A vintage 1980's PC power supply has started making a hissing and whining/squealing noise and the PC is now giving random errors like memory and video etc. Ive tried the PSU with just the Motherboard plugged in and its quiet but soon as I increase the load adding controller interface cards and drives etc, the noise starts. I think there is something about to fail but cannot see anything like a bulging cap or anything. Does anyone know whats the most likely suspect component? Here is a link to a video i took.
-
re-cap it
-
Thanks STJ, i was going to do that but just wondered if there was anything else that could make that noise. Will i need to replace those 2 large cans as well.Comment
-
coil noise is often caused by the psu running at the wrong frequency or being overloaded.
small caps can effect the pwm circuit.
*and warn people that your video is 150M in size
Comment
-
Thanks Stj, thats what i thought i had heard before that a whining noise was a coil or something. Thats interesting i signifies there is somethings not right. Ok will get all those caps changed. Thanks you thats a great help .Comment
-
When you do the re-cap, be aware that using the latest and greatest low impedance electrolytics could cause stability problems. I would suggest Nichicon PJ or PS series if either is available, and as second choices, PM or PW series.PeteS in CA
Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
****************************
To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
****************************Comment
-
I took all the electrolytic caps out of my PSU today and what a hard job it wad getting the 2 big 200v ones out as they were glued in good and proper. Well just out of interest i tried each one on my component tester and this are the results.. not sure what is a bad ESR etc so do any look like they are bad?
PSU Caps tested
==============
16v 3300 x2 off (C27+29)
(1) Measures: 307.4 uf
Vloss: 1.8
ESR: 0.06 ohm
(2) Measures: 3020uf
Vloss:1.6
ESR: 0.08 ohm
16v 47uf (C35)
Measures: 46.87
Voss: 2.1
ESR: 1.0ohm
200wv 680uf x2off
(1) measures: 602.5uf
Vloss: 0.6
ESR: 0.8
(2) Measures: 606.2UF
Vloss: 0.9
ESR: 0.8
16v 330uf x3 off (C21 + C24 + 30)
(1) Measures 281.9uf
Vloss: 2.1
ESR: 0.20ohm
(2) Measures: 792.6uf
Vloss: 1.9
ESR: 0.23ohms
(3) measured 282.6uf
Vloss: 1.9
ESR: 0.22ohm
16v 1000uf (C31)
Measures: 850.8uf
Vloss:1.9
ESR: .12 ohms
Comment
-
the 330uf cap that read as 782 is leaky as fuck.
i'm surprised the tester didnt catch that.
Comment
-
having difficulty finding capacitors of the series like you recommenced,. The two Big 200v 680uf nichicon caps in this PSU are marked PS(M) which google states "PS(M) is a series of polarized aluminum electrolytic capacitors with a P for polarized, S for a series designation, and (M) for a tolerance rating of ±20%., These are general-purpose capacitors designed for a wide range of applications" is this correct because I too think they should be long life type. if I can find some. Id there a special marking or prefix number that identifies this series of caps.Comment
-
I can see now Nichicon Caps beginning UP? denotes P series thanks and EL? is snap in type. Still hard to find a Nichicon Cap like you recommend. Does it matter that I use a snap in mounting type or how critical is the size? If for say I can find a P series cap but its a leaded type and a bit smaller than the original size would this matter? Also what is an acceptable impedance range?Last edited by roadrash; 11-30-2025, 06:46 AM.Comment
-
You can leave the big 200V caps alone, as in, not buy new ones. The old ones measure fine and won't give you issues. On non-APFC PSUs, those large HV caps almost never fail. So save yourself the money and hassle with trying to replace those. From your list of the caps that you posted above, the one 3300 uF (C27) cap that measures 307.4 uF is definitely bad... unless that was a typo as well?? Is that all of the caps in the PSU? I suspect there should be lots more small ones... and usually these are the ones to fail "silently" (ironic, given the PSU's symptoms, isn't it
) without bulging or leaking. So it might be worthwhile to check all of the small caps, especially ones near heatsinks or other large/hot power components. While at it, check the solder joints in the PSU too. Also, how are the motherboard caps? Any suspicious brands to beware of on there? Just asking, because I don't like to jump to the conclusion that the PSU is causing the issues here... at least not without confirming that the issues do go away with another PSU.
Comment
-
Hi all,
I am working on a sound processor, it tends to overheat so I fitted a fan inside. The fan is connected to the +15V of the PSU via a DC-DC converter based on the LM2596 to reduce the voltage to around 10.5V.
Unfortunately the analogue circuitry is picking up the noise from the fan in two ways:
1. The fan is close to the analogue section, the motor itself gets into the outputs so I'll have to move it somewhere else
2. Even with the fan running outside of the case, there is still some noise which is clearly going back to the processor via power line.... -
Surprisingly enough, this receiver doesn't have the DSP chip issue. The HDMI board does not get hot, and sound over HDMI works fine.
Regardless of the input, the right channel has noise that is clearly noticeable even on average volume level. The only cases when there's no noise is when VCR input is selected (some tracks on the board are damaged, maybe that's why), or if HDMI input is selected but nothing plugged into it. In all other cases, even when no input is connected I still have the noise.
There's some logic behind it. As soon as I select an input I get only left...04-23-2025, 10:09 PM -
Hi guys
I have a DynAudio DBM50 here - it makes a loud hissing noise.
It sounds just like an FM radio with no antenna (or tuned off-station). The volume of the hissing fades up and down, sometimes drops to almost nothing then comes back loud. It occasionally makes a loud bump noise too.
It does this even with nothing connected to the audio input XLR
Any suggestions?... -
Hello
I have since a long time a Philips HTS8010S/01 which has been old but was doing the job.
Since a few days, it starts by making a weird "static" nois when switches on for a few seconds to a minute and then works like a charm.
Noise loudly outputs from the 3 channels, even if no signal is sent by the controler.DVD to the subwoofer/amp unit.
I was thinking of a soldering that was starting to be damaged and that was only doing the job after a few seconds of heating, most probbaly on the power board
Removed each of tyhe boards
...02-08-2025, 08:22 AM -
Hello there, got a Thinkpad E15 on the bench, almost no vital signs. Only things: Power button white LED flashes several times when USB-PD gets connected (number of flashes varies from three up to twelve times, sometimes no reaction at all). Battery charge indicator LED stays orange. Most interesting is hissing / whining sound from Battery Charge Controller IC BQ25710 on the keyboard side of the main pcb. Board fuses tested and intact, no shorts found so far. BQ25710 is also the only thing on the board to become warm in thermal image (below 70 °C). Thanks for any hint.
Comment