions were best to use the smoother 225's and brighter 715's. I don't think I have ever seen two alike
in this respect. Your amp is a tweener between early and middle. The late amps George is referring to are the "Heinous Crunch" ones.
These have mostly Mallory 715P's and a different brand of ceramic disk caps in the lead stage. I don't think Mike was happy with these even when
they were being produced, but I have a late one that has stupid amount of gain, but it was built with two 225P's for the phase inverter so
it is not heinous, but smooth !!! Lastly, the Simul's don't have the same tonal attack as the 60/100's. They seem to sag much more whereas the 60/100
lets it fly a good bit tighter.

The mods at most trim a bit of treble off both channels
and will allow you to use a higher treble setting without feedback in lead mode.
You may find the notes in lead mode to have a bit more touch sensitivity. The best
thing is they are reversible in 30 seconds.

Check the 1K resistor off the B+. If it reads 1K it's good, but I have seen tons of these replaced. If it looses value
it could either cause too much preamp voltage or not enough and would lead to tonal issues.

This would have to be one of the best reply's i have Ever see to any question.




Amazingly insightful!

Thanks so much Ed.

 

[Boogiebabies]

1. Replace 20pf cap with 10pf cap. 1000C ceramic disc.
2. Add 1000pf/.001 1000V ceramic disc cap in parallel with 270K resistor.

As per this schematic, this is like using a 60 watt or 60/100 watt preamp board in a simulclass amp.

http://www.schematicheaven.com/boogieamps/boogie_mkiic_plus.pdf

Correct, but on some early ones there is also a 100K resistor from the Vol. 1 to the treble pot instead of buss wire.
This changes the load on the tone stack. Some have the resistor and some don't. The early ones also have a slightly different effects loop.
Somewhere around July-August of 1984 the 120pf cap on the V2B was removed and IMO lowered the gain of the loop. This is about the same
time the 22K resistor was added to the master volume. I stopped looking at that schematic a long time ago. It's a treasure map with too many X's !!!

 

[Boogiebabies]

Are you doing the work yourself Tom ?

There are a few other mods you may want to try before you button it back up.

 

[JOEY B.]

Somewhat off topic, but I did the C30 mod to my "greenie" MkIII, and it appears very similar to the number 2 brightness mod for the C+. Info is in this thread: http://forum.grailtone.com/viewtopic.php?f=3&t=27879&hilit=MkIII 8)

 

[Shep]

Are you doing the work yourself Tom ?

There are a few other mods you may want to try before you button it back up.

Yes i am Doing all the work myself. what else have you got Ed?


Also with componet removal, How strong it the trace on the Circuit board? Will it be smarter to just cut the leads and solder the new Cap's to the old lead's instead of trying the solder sucker and clean the componets completely out??

I have done work on amps where that NEEDED to be done in fear of uplifting the weakly drawn trace.

Thanks Alot Tom

 

[GIG4FUN]

Somewhat off topic, but I did the C30 mod to my "greenie" MkIII, and it appears very similar to the number 2 brightness mod for the C+. Info is in this thread: http://forum.grailtone.com/viewtopic.php?f=3&t=27879&hilit=MkIII 8)

When I saw the picture I thought the same thing!

I haven't doem MIII yet, but as you know.. stuff here and ready.

 

[Boogiebabies]

The filter cap board is pretty sturdy, so just heat the big blobs of solder and the caps should lift out.
Be sure to replace the black wire on the bottom as it takes B+ right off one of the caps. Don't forget the bias caps
while you are under there. A small tip, if you cannot turn the board over fully you may have to desolder the red lead going over the
board to the standby switch. Removed the two screws and plastic standoffs and you can flip it right over.

The main PCB traces are not that strong, so being easy with the iron will help. Almost all of the components are bend under the board to
hold them for soldering, so if a piece does not come out quick and easy, snip it.

Do you feel that you have enough gain ?