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Channel Switching Boards; Experience with Weber ones?

5/16/2005 10:37 PM
dave b
Channel Switching Boards; Experience with Weber ones?
I've just finished building a channel switching amp which utilizes two of the Weber channel switching boards.  
The relay and power supply are on the same board and the quality is pretty good. The problem is the boards are powered by the 6.3VAC heater circuit, the boards need to be near the volume controls because of layout and the AC supplying the boards is causing AC hum.  
I'm using shielded wire on the 6.3VAC and all of the signal carrying leads.  
I guess one option is to build another power supply located away from the boards and run DC to them bypassing the supply on the board.  
I'd really like to get rid of this hum!!!  
Any other ideas?  
5/17/2005 3:49 AM

Disconnect the 6VAC and trip the thing with a battery. IF the hum goes away, then teh AC was indeed at fault, but if there is some other reason such as grounding, then there will be no change. In other words we want to verify the hum source.  
Or is it the fact that the AC is near the rest of the circuit as opposed to getting into the system via the little board?
5/17/2005 8:16 AM
dave b

I did disconnect the AC and the hum does go away.  
The AC leads are shielded and up away from other components.  
So I'm thinking it's the board or the proximity of the board to the volume controls  
5/17/2005 9:03 AM

You may also try a separate power transformer to supply the relay boards so they do not have to share the heater winding.  
Then you have a few choices about whether to ground the DC from each relay board to begin with, then if you do ground it in common with the main chassis ground, you do not have to just settle for the same ground point as the heaters.  
5/17/2005 12:46 PM
Ben N

Did'ja ask Ted?
5/18/2005 6:30 PM
dave b

Yes, And I've recieved no reply. I'm sure he's busy running his business.  
5/22/2005 1:20 PM
Cathode Follower
I've had the same problem with my Weber CS boards....a buzzzzz is injected every time the 6v supply is connected.  
Ted said he hadn't had any reports of problems...well, here's at least 2.  
I hadn't thought of the 6v battery trick, though...I'll try that on the next build to see if it helps. (I removed the boards because the noise was unbearable)  
I did however try just a DPDT switch....worked perfect, no noise.  
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