MANLEY VOXBOX compressor doesn't work

[YannLu]

Hi there,

I have here a Manley Voxbox for repair.
The compressor doesn't work no matter the position of the comp bypass switch.

Without the schematics, where should I look at first ?

Thank you for your help.

Yann
www.yannluaudio.com

 

[gyraf]

You sure?

Voxbox compressor only acts on the mic/instrument-preamp input, so that insert-rerturn and line-direct can't be compressed. There's a signal flow diagram in the user's manual for reference.

Other than that, look for and verify the +/-15V power supply lines for the sidechain control opamps, IC1,2 and 3 that controls the led in the VTL5C2 opto placed at the input of first preamplifier stage.

Jakob E.

 

[YannLu]

Thank you Jakob.
I will check this

 

[YannLu]

Power supplies are all good on the IC's 1-2-3...

 

[YannLu]

I guess there is a problem with the IC3B because there is a very low signal (20mV) on  the PIN 1 (compressor attack in).
Am I correct ?

 

[YannLu]

Problem solved : I replaced the TL074 in the compressor section and it is working now