Re: Pass tube heater supply question


"Ned Carlson" <see-www-tubezone-net> wrote in message
news:386a9sx81t16$.su1mr17sidu4.dlg@xxxxxxxxxxxxx
> On Sun, 8 Jan 2006 11:21:50 +0100, Tom Schlangen wrote:
>
>> Which is the method you would prefer, and why?
>>
>> Thank you in advance!
>>
>> Tom
>
> If it doesn't affect the hum level in the output,
> I'd just hook one side of the filament to the
> cathode.
>
> You could use a 100 ohm hum-balance control, but it
> had better be rated for the DC voltage involved.
>
> --
> Ned Carlson www.tubezone.net
> South Side of Chicago,IL USA
> 1/8/2006 5:33:05 AM

I finished building a tube based regulated power supply a couple of months
ago, and I did as Ned says, just wired the heaters straight to the cathodes,
and I have had no problems with it.

One thing I thought about at the time was that doing this means your
filament transformer winding will be seeing the high dc voltage. Now in my
case I was getting the 6.3 volts from a combination plate and filament
transformer, so I figured the transformer as a whole had sufficiently high
winding to case voltage rating to handle the plate section AC voltage, so I
didnt worry about it. I didnt think about the winding to winding voltage
ratings, I just sort of hoped the transformer makers knew people might do
this sort of thing sith tube circuits. I do not know what the winding to
case voltage rating of a seperate 6.3 volt transformer might be, especially
a modern one not specifically designed for tube heaters. This may or may
not be an issue.


.

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