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Recapping: ESR values much better...before?

bass3d

bass3d

New Member
Hi everybody,
I decided to recap and re-trimmer my old but perfectly working Pioneer SA 7800 integrated amplifier (1979)
I have an ESR meter that I used to check old and new capacitors. No electrolitic seemed off, to the contrary, they measured exceptionally low values of resistance (@100Khz), well below the acceptable maximum values.
Today I started replacing the old caps with the new ones (Nichicon) . For all the substitutes I chose a Mauser codes list found here in AK.
Quite surprisingly, all the new caps have ESR values at least double than the original ones.
Am I missing something?

Thanks in advance.
Stefano
Italy
 
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Welcome to AK
Last years restoration of a Sansui AU888 showed all its caps still good, this one is even older than yours. In this amp, caps have an easy life because it is overrated for amount of iron/cooling versus power.

But I have seen bad capacitors too, several in my Pioneer SA8100

Renewing the caps does not guarantee the sound is better, also, many times expectation bias may be in control.

The "Am I missing something" experience is quite normal to me :)
 
You need to check leakage, esr and value of old caps. You can't check for value if the cap is leaking. You also have to test leakage at the capacitors rated voltage, which most modern testers can't.
As for new caps esr vs old caps esr. Modern caps are rated at a lower esr than these old caps when new. The results you're getting make me doubt your testing equipment. Also we (most members) tend to up the voltage when recapping, are you using the exact same values?
Mr. Carlson Lab, on youtube, always talks about leakage. He will show the value of an old cap at it's rating or higher but then he shows just how leaky that old cap is and then compares it to a new one. The difference is always startling.
For the other comment, we change caps not only to bring the sound back to specs but also to protect the equipment. Old caps have a tendency to draw more current and by drawing more current they make other components heat up which will shorten their live span or they will just burn up. A lot of these other components can be replaced but there are components that don't have a replacement and the gear will never work again. Expensive turntables that are waiting for a used replacement IC, an amp with non functioning FETs or an FM section that no longer works are just a few examples.
 
Please check out this video about ESR and caps. Start at minute 17:30.

Capacitors are some of the hardest electronic components to test. There is no perfect tester or method. If anything, using several methods together paints a better picture.
 
Thank you all for the replies. Measures have to be always judged with wisdom, I know.
The only thing that surprised me was the fact that every new capacitor I was replacing had at least twice the esr of the caps being replaced.
I understand that there may be an error in the esr meter I own, this one, but the tendency is clear, and opposite to what I thought it was reasonable.
I was also rather surprised to find, before getting the new set of condensers, that the old ones had a very very low esr, far below maximum acceptabe values.
I respected the original values, just maximum working temps are higher 105C instead of 85C
Anyhow...this afternoon I'll turn the power on...finger crossed.
Have a nice day.
Thank you
Stefano
ITALY
 
You may find that the ESR value of the new capacitors will go down substantially after they are put in service for a while ("reform"). I still believe that most of the time a total recap of a unit is an exercise in futility. Everyone will say that "The thing sounds so much better after the recap", but I think the "Placebo Effect" is very strong if you just went through the work to replace 68+++ capacitors. I troubleshoot devices, and replace defective components. Capacitors do fail, but I replace about 10 times as many noisy semiconductors as bad capacitors. I suspect some on this forum would "recap" a two year old Krell amplifier:)
 
I have noticed that a lot of caps from say 1975 to 1980 actually test better in ESR than brand new caps. I have also found a cap in a PowerSupply that tested great but once I replaced it the bloated bass and distortion I was hearing went away. Testing caps with a nice meter that tests for DF and ESR has helped me find plenty of bad caps but it is not perfect because some bad caps can handle the 1volt the meter sends just fine but not the 45v or 1amp of current it sees in the actual circuit.
 
The Sencore LC53, meter good for capacitance (200000MFD), leakage (600VAC). LC73 will do ESR readings also.
 
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