Importance of replacing the electrolytic capacitors in any vintage gears

[DanielT]

Quote from this part of the article below. In that link you can see how the values of the capacitors were measured and how much they deviate from spec/tolerance. The question is whether it is possible to generalize and say this:

As one can see from the test results about 30% of all original electrolytic capacitors removed from the power amplifier board exceed a factory capacitance tolerance. Some e-caps have relatively high ESR values. I also noticed that many of the original capacitors are leaky and have corrosive leads due to electrolyte leakage. All of these observations show the importance of replacing the electrolytic capacitors in any vintage gears because they are most susceptible to aging and degradation.

Is it true? What do you think who have knowledge and experience of refurbishing and replacing electronic components in vintage gears? Or is the Technics SU-7300 on which the recap was conducted in ...better...or worse.. condition than other vintage amplifiers of the same age class? You don't know, for example, how many hours it has been used over the decades and thus worn out the electronics.

In any case, it may be worth thinking about if you are considering buying vintage, even when you read tests on vintage stuff that is tested here at ASR. That is, its condition determines the results so it would be difficult to interpret the results. Or what do you think?

Technics SU-7300 Stereo Integrated Amplifier Restoration

Technics SU-7300 Stereo Integrated Amplifier Restoration

www.olegvintageaudio.com

https://www.hifiengine.com/manual_library/technics/su-7300.shtml

 

[computer-audiophile]

With old audio equipment, be it loudspeakers, amplifiers, record players, tape recorders, etc., you usually bring care cases into your home. You have to want to and be able to handle them. Many devices are damaged by technical amateurs. For example, I would never buy a device that was recapped by someone else, unless I did it myself.

 

[sergeauckland]

Before considering recapping, I firstly inspect and measure the item, and if there's no visible bulging or leaking and the equipment is to spec, I leave it alone. I've learnt this over many years when I recapped equipment just because of age and it made no difference whatsoever.

With recapping there's always the risk of board damage, especially with equipment that uses lead - free solder.

S

 

[computer-audiophile]

The circuit boards in old consumer devices are usually of very low quality. It is often a type of cardboard where the copper tracks easily peel off during re-soldering.

 

[Rick Sykora]

Agree on the soldering. Large caps can have large leads and so can be difficult to unsolder. More importantly, there should be a safety disclaimer in the article. You can get a nasty shock from a cap if it has not been allowed to drain its charge.

 

[SSS]

Had restored many vintage equipment like vacuum tube and transistor pre and power amps as well tuners and musical amps. On old tube amps often the coupling capacitors (foil type) are electrical leaky. That is the first to do. Second the electrolytic caps. Sometimes the power supply caps can be kept when meauring OK in terms of leakage current and ESR. It is hard to get the same outline type today so leaving it is an easy way.
At transistor amps with their relative low voltages the electrolytics have a long life. If measured OK I leave them in the circuit. And this with 50 years old amps. They work within spec still today. And, electrolytic capacitors have a wide value tolerance band as the datasheets show. This was considered by the circuit designer (hopefully), so a little degrade in capacity value is normal and torerable.

 

[computer-audiophile]

You can get a nasty shock from a cap if it has not been allowed to drain Its charge.

This can be very painful, especially with tube amplifiers. I therefore use so-called bleeding resistors in high voltage power supplies, which discharge the thick capacitors in a few minutes when the device is switched off.

 

[SSS]

Quote from this part of the article below. In that link you can see how the values of the capacitors were measured and how much they deviate from spec/tolerance. The question is whether it is possible to generalize and say this:

As one can see from the test results about 30% of all original electrolytic capacitors removed from the power amplifier board exceed a factory capacitance tolerance. Some e-caps have relatively high ESR values. I also noticed that many of the original capacitors are leaky and have corrosive leads due to electrolyte leakage. All of these observations show the importance of replacing the electrolytic capacitors in any vintage gears because they are most susceptible to aging and degradation.

Is it true? What do you think who have knowledge and experience of refurbishing and replacing electronic components in vintage gears? Or is the Technics SU-7300 on which the recap was conducted in ...better...or worse.. condition than other vintage amplifiers of the same age class? You don't know, for example, how many hours it has been used over the decades and thus worn out the electronics.

In any case, it may be worth thinking about if you are considering buying vintage, even when you read tests on vintage stuff that is tested here at ASR. That is, its condition determines the results so it would be difficult to interpret the results. Or what do you think?

View attachment 334698View attachment 334699

Technics SU-7300 Stereo Integrated Amplifier Restoration

Technics SU-7300 Stereo Integrated Amplifier Restoration

www.olegvintageaudio.com

https://www.hifiengine.com/manual_library/technics/su-7300.shtml

Most of the replacing capacitors was not necessary to my experience.

 

[computer-audiophile]

Most of the replacing capacitors was not necessary to my experience.

The problems are often not where you first look, echoing a variation of Murphy's Law.

 

[Killingbeans]

Is it true?

Yes. Electrolytic capacitors are one of the weakest links in electronics in terms of longevity and reliability.

What do you think who have knowledge and experience of refurbishing and replacing electronic components in vintage gears? Or is the Technics SU-7300 on which the recap was conducted in ...better...or worse.. condition than other vintage amplifiers of the same age class? You don't know, for example, how many hours it has been used over the decades and thus worn out the electronics.

Depends on who does the recap.

In the repair shop, I work in, we often do recaps as a "just in case" whenever the customer asks for a refurbishment. But thats only because desoldering and soldering is second nature to us.

Sometimes we have to deal with products that the customer or a "mate who has a soldering iron" has tried to recap, and the poor PCB is just a wreck. In those cases, it didn't do much good

 

[sq225917]

I completely recapped a krell ksa200 and a ksp-7b both had the psu caps done first. In both cases the psu and power rail decoupling caps recapping made measurable improvements, small signal caps did nothing.

 

[DanielT]

Thanks for your interesting answers. I don't have much to add myself, but I read with interest.

So a summary of it so far, if I understand it all correctly, will be something like:
Just doing a recap for the sake of it seems unnecessary, which can also do more harm than good if you don't know what you're doing. Sounds obvious but should probably be emphasized. But if it needs to be done, after the inspection, measurements of the components' values and they turn out to be bad, that is another matter and they can be replaced.

 

[DanielT]

With recapping there's always the risk of board damage, especially with equipment that uses lead - free solder.

S

Speaking of solder with lead in it. I have some rolls that my father had. Probably with lead in them since they are from the 1970s. Pretty unnecessary that I have those rolls because I only occasionally solder on banana plugs.

Plus I'll try to put together a pre amp with op-amp and some resistors and capacitors. But that is mostly a try and learn project. The quality there doesn't matter much. Just fun if it works, which is my goal.

 

[Killingbeans]

The problems are often not where you first look, echoing a variation of Murphy's Law.

Depends on how many times you've had to look in the past.

If 99% of all "defective" amps turns out to simply contain a silver plated switch that needs cleaning, it's a pretty safe place to look first

 

[SSS]

Depends on how many times you've had to look in the past.

If 99% of all "defective" amps turns out to simply contain a silver plated switch that needs cleaning, it's a pretty safe place to look first

Not always but often it is just oxidized contacts in switches and pots.

 

[Killingbeans]

That was my point

 

[RDoc]

It's not just old audio gear. I had to re-cap the AC controller in my 1991 Acura to get it to work correctly.

 

[computer-audiophile]

It's not just old audio gear. I had to re-cap the AC controller in my 1991 Acura to get it to work correctly.

Quality problems can happen anywhere. In earlier years I liked HP computers, precisely because of the quality, but then I once had a motherboard from them where dozens of electrolytic capacitors were obviously defective shortly after the warranty period had expired. As such computers were still relatively expensive at the time, I went to the trouble of replacing them. After that, everything worked again for years.

 

[Philbo King]

The problems are often not where you first look, echoing a variation of Murphy's Law.

Invariably problems are always in the last place you look (because you stop looking once the problem is fixed).

 

[RDoc]

Invariably problems are always in the last place you look (because you stop looking once the problem is fixed).

My wife and I have a saying when debugging software: "After you've tried everything it can't be, try what it could be". Works amazingly well.