Newbie help! Why is my input/output device squealing?!

[nipplecripple]

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!

[AlfBaz]

I've taken a short video. My apologies for the quiet audio.

No need to apologise unless you decide to share it

[nipplecripple]

I knew I forgot to do something!



D'oh!

[NadAngel]

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.

[AlfBaz]

Is it just my hearing or does the sound subside towards the end of the clip

[Greg Robinson]

Is the product otherwise functioning correctly?

[poorchava]

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)

[nipplecripple]

Is it just my hearing or does the sound subside towards the end of the clip

As 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.

[nipplecripple]

Is the product otherwise functioning correctly?

Yes it works but the performance is incredibly poor, massive loss in volume from my audio monitors compared with its nominal function.

[nipplecripple]

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! 

[ResR]

...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.

[Greg Robinson]

capacitors needs to be desoldered before testing

In circuit esr testers are common, that operate below Vbe thresholds. They don't work in all circumstances, but they should work here.

[nipplecripple]

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!

[Neilm]

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

[nipplecripple]

Negative. it's just switching on 12v 3.5amps or there abouts from the wall wart.

[EvilGeniusSkis]

I knew I forgot to do something!



D'oh!

A: turn your phone to landscape
B: it sounds like one of those big external camera flashes charging up

[Kingjamesnf]

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!

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!