Green pre random noise need help

[Hammond]

Hi All
It has been 5 years since I built my 2 channel green pre, and it worked very well, i love it, thanks Peter
In the mid of a session it started make a random noise on ch 1 only.
Here is the audio file http://www.datafilehost.com/d/6b27e39d
Please can someone direct me where start to look for troubles?
Thanks in advance.

 

[peterc]

Hi Hammond

Noise issues in the Green Pre usually stem from the front end.

So check the diodes, transistors and first opamp in line.

Peter

 

[Hammond]

Hi Peter
Changed first op amp checked for diodes and transistors but they seems to be ok.
i also noticed that switching phantom power on and off has some kind of interaction on the noise itself,
sometimes like triggering it other times like blocking it or nothing at all.
I definitely need help

 

[dmp]

Check that the input xlr pin 1 ground to chassis is solid.

 

[Hammond]

Xlr pin 1 to chassis is ok.
Any other ideas? I've a recording session monday :'(

Thanks in advance

 

[Hammond]

Ok
Changed the 4 diodes and the 2 transistors at the input, first and second opamp, and the two 47u phantom blocking caps.
Same random noise as before, it goes away a copule of minutes then it returns.
Any ideas?

 

[Jidis]

I'm interested to see how this goes. I remember an issue which sounded exactly like your .wav with something I modded way back, but can't remember what fixed it. I'm pretty sure it was my Symetrix 202 pre, but it could have been an ART Tube MP.

Hope you get it sorted,

George