Recapping-what exactly is it?

[Charles_b]

Ok, so as the title suggests, this is quite a nooby question (because I am one!). I thought I knew what recapping meant-bear with me...
I went to see a friend of a friend who works on amplifiers. I asked him if he could recap my amplifier to which he said "which caps?", which left me a bit perplexed, to which I answered those 4 big ones there (pointing at the 4 big power capacitors as I thought that this was a "recap" ). So, according to him there are power capacitors and audio capacitors (I think that's what he said).
So, im guessing that a FULL recap would include both the big power capacitors and smaller audio capacitors?
Also, when I went home, I had a look at the service manual for my Denon amplifier-I think there were about 40-50 different smaller capacitors-Mostly the Electrolytic type (SME), but some ceramic, some plastic film and some others which I have forgot about-does a recap of the "audio" capacitors include replacing ALL of the small capacitors in the amplifier or just a certain type (e.g Electrolytic?)

Many thanks, and apologies if this is confusing/poorly explained.
Charles

 

[Doodski]

Generally the electrolytic capacitors would be replaced. Sometimes the power supply capacitors will be replaced too.

 

[Charles_b]

Thank you! It seems like a bit of a nightmare to replace EVERYTHING! May as well build an amp from scratch!

Charles

 

[Doodski]

Thank you! It seems like a bit of a nightmare to replace EVERYTHING! May as well build an amp from scratch!

Charles

That's what it's all about. A bag of capacitors, a bunch of labour for soldering and controls and switches clean'n lube. It can get expensive. Some gear is worth reviving but other stuff is obviously fit for the recycling.

 

[Charles_b]

When recapping the audio caps then, is it best to use all of the same brand and same line of caps?
For example, I've heard good things about elna silmic capacitors, but say they don't produce some of the value of Electrolytic caps I need, can I mix and match (using mostly elna silmic) or is it best to stay away from this and find a brand and line of caps that my amp needs?
Thanks,
Charles

 

[Doodski]

When recapping the audio caps then, is it best to use all of the same brand and same line of caps?
For example, I've heard good things about elna silmic capacitors, but say they don't produce some of the value of Electrolytic caps I need, can I mix and match (using mostly elna silmic) or is it best to stay away from this and find a brand and line of caps that my amp needs?
Thanks,
Charles

Sure mix and match if you can't access standard values in the range. Many of those caps are for filtering and smoothing and will have little to no effect on sound quality but some are in the signal path. My advice is to get a 105 degree Celcius capacitor for the hot zones that showed signs of heat. They are probably a 85 degree Celcius rating that is installed because that's the way it's usually done in consumer domestic electronics. It doesn't hurt to up-rate a Celcius value on the temperature rating.

 

[GeorgeWalk]

I recapped my Nikko Beta II preamp and Nikko Alpha III power amp. Most of the electrolytics had started to leak and when they were in use there was a very distinctive smell. So I replaced the caps and cleaned the goo off the boards. They are now as good as new. I bought them in 1978.

I don't think there is a big difference between "audio grade" caps and others. Make sure you use the same mFarad and voltage rating and you should be fine. Most caps are produced in standard values. Also, it is ok to use higher voltage ratings, never lower.

You usually only have to replace electrolytics because they break down after about 10 years and they leak.

Also use the same type: don't substitute, replace elctrolytics with electrolytics and pay attention to the polarity on the leads. They are polarized. Bad things happen when reversed.

I went online and got the schematics and BoMs for my gear. It made it easier to order what I needed and with the correct values.

 

[Doodski]

Make sure you use the same mFarad and voltage rating

The voltage rating can be fudged up a little for some applications. It won't hurt like changing the capacitance value.

 

[Charles_b]

Thanks for your replies guys, very helpful!

 

[Doodski]

Thanks for your replies guys, very helpful!

If you decide to recap a amp/receiver your digital camera is your friend. For beginning the pics sure would help and get a system for organizing stuff across large tables so everything is in it's place and can be reassembled after being cleaned and serviced. There's no working off the floor That's guessing it's a worthy unit of the effort.

 

[restorer-john]

"Re-capping" is a shot-gun approach to restoration often done by people with little or no knowledge of what they are doing. If a vintage item has some issues, they should be isolated and repaired before any thought of wholesale capacitor replacement is considered. Then test the item to determine what, if any, improvements could be made and whether capacitor replacement would contribute to that.

Considering how many capacitors there are in typical integrated amplifiers, preamplifiers, and receivers, they have proved to be phenomenally reliable for many decades. New capacitors may not last even a fraction of the life of the original ones- people don't consider that.

Capacitors were chosen for various attributes by the designers/engineers, and Joe the Cap Jockey with his bag of random capacitors is likely to degrade the performance of most anything he touches.

Lastly, just because electrolytic capacitors have a form of "wet" electrolyte, people think of them like car batteries. They might need replacing because they "dry out". Yes, they can and do. Some leak and make a real mess, but resistors (both fusible and normal) change value, transistors get noisy as do zeners and other devices. Capacitors are just but one class of components, but seem to get all the attention because:

a) they are easy enough to replace for a weekend warrior
b) anybody can read the value on the sleeve
c) they don't cost much to replace
d) people like to attribute huge positive changes after spending $50 and a weekend burning their fingers and "fixing" an already working amplifier/receiver etc.
e) it makes them feel like they have done something useful, when in fact they may have ruined the item, made it less valuable and a poorer performer.

So the legend lives on, and you will hear cries from the peanut gallery saying "it'll sound better after a recap" or "you really need to recap it to get the best sound" or "huge changes to the soundstage and detail retrieval after a recap"...

Try to resist and get the item professionally tested first and any niggling issues looked at. Some may be capacitor related, many may not.

 

[Vasr]

If you decide to recap a amp/receiver your digital camera is your friend. For beginning the pics sure would help and get a system for organizing stuff across large tables so everything is in it's place and can be reassembled after being cleaned and serviced. There's no working off the floor That's guessing it's a worthy unit of the effort.

And no bottles of wine on the worktable working on open electronics like this German dude replacing the fan on the Behringer I posted earlier.

https://www.audiosciencereview.com/...0d-pro-dsp-amplifier-review.14544/post-448970

 

[Vasr]

"Re-capping" is a shot-gun approach to restoration often done by people with little or no knowledge of what they are doing.

I also have to wonder unless one happens to be a fairly well-experienced soldering master and with right tools what are the chances that one would get all of these caps replaced without screwing up somewhere which would be very difficult to debug.

Speaking from experience. Soldering and I have never gotten along well together in the past unless it is welding a soldering joint.

 

[Doodski]

"Re-capping" is a shot-gun approach to restoration often done by people with little or no knowledge of what they are doing. If a vintage item has some issues, they should be isolated and repaired before any thought of wholesale capacitor replacement is considered. Then test the item to determine what, if any, improvements could be made and whether capacitor replacement would contribute to that.

Considering how many capacitors there are in typical integrated amplifiers, preamplifiers, and receivers, they have proved to be phenomenally reliable for many decades. New capacitors may not last even a fraction of the life of the original ones- people don't consider that.

Capacitors were chosen for various attributes by the designers/engineers, and Joe the Cap Jockey with his bag of random capacitors is likely to degrade the performance of most anything he touches.

Lastly, just because electrolytic capacitors have a form of "wet" electrolyte, people think of them like car batteries. They might need replacing because they "dry out". Yes, they can and do. Some leak and make a real mess, but resistors (both fusible and normal) change value, transistors get noisy as do zeners and other devices. Capacitors are just but one class of components, but seem to get all the attention because:

a) they are easy enough to replace for a weekend warrior
b) anybody can read the value on the sleeve
c) they don't cost much to replace
d) people like to attribute huge positive changes after spending $50 and a weekend burning their fingers and "fixing" an already working amplifier/receiver etc.
e) it makes them feel like they have done something useful, when in fact they may have ruined the item, made it less valuable and a poorer performer.

So the legend lives on, and you will hear cries from the peanut gallery saying "it'll sound better after a recap" or "you really need to recap it to get the best sound" or "huge changes to the soundstage and detail retrieval after a recap"...

Try to resist and get the item professionally tested first and any niggling issues looked at. Some may be capacitor related, many may not.

Most if not all the craftsmen are long retired and too busy to be occupied rebuilding a battleship of a amp/receiver. I don't see them at the retail level anymore and parts is surely difficult at best would be a minimum order of let me guess $100.00

 

[MakeMineVinyl]

Power supply capacitors are the most likely to need replacement. In my experience, heat is a major contributing factor in shortening the lifespan of electrolytic capacitors; if you look at capacitor specifications, you will note significantly shortened lifetime verses increasing heat. Generally, capacitors in the signal path fare better than the ones in the power supply. Film capacitors should last forever, the exception being some really old wax or early plastic ones which have had their internals exposed to air. Capacitor life can vary greatly; for instance I have some original Dynaco MKIII tube amps which still have good power supply filter capacitors, this despite them being right next to heat generating tubes.

When you first power up a vintage piece, always use a variac to bring up the AC voltage slowly. Just plugging the unit in and throwing the power switch is a sure way of having some unpleasant surprises.

 

[restorer-john]

When you first power up a vintage piece, always use a variac to bring up the AC voltage slowly. Just plugging the unit in and throwing the power switch is a sure way of having some unpleasant surprises.

For people without access to, or the desire to pay for a variac, the classic dim bulb tester does the same thing, albeit a little faster but with overload/fail protection built in, all for a few dollars.

 

[anmpr1]

Most if not all the craftsmen are long retired and too busy to be occupied rebuilding a battleship of a amp/receiver.

One of the sad facts of today's hi-fi scene is a lack of repair facilities. When I entered the hobby a consumer could more or less repair their gear. In fact, they may well have built their gear from a kit. Then with solid state you had dozens of repair shops in an average city, many having factory trained techs doing warranty service.

The use of proprietary parts (ex: Audio Research 'analog modules') and unobtanium (ex: Sony V-FETs) hasn't helped. Or just 'regular' parts such as tape heads, etc. The old stuff was nice, but for the most part it's just memories. Like Roy Batty said, it'll all be forgotten like tears in rain.

 

[Bob-23]

At least for power supply electrolytic caps I prefer low ESR ones (105°) - they don't heaten as much and thus live longer.
Mainly with regard to high voltage applications (as power supplies): measuring ESR (equivalent series resistance) is the best way to tell the actual quality of an electrolytic cap, it may not (yet) be bulged, its capacitance may (still) measure correct - but when ESR is too high, it's time to recap. There are lists of the appropriate ESR values, and, of course, the cap has to be desoldered in order to measure it, and you need an ESR meter: there are very expensive ones and there is a very cheap one, which might not be absolutely accurate but which also does the job:
https://www.amazon.com/Treedix-Grap...d=1&keywords=esr+meter&qid=1594225969&sr=8-22
Measuring ESR of low value electros , though, remains difficult because reactance may be higher than ESR.

 

[shal]

"Re-capping" is a shot-gun approach to restoration often done by people with little or no knowledge of what they are doing. If a vintage item has some issues, they should be isolated and repaired before any thought of wholesale capacitor replacement is considered. Then test the item to determine what, if any, improvements could be made and whether capacitor replacement would contribute to that.

You describe perfectly my own case
I have very little knowledge
My old and venerable yamaha pc2002 , 35 years old worked well but had some strange noise. When it was cold the noise is stronger.
After made internal level and adjustement, the problem remains.

I have change all electrolytic caps with Panasonic 105° (FR ou FC ).
The noise gone.
And perhaps, yes, I found that the amp is better

Some people said that tantalum capacitor can become a problem with the long time , but I don't change them.

 

[Vasr]

One of the sad facts of today's hi-fi scene is a lack of repair facilities. When I entered the hobby a consumer could more or less repair their gear. In fact, they may well have built their gear from a kit. Then with solid state you had dozens of repair shops in an average city, many having factory trained techs doing warranty service.

The use of proprietary parts (ex: Audio Research 'analog modules') and unobtanium (ex: Sony V-FETs) hasn't helped. Or just 'regular' parts such as tape heads, etc. The old stuff was nice, but for the most part it's just memories. Like Roy Batty said, it'll all be forgotten like tears in rain.

This is true, just like auto repairs. There aren't many @restorer-john types any more and even if you find one they may specialize in only some specific brands.

Electronics is becoming more of a swap-board business than fix the board business unless it one of the vintage units for which that may not be a swap solution.

The problem really arises for older equipment for which it is not possible to get replacement boards, most local technicians just cannot afford to spend the amount of time necessary to debug a board for what they can charge or consumers are not willing to pay several hundreds of dollars for debugging or the enormous mailing costs for heavy amps.

So things like recapping become a last-resort attempt as a cheaper (but admittedly with some risk) alternative for many and I think this is a valid if sometimes futile approach.

What would be dumb is for people to attempt to do this to fix something that is not necessarily broken in hopes of making it sound better.