Re-Capping

[bigrod]

Since I finished the mancave last year I decided to have some of my vintage integrated amplifiers serviced as some are more than 40 years old ..
I found a local guy in Nottingham who specialises in early Japanese gear .
A retired engineer/electrician with a no nonsense approach to what should be done ..
I took him my lovely Pioneer SA 706 to have a chat about .
We connected it up and apart from a little crackle on the volume pot it still sounds great ..
I asked him about re-capping after he took the cover off .. his exact words were
“ everyone’s got this thing about re-capping, 99% of the time there isn’t a problem “
Looking into the 706 he said the caps
that were in there where as good as it gets , Japanese finest ..But he checked them for leakage with absolutely none whatsoever..
Bowing to his experience and knowledge I agreed that it didn’t sound any different to when I brought it from Comet .
So apart from cleaning switches and replacing the VU bulbs it is being left as is..
I see many amp advertisements on eBay and on various HiFi websites that say they have been recapped .. How do we know if it’s true when most people have no idea what they are looking at , and it’s just a con ?? Or even FOO ?

 

[Juancho]

I broadly agree with your tech but would normally replace the main PSU caps on an amp or other equipment of that age. Recently had some vintage Japanese gear in where the owner insisted I swap every electrolytic even though they all measured in spec and there was no leakage or bulging.......

 

[Firebottle]

It's true Julian that Japanese equipment from that era used really good parts. I take the same approach of looking for problems rather than a scatter gun total recap.

I have had top notch Pioneer equipment that needed replacements, particularly glass encapsulated capacitors, but only in certain areas of the circuit, certainly not all of them.
I think when people do a full recap they are doing it to 'cover all bases', for some they don't have the knowledge or equipment to diagnose which are actually needed to be replaced.

 

[bencat]

Would agree that the main PSU caps should be checked for any signs of leaking or bugling and that they are not widely out of spec . If all is fine then leave well alone if only one is failing then change them all in the Mains PSU section as it is bett in that case to have them all the same and if one is starting to fail the other are likely to be not far behind . If I remember right most Japan units of that vintage were designed to run very cool and this will certainly help to maintain the health of the components .

 

[Firebottle]

Would agree that the main PSU caps should be checked for any signs of leaking or bugling and that they are not widely out of spec . If all is fine then leave well alone if only one is failing then change them all in the Mains PSU section as it is better in that case to have them all the same and if one is starting to fail the other are likely to be not far behind . If I remember right most Japan units of that vintage were designed to run very cool and this will certainly help to maintain the health of the components .

Totally right, especially the keeping cool part.
I serviced a Krell KSA80 recently and the age and heat had dried out the original caps. They measured 10% or less of the original value.

 

[CBP]

Totally right, especially the keeping cool part.
I serviced a Krell KSA80 recently and the age and heat had dried out the original caps. They measured 10% or less of the original value.

I really can’t see why having a total recap or ground up rebuild isn’t a sensible thing. I get that some components may measure okay but they will still be aged, so a total overhaul essentially resets it to new build original spec / life expectancy

 

[rabski]

I really can’t see why having a total recap or ground up rebuild isn’t a sensible thing. I get that some components may measure okay but they will still be aged, so a total overhaul essentially resets it to new build original spec / life expectancy

First, it's a waste of time, money and resources. Second, 'aged' doesn't mean faulty. Third, not all new components are necessarily magically better than the originals. Some are worse. Fourth, removing and replacing soldered parts can cause incidental damage and can result in dry joints. Fifth, if you aren't extremely methodical, you can find yourself relying on PCB markings for installing new components. This can lead to disasters, as plenty are incorrectly marked. Lastly, a lot of the 'sound' of some equipment is down to very carefully chosen components, change everything and you risk changing the sound, and not for the better.

I would normally measure most things on an old amplifier. Personally, I prefer to replace power supply reservoir caps and dropper resistors in older valve equipment without even bothering to measure, as well as most non-electrolytic coupling caps, because modern equivalants are pretty much universally better. Everything else I would leave well alone if it measures fine.

 

[Beobloke]

I agree that blanket re-capping of electronic equipment is seldom necessary. Even if it is, the candidates should be chosen on the basis of visual problems and measured failures, not ‘gut feel’. The 108 capacitors that needed changing to restore my preamp to health all measured way out of spec!

As a friend of mine puts it - “Why would I remove high quality original Japanese capacitors and put cheap modern Chinese ones in instead?”!

If anyone brings anything to him to service and mentions that it’s been re-capped he has been known to add £10 to the price…

 

[Jessica_k]

The way an electrolytic capacitor is constructed is that it has a wet electrolyte between the metal plates to form a capacitor. With age, environment, and usage these caps can dry and fail.


High voltage caps used in valve power circuits often have a poor over rating, for example 500V cap in a 475V circuit. This is done for cost, or the designer has miscalculated the derating with temperature; the stress of this voltage means they can fail quickly if things go wrong.
Also, all caps have a life span, it is usually printed on the component and can be as low as 1000hrs, after which they are known to degrade and provide less capacitance, a common cause of increased hum.

So having said all this, it does not mean they have to be replaced after a time as it is fairly easy to determine if they are working correctly. Are they within spec? Are they physically leaking? Are they current leaking? All of those issues mean the cap must be replaced.
Going back to Bigrod’s initial post, Japanese amps of a certain age were built to last with high grade parts of high voltage ratings and are unlikely to fail or degrade with age.

Bear in mind too, old amps that have been in storage or of unknown provenance need to be brought up slowly using a variac as the power-on stress can cause caps to fail especially if they have lost polarity as it allows the cap to reform.

In conclusion, there is no simple answer to the question of recapping and just because a hifi component is working it does not mean there are no issues, at the same time it does not mean it has to be done either.

Jessica xx

 

[DomT]

Totally right, especially the keeping cool part.
I serviced a Krell KSA80 recently and the age and heat had dried out the original caps. They measured 10% or less of the original value.

Running cool is one of the reasons why I bought my Marantz Reference PM11S2 because despite being class A/B it runs much cooler than a class A/B Luxman. Marantz explain in their brochure that cool running equals long life.

@bigrod is it this place?

https://www.hifirepair.co.uk/

 

[DomT]

@bigrod was your ‘thumbs up’ a yes confirming that HiFi repair shop was the one I linked to as I am considering using them for something.