When to replace filter caps?

[JOEY B.]

Is there anything else that the owner of a 30 year old boogie amp needs to check?

If your '78 is like mine, I would say "your ears" :lol: . My MarkI sounds good at low to moderate volumes, but has a sweet spot just this side of free pest control. It can get in a tone zone that is in between the rhythm and lead channels of the MkII. It is very easy to tell why this is the amp that "started it all".

 

[kdove]

Sounding really good after a week of playing ... really satisified.

Even though I picked up on the filter caps due to the occasional volume loss, the change in sound was pretty gradual. I was clueless to the filter cap issue. So I still have the same question: Other than tubes and filter caps, is there anything else I need to be concerned about with a 30 year old amp that is played almost every day?

 

[stokes]

Other than a general clean-up,and possibly re-tensioning tube sockets,but if you arent having any noise problems a cleaning should be enough for the sockets,you should be okay.Tubes and electrolytic caps are the components that have a definate "life span",most other components are usually good for life of the amp.If other components fail there will be obvious symptoms.In defense of the 10 year life of filter caps,I am in the middle of refurbishing a Hewlett/Packard signal generator for someone and looking in the manual,it says the filter caps,which are Mallory and Sprague(originals),should be changed every 5-10 years.I just dont understand how Mesa can tell people not to worry about the filter caps.

 

[kdove]

Great ...

Even if they last this long, I wonder why guys would not want the improvement in the sound. It's better ... I'd have done it just for that if I'd of known sooner.

Thanks once again for the help ...

 

[stokes]

No problem,enjoy your "new" amp.

 

[6L6C]

I just dont understand how Mesa can tell people not to worry about the filter caps.

John @ Mesa Hollywood told me that Mesa uses higher quality parts than other manufacturers and he's seen filter caps last 20+ yrs on Mesas.

When I asked amp tech Jerry Blaha about the filter caps in my ex-JCM 800, he said "what's the problem?" He said they're using better materials for filter caps nowadays than back in the 1950's or so.

But the way I look at it is, you don't HAVE to change your engine oil every 5K miles but you MAY end up having problems sooner (accelerated degradation of components) is you don't.

I don't care as much b/c I'm not a pro...

I’m with you rabies as I stated earlier

“I changed my caps in my Mark IV this past year the amp was 13 years old, no bad signs just wanted them changed I also found my amp to be tighter sounding, but also found it more harmonically rich.
Keep in mind the amp sounded good before the cap job, I really wish I did a before and after recording of the amp.”
When I started asking cap questions I was getting confused real fast because there are allot of people on this board that know their stuff but that cap question seems to have them split. No one has said the other guy is wrong. The answers where more “I believe” or “I don’t believe” No one has ever slammed the other guy for his views. And this is great for I was not looking for the best debater.
So after a few emails with “stokes” I decided to do it and dam glad I did! I’m not a tech myself but my ears sure knew the difference! I still kick myself in the *** for not doing a before/after recording.
I plan on getting a Mark III within the next 6 months or so (depending on money and what’s out there) since the caps in that amp will most likely be over ten years old, depending on the owner and what they have done. I will do a before/after recording and post clips.

 

[stokes]

Although I have never tried the before and after recording comparison,I have a feeling you might not be so impressed with the results on tape as you would be with the actual "feel" of the amp when playing it live.The improvements are more with the feel and response of the amp,but it would be interesting to see how it comes across on tape.I would think it is like the time I was watching someone play thru a solid state Fender,I forget the exact model,but it looked like a Black Face Deluxe Reverb from the back of the room.It sounded great from the audience,I actually thought he was using a Black Face DR,but when I tried the amp out,it had that cold unresponsive feel of a typical solid state,although it sounded good from a distance,playing it sucked.I think a big part of the pleasure we get out of a tube amp is the feel and response,they can get a solid state amp to "sound" like a tube amp but they cant capture that "feel"we get from a tube.The next time I do a cap job on an amp that otherwise sounds okay,I'll run it thru the tape deck before and after and see what we get.

 

[Restless Rocks]

I have the privelege of occasionaly being asked to "go over" really old Fenders from the 50's and 60's, ya know the ones that are bringing an arm an leg these days's and I've seen a certain pattern develope. The ones's that are the most pristine and collectable all have dried up caps. The one's that are beat to **** and belong to a person who plays it all the time because it's a really great amp mostly work unbeleivably well. I also know some folks with some extra cool vintage tube stereo gear that still sounds killer with all the original 40+ year old components. The reasoning behind the greatest guitar amps and the finest home stereo equipment all being tube based has the same reason. It sounds best. So my observation: caps that get played last longer.

 

[kdove]

That matches my experience with 30 year old caps ... I have played it almost every day. But I think I had lost a bit of preformance from the caps over time and just got it back. I think the components I put in are as good as the ones I took out too.

 

[Restless Rocks]

You couldn't be more right about swapping the old caps with modern equivalents. The materials and electrolyte are much more refined now and you could get away with saying that the caps are "faster" now. This of course offers a marked improvement in the "feel" of an amp. And of course why get a cap job without a nice fresh set of tubes while you're at it.

 

[kdove]

I just retubed at the end of last year. Although, I can say that I left the V2 (ECC83) and V3 (12AT7) tubes in the amp ... they sounded better than the new ones I bought ... even though they are the originals from '78. I A/B them one at a time and there was no question which one sounded better ... the old pre-amp tubes. The power tubes ... new ones definitely better.

 

[stokes]

Preamp tubes can last a long time.I have a pair of old Ampeg Gemini II's from the '60's that still have the original Bugle Boy 12AX7's and they still sound better than any new production tubes I have tried.Restless' observation on the old pristine amps being the worst sounding is true.Most of the amps I work on are vintage Fenders,Ampegs and Gibsons and the ones that were stashed in the closet for years and look brand new always sound the worst for just that reason,if the amp isnt used for a long length of time the caps dry up.These amps should always be bought up to full voltage slowly, with a variac, to re-form the caps or they usually explode if just plugged in.If you have multiple amps and some dont get used very often it is a good idea to turn them on a couple of times a year to keep the electrolytics in shape.

 

[Monsta-Tone]

.I just dont understand how Mesa can tell people not to worry about the filter caps.

Although I agree, it would be a really hard sale.

"Here is your new $2,000 amp, by the way, you will have to sink a few hundred into it over the next few years, replacing the junky tubes that it comes with. Also, there is the slightest possibillity that some of the parts that we used to build it will fail in the next 10-15 years. Seeing as how the amp will be paid for by then, it may or may not seem like a bad thing to you, the proud owner of this $2,000 amp."


Honesty & Marketing go together like Politics and Reality.

 

[Restless Rocks]

Preamp tubes can last a long time.I have a pair of old Ampeg Gemini II's from the '60's that still have the original Bugle Boy 12AX7's and they still sound better than any new production tubes I have tried.Restless' observation on the old pristine amps being the worst sounding is true.Most of the amps I work on are vintage Fenders,Ampegs and Gibsons and the ones that were stashed in the closet for years and look brand new always sound the worst for just that reason,if the amp isnt used for a long length of time the caps dry up.These amps should always be bought up to full voltage slowly, with a variac, to re-form the caps or they usually explode if just plugged in.If you have multiple amps and some dont get used very often it is a good idea to turn them on a couple of times a year to keep the electrolytics in shape.

Good advice Stokes. For my own amps I haven't bought new preamp tubes for years other than to try out some that get a lot of hype. I've decided to go ahead and enjoy my box of vintage tubes instead of keeping them on the shelf to worship. There simply are no new preamp tubes made that can compare with the sound of the 60's vintage. ie Telephunken, mullard, sylvania, RCA, GE, Amperex and others.
Now as for power tubes: I play my main mark amps everyday and perform alot and I could easily change outputs every 4 months. And after 5 or 6 months a new set sounds like getting a new amp. I live 4 miles from the United Chemicon plant. Formerly Sprague. I know several of the folks who work there as well as some of the engineers and QC people. They tell me that the product they're producing now with the refined electrolyte should give 25 years of service (UNDER REGULAR OPERATING CONDITIONS) But they also told me that if I have any UNUSED CAPS in my parts bin to throw them out after 6 YEARS if they have never been regularly energized. Even when I install a cap that's brand new or been on the shelf for a couple years I bring em up on the variac over 24 hours. So in essence they tell me it's best to order electrolytes on an as needed basis, pay attention to the date codes and RE-AGE them before use.

 

[stokes]

Okay,so now they say they have improved the caps,but they have an unused shelf life of 6 years,and with regular use,25 years.Now does regular operating conditions mean daily use?If so,how much do they deteriorate if we use the amp 2 or 3 times a week?If the new caps sit on a suppliers shelf for 2 years before you buy them,how many years can we knock off that 25 year life span?We dont know for sure if the caps were "formed" properly when the amp was produced.What I am getting at here is that under very possible conditions we are back to the 10 year life expectancy.I am looking at a Sprague Atom that I purchased in the last year and I dont see anything that looks like a date code,the only numbers on it are 100uf/350v 85 deg C and TVA1620.So I have no idea how long this sat on someones shelf.So for me,even if the caps are made "better" than they were in the old days,I feel safer going with the old school rules.Cant teach an old dog....

 

[Monsta-Tone]

[/quote]Okay,so now they say they have improved the caps,but they have an unused shelf life of 6 years,and with regular use,25 years.Now does regular operating conditions mean daily use?If so,how much do they deteriorate if we use the amp 2 or 3 times a week?If the new caps sit on a suppliers shelf for 2 years before you buy them,how many years can we knock off that 25 year life span?We dont know for sure if the caps were "formed" properly when the amp was produced.What I am getting at here is that under very possible conditions we are back to the 10 year life expectancy.I am looking at a Sprague Atom that I purchased in the last year and I dont see anything that looks like a date code,the only numbers on it are 100uf/350v 85 deg C and TVA1620.So I have no idea how long this sat on someones shelf.So for me,even if the caps are made "better" than they were in the old days,I feel safer going with the old school rules.Cant teach an old dog....

"Never get involved with a Sicilian when death is on the line."

 

[STUART]

Stokes

What would be the method to "form"the 220uF and 30uF caps in my MKIV Boogie after they have been replaced.
I understand the principles of the variac , is it just a case of reducing the supply voltage into the amp when on standby and raising it over a period of several hours

Stu..

 

[PRS-Ian]

Ok, I've read all these posts and I kinda think I know what you guys are talking about. So forgive my question, I have a 60W MK2C+ that I don't use that often and the last time I did the bottom end was incredibly flabby on the lead channel. So much so that I thought it was unusable. Do I need a cap change?
Ian

 

[Shep]

Ok, people. It's very good to have a solid understanding of what the filter caps' purpose is in a tube amp:

"Put simply, electrolytic capacitors are used to remove AC ripple that's left in the DC power supply after it has undergone the rectifier's AC-to-DC conversion. Left untreated, this ripple can cause a number of problems generally associated with unwanted noise: these can take the form of pulsating current, a dirty hum, a flabby and distorted low-frequency response, or even ghost notes, which sound something like a dissonant harmonic following along behind the actual note played. None of these are desirable, and it's the filter capacitor's job to eliminate them."

source: Dave Hunter's "The Guitar Amp Handbook" p. 29.

GREAT BOOK, I just got it yesterday from amazon.com!

Understand the symptoms of faulty filter caps and go from there...

i was shown by a tech friend that you can mearsure to see how well those cap's are smoothing that ripple... and that can give you a idea of when to change them..

 

[Restless Rocks]

Okay,so now they say they have improved the caps,but they have an unused shelf life of 6 years,and with regular use,25 years.Now does regular operating conditions mean daily use?If so,how much do they deteriorate if we use the amp 2 or 3 times a week?If the new caps sit on a suppliers shelf for 2 years before you buy them,how many years can we knock off that 25 year life span?We dont know for sure if the caps were "formed" properly when the amp was produced.What I am getting at here is that under very possible conditions we are back to the 10 year life expectancy.I am looking at a Sprague Atom that I purchased in the last year and I dont see anything that looks like a date code,the only numbers on it are 100uf/350v 85 deg C and TVA1620.So I have no idea how long this sat on someones shelf.So for me,even if the caps are made "better" than they were in the old days,I feel safer going with the old school rules.Cant teach an old dog....

I'm an old dog too when it comes to breaking perfectly good habits and playing it on the safe side. Apparently these newly developed electrolytic solutions resist certain molecular changes longer which lead to it's crytalization and resulting lower resistance over time. Stokes, I never finished my degree in physics but as I understand it (these guys did not explain it in laymen's terms) As the resistance of the electrolyte seperating the layers of aluminum foil of the anode inside the can gets lower, the ability of the capacitor to hold it's charge is reduced. This affects the impedance of the capacitor. Also in the electrolytic capacitor the electrolytes ability to remain polarized diminishes over time. The process of "aging" the capacitor is the process of polarizing the electrolyte giving it the ability to act as the negative charactor or cathode. When these things are "aged for the first time they do it in huge ovens, not only bringing up the charge over time but the temp as well. When the electrolyte is unenergized for long periods of time the molecules and atoms crystalize and form new ones that can no longer be polarized and over time develope conductivity.
Anyway I totally agree with you that replaceing electrolytes every ten years is a very good idea for those of us who depend on our amps having the best possible and most reliable sound and performance. You've got me curious again and I'm thinking about a visit with one of my tech buddies at Chemi Con to get the real nitty gritty on pin pointing the exact date of manufacture. I'll let ya know. And by the way I really enjoy sharing info and opinions with you and the other techs here and learn new tricks everyday from it. But I'm still an old dog!!!!