Adding Ferrite to modern replacement PSU

[Tz_Amiga]

Hi to all,

A few years ago I bought a few of the modern switching power supplies for my A1200's from a seller in Poland. I've not been able to make use of them however due to the terrible amount of high frequency noise they produce (see the attached photo of the A1200 running the Coma demo). I'd like to try adding a ferrite to eliminate the noise. Does anyone know if the type that clip around the cable would be sufficient? I seem to recall reading some info in the past that such switching power supplies producing high frequency noise need a pretty large ferrite and perhaps coiled around the ring type? I'm hoping that the clip-on type such as the ones you commonly see on laptop power supplies will be sufficent as coiling the cable through a large ring would be pretty ugly and also would lose a lot of its length.

[r.cade]

I don't think ferrite will fix it, but you could try and see. The problem here is lack of proper HF filters. It should never have been sold this way.

[pandy71]

Originally Posted by Tz_Amiga

Hi to all,

A few years ago I bought a few of the modern switching power supplies for my A1200's from a seller in Poland. I've not been able to make use of them however due to the terrible amount of high frequency noise they produce (see the attached photo of the A1200 running the Coma demo).

And what seller says? Did you checked quality of power in this PSU? Noise and ripple? Obviously something is wrong but this can be bad PSU or incorrect wiring (like poor contact, poor grounding etc).
Ask seller for support. Assumption is your A1200 was recapped properly so it is not problem on your side.

[Tz_Amiga]

Originally Posted by r.cade

I don't think ferrite will fix it, but you could try and see. The problem here is lack of proper HF filters. It should never have been sold this way.

Ah ok probably not worth trying the ferrite then. I guess perhaps I can look into modifying them.

Originally Posted by pandy71

And what seller says? Did you checked quality of power in this PSU? Noise and ripple? Obviously something is wrong but this can be bad PSU or incorrect wiring (like poor contact, poor grounding etc).
Ask seller for support. Assumption is your A1200 was recapped properly so it is not problem on your side.

Sadly not, it is unfortunately the PSU's themselves that are just poorly designed. I checked out all 3 of them on 3 different A1200's, one of which has not been recapped and they all have the same result with these PSU's. I don't have a scope unfortunately to look into the output.



I have an AT power supply for my main A1200 which is fine and also have my 90's towered 060 A1200. I intended to give one of them to my brother for his A1200 which now has a pistorm installed so it'd be good to resolve the noise.



The seller said at the time something lame along the lines of "we can't make power supplies with the same standards today".

[idrougge]

Please mention the seller and the model so the rest of us know what to look out for.

[Thorham]

Originally Posted by Tz_Amiga

The seller said at the time something lame along the lines of "we can't make power supplies with the same standards today".

Are they serious? Just wow

[pandy71]

Originally Posted by Tz_Amiga

Sadly not, it is unfortunately the PSU's themselves that are just poorly designed. I checked out all 3 of them on 3 different A1200's, one of which has not been recapped and they all have the same result with these PSU's. I don't have a scope unfortunately to look into the output.

Scope will be very useful but using some capacitive coupling to remove DC and some truerms capable multimeter you could at least try to verify noise and ripple level.

Originally Posted by Tz_Amiga

I have an AT power supply for my main A1200 which is fine and also have my 90's towered 060 A1200. I intended to give one of them to my brother for his A1200 which now has a pistorm installed so it'd be good to resolve the noise.

Then it looks like PSU issue - perhaps capacitors need to be replaced in output filter.

Originally Posted by Tz_Amiga

The seller said at the time something lame along the lines of "we can't make power supplies with the same standards today".

Indeed this is very lame - i assume after few years they are no longer on warranty but still - seller could at least try to support you on the ways how to mitigate problem (as my impression not only you being affected by such problem).

I would inspect visually PSU and search for capacitors issues...