Mic preamp latch off

[plimousse]

Hi,

Mixing desk

On some channels, after powering up, the mics inputs are latched off, to get them started, simply switch On / Off the 48V ... :
I connect signal generator on mic input, we power on the console, no signals are displayed on the meter. We switch On / Off the 48V on this channel, and then the signal is displayed.
I changed the input capacitors, and links capacitors on all relevant channels. We also check the Input connector, and ribbon to the connectors panel.
For some, there is ok, for others the problem remains uncertain ...

Does anyone have an idea ?
Thanks,

 

[radardoug]

You likely have bad contact problems somewhere in the chain. It may actually be after the mike preamp.
A scope is your friend, put it at various points along the chain.
What kind of desk?

 

[gyraf]

And schematic?

 

[plimousse]

Hi all,

Thanks. I have scope and schematic.
It seems that this is due to problems of contacts, either at the XLR or the connectors (HE10) between the rear panel, and channels.

Regards,
Pascal