Humming

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Jorgitox

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Joined 2006
#1
Hi!

I just have bought an old ELECTROCOMPANIET AW250 power amp, which uses a 1.200Va massive toroid. Well, when connecting, appears a "hum" sited inside the amplifier, not through the speakers (mechanical humming). Well, the toroid rests directly over the chassis, as seen in the following pic:
An externally hosted image should be here but it was not working when we last tested it.


The hum within is a constant 50Hz noise, mostly negligible when listening, but if you get concentrated, the noise is there, so now it's inside my head :smash:.

Well, somebody know any grandmo trick do minimize this mechanical noise? I have heard that using a kind of hule/rubber between the toroid and the chassis could make this noise sensation ends.

Best wishes,

Jorge.
 
#7
Hi, Andrew; thanks for your reply.

I think it's something within the power amp, because that hum doesn't appear in my Vincent SP-991 Plus mono power amps (each one got a 1.500Va power toroid, but fully covered to avoid humming, I think), neither in other amplifiers. Do you still think that could be caused due to DC passing through the trafo?

Thanks in advance,

Jorge.
 
#8
Mechanical hum/vibration can be due to any resonance brought on by the mains frequency.
Some toroids seem to be tolerant of DC on the mains and others hum badly.
The clue can be that the mechanical hum varies at different times of the day when other industrial loads are on/off.
 
#9
AndrewT said:
Mechanical hum/vibration can be due to any resonance brought on by the mains frequency.
Some toroids seem to be tolerant of DC on the mains and others hum badly.
The clue can be that the mechanical hum varies at different times of the day when other industrial loads are on/off.
Click to expand...

It is said that toroids don't use to be noisy, but reality, sometimes, says the opposite.

I was said that depending on the time of the day, the humming can volume up or down, but I just listen the same 50Hz desgasting noise up there. Maybe by isolating the toroid using silicon?

I really don't know what to do, but the only things I think that can end up the problem are or a silent toroid change or by isolating the toroid from the chassis. What do you think about?
 
#12
Perdonado, Jacco (very good Spanish!).

Yes, the 250-R model got two toroids, but one over the other. Sorry, but I was wrong when I stated it (the new model is balanced and using a dual mono configuration).

No, I haven't tried any movement in it, but I have screwed the toroid's screw tightly and the noise is still there :smash:

I will try a little movement as you have mentioned.

Pd.: Me alegra que te gusten las chicas 🙂
 
#13
Puedo preguntar que transistores fiertes utiliza el 250r ?
Click to expand...

I do know the ones used in my old 250, but the new ones used in the "R" design, sorry. An electronic technician friend of mine told me that he preffers the ones used in the first edition (apart from everything else) in instead of the ones used in the modern and fashionable "R".
 
#15
jacco vermeulen said:
With two toroids on top of eachother, sometimes it helps to turn one a bit, don't ask me why.
The very first 250 edition had Toshiba RETs, those weren't avaialable very long.

Seguro ? Me gustan los mas grandes.
Click to expand...

I never heard of stop humming by moving the toroid, but there are many paths to go across... I will try, Jacco. I am also reading on the Internet the neopren isolation option, described by Jaycee some posts before.

I got the full schematics of my model, but neither the new one. ECI refuses to gift their information, that is why it is almost impossible catch information about their amplifier's guts.

Repito, muy buen español... ¿has vivido en algún país hispanoparlante?

Saludos,
Jorge.
 
#18
Jorgitox said:
That's nice!
Click to expand...

Yeah, especially when they cook for you, even tripa en estilo Catalunian tastes good.
Think i hate Dutch food even more than Manuel does.

A DC filter on the input is a good suggestion, lots of schematics have been posted here. The humming was a familiar problem of the 250DMB, S/N figure of the first model was not spectacular either.
 
#19
jacco vermeulen said:


Yeah, especially when they cook for you, even tripa en estilo Catalunian tastes good. Think i hate Dutch food even more than Manuel does.
Click to expand...


All in all, Spanish food is very well considered outside Country's frontiers. I really love Spanish food over other Countries I have ever been, but maybe I am not objective enough to say that 😎




jacco vermeulen said:

A DC filter on the input is a good suggestion, lots of schematics have been posted here. The humming was a familiar problem of the 250DMB, S/N figure of the first model was not spectacular either.
Click to expand...

I have bought this one, but I have not installed it yet:

product3-s.jpg


I also didn't know that this problem was usual in the old 250 models, but if you check the way the trafo is located within the chassis, everything takes sense.
 
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