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| LC PSU Line Filter Cap |
Posted by: CompuNurd on 2014-12-08 21:03:32
I am going to start replacing the line filter cap (big round one) in TDK PSUs every time I do a recap.
I see it is rated at 180uF 385WV..?
What is a suitable replacement from Mouser?
I ask because I have no idea what WV is.
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Posted by: MidnightCommando on 2014-12-09 07:33:28
WV = "working voltage" iirc.
As with voltage on any other caps, make sure that the replacement is rated for the same or higher.
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Posted by: CompuNurd on 2014-12-09 10:24:17
The PSUs take 100-240VAC, so why would there be a 385V cap in there? Seems overkill...
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Posted by: rsolberg on 2014-12-09 11:54:30
IIRC, line filter capacitors should be rated for peak, not RMS voltage. Domestic AC power is nominally 120v RMS, but 170v peak to peak. European mains at 230v RMS is approximately 325v peak to peak. (or 340v for 240v RMS 60HZ)
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Posted by: Elfen on 2014-12-10 08:40:12
It is also to handle voltage spikes going into the system. I've seen PSUs go up when the local power lines get a lightning strike, but in going up, they managed to save the motherboards and attached devices to it at their sacrifice.
If it were me and if it were possible, I would put something bigger in there - 400wv or higher.
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Posted by: CompuNurd on 2014-12-10 09:01:29
It will still work even if it is rated at 385VDC instead of 385WV
Aren't they the same thing?
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Posted by: rsolberg on 2014-12-10 18:25:43
WV/ Working Voltage is simply an alternate term for the voltage rating. 385VDC is an equivalent rating to 385WV.
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Posted by: techknight on 2014-12-13 19:14:06
Sorta... the WVDC term was coined back when capacitors commonly needed two voltage ratings. working voltage, and surge voltage.
Working voltage is the maximum allowed voltage the capacitor could sustain continuously without damaging it. The reason this was needed was for vacuum tube circuitry.
in most cases, the 5U4, or 5X3, etc.. rectifier tube would warm up and start to supply DC voltage before the rest of the tubes warmed up. this would cause a surge in B+ current initially, sometimes 150+ volts above the operating voltage, maybe even more. An example would be a 350VDC B+ power supply initially starting off as 500V or more before quickly falling down to the correct operating range.
Then the rest of the tubes would begin to warm up, and draw current. This would overcome the resistance and losses in the power transformer, allowing the B+ voltage to fall. in safe ranges.
Todays capacitors are not rated for this. they just have a working voltage. So they are now relabeled as just VDC, or VAC. So when recapping vintage gear, you want to overrate the capacitors past the surge voltage.
Before you ask, yes.. vacuum tube technology was in and gone way before my time, but I still understand alot about the technology behind it as I do service the stuff from time to time. Also its hard to understand todays technology without knowing the roots behind it, and where it all came from.
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