pls clear up filter cap replacement talk

winny pooh · February 11th, 2006, 11:53 AM

I have a 69' 100w SLP Marshall and have read things on the net about some people recommending that the filter caps be replaced. I spoke to a local amp guy and his thing was, If it works then it works. So i have decided to keep them, also because nothing inside has been tampered with or replaced plus the original solder joints are intact.

So i want to know, How does replacing them it make a difference?
If the caps are old and they perform the function fine will it still affect the tone?
How exactly do they affect tone, does it have to do with stopping noise from power supply and such?

Tim Swartz · February 11th, 2006, 12:15 PM

The filters drift in value over the years and leak. Changing them will typically raise your B+ voltage a bit and overall tighten the sound of the amp. I've changed them in some old Marshalls and actually changed them back because the customer preferred the spongey response of the older ones. I think in general can caps last a lot longer than the axial varieties used in Fenders due to them being sealed better. FWIW, I have a '68 100w with original caps and I just don't want to change a thing on it... I also have a '71 50w that I did change them on, it was a low voltage variety and was a bit too spongey... changing the caps brought the voltage from 380V to 405V.

FWIW, SLP is the name of the reissue... .

Wally · February 11th, 2006, 12:50 PM

What I find with old electrolytics is that in addition to the 'sponginess' that Tim points out, the amp also will evidence a few other symptoms. There is a loss of definition and articulation. THe highs lose their sparkle. There will be some out-of-tune subharmonics....5th fret, 6th string is a good note to listen to for this. Overall, the amp's sonics also lose dimension. In short, for my personal taste, I prefer to hear amps functioning with good, strong elecrolytics. That is the way they start life, and imho is the way they should be made to sound when the caps degrade. If sponginess is the goal, a good compressor with a well-maintained amp yields better sonics, imo, than an amp that is not functioning as well as it was designed to function. Also, at some point, weak caps jeopardize the well-being of more expensive...and virtually irreplacable.. transformers. And we all know that a vintage amp with a replacement transformer will not sound like the original and is also less valuable on the market. There is one world class guitarist who is busy burning down vintage amps because he prefers 'complete originality' and refuses to play a vintage amp that has been recapped. I wonder if he would have refused to play them when they were new? Is anyone producing underfiltered new amps to achieve that 'spongy' sound?

NTC · February 11th, 2006, 01:16 PM

Quote:

Originally Posted by Wally

Is anyone producing underfiltered new amps to achieve that 'spongy' sound?

Tweed reproductions, especially of the smaller or older models. a 5F6A is not particularly "underfiltered," though it is in comparison to some of the later clones (Marshall and Traynor come to mind).

NTC

tazzboy · February 11th, 2006, 06:18 PM

If you are looking to do a recap job get mustard seed caps from http://www.sozoamplification.com/purchase3.html
and check out http://www.metroamp.com

winny pooh · February 12th, 2006, 09:25 AM

Thanks for the info guys, if you had to take a guess, what percentage of the 60's amps out there used by professionals have been recapped?
I'm curious as to how commonplace it is.

jjmantele · February 12th, 2006, 07:30 PM

Electrolytic caps are sort of like batteries. Eventually they are likely to leak nasty corrosive fluid. My '71 Fender had a leaker replaced before I bought it and my '67 Harmony's multi-cap can had leaked before I bought it a few years ago.

AtomicMassUnit · February 14th, 2006, 03:23 AM

btw tazzboy, the sozos are not electrolytic caps. They're used as coupling caps in amps, which is not what you change when you get a cap job. Cap jobs are strictly the electrolytics.

My take on it is, change the caps. None of these amps originally came with leaky old caps. If you do a cap job on an otherwise healthy amp, it will definitely increase the reliability by a good bit. I feel it's akin to having a vintage car. You want to put new tires on it or you might find yourself having a blowout.

tazzboy · February 14th, 2006, 06:31 PM

Quote:

Originally Posted by AtomicMassUnit

btw tazzboy, the sozos are not electrolytic caps. They're used as coupling caps in amps, which is not what you change when you get a cap job. Cap jobs are strictly the electrolytics.

My take on it is, change the caps. None of these amps originally came with leaky old caps. If you do a cap job on an otherwise healthy amp, it will definitely increase the reliability by a good bit. I feel it's akin to having a vintage car. You want to put new tires on it or you might find yourself having a blowout.

Yes I know that. the sozo one are for changing the the main board not the power board.

frank6v6 · February 15th, 2006, 12:45 PM

Quote:

Originally Posted by Tim Swartz

The filters drift in value over the years and leak.

First, leaking caps is one thing...and would be cause for a cap change...

But drifting in value is laughable...the tolerance for electrolytic caps back then and even today, unless you spend an assload on the caps, is very large...sometimes as much as 20%....that means a 50uf cap might be, brand new, really a 40uf or a 60uf cap....

There's a rule of thumb that these things dry out or leak after x number of years and need to be replaced....but there are plenty of amps out there working perfectly as spec'ed with the original caps, tubes and resistors. However....Don't go replacing things unless they call for it....because you'll find yourself in a vicious cycle of swapping parts for the sake of....

Regardless.....
You need to make a determination if the current caps are causing a problem with the way the amp is supposed to perform.

I would take the amp to more than one reputable tech, to get a firm opinion on whether the amp needs it....If the guy you took it to says 'If it works, it works' ...you might want to take it to another guy.

It's not enough to look at a vintage amp and go "it looks ok, dont do anything."

Did this guy check the caps with a meter to make sure they're working properly? Did he look for voltage on the south end of the cap? etc.etc..

If not, he's not doing a good job determining if what you need is needed. He may be thinking about saving you money, but if he misses a potential problem in the amp now, he may cost you more down the road...

Wally · February 15th, 2006, 06:02 PM

I've re-read this thread several times, and there is good advice here. Vintage amps are valuable. They are more valuable if the major components..transformers, speakers...are original. These amps also yield the sonics that they were designed to yield when they have strong, fresh electrolytics.
Voltage measurements can tell a tech some things. I don't pretend to understand exactly everything about how a filter capacitor works, but I do know that static measurements will not tell you how the component works in an actual working situation with signal applied, frequencies changing, volumes changing, attack changing.
Long before a capacitor begins to cause the circuit to hum loudly and long before the capacitor decides to catastrophically fail, a capacitor loses the ability to provide strong, steady, totally ripple-free voltage to the circuit.
Many of these "amps out there working perfectly as spec'ed with the original caps, tubes and resistors" do not yield the sonic palette that they were designed to deliver. These amps are 'skating on thin ice' and many of them SURPRISE their owners by suddenly giving up in the middle of a song. The sound of a gun firing, some smoke rising from the chassis, and if luck is really bad that night...a dead transformer reduces the amp to much less than it should be. With experience of before and after sonic results of cap replacement, a player can appreciate the sonic differences. If one waits until catastrophic failure...oh, it ISN'T working now. It must need new caps!.....one gets to appreciate the before and after sonic results of a cap job AND a replacement transformer. Except for ascertaing whether or not the amp's major components are functional, I don't run vintage amps much before doing electrolytic cap replacement. IME, every amp from the mid-'70's or before will greatly benefit from a cap job. IF someone thinks diferrently, that is their perogative...and it is their amp, their ears. To each his own. However, the tech mentioned in Winny pooh's first post in this thread is misguided imho. Just because it is working desn't mean that it is safely working properly and yielding the best sounds that can be had from that circuit.

winny pooh · February 16th, 2006, 02:30 PM

After reading all the posts i had some food for thought and a few things started to shift for me, i was under the impression that if the cap performs then all is fine, i didn't figure that they degraded.
So i plugged in and the problems i have had with it since i got it 2 years ago are apparent, its always been a bit mushy and never had enough definition to the sound. I find that the amp has a substantial amount of hiss and for that reason treble or pres never go past 12 o clock.

It seems a recap is in order, so now, where do i find Good replacement caps?

silentkid · February 16th, 2006, 08:32 PM

Yeah, just to restate what everyone else said, electrolytics absolutely have to be replaced every 10 -15 years.

The one thing I wanted to say was how it annoys me when people advertise vintage amps as "totally original" - including those electrolytics, as if it's a good thing. I saw one once on ebay (tweed champ) where the guy said "original caps and resistors" as a selling point. When you looked at the chassis, two of the electrolytics had this swollen look to them as if the second you fired it up they'd just explode everywhere. Insane.

(Edited to include places to get caps)

Try vibroworld or antique radio supply, both sell great products and are fine to deal with.

Wally · February 17th, 2006, 12:59 PM

I may need to revise my opinion on this recapping thing. I have always been adamant that old amps be recapped, but reading Silent Kid's post made me stop and think. That Champ ready to blow...hmmmm, what if it did? What if someone brought that amp with a blown cap and no sound production? What if the owner was frustrated and wanted just chuck it and go by a new HOt Rod Deviluxe>?What if I offerred low bucks because I explain to him that without hearing the amp, I cannot be assured that the transformers are functional and therefore the amp's orignality and value could possibly be much compromised? He doesn't like that proposal but understands the truth and the validity of it. So, we do a deal that yields him some money for a dead, unknown-quantity amp. I get an amp that needs work before I can truly know what I have bought.

I get lucky. :) Except for a blown cap along with the other weak ones and after recapping, I have a wonderful vintage amp in perfect working order that by good fortune is worth a fair amount more than I put into into...cash, parts, work included. Profit..whether in a wonderful amp or proceeds from a sale of said amp....that is the reward for the game of chance that has taken place. I would mention what amps I personally own that have travelled this path, but then you all might start recapping these old amps so that their usefulness and value are not compromised. Does this mean I won't get to risk buying amps in these situations? Nah, not everyone reads this stuff...
8)

February 11th, 2006, 11:53 AM	#1 (permalink)
winny pooh Tele-Afflicted Join Date: Jan 2006 Location: South London Posts: 1,612 7 Photos	pls clear up filter cap replacement talk I have a 69' 100w SLP Marshall and have read things on the net about some people recommending that the filter caps be replaced. I spoke to a local amp guy and his thing was, If it works then it works. So i have decided to keep them, also because nothing inside has been tampered with or replaced plus the original solder joints are intact. So i want to know, How does replacing them it make a difference? If the caps are old and they perform the function fine will it still affect the tone? How exactly do they affect tone, does it have to do with stopping noise from power supply and such? __________________ my afro ambient side project: http://www.myspace.com/theswyambusessions

February 11th, 2006, 12:15 PM	#2 (permalink)
Tim Swartz Tele-Afflicted Join Date: Mar 2003 Location: Michigan - Tweenst the Great Lakes Posts: 1,887	The filters drift in value over the years and leak. Changing them will typically raise your B+ voltage a bit and overall tighten the sound of the amp. I've changed them in some old Marshalls and actually changed them back because the customer preferred the spongey response of the older ones. I think in general can caps last a lot longer than the axial varieties used in Fenders due to them being sealed better. FWIW, I have a '68 100w with original caps and I just don't want to change a thing on it... I also have a '71 50w that I did change them on, it was a low voltage variety and was a bit too spongey... changing the caps brought the voltage from 380V to 405V. FWIW, SLP is the name of the reissue... . __________________

February 11th, 2006, 06:18 PM	#5 (permalink)
tazzboy Friend of Leo's Join Date: May 2005 Location: Eugene, Oregon Age: 31 Posts: 3,188	If you are looking to do a recap job get mustard seed caps from http://www.sozoamplification.com/purchase3.html and check out http://www.metroamp.com __________________ tazzboy

February 12th, 2006, 09:25 AM	#6 (permalink)
winny pooh Tele-Afflicted Join Date: Jan 2006 Location: South London Posts: 1,612 7 Photos	Thanks for the info guys, if you had to take a guess, what percentage of the 60's amps out there used by professionals have been recapped? I'm curious as to how commonplace it is. __________________ my afro ambient side project: http://www.myspace.com/theswyambusessions

February 12th, 2006, 07:30 PM	#7 (permalink)
jjmantele Tele-Holic Join Date: Aug 2003 Location: New Jersey Posts: 850	Caps Electrolytic caps are sort of like batteries. Eventually they are likely to leak nasty corrosive fluid. My '71 Fender had a leaker replaced before I bought it and my '67 Harmony's multi-cap can had leaked before I bought it a few years ago. __________________ JJman If it says "Vintage" on it -it isn't.

February 11th, 2006, 12:50 PM	#3 (permalink)
Wally Friend of Leo's Join Date: Mar 2003 Location: Lubbock, TX Posts: 4,030	What I find with old electrolytics is that in addition to the 'sponginess' that Tim points out, the amp also will evidence a few other symptoms. There is a loss of definition and articulation. THe highs lose their sparkle. There will be some out-of-tune subharmonics....5th fret, 6th string is a good note to listen to for this. Overall, the amp's sonics also lose dimension. In short, for my personal taste, I prefer to hear amps functioning with good, strong elecrolytics. That is the way they start life, and imho is the way they should be made to sound when the caps degrade. If sponginess is the goal, a good compressor with a well-maintained amp yields better sonics, imo, than an amp that is not functioning as well as it was designed to function. Also, at some point, weak caps jeopardize the well-being of more expensive...and virtually irreplacable.. transformers. And we all know that a vintage amp with a replacement transformer will not sound like the original and is also less valuable on the market. There is one world class guitarist who is busy burning down vintage amps because he prefers 'complete originality' and refuses to play a vintage amp that has been recapped. I wonder if he would have refused to play them when they were new? Is anyone producing underfiltered new amps to achieve that 'spongy' sound?

February 14th, 2006, 03:23 AM	#8 (permalink)
AtomicMassUnit Tele-Meister Join Date: Apr 2003 Posts: 153	btw tazzboy, the sozos are not electrolytic caps. They're used as coupling caps in amps, which is not what you change when you get a cap job. Cap jobs are strictly the electrolytics. My take on it is, change the caps. None of these amps originally came with leaky old caps. If you do a cap job on an otherwise healthy amp, it will definitely increase the reliability by a good bit. I feel it's akin to having a vintage car. You want to put new tires on it or you might find yourself having a blowout.

February 15th, 2006, 06:02 PM	#11 (permalink)
Wally Friend of Leo's Join Date: Mar 2003 Location: Lubbock, TX Posts: 4,030	I've re-read this thread several times, and there is good advice here. Vintage amps are valuable. They are more valuable if the major components..transformers, speakers...are original. These amps also yield the sonics that they were designed to yield when they have strong, fresh electrolytics. Voltage measurements can tell a tech some things. I don't pretend to understand exactly everything about how a filter capacitor works, but I do know that static measurements will not tell you how the component works in an actual working situation with signal applied, frequencies changing, volumes changing, attack changing. Long before a capacitor begins to cause the circuit to hum loudly and long before the capacitor decides to catastrophically fail, a capacitor loses the ability to provide strong, steady, totally ripple-free voltage to the circuit. Many of these "amps out there working perfectly as spec'ed with the original caps, tubes and resistors" do not yield the sonic palette that they were designed to deliver. These amps are 'skating on thin ice' and many of them SURPRISE their owners by suddenly giving up in the middle of a song. The sound of a gun firing, some smoke rising from the chassis, and if luck is really bad that night...a dead transformer reduces the amp to much less than it should be. With experience of before and after sonic results of cap replacement, a player can appreciate the sonic differences. If one waits until catastrophic failure...oh, it ISN'T working now. It must need new caps!.....one gets to appreciate the before and after sonic results of a cap job AND a replacement transformer. Except for ascertaing whether or not the amp's major components are functional, I don't run vintage amps much before doing electrolytic cap replacement. IME, every amp from the mid-'70's or before will greatly benefit from a cap job. IF someone thinks diferrently, that is their perogative...and it is their amp, their ears. To each his own. However, the tech mentioned in Winny pooh's first post in this thread is misguided imho. Just because it is working desn't mean that it is safely working properly and yielding the best sounds that can be had from that circuit.

February 16th, 2006, 02:30 PM	#12 (permalink)
winny pooh Tele-Afflicted Join Date: Jan 2006 Location: South London Posts: 1,612 7 Photos	burn babies burn After reading all the posts i had some food for thought and a few things started to shift for me, i was under the impression that if the cap performs then all is fine, i didn't figure that they degraded. So i plugged in and the problems i have had with it since i got it 2 years ago are apparent, its always been a bit mushy and never had enough definition to the sound. I find that the amp has a substantial amount of hiss and for that reason treble or pres never go past 12 o clock. It seems a recap is in order, so now, where do i find Good replacement caps? __________________ my afro ambient side project: http://www.myspace.com/theswyambusessions

February 16th, 2006, 08:32 PM	#13 (permalink)
silentkid Tele-Meister Join Date: Dec 2004 Location: Canvey Island, UK Posts: 127	Yeah, just to restate what everyone else said, electrolytics absolutely have to be replaced every 10 -15 years. The one thing I wanted to say was how it annoys me when people advertise vintage amps as "totally original" - including those electrolytics, as if it's a good thing. I saw one once on ebay (tweed champ) where the guy said "original caps and resistors" as a selling point. When you looked at the chassis, two of the electrolytics had this swollen look to them as if the second you fired it up they'd just explode everywhere. Insane. (Edited to include places to get caps) Try vibroworld or antique radio supply, both sell great products and are fine to deal with.

February 17th, 2006, 12:59 PM	#14 (permalink)
Wally Friend of Leo's Join Date: Mar 2003 Location: Lubbock, TX Posts: 4,030	Wait a minute... I may need to revise my opinion on this recapping thing. I have always been adamant that old amps be recapped, but reading Silent Kid's post made me stop and think. That Champ ready to blow...hmmmm, what if it did? What if someone brought that amp with a blown cap and no sound production? What if the owner was frustrated and wanted just chuck it and go by a new HOt Rod Deviluxe>?What if I offerred low bucks because I explain to him that without hearing the amp, I cannot be assured that the transformers are functional and therefore the amp's orignality and value could possibly be much compromised? He doesn't like that proposal but understands the truth and the validity of it. So, we do a deal that yields him some money for a dead, unknown-quantity amp. I get an amp that needs work before I can truly know what I have bought. I get lucky. :) Except for a blown cap along with the other weak ones and after recapping, I have a wonderful vintage amp in perfect working order that by good fortune is worth a fair amount more than I put into into...cash, parts, work included. Profit..whether in a wonderful amp or proceeds from a sale of said amp....that is the reward for the game of chance that has taken place. I would mention what amps I personally own that have travelled this path, but then you all might start recapping these old amps so that their usefulness and value are not compromised. Does this mean I won't get to risk buying amps in these situations? Nah, not everyone reads this stuff... 8)