[sdiy] aging transformer replacement

[harrybissell]

Hi jhno (et al)  comments inline

jhno wrote:

> thanks for the helpful advice; i had not thought to address transformer
> buzz in a direct, mechanical way...
>
> >With older transformers of the open construction kind the coils can get
> >"loose" overtime.
> >A blob of PU construction glue (this stuff expands to fill gaps, a glue
> >cousin of PU foam) or
> >sometimes just some tactically inserted folded paper, usually fixes the
> >problem.
>
> this sounds promising, i'll try a little gorilla glue.
>
> my best theory is that when it heats up, the physical characteristics of
> the transformer are altered such that a resonant mode is exposed. i don't
> think that unusual current is being drawn.

Could be a loose winding or a loose stack in the core. Usually these are dipped
in varnish so getting glue in the right place can be very difficult. You might
try to
homebrew a vaccum system to get all the air out...

>
>
> >See above.  Another,  more likely cause,  is aging electrolytic caps,
> >particularly those large ones in the power supplies.  These seem to be quite
> >a common problem in a lot of equipment.
>
> yeah, but is it typical that they would cause a transformer to start buzzing?

Yes... imho.   The increased ripple current from a leaky or too small (from age)
electrolytic could cause this. Transformer saturation could result (commecial
designs are not KNOWN for being spec'd with lots of margin...) and that would
probably raise the temperature a lot more...

>
>
> >> as an aside, i have bought a few 110 to 110 transformers for isolation and
> >> power conditioning purposes. these have buzzed louder than anything. very
> >> industrial.
> >
> >Oh really?  I can't imagine why that would be,  unless there was some defect
> >in the construction of them.
>
> i think that some industrial transformers, especially the big mothers, just
> buzz and/or hum by nature. they are expected to be installed in places
> where no one is present to be annoyed.
>
> the devices i have seem somewhat common: 'mini-computer' power
> conditioners. at least, common at Quinn's (bay area scrap electronics
> mecca). typically just a big transformer and perhaps a couple of capacitors
> sized to match.

If you see a transformer with caps, for power conditioning... it is probably a
constant voltage (Sola) design. These have a deliberate gap and WILL hum
to beat the band (literally).

All transformers have some amount of magnetostriction (sp?) in the core
material...
magnetize it and it changes shape.  I don't KNOW but I bet the more permeable
materials that would give a smaller core, probably do this even more. More hum...

> at the time i theorized that power problems in our warehouse were causing
> noise and artifacts in my equipment. my current view, however, is that
> whatever the case, an additional isolation stage does not provide any
> advantage. after all, every device already has an isolation transformer - !
>
> i am not sure what difference big capacitors could make.
>
> the more exciting (and possibly, yet more bogus) possibility would be to
> run on 'balanced power' as seen in the audiophile world. manufacturers of
> multi-K$ power conditioners claim noisefloor improvements. i might try it
> sometime, if i can convince myself that a device will not mind receiving
> 120 volts center-tapped (60 per side, ground tied to center).

Be convinced. I'm doing it with a 1300VA custom toroid I had made... It was
expensive
(over $200) but I have had NO problems running my studio from it. HOWEVER don't
mix and match Hot / Neutral power and balanced power of you are asking for
trouble...
in some cases MAJOR LEAGUE trouble...   (I have total control of my personal
studio...
if others can "plug in" you better make plans !!!)

> the audiophile industry has more snake oil and outright con artistry than
> any other i have seen...

It really does work. I think my system benefits more from isolation and a
separate
(yeah Larry... an illegal) ground than from the balanced power itself.  It really
is quieter...
but is it worth the money ???

> >I've actually seen a
> >transformer blow, apparently to protect the fast-blow fuse connected to it
> >from harm.   :)
>
> ah, a design flaw. this circuit should not use a super-fast-blow
> transformer. replace with sort-of-fast or slower coil.

LOL !!!  It is well known that the more expensive, harder to replace component
will
ALWAYS protect the cheap, accessible fuse...

H^) harry