[sdiy] Fixing humming transformers in 1u rack units

[Altitude]

Nope, nothing is connected electrically to the shield (I check for shorts to
everything with a meter btw).  I have heard people dampening the vibration
mechanically like MTG mentions but this fix was in the Tx-81z service notes
specifically to "prevent vibration due to leak magnetic flux" and definitely
does the trick..

-----Original Message-----
From: cheater cheater [mailto:cheater00 at gmail.com] 
Sent: Saturday, February 20, 2010 9:03 AM
To: Altitude
Cc: synth diy
Subject: Re: [sdiy] Fixing humming transformers in 1u rack units

Very interesting. I always thought it was a problem internal to the
transformer. Someone even mentioned to me that it could be because of
the lacquer used..

I'll make sure to try this stuff out.

Did you have to ground the steel cap? Did you need to isolate it from
the transformer?

The hum on the M1000 is really terrible, you're right.

D.

On Sat, Feb 20, 2010 at 14:38, Altitude <altitude at optrand.com> wrote:
> Pardon me if this is common knowledge but for me it was quite a
revelation:
>
> I have/had a couple of rack units that have a hum when turned on (M1000
and
> Tx-81z specifically) which is rather irritating.  Some quick research
> revealed that this is caused by magnetic flux from the transformer
vibrating
> the top of the case and the general solution I could find was a vague
"cover
> it with something". So finally got around to looking at this on my TX and
> per the Tx-81z service notes which has a diagram of the fix, 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 its shape so just bending the flanges in is enough for it
to
> clamp on to the transformer.  Not sure if aluminum would work or not, the
> steel works great.  The trafo is conformal coated so it is not
electrically
> connected to anything.
>
> The results are perfect. The hum is completely eliminated. I wish I tried
> this earlier when I still had my Martrix 1000.
>
> Pics:
>
> http://midiot.net/TX_side1.jpg
> http://midiot.net/TX_side2.jpg
> http://midiot.net/TX_top.jpg
>
>
> Cheers,
> Alt
>
>
>
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