Studer 089 MK II input unit problem

[FLM]

Hi,

I have lot of Studer MK II 1.090.017 Input units and faders. And I´m trying to bench test those before racking them.

I´m feeding -20v to pin 10 (my PSU does max 20v.) and sine wave to pins 27-26. Signal stops at input transformer. This is constant with all modules i have tested so far.

Any advice where to look? Can my too low voltages stop the signal completely?

Thanks a lot in advance!

 

[q2audio]

I'm not a Studer expert, but I've worked on a few. You may need to have the relays powered to pass signal. It looks like A6 is the -22V relay (signal) and A5 is it's 0V. Since there is a 22V to 20V regulator, your 20V may not quite be enough to get it working... or it may just pass the 20V unaltered. If the relays are not audibly clicking as you change the input source selector, I think that may be the source of your problem. IIRC either line 1 or line 2 are selected by default. You may be able to change your input feed to the other to see if that works.

Studer has been kind enough to post the schematics on their FTP site which you likely have found. If not, it is here: ftp://ftp.studer.ch/Public/Products/Mixing_Analog/089MkII/Manuals/089MkII_Op_Serv.pdf

Your 1.090.017 module is on page 102.

 

[FLM]

Hi,

Thanks for the great info!

Unfortunately I can´t confirm if that was the problem. Because I build a temporary PSU with the right voltages,  and still got no signal.
And as it turned out problem was signal routing.  Signal did not reach the faders at all with my wiring. Once fixed, everything is working great.  Except of some hum and noise, which I believe are quite easy to get rid of.

Next I have to figure out way to balance the signal and do some work with the housing.