When to replace filter caps?

[rippingrudy]

Ghost notes for sure - I had a Mark III green stripe and the ghost notes were driving me nuts.

FWIW, if I had a 17 year old amp I'd send it into my tech for a cap change and a once-over if it needed it or not.

 

[Schmoog]

best way to tell is to crack the beast open and look at em. are they leaking? is there signs of corrosion at the ends? do you have ghost notes? channel bleed? to be honest, when the filter caps start to go, you'll know. if you're just sitting there wondering, they're probably fine

 

[Schmoog]

when you pop the beast open, if you look down with the back of the amp towards you, they are on the left hand side I believe. there are 4 of them with a PCB between pairs. they are large blue cans. marshall uses a different type of cap which has the connectors on one side. these have leads on both

 

[Monsta-Tone]

Be careful not to touch anything in the amp if it has been on within the last 2 days.

The filter caps on all amps store a voltage.

The filter caps on some amps do not have a resistor to bleed off the stored voltage when they are off.

This can kill you!!!!!!!!!!



That being said:
Your filter caps may or may not last more than 20 years. Just because you are not having problems now, does not mean that they may or may not fail at any given moment.......this means during the gig for some reason.


The caps that Mesa uses seem to be very high quality. So were the caps that Fender used to use (Mallory). I have a Blackface Pro Reverb that I just changed all the filter caps in, the original ones were still in there. They looked fine, and there were no problems with the amp, other than the fact that it was missing some parts, speakers and the output transformer when I bought it.


The filter caps will dry up and fail prematurely if the amp is not used for long periods of time, for instance, it is only used once a year.



If a filter cap fails, it can do 1 of several things:
1 - blow the mains fuse, or the HT fuse
2 - take out your power tubes
3 - take out your output transformer
4 - take out your power transformer
5 - take out any component in your power supply
6 - burn traces on your circuit board


If a filter cap is going bad, it can do 1 of several things:
1 - hum
2 - ghost notes
3 - low power
4 - popping noises coming from the amp
5 - power fluctuation or volume fluctuation





Basically, I look at like this:

If you only use the amp once in a while, it may not be something that you need to do right away.

If you gig regularly with the amp, I would do it.

If you plan on selling the amp soon, let somebody else do it once they have bought it.

If the amp will be a collector's item that you will never play, don't do it till you have to.


I don't try to sell my customers snake-oil, or BS. I try to get them to do what makes sense for them and their particular situation.




All of this being said, if you don't have the money right now, and your amp is not malfunctioning, it is ok to wait.


Personally, and this may be because I work on amps for a living, I change all of mine once they are about 15 years old, or when I have to do major repairs to them. If I have decided to add an adjustable bias, I will change the caps while I am in there if the amp is over 10 years old.

I also highly recommend replacing the Bias circuit capacitors as well when doing a cap job. If the amp is really old, I will replace all Electrolytic caps in it, including the Cathode capacitors on each of the preamp tubes. If any of these fail, it will cause your amp to malfunction. If the Bias capacitor/s fail, it will usually take the power tubes with it.



Hope that my 2 pesos helped and it wasn't just the ramblings of a lunch deprived music nerd in desperate need of a sandwich.

 

[stokes]

I never let my caps go more than ten years without changing them,even if I dont notice any symptoms,but I always notice an improvement in the amps response especially the bass.When you use an amp regularly,you dont notice the bass response starting to deteriorate until it gets severe.If someone brings an amp to me with caps that are 10 yrs or older I always recomend changing them,and I give the guarantee that if the customer doesnt agree that the change was worthwhile,I'll put the old ones back,no charge.I have yet to put a set of caps back in an amp.I recently did a cap job for a fellow poster here who wondered if it was worth it and he can attest to the improvement in his MKIV,he was amazed at the improvement,I wont mention his name,but if he is out there I would bet he will respond.I agree with Monsta-Tones post,but he left out one very important result of a failed cap-if the cap explodes,which they often do when they fail,they leave a mess that is almost impossible to clean up.And the caps dont always exhibit any leaking or other symptoms,if you ever have the misfortune of this happening you wont let it happen again.I have a lot of amps in my own collection and try to change them after 6-8 years,gets expensive,but it is worth it.I would suggest changing 17 yr old caps,you will see a difference.

 

[Russ]

My 77 JMP still has the original cans in it and sounds great. 30 years and still ticking.

 

[Monsta-Tone]

and I give the guarantee that if the customer doesnt agree that the change was worthwhile,I'll put the old ones back,no charge.I have yet to put a set of caps back in an amp

That is a great idea! I think that I might have to start doing this too.



I have always noticed a severe improvement in the tone and responsiveness of an older amp once the caps have been replaced.

 

[stokes]

"I have always noticed a severe improvement in the tone and responsiveness of an older amp once the caps have been replaced"

Like I said,I change them after about 8 years,but of course that often ends up being closer to ten,and I always see a big improvement.Even tho the amp sounds good,after the caps are changed that improved "tightness" really sounds great.
Russ,30 year old caps are just an accident waiting to happen,I am sure you are happy with the sound of the amp,and I understand the "mojo" attached to a stock amp with original parts,but if they explode you will likely have other non-stock parts afterwards.I am sure if you changed those caps with some high quality new ones you will be amazed with the improvement,but you do have to use good quality,not those taiwanese or Jap caps,they can kill your tone.

 

[Russ]

I am aware of the risks but it is just too tasty right now.

 

[Monsta-Tone]

https://secure.tubesandmore.com/



These guys have a good selection and decent prices. I have been dealing with them for years and have had zero problems.


For Marshall, capacitor cans:
The F&T are great. The JJ's are really good too, so far.


I think that 30 year old caps are a gamble too.

 

[Russ]

Maybe I could find some NOS Daly's? I would like to keep things as original as possible.

 

[stokes]

F&T's are my current favorites,I still like the Sprague although they are reputedly not as good as they used to be and getting quite expensive,still havent found anything better yet,except the F&T's.I havent tried the JJ's,but I have heard enough bad things to keep me away from them for now.I have a bunch of Mallory NOS cans that I have been lucky with so far,even tho I dont like to use NOS electros,I have formed them verrrry slowly and crossed my fingers in a couple of cases and so far....but I would never recomend using a NOS filter cap to anybody.So far I have been lucky and have been able to talk customers into leaving the old can in there for appearances and squeeze axials in somehow when needed.I've had a few problems with tubesandmore in the past,and find their shipping prices to be very high,could be that they are just too far from me,I have a few choices that are closer.

 

[stokes]

Russ,you inquired about the NOS caps as I was typing my last reply.I would stay away from NOS electros.Sometimes you have to trade off appearance for performance.I am not a big proponent of keeping things stock for the sake of any re-sale or collector value,I have no problem modding any amp in any way( my own amp,of course) to get it to perform as I want.NOS filter caps are risky because when a cap sits too long without some current going thru it,the electrolyte dries up.you could get lucky by reforming them,but there really isnt any way to know for sure that the cap is up to snuff.A supplier I used to use in lower Manhattan years ago showed me something from a manufacturer that recomended no more than a 10 year shelf life for electros,so that ten year thing is not just a myth.I dont know for sure that this is still a standard,but I cant imagine anything being changed in a caps manufacture that would make them so much better today.

 

[Monsta-Tone]

I removed the capacitors from a newer F & T and placed them gently inside the originals on a friend's Plexi.

You cannot tell the difference once they are in the retainers.

I have heard bad things about JJ's too, but haven't had any fail yet.

I will probably switch over to using only the F & T's though just to be on the safe side, but they are twice the price.


The axials is a great idea. I might try that too. That way, the amp looks completely stock and you still get the upgrade.

Removing the insides of the caps is a pain in the *** to say the least.

 

[Russ]

About a year ago I was thinking about doing some work on my JCM800. I saw that they had some that were identical to the LCRs except screened something else. They were even the same baby blue. Would you say that those might be ok? I have thought about the option of slipping new ones inside the old ones. That might be the best option for me because I have grown fond of the look inside of my amp.

 

[stokes]

Russ,what I do is disconnect the can cap leads and then leave the can in place.I then find room inside the chassis to fit some axial equivalents.I have never tried to "gut" a can cap and then fit new caps inside,like Monsta said it is a pain,I never found the need to put myself thru the process,but have heard from others who have.I have done axial replacement to many Ampegs over the years,but not a Marshall,but I think it would be easier than the "gut" technique.If you can get the F&T cans in the right value and the can will fit in the hole in the chassis,the F&T's are the way to go,they are expensive,but they are probably better than the current LCR's.If your only reason for wanting to keep the cans is for the look then by all means just get some axials and squeeze them in and leave the disconnected can,its the easiest way to go,and you will certainly like the improvement in the amps response.

 

[Russ]

So, what? Disconnect the leads then install axials to them? Hot glue them to a piece of board and double sided tape the board to the chassis? That sounds painless. I could go for that. The original caps would be there for looks and the real ones would be easily replaceable. I would want a solution that would be easily rectified. That sounds the easiest to rectify. I don't want holes nor do I want anything messing with the original circuit board. I just hate the look of those other cans that they have. Those old Daly's are pretty. I know that sounds stupid but to me it is what I am accustomed to seeing in there. I have seen the green ones too and even the lighter blue ones in some amps. I guess it is a sentimental thing with those old blue tin cans. It is silly, huh?

Watch the caps go now the next time I plug in. :?

 

[user 2126]

where I can find long original blue 220uf 300v caps seems that the F&T are smaller and dont fit in:

 

[stokes]

Russ,that sounds like it will work.I have used those wire ties,I have various sizes and double them up if I need more length,try to sit them where they will fit on an existing board and secure a wire tie around the cap and the board,and run wires if I need to situate them at the other end of the chassis.As for the original cans,I dont necessarilly use the original wires,just disconnect the leads and leave the can where it is.If the looks are what matters to you,then there is nothing silly about it,aesthetics are important to some people.If you can keep the looks and get the tone,then you hit a home run,right?
DarkIrish,I never have a problem fitting those F&T's.So what if they are a little shorter?The length of the leads are long enough to reach.But if you are hell bent on getting the originals,they are Illinois brand,with that blue shrink wrap with the Mesa logo on them.Just order the Illinois 220uf/300v.Although the Illinois name seems to infer they are made in the USA,they aint,Taiwan I believe.

 

[user 2126]

thanks strokes