Hi All,
Me again!!!! i have 8 Neve preamps that i have always thought worked fine, but as i have been using the API's and nothing else.
Now i've gone back and tested all my Neve 1290's and they all hum?
I have done the usual trawl through the treads and fine a post which seem to specify exactly how to wire the 1290 and have spotted a few mistakes i have made.
I have wired them back up and still getting hum?
my IEC gnd tab is connected and checked to case, i have also checked when i put the top on that this is also becoming part of the circuit.
my toroidal is then connected to IEC and then to an adapted SSL 9k PSU pcb delivering 24v and 48v, i have tested and i'm getting both voltages fine. check!!!
from the other information i have seen and checking the schematic i have connected pin 1 from XLR input to GND on pcb this then connects through 10ohm (i only had a 12ohm) resistor 1W to the IEC gnd connection.
pin 1 on output XLR is disconnected, and the tabs which sometimes are on the XLR sockets are not connected to pin 1.
I have checked and when i remove gnd from PSU pcb and measure from input pin 1 there is no connection to IEC GND.
I have also checked that i am getting 12ohm from input pin1 to IEC GND.
there is still hum? any ideas?
thanks in advance.
regards
Spence.