A Mark IV caps question.

[Varulf]

Hello every one!

I´m gonna mod a tube amp i got into a more boogey style amp. I´ve been looking at the Mark IV schematics and i just got to questions that i need answer for.

1. What kind of caps is the bipolar caps that has no voltage printed. Type and voltage? polyfilm caps, 63V?
2. The values that are printed (.047, .001 etc) is that pf or nf or what?

 

[Boogiebabies]

If you don't already know the answer to your questions you have no business modding or cloning
a tube amp. For your own safety, please don't.

 

[Varulf]

If you don't already know the answer to your questions you have no business modding or cloning
a tube amp. For your own safety, please don't.

I know that is dangerous and even lethal! I not going to be near it when i plugg it in. But if no one here can help me then I´ll find my answers somewhere else!

 

[Boogiebabies]

No prob here broheem. I'll sleep tonight knowing that it was not me who helped you electrocute yourself.

 

[stokes]

As well as what Boogiebabies said,do you really think you are going to turn some other amp into a Boogie,a MKIV no less?Its great that you want to learn about amps,modding and building,but what you seem to want to try isnt the best way to do it.There are many here,Boogiebabies included,that will gladly give you advice,but the endeavor you want to begin is going to turn into 2 years and a 1000 threads with you chasing yourself,ending up frutrated and more confused than when you started.Find a simple Champ type schem,get your parts together and start with something simple.You will see that even the most complicated seeming circuits are all based on the humble Champ.I mean no offense,and BB didnt either,but you really dont know enough to go poking in an amp,yet.Its great that you "know its dangerous" and that you dont "intend to be near it when plugged in".But there are going to be things you have to do working on a live chassis and that is no place for a novice that has to ask the rudimentary questions you have started with.You can go someplace else for help,but you wont find better help than you can get here,just be more realistic and start small.

 

[MesaDCLP]

If you don't already know the answer to your questions you have no business modding or cloning a tube amp.

BURNED by the master!!! :twisted:
:lol:

All jokes aside, no pun intended.

... no one here can help me ...

Great additude to have when you seem to have done no research. This is probably the best place to get technical details aside from calling Mesa Boogie themselves. If you are not trained to work on amps, it would take a lot of research to know how everything works and the safety precautions in dealing with high voltage even when the amps unplugged. Read some books and take some classes. That's what I would do if I were trying to build a tube amp or any electronic device for that matter.

... I mean no offense,and BB didnt either ...

+1
but I have to admit I did laugh when I read BB's statement, broheems. 8)

 

[Boogiebabies]

These freaking cloners bug the life out of me with this junk !!!! When I refuse to answer I'm called
arrogant. I'm so sick of the gotta have it now I'm entitled and you can do it for me BS.

DON'T PM ME WITH YOUR **** CLONE ISSUES !!!!!!!!!!!!

 

[CudBucket]

I not going to be near it when i plugg it in.

You may not get that far.

PS

Your screen name reminds me of song I heard...

"Varulf! Varulf! Varulf is on fire! We don't need no water let the motha-fucka burn!"

 

[Varulf]

okey, thanks stokes for at least being polite! What I´m gonna try and do is to change the preamp section a little bit. I not gonna try and make the amp into reall Mark IV clone. Maybe i´m a dreamer and it wont work at all or even explode. But a least i tried. The amp i pretty useless as it is now any way.

And to all the other, please keep och laughing mocking cause that so cool and i really envy you so much!

and for the record i haven´t PM any one...

 

[stokes]

What amp are you starting with?Look,I am not asking this to try to tell you its going to be okay,in reality I am going to try to disuade you.There is more to getting some amp to sound or perform like a Booigie than just changing cap values.Hey,we all started someplace,but I doubt anybody here started by jumping into such a big project,like I said earlier,you should set your goals on a more realistic learning project.If you want to learn about amps,I am more than glad to help,so lets start by telling me what amp you want to mod and I will point out the problems and maybe give some advice on things to do to help you understand what you are getting into.

 

[Varulf]

What amp are you starting with?Look,I am not asking this to try to tell you its going to be okay,in reality I am going to try to disuade you.There is more to getting some amp to sound or perform like a Booigie than just changing cap values.Hey,we all started someplace,but I doubt anybody here started by jumping into such a big project,like I said earlier,you should set your goals on a more realistic learning project.If you want to learn about amps,I am more than glad to help,so lets start by telling me what amp you want to mod and I will point out the problems and maybe give some advice on things to do to help you understand what you are getting into.

Once again, thanks stokes!

maybe i should have been more clear from the beginning, but i had no idea it was going to be such a big deal.

The amp is from the 70th i think. It´s some sort of multi amp with one ecc81 and two el34 in the power amp.
What i want to do is NOT to make a MarkIV clone. I know that the amps are totally differnt from each other and that i just as well could try to build one from scrath(not that im gonna!) The amp has no gain channel so that what i want to try and make. I pay like 50$ for it, with the only intension to try and modify it, and to learn more about tube amp. The MarkIV and the MarkIIC+ seams to be really nice amps so i aim at that direction. I´m not planing on making all 3 channels like on MarkIV and i not gonna do the fx loop nor the eq or reverb. The power supply and power amp i not gonna touch. It´s the preamp that i want to replace, and make a lead stage. I have no hopes that it will sound anything like the real deal. I do this cause i like to know how things work and because i´m intressed in tube amp.

I think i have most of it figured out, and if it doesn´t work then i´ve wasted 50$ and that i can live with.

 

[Fronzil]

the reason people didn't want to help is because you clearly don't know enough to work on amps. a massive give away for me was when you said "don't worry I'll unplug the amp"...since the first year I started playing electric guitar 10 years ago, I knew the potential that amps have to shock you..unplugging it will do ****, unless you want to let the amp sit for a few years. Charges can hold in certain parts of the amp (i dont know which, im not an E.E.)..but anyway, plugged in or not, this job is not for any amateur..please be careful, you can receive lethal shocks even when the amp is off.

 

[Boogiebabies]

I am not saying you can't try, but you should at least buy a book on tube circuits first.
Apart from taking 490V up your arms, there are many other gremlins in a tube circuit.
My best guess is that the first tone you will hear is a "Wooooo" from the tube going into cutoff or
a nasty high pitched squeal from improper cabling or not enough filtering of the oscillation to ground.

Lastly, I did not say it was you who PM'd me. It was a general notice to everyone who felt like
they had the right to pick my brain and Muther F•ªk me when I did not take the time to basically
draw it out or do it for them.

Where in Europe are you from anyhow ?

 

[ryjan]

Maybe as a P.S.A. someone should take a gutshot of some amps and point out the areas and components to avoid for safety reasons. I know many amps that need to be open to adjust bias and the Mesa rackmount power amps have to have the chassis covers removed to replace the 12ax7's inside.

 

[Mongo1]

Mesa rackmount power amps have to have the chassis covers removed to replace the 12ax7's inside.

Mesa tubes are assessable below the chassis, safely away from lethal component access.
This is for Combo, head or rack configurations.

Edit: Brainfart.... Nevermind :roll:

 

[ryjan]

Mesa rackmount power amps have to have the chassis covers removed to replace the 12ax7's inside.

Mesa tubes are assessable below the chassis, safely away from lethal component access.
This is for Combo, head or rack configurations.

Not on a 2:90 power amp. They put 3 tubes inside. The 6l6's are all sticking out the back but the 12ax7's aren't.

 

[Mongo1]

Mesa rackmount power amps have to have the chassis covers removed to replace the 12ax7's inside.

Mesa tubes are assessable below the chassis, safely away from lethal component access.
This is for Combo, head or rack configurations.

Not on a 2:90 power amp. They put 3 tubes inside. The 6l6's are all sticking out the back but the 12ax7's aren't.

:roll: :lol: :mrgreen:
Yup, 100% correct. I should know better than to post while distracted.
I was thinking of a Mark series. My 50/50 is exactly as you say.

No one should ever pull the cover on a tube amp unless they are aware of the dangers inside. I look at amps like old CRT televisions, open one up in ignorance and it may kill you before you learn a single lesson...

 

[stokes]

Varulf,if I'm understanding correctly,you have a "hybrid" amp,that is,it has a tube power or output section and a solid state preamp.If that is so,I have to say again,this is way over your head.You may very well need a new power transformer to support the additional tubes,quite possibly a different chassis,depending on how much room you have when you completely remove the solid state components,even if you can use the existing chassis you will have to cut holes for the new tube sockets.You will have to determine if the power tranny can supply enough current to add a couple more tubes,I would guess it wont.You are talking about building a high gain preamp to go into this out put.High gain circuits are a ***** to stabilize,even if we were to give you step by step,drawn out instructions,it is very likely you would not be able to trouble shoot it when you get instabilities from the layout causing squeeling and oscillations.I have been fixing and building tube amps since 1969 and I still cringe when someone brings me a high gain tube amp,there are many ocassions I wont even touch one.Look,like I said before,I would be happy to give you advice and to help you learn about tube circuits,but this isnt a project for your experience level.The fact that your first question involved cap values is disturbing because you arent even close to the point where you should be worrying about the cap values,you have to start by completely removing the solid state preamp,and again I mean no offense,but you likely cant identify what should be removed and what should be left intact.Okay,heres the answer to your first 2 questions,and we'll see where it goes from there.Your signal or coupling caps and tone caps should be 500 to 600 v's at least.Any preamp tube cathode bypass caps should be a minimum of 25 v's.Any plate bypass caps should be a minimum of double the voltage present at the plate of that particular stage.The values unless otherwise noted are usually in uf,if it were pf,it would say so.In fact most schems will have notes that say just that,as well as your resistors wattage.

 

[Shep]

I Think you should Get some of Gelard webbers books or any real Tube amp books. Then start on Basic amp Architecture. Fender Bassman sort of thing. THEN

Once you understand how tube amps work and what basic parts you need to make it work then you can start to see how much trouble your putting yourself into by modding a hybrid amp to sound like a mk IV.

Do the research!!!



I did this a few years ago. Bought some books, Read them a few times. Rebuilt/ Fixed a fender showman amp and a jcm 800, Which both offered a huge amount of learning experience. Then i started with my mesa's. First my mk IV and changing the whole power transformer from a 110v to 240v with a whole New tranny, making sure everything was working at the right voltages. Then there was my mk IIc+, Full Cap change Plus small mods to pre amp section and change of power supply Back to the 105 it came with.


I have annoyed Boogie babies a few times with my questions but He is a HUGE help with alot of more technical question. and i am pretty sure i owe him a Few Aussie Beers (Not that Fosters Crap) for the help he has given me.