[Amps] PROBLEM WITH HUM

[k7rdx]

The YC-156 will not work with conventional center tap B-.B- needs to be 
brought to the cathode seperately thru an rf choke similar to 8877 
designs.Using center tap connection will cause filament modulation. Another 
way is to use half of the filament choke to connect B- to the tube cathode. 
I have done this in my YC-156 decks and have no filament hum.. Look 
at:www.k7rdx.w4zt.com for detailed pics..Jim..K7RDX..
----- Original Message ----- 
From: "Bob Gibson" <w5rg at yahoo.com>
To: <Amps at contesting.com>
Sent: Monday, November 10, 2008 10:29 AM
Subject: [Amps] PROBLEM WITH HUM


> Hi..I have built a YC156 amp and I have a problem with hum in the audio..I 
> key the radio in SSB with the amp in line but not keyed and I get this hum 
> and its coming from the filament transformer..I opened it up and 
> disconnected the filament transformer then again keyed and no hum..I have 
> tried grounding all kinds of ways and still hum..Would some beads help 
> out? Thanks Bob W5RG
>
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