mata_haze

Telefunken V676 question and ANSWER!
« on: November 28, 2006, 03:55:23 PM »
Hi everybody.
I just got a couple of awesome Telefunken V676 to rack up.
bought the rack , built a decent ramped phantom power supply,connected them on and BUM the Phantom power doesn't work.
I tried pretty ,much everything I could but everytime you plug the module in the rack the phantom power supply gets cut off like if there is some sort of short circuit..
I tried connecting the phantom power directly from my U*A*6*1*0 preamp and from a c*h*a*n*d*l*e*r channel which I own, but not luck..the phantom power just dies...
the schematic it's pretty straight forward as there is not much before the input transformer, apart from a line pad + it's own relay: which I disconnected already to prove it's not due to that.
I am lost..the same "fault" on both modules...on both bays and with any kind of phantom power attached to either one of them.no patch bay connected or anything like that that could cause shorts..just the module and the 48V rail..
Does any of you ever come across something like this before???
every help will be much much appreciated!
I attach a schemo



http://img113.imageshack.us/img113/4945/schematicsv676yt9.jpg


Harpo

phantom fault
« Reply #1 on: November 28, 2006, 05:27:30 PM »
Hi,

did you connect your +48V via 2x 6k8 resistors to pin 1 and pin2  :?:
this will limit the current a mic or faulty cable will pull to 14ma.
A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.  -Douglas Adams

martthie_08

Telefunken V676 question and ANSWER!
« Reply #2 on: November 29, 2006, 05:17:12 AM »
how did you do the input wiring on the V676?

I think you'd need to connect XLR in + and - to pins 1 and 2 and then short pins 3 and 4 (not to ground!!) for the input transformer.

cheers, Marten

mata_haze

Telefunken V676 question and ANSWER!
« Reply #3 on: December 01, 2006, 04:50:16 AM »
thank you guys for your replies!!
Harpo:
the phantom power supply it's fine as I use it for 2x V78 and 2xV672, and yes, 2 x 6.8K 1% resistors.

Martthie_08
yes I did it like that.
ground for the audio path abd chassis are not connected.
 
the preamp works fine and passes audio through until you plug the phantom in..from that point something happens and audio still goes through but phantom power gets cut off!
and I have tried to send phantom power with other pieces of equipment (UA 610 and chandler channel) and the same thing happens.
I don't think is due to the panthom power supply..
I am lost as I checked connections 3 times now...

all the best,
Mattia.

mata_haze

Telefunken V676 question and ANSWER!
« Reply #4 on: December 02, 2006, 07:37:13 AM »
great!
I actually got it working by removing the center tap of the input transformer from ground!
martthie_08 was right, i just did not see the reason: floating input...
many thanks guys!

martthie_08

Telefunken V676 question and ANSWER!
« Reply #5 on: December 02, 2006, 10:24:56 AM »
Great news! Nice you got it fixed...  :thumb:


 

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