A word about bad Electrolytic Capacitors:
Capacitors are of a series of components that are frequently used in electronic devices where AC and DC voltages are present. They are often used to filter the DC supply voltages for a clean DC supply that the device can use. Aluminum electrolytic capacitors use a wet dialectric that after time dries out and/or leaks. As a result, the capacitor loses its ability to filter and often becomes resistive. This leads to heat being created by the device which, in turn, adds to the drying out of the device which again leads to more heat. Eventually the device will fail completely.
Sometimes the device will "open" when it fails, in which case no filtering is being done and the usual result is a circuit that is supposed to run on DC now running on AC (not good). The other result is when the device "shorts" and this can lead to fire or damaged circuit boards and wiring (also not good).
Look for "bloated" capacitors, where the "X" on the top of the part is puffed outward or even cracked open. Also look for discoloration or a leak of the electrolytic fluid around the base of the cap, or in the "X" on the top. Also look for the obvious heat damage or shrunken sleeve.
Typical symptoms of bad capacitors in Marantz recivers include long (or short) speaker protection relay wait, audible hum in output, weak bottom end in audio, strange cracking and popping. I recommend low ESR, hi-temp electrolytic capacitors be used when recapping your Marantz. I also recommend removing the tantalum caps and replacing them with foil or monolithics for better fire security--not to mention better sound. Here is a good source for parts: Mouser
For more info on electrolytic capacitors, go here.
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