Caps for MKIIB

[Harry the Horder]

I am about to re-cap my 81 MKIIB what caps do you all recommend?
I am thinking about either F&T (for higher temp) or Tube Amp Doctor or should I stick to good old sprague or mallorys? anyone know of any tone difference in using these? Harry.
AND DON'T SPRAY THAT TOLEX!!(other mkIIb owner)

 

[Boogiebabies]

Harry,

Where you been?

I would say that Srague Atoms are just fine. They have been doing the job in Mesa's for 30+ years, but I personally would love to try F&T's. I have recapped a few Marshall's with these and found them to have a better touch response and the amp was quieter. They somehow sweetend the amps up and had a better bottom end. Am I crazy in saying a filter cap can do this?
In your case, Watford Valves has 30uf/500V and 220uf/300V caps in stock.
Either way, you will be covered, but I am only basing my experience with F&T's on Marshall's.

 

[Elpelotero]

BB,

since we're on this issue, when is a good time, if any, to replace caps. Are there signs to watch for? (sorry harry, didn't mean to hijack, but just to save from making a completely new thread)

 

[Harry the Horder]

A BIG!! HI THERE !!TO YOU BOOGIEBABIES!!
Well I've been around Blackfacing a Silverface Fender Twin.in the end I am doing a total re-wire on it I've also got a dry solder on my 64 Vox AC30 to sort out and been out and about gigging like you do.
I don't mind being Hi-Jacked at all.If you don't ask you don't get!!
On the subject of changing Caps this could open a can of worms as there are so many differing opinions. from what I've read every 6-7 years is about the average but if you have your Amps laying Idol they should be fired up now and again to stop the electrolytic from crystalizing it reacts a bit like.. well imagine Honey! Honey!! the big question is SHOULD NEW CAPS BE FORMED AFTER FITTING?? or is this a Load of Bull?
Harry

 

[stokes]

Have used the F&T caps in my own IIC+ and some other amps and they seem to be fine.Sprague doesnt make the values needed for the main caps in the Mark, so IMHO they are the best choice after Sprague- they may even be better than the Sprague, but in my experience Sprague is the only cap to use in any power supply.As far as the question on forming filter caps,even though you buy new caps you dont know how long they have been sitting or how they were stored so forming them first is good insurance that they will perform their best.There is no good reason not to pre-form them,so why not just do it?

 

[Harry the Horder]

Thanks for your input Stokes I think I'll go for the F&T Caps and I do agree that it is best to form caps and always do as the die-de-die-de-electric must be formed before putting full power through a bit like running in a new car really.thanks again Harry

 

[JAMz]

Please excuse my ignorance, but what is forming or pre-forming a cap?

Thanks,

JAMz

 

[Boogiebabies]

Not slamming them with full voltage after you replace them. Forming them is bringing them up to operating voltage slowly over a period of time to get a proper layer of oxide film.

 

[Harry the Horder]

We were all ignorant at one point. I am still learning and if you don't ask you don't get. I'll try to explain it
Electrolytic caps are made up of two plates rolled up and placed in a cylindrical container with one of the plates connected to the container this acts as the negative terminal (some times these are made with several caps in one container) these two plates are made up with an electrolyte paste placed between them (dielectric) when new this paste is not formed it needs a DC voltage across it to form the dielectric or paste.
How do we form caps? Once fitted and all work is checked leave the Amp/speaker on a variac overnight at 40 volts then slowly increase the voltage by 10 volts per hour until you reach working voltage thats what Mr Webber recommends so it's good enough for me.all the Electrolytic caps are now FORMED.Further to this it is also advisable to re-form in the same way any old amps that have been sitting around for a while as the dielectric can crystalize I suppose it behaves a bit like Honey so keep flashing any Amps up that are sitting around to avoid this. they also recommend changing all Electrolytic caps at about six to seven years old.
I understand that pre-formed caps can be purchased but I have never seen these advertised
When a Cap goes normally a small bubble will appear on the positive end if this happens it is a good indication that the rest are getting tired and all will need changing. WOW!! I bet I've started something now!
Hope this answers your question. Harry :wink:

 

[stokes]

Kendrick used to sell pre-formed caps,not sure if they still do.

 

[JAMz]

Harry & Boogie babies thanks for the Info.