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Default Prism Orpheus Interface with High Pitched noise and hum from SMPS PSU any help?

Discussion in 'Troubleshooting and Repair' started by Rixsta, Apr 21, 2017.

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  1. Rixsta


    Apr 21, 2017
    Hi all

    Was really hoping someone could help me with the power supply on this lovely device I got second hand. its a high end recording interface but the problem is is there is an awfull high pitched noise that I thinks comming from transformer but not sure.

    Ive done a little vid of the problem

    Ive heard that sometimes capacitors can be at fault causing the transformer to whine like that, my father cant even hear it as the freq are too high!
    I actually overdubbed audio onto the video as the video camera could not pick up the noise

    anyway any help would be appreciated!
  2. Chris Hill

    Chris Hill

    Apr 17, 2017
    It's likely the transformer core is slightly loose or damaged and is vibrating in sympathy with the switching frequency. If that is the case then your only options are a) replace it if you can (could be difficult) or b) live with it. Not sure how capacitors could be causing the problem, unless one has gone short-circuit and is pulling excessive current through the transformer - which can sometimes cause audible noise in my experience. Is the transformer running unexpectedly hot?
    davenn likes this.
  3. Rixsta


    Apr 21, 2017
    Thanks for that, yes I think its the transformer as ive lightly pushed against it and the tone slightly changes. this transformer is going to be hard to find. I suppose i could find out its voltages and see if there are similar avalible but there's a fair few pins on it so a fair few voltages. Looks like I might have to send it to Prism for them to repair it as when I tried to hunt down the transformer they put me onto parts supplier but it lead to dead end, nobody had the parts lol.
    the transformer is not running hot no, so I guess its safe to use like this unless the sound gets a lot worse.

    I did check the main electro capacitors and most 270uf caps read between 205 ish to 230uf. and on the ESR meter they seemed to read the same which was around .04 to .09 ohms. taken on a cheap Chinese meter thing.

    Thanks a lot for the reply :)
  4. tedstruk


    Jan 7, 2012
    I think thats the power caps... but there is only one. so it may be a few of the smaller ones beginning to go. Even when they don't bulge, especially in the power block, they commonly whine. take it to a shop and get their opinion, It isn't a good idea to put any pressure on the transformer, that bends the board under it and with a failing cap, it might damage something else. It also could be a bad connection to the transformer. heck with the right parts, and the proper ability, who knows what it might sound like...
  5. Rixsta


    Apr 21, 2017
    Hey, thanks a lot
    Do you think those capacitors I tested were bad or ? theres a lot of surface mount ones I could not test.
    yeah I didn't realy push transformer much force at all, have checked all the solder joints to transformer and caps and checked the larger caps out of circuit.

    Do you know what Kind of place to take this to ? just general repair person ?
    Im in England btw, I can also send it back to the company who made it but they will charge £250 just to look at it.
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