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Old 30th March 2015, 09:04 PM   #1
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Default Firstwatt F5, some Problems...

Hi,

I got it running. The sound is very good, but there is some hum.

My setup: 800VA transformer, 4x 47000uF, 2 Bridge rectifiers, CRC as in manual.

The switch on is with a switch-on-unit (resistor, delay, relais), the ground connection with 10R, 2Diodes from a bridge and a small film cap (100nF or so...)
The two supply voltages meet in a single point - the copper bar.

If I switch off the transformer, the hum immediately stops. If I source the power with the lab supply, there is no hum either. I connect the lab supply ground as well to the 220V inlet ground.

How can I solve the humming trouble?

Regs, Dirk
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Old 30th March 2015, 09:16 PM   #2
Zen Mod is offline Zen Mod  Serbia
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Location: ancient Batsch , behind Iron Curtain
those inner red and black wwires , going from bridges to first caps - re-route them to middle of the ground bar

if needed , rotate toroid - maybe there is some stray field , too
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Old 30th March 2015, 09:28 PM   #3
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In addition, Click the image to open in full size. so as to avoid ground loops, the heatsinks also need to be earth grounded.
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Old 30th March 2015, 09:52 PM   #4
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Hi,

@ZenMod: Changed wires, no effect
@prooptiki: Added Earth from copper bar to cooling fins - no effect.

Any Ideas???

Regs, Dirk
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Old 30th March 2015, 09:57 PM   #5
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Another Problem: I cannot rotate the toroid: It's fixed with 2 screws!
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Old 30th March 2015, 10:22 PM   #6
fdlsys is offline fdlsys  South Africa
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Are you sure it's not the transformer itself "humming" mechanically?
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Old 30th March 2015, 10:38 PM   #7
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There is a slight mechanical hum. But a much bigger electrical hum. With speakers, it's 2 or 3 times louder.
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Old 30th March 2015, 10:58 PM   #8
Zen Mod is offline Zen Mod  Serbia
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ok

without nothing on input - what's happening ?
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Old 30th March 2015, 11:04 PM   #9
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Hi,

removed cinch cables, still the same.

Hmmmm....

;-(
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Old 30th March 2015, 11:25 PM   #10
rayma is online now rayma  United States
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Quote:
Originally Posted by HVfanatic View Post
Another Problem: I cannot rotate the toroid: It's fixed with 2 screws!
Is the metal plate (under the pcb on top of the toroid) grounded, or connected to the pcb electrically in any way?
Exactly how is the toroid mounted - you said there are two screws?
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