On 23/08/2015 22:24, Fernando Rodriguez wrote: > On Sunday, August 23, 2015 12:14:58 PM Mick wrote: >> On Sunday 23 Aug 2015 01:11:03 Fernando Rodriguez wrote: >>> On Saturday, August 22, 2015 3:19:50 PM Alan Grimes wrote: >>>> Isn't this the filthiest oscilloscope u've seen recently? >>>> >>>> The only bare metal contact that I could safely use to get a reading off >>>> was a +12v line on a spare PCI-E gpu plug. The ground reference is the >>>> chassis. >>>> >>>> You can see the machine's settings in the photo clearly enough. The >>>> waveform is fairly constant, it stays in this mode most of the time but >>>> sometimes goes into a "low ripple" mode where the ripple falls to +/- >>>> 20mv and holds tight. The scaling indicates the upward spikes are around >>>> 0.120 volts and the downward spikes are about 0.22 volts. This >>>> __SHOULD__ be within the input tolerances of the motherboard's >>>> regulators. >>> >>> Regulators don't filter noise, they introduce it. Capacitors do that as >>> somebody pointed on the other thread. >>> >>> So if you're on a tight budget and you have an electronics surplus store >>> nearby you can replace all the capacitors on your mobo and PSU (except the >>> big bulky ones on the PSU) for about $3. >> >> It is quite likely that only the secondary circuit on the PSU needs to have >> its electrolytic capacitors replaced. We're talking of anything between one >> to half a dozen of capacitors. In all likelihood less than a $1 to $3. If >> any are even slightly domed I'd start with those and spend no more than a > few >> cents. >> >> Primary circuit ceramic capacitors (transient protection) could have been >> affected if the PSU was submitted to high surges in the mains supply. I had >> one go bad on me after sheet lightning hit the area once. Its replacement >> along with a resistor fixed the PSU without any further problems and to much >> of my surprise - I thought it was a gonner! >> >> Domed capacitors on the MoBo is a different story. Quite likely other >> components would have been affected and many of them are surface mounted. >> You'll need a magnifying glass and steady hands for those. It is not >> something I would attempt in haste, as it is easy to damage more components >> than what you fix on a MoBo. YMMV. > > I don't think it's very likely to have damanged something else if it's just > noise, but then again I'm not an electronics engineer, this is just a hobby > of > mine so you may be right. Though I can tell you that I have gotten a few > damaged boards to work like new by just replacing the electrolitic caps.
That's quite normal - electrolytic caps are the only electronic components that can be considered to "wear out". Apart from batteries of course :-) Getting the caps off modern motherboards is a real PITA though - surface mount caps need semi-specialized equipment: a proper soldering iron or hot air pencil with a very fine tip, desolder braid, a magnifier and a very steady hand > >> PS. Noisy PSUs are nothing new. The noise is can be caused by the > capacitors, >> or the coils. Although annoying it does not necessarily mean that there is > an >> electrical problem with the components. If the fan is rattling, then a drop >> of oil on its bearing should soon put a stop to this. As Dale mentioned, a >> stalled fan will not help the longevity of the remaining components. :-) I recall an ancient TV from the mid '70s (Blaupunkt) that would sometimes develop a rattle in one of the drive circuit coils. Damn thing would sound like a hive of bees inside the cabinet! > > Agreed. -- Alan McKinnon [email protected]
