GlennW

Did you find? I have a single unused 206-0117 ADS tweeter. I have been saving it as a spare for my 1090s, but haven't needed yet, so could part with it. PM if desired.

The mid looks ok. Early model used a Braun mid, that is what we see here. Tweeters don't look right.

Congratulations on finding a vintage amplifier that you like. I did a quick Google search - SAE A202 looks very nice. A hum - is this hum that is heard through the speakers? Or hum that comes from the chassis of the amplifier? If hum is from chassis of the amplifier, probably not much can be done. Sometimes transformers have a mechanical vibration that is excited by the magnetic forces of the power conversion of the transformer. Replacing the transformer is a large expense and suitable replacement may be impossible to find. Best solution is having the amplifier behind a door so it cannot be heard. I have two Dynaco Stereo 150 amplifiers, one is dead quiet, the other has this issue. Hum heard through the speakers is one of the most difficult problems to solve. It can come from many causes - design of the grounding scheme, routing of wires, filter capacitors getting old and tired. Converting to dedicated earth AC mains wiring (3 wire AC wiring with ground connection) is primarily a safety consideration. It forces a fuse failure or home wiring circuit breaker trip if there would ever be a short circuit between the AC wiring and the case of the amplifier. With 2 wire connection it is possible that a short circuit between AC mains and chassis can leave the chassis at dangerous AC voltage without causing any fuse or breaker trip - obviously a bad thing. It is not likely that dedicated earth will solve a hum. It may even cause one since it can create a ground loop. It is a safer wiring scheme. Be very careful if you modify the amplifier, this conversion is wiring used at dangerous voltage levels.

Do capacitors need periodic replacement? Depends on the type, and usage. Film capacitors such as are used in your crossovers have extremely long life. Unless operated beyond their rating, they should be fine practically forever. Electrolytic capacitors use a liquid between the foil. This type has more limited life. This life is also dependent on part quality, with well made parts lasting well past ten years, others perhaps not. I have seen failures of old electrolytic capacitors, but never film types. If the parts were stressed by operation beyond rating their life may be shortened. The 63 V rating of your capacitors is approximately the maximum voltage output of an amplifier rated over 100 W / channel. This is a reasonable rating for capacitors used in a speaker network. It is not likely they have been stressed.

I do not recognize the blue cap. All of these are good quality film types. I would not replace them. 63 is the voltage rating, Caps are rated DC, AC rating is same or higher. Rating is testable only by destructive test.