48 volt on 82e33 card

[skipburrows]

Hi all,
I am doing a service call at the end of this week and have a question.
In a later g series desk there is not any 48 volt on the listen mic. The amp works fine with a dynamic so the circuit is functioning well. In looking at the schematics, I see that there is r12 that is a 1k resistor for the 48 volt on pin 47 or 45. Is it common for ssl not to stuff this resistor? Or could there be another reason the 48 isn’t there for that listen mic. Also if I do get the 48 volt working and someone patches in  an output from an effect unit or a protools hd output, couldn’t that damage the sending device? Most caps on differential outputs are only 25 volts.. thanks  for the advice … love this place..
Cheers
Skip.

[amillar]

Hi,

As far as I know there's no design / build reason why the 48V shouldn't be there, but there's always a chance that the card's been modified later. Or the resistor's burned out, or the cap's gone s/c, or, or, or etc.... Fortunately should be a very easy fix!

On your second point, good point. IF it's a properly balanced feed it may not be an issue, if it's an unbalanced feed you're right it's not going to be too good for the feeding equipment - when the 651 was designed it was never dreamed that someone would do that! So you may find that somebody has removed R12 (or cut the link from pin 45 to 24 and 39 on the 651 backplane if I've got that right?) for exactly that reason.

I guess you possibly could rewire the listen cut switches (pull on the pot) as listen 48V on/off switches???

Good luck!

Andy

[skipburrows]

Hey Andy,
Thanks.. I’ll get into it on Friday.. I’ll report back and let everyone know what was wrong..
The console has been in use for many years however until recently they never used the listen mic system..
Thanks for everything…
Cheers