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.
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re-cap it
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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
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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
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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
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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.
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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
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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
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the 330uf cap that read as 782 is leaky as fuck.
i'm surprised the tester didnt catch that.
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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.
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