Original SONTEC EQ MEP 250C Hum noise problem, need help !

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digiteck

Active member
Joined
Jun 12, 2007
Messages
28
Location
Marseille - France
Hi,

i'm new to DIY, and would like to start with DIY project to learn and know some things and be able to make some servicing to my hardware...since it's difficult for me to find a good tech near from me. (I try to collect some infos too about the modification when you use a VCA DBX2001 in a GSSL see in this thread "SSL Clone compressor ratio measurements" http://www.groupdiy.com/index.php?topic=944.140 if you have some other infos.

So i have a Sontec EQ that i bought from Vintage King (USA) they make some servicing since they are old unit, and changed the transfo from 120 V to 220 V. The unit is working great and i'm really happy with it.
I believe Vintage King have good tech, and maybe my unit is ok but i have a small hum noise (start at 50Hz with a "bigger harmonic - volume" at 100 hz...) and it seem to be on the right channel (this is on this side that is the transfo). Maybe is it normal, but i would like if it could be possible to remove this (or reduce).

Maybe i can post later a sample of the noise if it could help...

Thanks,

Lionel
 
If this is the power transformer it's possible the power transformer is inducing the hum. Try turning the transformer a little and see if the hum gets louder or softer. You may need to shield it.
 
pucho812 said:
If this is the power transformer it's possible the power transformer is inducing the hum. Try turning the transformer a little and see if the hum gets louder or softer. You may need to shield it.

Just turning the transfo ? I will try this... I imagine i should disconnect the unit from AC before doing this ?
How can i shield it ? Just put some metal or other around the transfo ?

Thanks,

Lionel
 
digiteck said:
pucho812 said:
If this is the power transformer it's possible the power transformer is inducing the hum. Try turning the transformer a little and see if the hum gets louder or softer. You may need to shield it.

Just turning the transfo ? I will try this... I imagine i should disconnect the unit from AC before doing this ?
How can i shield it ? Just put some metal or other around the transfo ?

Thanks,

Lionel

normally I do this with the unit powered up so I can hear if there is a difference but be careful not to make contact and shock yourself... well you could put metal between the transformer and board if there is space...  Lately for all my DIY stuff I have had the transformer external from the units and it has worked great.
 
pucho812 said:
digiteck said:
pucho812 said:
If this is the power transformer it's possible the power transformer is inducing the hum. Try turning the transformer a little and see if the hum gets louder or softer. You may need to shield it.

Just turning the transfo ? I will try this... I imagine i should disconnect the unit from AC before doing this ?
How can i shield it ? Just put some metal or other around the transfo ?

Thanks,

Lionel

normally I do this with the unit powered up so I can hear if there is a difference but be careful not to make contact and shock yourself... well you could put metal between the transformer and board if there is space...  Lately for all my DIY stuff I have had the transformer external from the units and it has worked great.

Ok i'll check that and let you know.
 
So i can't move the transfo... see the picture but it seem to be well mounted ?

Here is a link to some samples of the Noise Floor (i hope it can help), one in BYPASS the other ON with all gain set to 0dB. I have boosted the files by +24dB...

https://www.yousendit.com/download/YWhQMWZOQ1JOMUEwTVE9PQ

I can hear (something similar to the noise sample) when i put my ear around the unit, so the transfo seem to be noisy(or another components ?), is it normal ?

Thanks,

Lionel

 

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