[Angel III]

Thanks for the photo.
Initial assessments can also be made visually. I would say your capacitors are perfectly cylindrical. The 120° slits are clearly visible and engraved (a nice groove). If the amplifier feels warm as usual, I would say lukewarm (you know it well I imagine), this is also an indication that the capacitors are perfect. Old capacitors cause the amplifier to heat up abnormally, therefore causing deformation to the point of raising the slots to 120° (flattening so to speak).

 

[Angel III]

There are all around Jamicons SK: 22uf 50v 3pc, 100uf 10v 2pc and 1000uf 35v 16pc. Do you have different ones?

-Jamicon SK 1000uF 35V 85°C-
After 2000 hours application of W.V. (Working Voltage), and +85°C ripple current value, the capacitor shall meet the following
limits. (DC + ripple peak voltage <= rate working voltage).

It seems like a warning (at 85 °C) rather than an aging of the electrical component.:

 

[sazzz]

1. Although none of the specified parameters are primary, the limits for deterioration of characteristics when they are combined are mentioned. Do you believe that capacitors will stay unchanged until 85C is reached?

2. The operation in these conditions "as new" is not guaranteed, and the indicator for deterioration is limited to 200% but not zero.

3. Not only do I consider the manufacturer's characteristics, but I also draw from my personal experience. After 5-6 years, my active Sven speaker started making noise because the capacitors had completely swollen. Small capacitors in the laboratory power supply reached a normal ESR limit of approximately ten years, and so on.

4. Old equipment doesn't explode due to aging or start to emit acrid black smoke necessarily, it just sounds worse. If this degeneration happens slowly from day to day, it may not be obviously noticeable.

5. The capacitors in a random amplifier could be in excellent condition, it's possible. Maybe not. This depends on the specific capacitor, environment's thermal conditions, gain level used, capacity, closeness to the hot spot and other variables. My preference is to inspect it. If you believe it's not necessary, you can count on their long life. That's perfectly acceptable.

6. Other than that, Jamicons are not considered exceptional for sound and do not have any special characteristics. It may well be that replacing even well-functioning Jamicons with more euphonious capacitors can have a positive effect for sound.

It would be interesting to know if anyone has tried replacing them.

 

[Angel III]

If you replace them it would be interesting to know how much the old capacitors measure. I don't know if you can measure them now that they are soldered onto the board.

Equipment with old generation components (80s, better/worse)? After 20 years of work in metrology, the instrumentation that creates the most problems for us is the current one.

The 80's HP instruments we have, (we don't know how, never repaired) are still high precision instruments today with measurement values and manufacturer tolerances. Instrumentation that is calibrated annually with the current Keisight. They have a lot of components inside them to sell.