Control 24: Preamps not working and Peak leds are lit at all times

[andreconde]

I recently bought a Control 24 and its preamps don't work.

Peak led is always lit red, from the moment I turn the console on.

There's very low signal coming into Pro Tools from the channels I try to record. I mean... I can see very low signal but not hear a thing.

I live in an island in Portugal and there are no techs available. I really need some help to try to sort this out on my own.

PS: If I disconnect TB6 or TB7 (connections for the mic preamps sub-regulator board I believe) from the power supply the Peak leds come to normal (they are not lit anymore) but now there's excessive weird noise from the moment I turn the console on.

PS2: C20 capacitor was already exchanged but nothing changed.

Does anyone have experienced these symptoms before?

I'd be much appreciated for any help.

All the best,
André

[andreconde]

Update:

It seems that the culprit is the sub-regulator board for the preamps.

Disconnecting this board and connecting the rails directly to the PSU puts it to work, with what seems to be a normal noise floor.

On the sub-regulator board, for each harness it reads GRD 10V -10V 10V -2V. This last value seems off to me. When connected directly to the PSU, the last value is -10V.

Does anyone know what's the actual function for this sub-regulator board? Lowering the noise floor for the preamps is my guess but I don't really know.

Will I be damaging the preamp cards running the power directly for the PSU without passing through this sub-regulator board?

To my knowledge, information about this is non-existent on any of Digi's websites.

Btw, the regulators on the sub-regulator board are: 1x LT1963A and 2x LT1175.

LT1963A: http://cds.linear.com/docs/Datasheet/1963afe.pdf
LT1175: http://cds.linear.com/docs/Datasheet/1175ff.pdf

[beecher]

I have the same prob on channels 1-8 but fortunately I don't use the inputs just for a controller. I do have noise in my headphone mix because of this. Were you able to fix the problem? I am thinking of just disconnecting from PSU.