DBX 160a Power transformer

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timtom

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My DBX 160a power transformer started to hum annoyingly. I opened the unit and it's called Billion 26-0240 49/ 95.
It has 3 wires going to the board. I measured 23vac between the center and the outer wires, and 47vac between the two outer wires.
I already recapped the 1000uf smoothing caps.

Is there any replacement available?

On the board the voltages labeled +24/-24V and +15/-15V are ok.
 

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Whoops

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Does it work correctly and the problem is only Acoustic Hum or Buzz?

If that's the case,
remove it and dip it 3 times in varnish, let the varnish impregnate.
Normally the acoustic buzz is gone after that
 

timtom

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Yes it's only acoustic hum or buzz that gets amplified by the housing.
I'll try this out. Otherwise I will replace it with a 2x18v transformer. It should be enough voltage as only the the +24v is used for the leds.
 

scott2000

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Extra current draw can make a transformer noisy as well. Like swapping higher current op amps or maybe even a problem somewhere. Is the power supply set up for using a different secondary voltage like you're planning?
 

Whoops

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Yes it's only acoustic hum or buzz that gets amplified by the housing.
I'll try this out.

Normally that acoustic buzz is the Lams starting to vibrate over time, it starts to happen with some Power transformers with age, where the old varnish just got too dry and breaks.
Impregnate it again is easy and cheap.

if it doesn’t work then that’s also a simple transformer so easy to replace for a new one.

like Scott said excessive current draw can also cause that , plus extra heating, but if you didn’t change anything in the circuit that needs an higher current draw than it’s just normal transformer aging
 
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CJ

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actually low current draw can make the xfmr hum also. especially a no load situation. the secondary is trying to fight the flux of the primary but it has no current to work with and therefore no counter voltage as per Lenz's Law. This causes the flux created by the primary to soar until the core reaches saturation. When the core saturates, it makes noise.

Sometimes the blocking which goes in between the coil and core in the form of some type of shim made of wood or Glastic can develop excess clearance. So if you re-block the coil with a bigger shim, the hum might stop. if no blocking is used, then it might be a matter of the varnish or air dry epoxy no longer gluing the coil to the core.
 

timtom

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Does it work correctly and the problem is only Acoustic Hum or Buzz?

If that's the case,
remove it and dip it 3 times in varnish, let the varnish impregnate.
Normally the acoustic buzz is gone after that
I dipped it in varnish and the noise is gone! Thanks for that advice.
 

Whoops

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I dipped it in varnish and the noise is gone! Thanks for that advice.

Very nice,
I’m happy that it solved the problem.

CJ gave really good advice also,
But if the varnish itself solved it that’s great, I already solved buzzing in a lot of old/aged Power transformers just by dipping it in varnish

best regards
 

CJ

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i just read that lamination buzz happens at 120 Hz in a 60 Hz unit, no wonder they can get loud!

don't know why lam buzz is twice F, now i have something to think about,

just figured it out, thee are two peaks for every cycle, doh on me.
 

Whoops

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With the plague of cheap Switch mode PSUs in consumer stuff I had a lot of 10khz whine at home,
I'm quite sensitive to it and it's just an horrible and irritating noise.

Some of those SMPSU I has able to take out the offending small transformer and dip it in transformer varinish, It doest work all the times but at least around 70% of the times it solved the SMPSU 10khz acoustic noise
 

Tubetec

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Ive cured a few buzzy transformers by simply applying varnish with a brush between the bobbin and core , no need to dismount anything , although you might place some paper or card underneath to catch any drips .
 

CJ

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nice to bake the xfmr at 200 F overnight so you don't huff varnish when it warms up, unless you want a free buzz, not lam buzz but cerebral buzz,
 

rogs

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I had a similar issue with my dbx286s. A low level - but annoying - lamination buzz from the internal supplied transformer. I just replaced it with a suitably specified toroid.
Now totally silent - and runs less hot.
 

Whoops

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Ive cured a few buzzy transformers by simply applying varnish with a brush between the bobbin and core , no need to dismount anything , although you might place some paper or card underneath to catch any drips .

That might work sometimes, but you don't achieve the same level of varnish impregnation as when you dip it in a bowl of varnish and let all the air out.
 

Tubetec

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I suspect as often as not its an outer lam thats buzzing ,not one in the middle of the transformer , if I can save myself time , product, associated 'cerebral buzz' from the thinners and effect a repair good enough for rock n roll I'm winning , if it doesnt work I'd consider dunking , but not before at least trying the five minute fix . If I was to try baking transformers I'd probably do it in my boiler out house sitting them on the top plate of the furnace , that crap doesnt belong anywhere in your indoors.

Did you you ever cook a motor stator to 260 C Whoops ,then get out the cold chissel and lump hammer and cut the windings at one end , then pull the remainders out of the housing with a special pry bar , hells kitchen we used call it, even Ramsay would have shit his pants . I learned a lot from my touch with the industrial , I always knew it was a filthy mess , maybe I just needed a touch of confirmation just to be sure bias wasnt creeping in ,
Upside is any grade of Essex magnet upto mid 30 AWG wire is available off the shelf ,

I'd be happy enough with beexwax for small signal/potted transformers and gold shellac/ethanol based laquer for output/power transformers , it need be no more complicated chemically than that as far as I can see ,
how about a hemp fibre based spacing between sections CJ ,
 

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Whoops

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I use Dolph's AC-43 transformer varnish
It does a pretty good job.
Bought a can some years ago and it's still lasting

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