[HomeBrew] Need info/suggestions

[n6kyr at netzero.net]

Thanks Carl:
I'll definitely look into your suggestions. The only trouble is that my chassis is sooooo small that it won't support a choke, otherwise, I would have included that into my design. 

Well, the reason why I wanted to include the VR-150 as a regulator is not only for the so called "stability" but for the glow-in-the-dark aspect. Ditto for the #47 bulb. Yeah, I know...bad engineering but hey, maybe it's fine for the BA experience! 
BTW, you must have had exciting times at National. What a dream job that can only be reflected on the pages of ER and James Millen's memoirs. Cal. 

-- "km1h" <km1h at jeremy.mv.com> wrote:
Even brand new the VR150 is far from stable. You can take 6 at random and 
maybe one will meet specs. If you want stability use a Zener. Mouser has 
them at cheap prices. Be sure to bypass for RF.

No problem with the AC. A 47 lamp adds to chassis heat plus they burn out ; 
consider a NE2 and a suitable resistor depending upon voltage source. 
100-220K is OK for 120VAC.

The transformer is suitable but your filter is not. If you cant find a choke 
use a 330-470 Ohm wirewound as a poor mans choke input substitute. The 80mF 
is OK. A 10-20H 50-100ma choke should not be hard to find either. In a pinch 
use the primary of a 6AQ5/6V6/35L6/50L6/50C5 or similar audio output xfmr.

Carl
KM1H
National Radio 1963-69


----- Original Message ----- 
From: <n6kyr at netzero.net>
To: <homebrew at mailman.qth.net>
Sent: Wednesday, July 13, 2005 7:46 AM
Subject: [HomeBrew] Need info/suggestions


> ** Please do NOT cross-post messages when posting to HOMEBREW **
>
>
> All:
> I'm in the process of building a 2 tube cw transmitter (6AG7 with an 
> OD3/VR-150 reg on the screen). It's going to be s/s on the rectifier, 
> using an 80 uF/450 VDC filter (no choke,sorry). I have recently gotten a 
> hold of a Stancor transformer rated at 440 VAC CT at 50 mA with a 
> 6.3VAC/.5 A filament and a 25.2 VAC 100 mA xtra winding (perhaps a biasing 
> winding).
>
> First off, on the transformer: I think it is good enough to handle the 
> 6AG7 current demands. Does this sound right?
>
> Also, I would like to place on the screen of the 6AG7 the VR-150 tube to 
> stabilize the voltage "behind" the 47K screen supply resistor. Good enough 
> to pipe down "the chirps?"
>
> Finally, on the placement of the crystal socket, I may be placing the 
> socket near some AC sources (about an 1" or so away from the pilot lamp 
> and power switch). Now I shouldn't expect any hum pickup now, right? Let 
> me know as I haven't punched the 7" by 5" by 2" chassis yet. I'd like to 
> get any lingering tech issues out of the way before "Mr. Greenlee comes 
> punching."
>
> 73 de Cal, N6KYR/8
>
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