[Heathkit] Thanks to all

[Tom NØJMY]

Okay, Glenn and Buck.  Let me chime in here a second.  We just had a 
discussion about this on the Yahoo list and Glenn, your name even came up(!)

Am I wrong to say to Buck that if he uses your suggested set-up (which I 
heartily endorse, by the way!) he should probably change out the 15K 5W 
series current limiting resistor in the VF-1 as well?

My thinking is this.  With 150V in from that power supply, and 108V 
regulated, the 0B2 will be dropping 42V.  It likes to see about 20 mA. 
current flow, so R=E/I, or 42/.02 = 2100 ohms.  Therefore, if he swaps 
out the factory 15K ohm resistor for a standard 2.2K resistor he should 
get roughly 19 mA. which is good.

If he left the 15K resistor in there it would seem to me he'd only have 
a few mA of current - not enough to ensure reliable operation of the VR 
tube.

Power-wise, P=IE, or .02 x 42 = .84 watts...I guess I'd probably still 
use at least a 2-watt resistor for the sake of overkill.

Is this good theory or just more of my poppy-cock?

73,
Tom NØJMY .   .

Hayseed Hamfest Co. - Multi-section Can Capacitors
for vintage Heathkit, Drake, Halli, Hammy, more...
www.hayseedhamfest.com

On 1/21/2010 10:06 AM, Glen Zook wrote:
> Are you powering the VF-1 from the AT-1?  If so, this isn't really a
> good idea.  Power the VF-1 from an external 150 volt regulated
> supply, change the 0A2 screen regulator tube to an 0B2, and then
> replace the 6AU6 oscillator tube with a 6AH6.  No wiring changes are
> needed.
>
> The VF-1 will be much more stable and the AT-1 will be MUCH happier.
>
> Glen, K9STH
>
> Website:  http://k9sth.com
>
>
> --- On Thu, 1/21/10, randy perkins<w5kcm_randy at verizon.net>  wrote:
>
> Hi Buck, I have a restored AT-1 and with the crystal (80 Meters) I
> get about 9 to 10 watts output. With the VF-1 VFO, I only get about 6
> to 8 watts output. I tried several 6L6's and have the same results.
> My power transformer is not original and the B+ is a little lower
> than it should be. This is most likely why my output is not that
> great but still in the normal range. If I solid state the rectifier,
> I can get about 15 watts output. I tried to keep it mostly original,
> so I kept the 5U4 tube in there. Glad to see more AT-1's on the air.
>
>
>
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