FCS-920 Buzzes
vacosound
Posts: 4
Anyone read this anymore?
I have a FCS-926 Vari-curve and a FCS-920 Slave unit installed in a club system. The Master unit works great but the Slave unit has a buzz. I've tried ground lifting at different points and using a/c ground lifts as well. I've had no luck though. The slave unit uses the same snake and the a/c outlet as the Master unit too. The buzz does go away when I disconnect the input to the Slave from the snake's stage box, but not if I disconnect the send from the other end of the snake. All cables and the snake test good with my cable tester.
Here's the biggest puzzling part. If I keep the Master unit in the amp rack and move the Slave unit to the FOH effects rack the buzz goes away.
Yesterday I was reading the manual online and came across the bit about the 0v/Chassis link inside the units. I checked the Master and it is connected but I couldn't find this link in the Slave unit. Was it left out of Issue 6 pcb? I found a LK12 on the pcb with no jumper but seems to show continuity on my meter even without the link.
Some people thought maybe it was too close to the amps but I moved it 10 from them and it still buzzes.
Any ideas what could be wrong? I might even be interested in sending it to a repair center to get this figured out.
I have a FCS-926 Vari-curve and a FCS-920 Slave unit installed in a club system. The Master unit works great but the Slave unit has a buzz. I've tried ground lifting at different points and using a/c ground lifts as well. I've had no luck though. The slave unit uses the same snake and the a/c outlet as the Master unit too. The buzz does go away when I disconnect the input to the Slave from the snake's stage box, but not if I disconnect the send from the other end of the snake. All cables and the snake test good with my cable tester.
Here's the biggest puzzling part. If I keep the Master unit in the amp rack and move the Slave unit to the FOH effects rack the buzz goes away.
Yesterday I was reading the manual online and came across the bit about the 0v/Chassis link inside the units. I checked the Master and it is connected but I couldn't find this link in the Slave unit. Was it left out of Issue 6 pcb? I found a LK12 on the pcb with no jumper but seems to show continuity on my meter even without the link.
Some people thought maybe it was too close to the amps but I moved it 10 from them and it still buzzes.
Any ideas what could be wrong? I might even be interested in sending it to a repair center to get this figured out.
0
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Comments
It looks like you've already identified the source of the buzz. If unplugging the snake at the device removes the buzz, but unplugging it at the stage does not remove the buzz, then the snake is directly involved in causing the buzz. Bad shield, shared common, something like that. It could even be the weight of the snake pulling on the device and flexing the chassis or pcb.
Dan
Obviously when I take the FCS-920 out of the chain everything works fine and no buzz. Also with the 920 in my FOH effects rack everything works with no buzz either.
I did notice the inputs on the 920 do not like Neutrik XLRs. They will not lock into place and it causes dropouts etc. Funny since the input jacks are Neutriks brand themselves. I've installed Switchcraft jacks on the cables that I use patch in the 920.
I don't have any of these problems with the 926 btw.
I just found the problem! This has been driving me crazy for a couple months now. In case someone else runs into this problem, the pin 3 contacts on the input XLR had broken off. I replaced the XLR with a standard D series.
This explains why the unit was also quieter than the Master 926. A whole 6db quieter to be exact!