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You can drain them by shorting their terminals with a high resistance resistor taped to the end of a pencil or something.
I can't speak for other makes, but vintage Marantz & Philips CD players with CDM radial-transports that skip can often do with replacement of the electrolytic caps used in the tracking & focus servo circuits. I think it is the increased ESR of the old caps that is causing issues. A simultaneous service of the disc hold-down bearing is also advised.I know of two reasons to change caps.
1. In older speaker crossovers and electronics - esp. over 30 years old. One replaces or has it done for a classic or beloved piece. When it gets to discrete electronics with lots of coupling caps, signal path caps, power supply caps it can get tight and burning components and lifting pads is possible even for experienced hands.
2. The other reason is sonic improvement or mods and inductors and capacitors can both be improved. Generally film caps and open core inductors get the audiophile nod.
Personally, I will spend for tweeter caps and midrange caps in speakers - upgrading to film caps. For both speakers and amps I'll put a bypass cap (for very high frequencies that if they oscillate can be heard audibly) on the output caps of an amp (.01 uf and high current like 250, 500, 630 v) and the tweeter cap on the speaker. Basically if the value of the tweeter cap is 2.2 uf, then the bypass would be .022 and again high voltage which is cheap at that size. There are sites that rate sound of caps and you can get really crazy with Duelands and silver/oil Mundorphs, etc. As in hundreds of dollars a pop.
Every speaker I upgraded sound clearly better
But well over built amps? nothing really. But I did the bypass to a Yamaha and two Denon recievers from the mid 80's into the early 90's and they jumped in quality. Much quieter and the highs were much more cohesive and smooth.
Interesting details.I can't speak for other makes, but vintage Marantz & Philips CD players with CDM radial-transports that skip can often do with replacement of the electrolytic caps used in the tracking & focus servo circuits. I think it is the increased ESR of the old caps that is causing issues. A simultaneous service of the disc hold-down bearing is also advised.
(but TBH on players that age all electrolytic caps should be replaced by now really)
(Before anyone mentions the lasers; on the older CDM transports they are usually fine. As long as no one has tried to "fix" the player by setting the laser-diode current higher than the standard 50mA, those lasers are veeeeery long-lived. If there is a problem with the actual optical unit, it is more likely to be a failure of one of the ESD-sensitive photodiodes rather than the laser.)