Mark IIB stock Filter cap/resistor values

[MK IIB]

Hi folks,
I'm needing to get new filter caps and a few other resistors and stuff for my mark IIB.
Some parts have been changed in the amp over the years,before it belonged to me and I want the amp put back to stock.The filter caps are still the originals.
The screen grid resistors were changed and I would like to have the original carbon comps put back in the amp.
I have been asked by MESA's distributor for the volts and uf from the caps but I can't see any info from just looking at them?
I also want the power supply dropper resistors returned to original carbon comps.
I would really really appreciate if someone could tell me what the values should be on the filter caps for the main filter caps and also the pre amp board Filter cap.
I also need to know what the values should be for the original stock screen grid resistors and power supply dropper resistors I need as I would like to source the parts needed myself and then the tech only has to charge for the work he does for fitting them etc.(He is fine with this)
Here is a thread with pictures of the amp showing what has been changed,and what is needed to return to stock. http://forum.grailtone.com/viewtopic.php?f=27&t=67930
Many thanks in advance.

 

[MK IIB]

Any help with this please guys?
Mesa's distributor is asking me what the volts and Uf are on the filter caps but there are no markings?
I've managed to work out (I think)that the screen grid resistors should be 470 ohm 2 watt carbon comps and the dropper resistors on the power supply board 1000 ohms?
Any help from those with more knowledge would be much appreciated.
It is my intention to source the parts myself and then take the amp with the parts to be fixed as I want the original stock parts/values if possible.

 

[stokes]

The 2 longer blue filters are the mains,wired in series are 220uf/285v probably the available parts will be 220/350v's.The shorter blue filters are 30uf/500v's.The B+ rail is the main caps then a choke to a 30uf with a 1k dropper to the next 30uf then a 5.6k to the next 30uf.The 1k and 5.6k are 2watt,but 5watt will give a better safety margin.The screen resistors are 470ohm 2 watt heres a link to the schem http://tubefreak.com/mk2.gif

 

[MK IIB]

Thank you Stokes for that info.

 

[MK IIB]

I'm just wondering if I would be better off getting Mesa filter caps?would this be the best route or is there any benefits to be had by opting for another brand like Sprauge,F&T etc?
Also what would be the best brand of screen resitors and power supply dropper resistors?I'm wanting to replace them with the original carbon comps the amp would have came with as I want the boogie to be returned to as stock as possible?
Sorry for all the questions guys but I'm not that clued up on parts etc.I'm "just" a player with not a lot of knolwedge of the inner workings of amps.Although I would love to know/learn more.
It must be great to be able to self diagnose a problem with your amp and even better to be able fix your amps yourself
Thanks folks.

 

[b00g13mk2B]

There are different opinions, but if you contact Mesa directly, you will get good parts. The electrolytic caps they use are made in the USA. They will also tell you if they don't have an exact match and recommend substitute values. However, some prefer F&T caps and other brands.

I replaced my screen resistors with metal oxide types, they do not burst into flames quite as easily as carbon comp. But just a preference. Don't replace parts directly in the signal path unless you know they are bad, or really know you want something different. A lot of opinions on coupling capacitors, Boogie did not use anything esoteric.

The places I looked besides Mesa Boogie include Antique Electronic Supply, Parts Express, partsconnextion. Some have different values. Shop around. Also note the part size and lead length. Some of the Boogie replacement electrolytics weren't quite as big as the originals. I left the leads from the old caps soldered and wrapped the leads of the new caps to the old leads.

I replaced EVERY electrolytic in my MKIIA, including the cathode bypass caps on the preamp board. Some just replace the big caps in the main power supply. All electrolytic caps will eventually dry out. Took care of it while the amp was apart.

 

[stokes]

Mesa used to use Illinois for the 220uf's and Sprague Atoms for the 30uf's.They now use BMI,which are made in the same factory on the same machines as Sprague Atoms....at a much lower price.I havent ordered from Mesa,yet,but another well respected and very knowledgeable tech on this site recommends using the BMI's from Mesa.I've looked and cant find anybody offering the BMI's,so try Mesa.

 

[MK IIB]

Thanks guys.
Yeah I'm having all 6 of the caps in the amp replaced as they are still the origial 34 year old caps.
I'm in the UK so any parts I need are being ordered via Mesa's UK distributor.It was them who asked the values of the filter caps.The only parts I'm having replaced are parts that were changed before I got the the amp so I was going the have the stock parts put back in.
I'm not sure what type the screen resistors that are in there are just now they're white?Same with the Power supply dropper resistors they've been changed out for big rectangular shaped ones.
I would like the amp returned to stock,the way it was meant to be.There's not any mods been done(except a bias pot added)but I'd just like any little things that have been changed to be put back while it's being worked on!
P.s If you can have a look at the link you'll see what's i there now.
Thanks a lot guys.

 

[McBarry]

BEing Down Under, Sprague Atoms are silly expensive.
And a SINGLE 30uf/500v Mesa electro caps was FORTY-FIVE DOLLARS (au) from the distributor about 12 months ago...

As such, I've used F&T for years and never had a problem.

Given you're in UK, I'd suggest ordering through Matthew at Audiocap - brilliant online store and heaps helpful gent.
I actually do bulk orders from him and it saves me buckets !!

Dave

 

[stokes]

I've been using the F&T's for years because of the price of the Spragues here in the US.As I said earlier I havent ordered from Mesa yet,but I was under the impression they were cheaper than the Spragues.$45 for a single cap is surely a deal breaker.Just curious Dave,what do they get for the Sprague Atom 30uf down there?

 

[MK IIB]

I can get the Mesa 220uf 300V caps for £10.20 each and the 30uf/500v's for £6.65 each.
What do you think?

 

[MK IIB]

BEing Down Under, Sprague Atoms are silly expensive.
And a SINGLE 30uf/500v Mesa electro caps was FORTY-FIVE DOLLARS (au) from the distributor about 12 months ago...

Dave

$45 for one?That's crazy man!Over here the equivalent is (au)$12.50 for a 30uf/500v

 

[stokes]

I can get the Mesa 220uf 300V caps for £10.20 each and the 30uf/500v's for £6.65 each.
What do you think?

If that is the BMI caps its a good price.Not sure about the 220's if they are the Illinois I would go with F&T 220's,a much better choice,IMO.As I said earlier,the BMI's are made in the same factory,on the same machines as the Sprague Atoms but sell for less.Only problem I had is finding anybody that sells them.I'm told Mesa sells them,but havent had to re-cap a Boogie in a while so havent ordered any yet.

 

[BlackBoxy]

on my mesa, i just tested changing blue filter caps with F&T, TAD and Atoms!

left it breaking through time, results are the sprague atoms "even if dearer" are what make Mesa tone the most!

so experimanting this, iwould advice any change to srague atom !

my humble opinion

 

[MK IIB]

What were the originals that Mesa used in the 2B.It's still the originals that's in there.
Can replacing the filter caps change the tone/feel of the amp dramatically?
This amp sounded amazing and my aim is to get it back to sounding the way it used to/should do!

 

[stokes]

Those longer 220uf's are Illinois,the shorter 30uf's are Sprague Atom.They are both re-labeled with Mesa heat shrink labels.You will see a big improvement in the amps tone and response,much tighter,particularly in the bass,with a re-cap.Those old caps are done,you dont want to wait till they fail,could be a big mess.

 

[MK IIB]

Hi guys.
What were the stock values of the dropper resistors used on the power supply board in the IIB?
I thought they were 1000ohms and had requested some but I've been told that most often used were 2 x 5600 ohm(2 watt)resistors?

 

[MK IIB]

sorry to bump this guys but I really need to know fro the experts what the proper dropper resistors I need are?
Mesa have said that they are variabe but most oten used were 5600 ohm 2 watt?
In case you're wondering rather than take it to a tech and have him order/supply the caps and parts needed I am going to order the correct and best parts I can get to put it back to stock and just have the tech carry out the work.
Will likely save me a bit too?

 

[McBarry]

So sorry for delay in replying Stokes..
the Mesa dealer here gets his caps directly from the mothership..
And yeah.. $45 is insane...
MkIIB - have U tried Matthew at Audiocap? He's given me some stellar deals over the years..!!
I notice U have a bias pot on your PSU board too - doesn't look original - the originals were blue, round shaped..
Droppers - I think Stokes replied, but if not.. 150k/1W across each 220uf and 1k/2W after choke and EITHER 1k/2W OR 5.6k/2W next.
FWIW, my 100W MkIIB has the two 1K< but by 60W MkIIB has the 1k the 5.6k. Go figure.......
Buying yourself may or may not save U $'s... But U will def know what is being installed ( - so I'm a bit cynical... LOL...)..
Don't forget the bias and cathode bypass caps. They're also 30yrs old and getting very tired too......
Let us know yr progress..!!!!

 

[MK IIB]

Thank you for your input.
I have sent Matthew an email but not heard back from him yet.
Yeah that bias pot was added by a tech in the past.Not sure wether to keep it installed or have it removed?
Mesa's distributor over here has said that the dropper resistors are variable and most often used were 5.6K each and that is what they advised should be ordered but I thought it should have been 2 x 1k?I've been advisd by a very knowledgable member that the carbon comps can't be got from Mesa anymore so not sure what best to go for?
My main aim is to have it returned to stock or the best it can be.
I've used this amp years ago for a time and it sounded amazing.I'm hoping I can get it back to it's former glory.
P.s where on the circuit is the bias and cathode bias caps?
As you've probably guessed I am no tech.
I just want to supply the tech with all the correct/best parts possible and have him carry out te work to bring the amp back to life again.
Cheers folks.