Newbie help! Why is my input/output device squealing?! - Page 1
Forum section: electronics / beginners

author: nipplecripple
author_rank: Newbie
timestamp: January 16, 2014, 12:14:37 am
content: Hi everyone, I'm an electronics student, pretty new to it, but getting to the point my audio input/output device isn't happy....After what I think was possibly a power cut earlier in the year, my M-audio profire 2626 decided to get ill and i'm attempting to seek out the problem.My question is why is it squealing!? When its working normally, it does not do this. I'm having trouble locating the noise but its coming from around the power switch or the surface mounted coiltronics transformer. It just so happens the two are close to each other. The power switch itself gets rather hot when its been powered on for a little while which I don't think is good....I have a suspicion a capacitor has failed.I've taken a short video. My apologies for the quiet audio.Any help regarding this high pitched squeal would be greatly appreciated!Thanks!

author: AlfBaz
author_rank: Super Contributor
timestamp: January 16, 2014, 12:17:25 am
content: Quote from: nipplecripple on January 16, 2014, 12:14:37 amNo need to apologise unless you decide to share it

author: nipplecripple
author_rank: Newbie
timestamp: January 16, 2014, 08:44:52 am
content: I knew I forgot to do something!D'oh!

author: NadAngel
author_rank: Contributor
timestamp: January 16, 2014, 10:14:19 am
content: Inductors and transformers can generate audible noise due to electromagnetic forces generated by frequencies in the audible range - magnetostriction. This can also happen in ceramic capacitors where this phenomenon is called piezoelectric effect. My inductors usually buzz when I saturate their cores, and the ceramic capacitors when the ripple current is too high. I would first check the electrolytic capacitors and work from there.

author: AlfBaz
author_rank: Super Contributor
timestamp: January 16, 2014, 10:33:34 am
content: Is it just my hearing or does the sound subside towards the end of the clip

author: Greg Robinson
author_rank: Regular Contributor
timestamp: January 16, 2014, 10:52:49 am
content: Is the product otherwise functioning correctly?

author: poorchava
author_rank: Super Contributor
timestamp: January 16, 2014, 11:34:31 am
content: It's hard to tell without knowing the exact topology of that power supply (I'm assuming it's switch mode). In general inductors squeek if you drive them at audible frequencies (say, less than 20kHz) or when your frequency is correct, but it's high power and subharmonic components are strong enough to be heard by human eye.If In had name possible problems, I'd say:-secondary winding going into short / converter overloaded-input capacitors degreded resulting in high input ripple-output capacitors degraded resulting in high currents flowing-control circuit manfunction causing switching frequency shift. Mostly found in non-constant frequency topologies-physical damage to the transformer (like a hairline crack in the core)

author: nipplecripple
author_rank: Newbie
timestamp: January 16, 2014, 05:35:13 pm
content: Quote from: AlfBaz on January 16, 2014, 10:33:34 amAs I press the switch so its fully depressed, it has a few mm from being fully depressed to where it latches to the 'on' position, it seems that the audible noise goes lower in frequency a little when its fully depressed.

author: nipplecripple
author_rank: Newbie
timestamp: January 16, 2014, 05:37:34 pm
content: Quote from: Greg Robinson on January 16, 2014, 10:52:49 amYes it works but the performance is incredibly poor, massive loss in volume from my audio monitors compared with its nominal function.

author: nipplecripple
author_rank: Newbie
timestamp: January 16, 2014, 05:50:18 pm
content: Many thanks for the replies guys!I'm concerned about the heat coming off the switch itself, so going to investigate that and the electrolytic's local to it, all the caps look ok from the top it seems.How would you go about testing an electrolytic cap without removing it? Is it as simple as testing to see if theres any continuity between the two terminals?Thanks again!

author: ResR
author_rank: Regular Contributor
timestamp: January 16, 2014, 06:31:38 pm
content: ...strong enough to be heard by human eye.Best laugh this week, thanks poorchava.About the topic: capacitors needs to be desoldered before testing electrically due to various other electronics (diodes, power led, various bits and pieces) interfere the measurements, but if it has a bulging in it, then it needs to be replaced. Keep in mind that capacitance and voltage same or little higher than old one has, never lower, low ESR type capacitors needs to be used in this type of power supply, the regular ones don't work well. Problem with measuring continuity is that with most common failure mode the capacitors equivalent series resistance (ESR) gets higher, but the capacitance is same throughout.

author: Greg Robinson
author_rank: Regular Contributor
timestamp: January 16, 2014, 06:43:34 pm
content: Quote from: ResR on January 16, 2014, 06:31:38 pmIn circuit esr testers are common, that operate below Vbe thresholds. They don't work in all circumstances, but they should work here.

author: nipplecripple
author_rank: Newbie
timestamp: January 19, 2014, 06:24:23 pm
content: Thanks for all the help everyone! Though I've fixed the problem and now have a working device I'm going to go and build an ESR meter as they seem pretty handy things to have kicking about.The problem was the simple power switch. I have no clue what happened but I removed it from the board, jumped it with some wires and voila, starts working again. Its just a simple mechanical DPDT switch and for whatever reason broke.Anyway, thanks again!

author: Neilm
author_rank: Super Contributor
timestamp: January 19, 2014, 09:13:49 pm
content: Does the switch actually switch the mains? If so it could be breakdown arcs within it. That would explain both the heat and the noise

author: nipplecripple
author_rank: Newbie
timestamp: January 23, 2014, 08:56:29 am
content: Negative. it's just switching on 12v 3.5amps or there abouts from the wall wart.

author: EvilGeniusSkis
author_rank: Regular Contributor
timestamp: February 12, 2014, 03:10:50 am
content: Quote from: nipplecripple on January 16, 2014, 08:44:52 amA: turn your phone to landscapeB: it sounds like one of those big external camera flashes charging up

author: Kingjamesnf
author_rank: Newbie
timestamp: April 07, 2016, 12:22:43 am
content: I know it's been a while since this was posted this, but would you mind elaborating on how you repaired this issue? I'm not sure looking at the switch how you bypassed it. I'm unfortunately dealing with the same exact issue with the same piece of equipment. Thanks much!Quote from: nipplecripple on January 19, 2014, 06:24:23 pm