Fixing the transformer hum in the TX-81z

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Fixing the transformer hum in the TX-81z

Postby Altitude » Sat Feb 20, 2010 2:29 am

I posted this on the DX yahoo group but figured people may be interested here also:

So finally got around to looking at this and am happy to report that the fix is trivial. Per the service notes, all that needs to happen is a metal shield needs to be clamped on top of the transformer. I used 0.016" thick cold rolled steel which is nice and formable but rigid enough to hold it's shape so just bending the flanges in is enough for it to clamp on to the transformer.

The results are perfect. The hum is completely eliminated. I'll bet that this would also be effective for the Matrix 1000 which has the same issue.

Cheers,
Alt

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Re: Fixing the transformer hum in the TX-81z

Postby madtheory » Sat Feb 20, 2010 1:42 pm

Great, thanks for the info!
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Re: Fixing the transformer hum in the TX-81z

Postby ddarmstrong » Sat Jan 31, 2015 8:48 pm

Super advice, works like a charm! Thanks !!

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Re: Fixing the transformer hum in the TX-81z

Postby db0451 » Sun Feb 01, 2015 7:34 pm

Interesting, I remember reading about these sorts of mods before but forgot them. In the meantime I have accumulated several old synths that might benefit from such shielding. But assuming the humming ‘issue’ is purely acoustic (i.e. no risks to user or product lifetimes), it can be bearable – and perhaps an encouraging sign of a genuine retro product. :D
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Re: Fixing the transformer hum in the TX-81z

Postby Knas » Mon Oct 01, 2018 11:37 am

Okay, Ill try to resurrect this tread... I have a noob question regarding this hack.

Is it safe to wrap a metal sheet around the transformer in that way? Arent there electricity going through parts of it?
I have the same hum in my TX81Z transpformer and would like to treat it, but dont want to blow the thing up.
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Re: Fixing the transformer hum in the TX-81z

Postby Mooger5 » Mon Oct 01, 2018 10:57 pm

The current inside a transformer has to flow through insulated windings. If it´s working then it is a sure sign there is no leakage or shorts. The only parts that are exposed (uninsulated) are the windings terminals and those are soldered to the underside of the PCB.
That transformer looks like would benefit from a bell shield. In its absence, the windings despite being electrically insulated still radiate electromagnetic fields that will resonate with the top panel of the chassis and then vibrates at 50 or 60 HZ due to the PCB it´s attached to being rather flexible.
Mu-Metal offers the best magnetic permeability, but if that steel plate works, use it.

A disclaimer should go here: voitages can kill, etc etc. better ask someone who knows what they´re doing to do it for you. A safe bet is to insulate the metal plate itself with packing tape all around...
Herrare umanum est.
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