Importance of replacing the electrolytic capacitors in any vintage gears

[DanielT]

The CR-2040 had a complete recap and wouldn't power on, unfortunately entirely due to the recap:
View attachment 470755
As part of the capacitor replacement, the larger capacitors forced whoever modified this to bend the original retaining bracket (middle arrow), which they tried to stabilize with a wedged piece of cardboard instead of a more secure method (top arrow). This caused the supply board to crack when due to the unsupported weight of the larger capacitors (bottom arrow).
View attachment 470767

This Yamaha is a particularly bad example, but this I see varying degrees of fail in recaps.

I don't personally enjoy much of this rework, so I try to go after the more common issues in my experience, like relays and some of the Si components that do tend to wreck havoc when they degrade. Even if a no-stone-unturned approach might make sense for some enthusiasts, I'm not convinced doing it as a rule is the right approach. So I avoid doing it as a rule. I have vintage stuff, which for the most part I keep as original as possible. I may be erring a bit on that side, but the above CR-2040 above is a bit of a heartbreak that offends my sensibilities more than if it had an original part that aged. I am going to fix this cracked board and traces, so all isn't lost.

A bit stupid of the person who made the recap to try to squeeze in bigger power supply capacitors in the hope that the tune up operation will result in better sound. Which I suspect was the intention.

I changed to bigger power supply capacitors in my Sela power amp. Because of, well my friend had a suitable one at his house. That amplifier is after all around forty-five years old plus it was very easy to change them so why not. In fact, I think it was the easiest possible change of capacitors that can be made on an amplifier. They were very easily accessible, on a rail. Two capacitors for each channel.

Did I hear any difference after the change? I don't think so but now the new power supply capacitors will not need to be replaced for a long time.

The new ones,bigger caps in uF value but actually smaller in physical size (the new ones, the black ones in the picture below).

 

[MAB]

A bit stupid of the person who made the recap to try to squeeze in bigger power supply capacitors in the hope that the tune up operation will result in better sound. Which I suspect was the intention.

I changed to bigger power supply capacitors in my Sela power amp. Because of, well my friend had a suitable one at his house. That amplifier is after all around forty-five years old plus it was very easy to change them so why not. In fact, I think it was the easiest possible change of capacitors that can be made on an amplifier. They were very easily accessible, on a rail. Two capacitors for each channel.

Did I hear any difference after the change? I don't think so but now the new power supply capacitors will not need to be replaced for a long time.

The new ones,bigger caps in uF value but actually smaller in physical size (the new ones, the black ones in the picture below).

View attachment 470805View attachment 470806View attachment 470807View attachment 470808View attachment 470809View attachment 470810

Yeah, any cap of different dimension is going to be a reliability issues in that Yamaha power supply without careful consideration.
They were likely trying to be heroes with the Yamaha I am working on.
Glad to see you took care to keep your amp safe!

 

[DanielT]

Yeah, any cap of different dimension is going to be a reliability issues in that Yamaha power supply without careful consideration.
They were likely trying to be heroes with the Yamaha I am working on.
Glad to see you took care to keep your amp safe!

Thanks, it's part of Swedish PA history so that's why I did it.

I only increased the uF value a little. There was a discussion about increasing it or not and how much in the thread where I was wondering what kind of power amp it was, its construction that is.

From #105 . Take no notice of what I write in that Sela thread. I've learned a little more since then:
Solderdude:

'Why 12 power transistors in a class AB (?)120 W (?) amplifier?'

Oct 24, 2021

Why 12 power transistors in a class AB (?)120 W (?) amplifier in .. 4-8 Ohm (?)
What is the point of 6 power transistors per channel in such an amplifier? Information and pictures below .

I would be very grateful for clarification. The stuff works, but I'm just curious.

Some facts. Sela, a Power amplifier, built sometime in the 80's. Unfortunately, there are no facts about it. It has probably mostly been used for PA. Maybe class AB, but I do not know.
Well, if I compare with a hifi intended vintage amplifier, from about the same time period, a Luxor 7082 integrated at 70 W in 4 Ohm...

• DanielT
• Replies: 144
• Forum: Audio Newbie/Beginner Technical Forum

• 

Sitting and idly reading various posts and then fell into the thread about the power amp ea232 from SELA. At the time when it happened, I was working extra as a cinema operator. In 1978, the sound system at the Royal Cinema in Gävle was modernized, which then received the then new "Dolby Stereo", which was an two-channel soundtrack from which four channels were extracted. the output stage that was installed was precisely the ea232. They gave 2x125Watt. These were in daily operation for eleven years without a problem.
Attaches a picture of the sound rack (engine room).

 

[SSS]

Yeah, any cap of different dimension is going to be a reliability issues in that Yamaha power supply without careful consideration.
They were likely trying to be heroes with the Yamaha I am working on.
Glad to see you took care to keep your amp safe!

True. It needs to view the specs of both original and replacement electrolytic caps (if data available). One criteria is the acceptable continues ripple current where differences may be. If the replacement can't meet this it may get hot under operation.

 

[MAB]

Thanks, it's part of Swedish PA history so that's why I did it.

I only increased the uF value a little. There was a discussion about increasing it or not and how much in the thread where I was wondering what kind of power amp it was, its construction that is.

From #105 . Take no notice of what I write in that Sela thread. I've learned a little more since then:
Solderdude:
View attachment 470819

'Why 12 power transistors in a class AB (?)120 W (?) amplifier?'

Oct 24, 2021

Why 12 power transistors in a class AB (?)120 W (?) amplifier in .. 4-8 Ohm (?)
What is the point of 6 power transistors per channel in such an amplifier? Information and pictures below .

I would be very grateful for clarification. The stuff works, but I'm just curious.

Some facts. Sela, a Power amplifier, built sometime in the 80's. Unfortunately, there are no facts about it. It has probably mostly been used for PA. Maybe class AB, but I do not know.
Well, if I compare with a hifi intended vintage amplifier, from about the same time period, a Luxor 7082 integrated at 70 W in 4 Ohm...

• DanielT
• Replies: 144
• Forum: Audio Newbie/Beginner Technical Forum

• 

Sitting and idly reading various posts and then fell into the thread about the power amp ea232 from SELA. At the time when it happened, I was working extra as a cinema operator. In 1978, the sound system at the Royal Cinema in Gävle was modernized, which then received the then new "Dolby Stereo", which was an two-channel soundtrack from which four channels were extracted. the output stage that was installed was precisely the ea232. They gave 2x125Watt. These were in daily operation for eleven years without a problem.
Attaches a picture of the sound rack (engine room).
View attachment 470820

Yeah, most power supplies and rectifiers can handle the additional stress at turn on.
In the past, I upgraded caps hoping for a miracle, and in my naïve youth thought that I made an improvement, while more likely chasing my tail.

 

[nanook]

To keep in mind is that an old pcb board can be easily be destroyed by lifting off the traces

I agree, the old "cardboard" PCBs require carefull handling and since they usually are single-sided, lifting off tracks is a lot more likely.

This is a bit similar issue with SMD caps, but for those you don't have good access to the solder joints underneath the case and they mostly were soldered leadless (-> needs higher temperature) and sometimes even glued to the PCB to prevent falling off before reflow...
This is meant as a serious warning to those who want or need to exchange SMD electrolytic caps

On the other hand, desoldering through-hole components is so much easier with single-sided PCBs. Using a good desoldering iron at moderate temperature works fine for me.
And of course I use lead based solder when working on old equipment (lower temperature and a reliable material composition when the old solder was not removed completely).

For HiFi vintage it's a hobby and time doesn't really count - peace of mind is more important.
Of course I assume an experienced hobbyist - the spoiled Yamaha that was mentioned above is definitely not what I want to encourage here.

At work I'm regularly restoring old equipment that is running 24/7 like controllers for ion-getter- or turbo- pumps or vacuum gauges, etc.
For those I replace all electrolytic caps if some caps show elevated ESR or a dry electrolytic cap was faulty - the unit shall run another 10 or 30 years without failing due to dried out capacitors

 

[MAB]

I agree, the old "cardboard" PCBs require carefull handling and since they usually are single-sided, lifting off tracks is a lot more likely.

This is a bit similar issue with SMD caps, but for those you don't have good access to the solder joints underneath the case and they mostly were soldered leadless (-> needs higher temperature) and sometimes even glued to the PCB to prevent falling off before reflow...
This is meant as a serious warning to those who want or need to exchange SMD electrolytic caps

On the other hand, desoldering through-hole components is so much easier with single-sided PCBs. Using a good desoldering iron at moderate temperature works fine for me.
And of course I use lead based solder when working on old equipment (lower temperature and a reliable material composition when the old solder was not removed completely).

For HiFi vintage it's a hobby and time doesn't really count - peace of mind is more important.
Of course I assume an experienced hobbyist - the spoiled Yamaha that was mentioned above is definitely not what I want to encourage here.

At work I'm regularly restoring old equipment that is running 24/7 like controllers for ion-getter- or turbo- pumps or vacuum gauges, etc.
For those I replace all electrolytic caps if some caps show elevated ESR or a dry electrolytic cap was faulty - the unit shall run another 10 or 30 years without failing due to dried out capacitors

Yes, as a hobby it makes sense, especially if you are skilled or are serious about building skill and experience.

 

[SSS]

I agree, the old "cardboard" PCBs require carefull handling and since they usually are single-sided, lifting off tracks is a lot more likely.

This is a bit similar issue with SMD caps, but for those you don't have good access to the solder joints underneath the case and they mostly were soldered leadless (-> needs higher temperature) and sometimes even glued to the PCB to prevent falling off before reflow...
This is meant as a serious warning to those who want or need to exchange SMD electrolytic caps

On the other hand, desoldering through-hole components is so much easier with single-sided PCBs. Using a good desoldering iron at moderate temperature works fine for me.
And of course I use lead based solder when working on old equipment (lower temperature and a reliable material composition when the old solder was not removed completely).

For HiFi vintage it's a hobby and time doesn't really count - peace of mind is more important.
Of course I assume an experienced hobbyist - the spoiled Yamaha that was mentioned above is definitely not what I want to encourage here.

At work I'm regularly restoring old equipment that is running 24/7 like controllers for ion-getter- or turbo- pumps or vacuum gauges, etc.
For those I replace all electrolytic caps if some caps show elevated ESR or a dry electrolytic cap was faulty - the unit shall run another 10 or 30 years without failing due to dried out capacitors

Professional industrial equipment is a different story in relation to home audio. There of course reliability is a major point in order to have no or minimum downtime.
My opinions here in ASR are solely on home audio.

 

[levimax]

One concept often overlooked is the "Bathtub Effect" where new components fail at a higher rate than older components. This means that replacing "all the caps" regardless of condition will most likely result is LESS reliability not higher reliability. https://gesrepair.com/bathtub-curve-reliability-and-how-repairs-affect-it/

 

[Audiofire]

This means that replacing "all the caps" regardless of condition will most likely result is LESS reliability not higher reliability.

Not most likely (and closer to least likely) with good brands like Nichicon, which performs measurements of capacitor specifications in a production line of random samples, in accordance with JIS.

Measuring dissipation factor (and capacitance) of new electrolytic capacitors gives peace of mind for end users.

 

[levimax]

Not most likely (and closer to least likely) with good brands like Nichicon, which performs measurements of capacitor specifications in a production line of random samples, in accordance with JIS.

Measuring dissipation factor of new electrolytic capacitors gives peace of mind for end users.

Are you saying that Nichicon capacitors don't follow the "bathtub" curve like every other electrical component? Do you have backup for this claim? What if all the capacitors you are replacing are Nichicon? New parts on average are always less reliable than"mid-life" parts and this is why replacing parts that don't need it reduces reliability rather than increasing reliability. This does not even take into account the rather high chance of damaging things during the parts replacement process.

 

[Audiofire]

Are you saying that Nichicon capacitors don't follow the "bathtub" curve like every other electrical component?

No, your statement was just incomplete

 

[SSS]

One concept often overlooked is the "Bathtub Effect" where new components fail at a higher rate than older components. This means that replacing "all the caps" regardless of condition will most likely result is LESS reliability not higher reliability. https://gesrepair.com/bathtub-curve-reliability-and-how-repairs-affect-it/

The so called "bathtub" curve failure distribution is an old well known one. But in the case here it is hard to calculate whether the replacement of all electrolytic caps compared to few replacements yield to higher or less reliability of the entire system. It may not known where the used caps in a system are sitting on the bathtub curve nor is known how the bathtub curve of the new components look. Failure rate is a statistical figure measured on a big sample. A single item has not really this curve except at end of life. And components like wirewound resistors in general are very reliable from the start on. So it is hard to extrapolate the reliability of a small sample (which audio gear is) from the data for a big sample like production quantities.

 

[nanook]

I have seen "tons" of worn out electrolytic caps and I've seen a couple of them dieing making a short circuit. But I have so far never seen a new cap (even ones stored for years) that failed.
I thus doubt that early fails are frequent for liquid electrolytic caps (tantalum caps had a tendency to early failure in the past, but production testing introduced a stress test (high dU/dt and thus high transient current) that "blows up" weak parts such that early failure has gotten rare for them too).
I also doubt you can transfer the classical bathtub failure model 1:1 to liquid electrolytic caps. The end of life clearly is very predictable.

The reason why I replace "all" capacitors when I come across a high ESR or a higher ESR variation among nominally equal caps is that this indicates that the unit has had a lot of operation hours at elevated temperature.
This is why I - when only the 85°C rated caps show high ESR variation - often leave the 105°C rated caps of comparable case size in if the ESR looks good; they should survive ca. 4x as long as their 85°C companions and thus should not fail soon.

I want to make clear, that this is about classic liquid electrolytic caps. Solid electrolytic caps like tantalum behave much different, they do not have this wear-out, but rather infinite lifetime with statistical failures when operated properly (no high transient currents, voltage derating).

 

[DanielT]

Now we have talked about amplifiers/receivers that can be up to half a century old but can you say something generally about crossovers in equally old speakers? Does the principle If it ain't broke, don't fix it apply to such old crossovers?

I don't have much experience with such old speaker crossovers but I suspect that they differ in component quality/lifespan between different manufacturers/models.

A little OT since it's not about electronics. What I've done is replaced rotten foam surrounds on speakers that were around thirty years old. Absolutely no imagination that they needed replacing because...well they weren't there on the woofers.
Always check the material on vintage woofers, if they are foam based surrounds then they need replacing. Not a question of if but when it needs to be done.
Old tweeters with dried out ferrofluid. Speaker drivers that don't match in values between them. There are probably a lot of things other than the vintage crossover that can create bad sound in old speakers.

 

[SSS]

Now we have talked about amplifiers/receivers that can be up to half a century old but can you say something generally about crossovers in equally old speakers? Does the principle If it ain't broke, don't fix it apply to such old crossovers?

I don't have much experience with such old speaker crossovers but I suspect that they differ in component quality/lifespan between different manufacturers/models.

A little OT since it's not about electronics. What I've done is replaced rotten foam surrounds on speakers that were around thirty years old. Absolutely no imagination that they needed replacing because...well they weren't there on the woofers.
Always check the material on vintage woofers, if they are foam based surrounds then they need replacing. Not a question of if but when it needs to be done.
Old tweeters with dried out ferrofluid. Speaker drivers that don't match in values between them. There are probably a lot of things other than the vintage crossover that can create bad sound in old speakers.

For my own loudspeakers (~ 40 years old) I contacted the factory whether something should be replaced in the passive crossover. Answer was that the foil caps schould be still OK. But the non-polarized electrolytic caps can deteriorate and should be replaced if necessary. I agree to this by my technical knowledge. Although the voltages are not high, the caps can dry out and the capacity decreases. Never had a short on any of my speakers.

 

[Audiofire]

New parts on average are always less reliable than"mid-life" parts and this is why replacing parts that don't need it reduces reliability rather than increasing reliability.

Mid-life is officially about 7 years after the manufacturing date for aluminum electrolytic capacitors. I have only seen this strict time limit used for replacement in the kind of industrial company, which has more employees and money than it knows what to do with

I don't have much experience with such old speaker crossovers but I suspect that they differ in component quality/lifespan between different manufacturers/models.

Definitely, so a visual inspection is a really good idea. I have seen severe thermal degradation (visible like melting material) on non-polarized electrolytic capacitors in passive crossovers. These are always good to replace with film capacitors.

 

[nanook]

These are always good to replace with film capacitors.

I agree that - especially for the tweeter and if size and cost allow also for the midrange - film caps are preferable.
You might notice a slightly more "forward" tweeter when the series cap is electrolytic and you replace it with a film cap. Electrolytic caps with small capacitance may have noticible ESR and you may want to compensate for this by increasing the value of the series resistor that is often found in the tweeter path. I'd recommend to measure the ESR of the electrolytic cap so you have an idea what to expect.
I would however expect, that in reasonably good speakers electrolytic caps are only to be found in the woofer path and maybe in the HPF of the midrange path.

I do not have much experience with passive crossovers since I mainly own (vintage) active speakers.

 

[Audiofire]

Since many use a digital player nowadays, there is often EQ software accessible.

 

[nanook]

Since many use a digital player nowadays, there is often EQ software accessible.

Absolutely, and there's no good reason not to make use of it. I'm doing combined room / speaker equalization (speakers are a bit flawed and the positioning in the room is a desaster)

I just wanted to point out, that the tonality might change when replacing electrolytic caps in the crossover (caps that are in the path towards the transducer; caps going towards ground are not critical) with film caps.