[Milsurplus] BC-230, -430 Without AudioPhoolery

[Al Klase]

Hey Dave,

Why don't you get out of the triode rat race entirely?  Try something 
like triode connected 6F6's, or whatever you have a surplus of.  There 
may even be some BB-gun-target TV tubes that would do a good job.

Al

On 4/20/2010 12:29 PM, David Stinson wrote:
> As you know, the tubes for the SCR-183 / -283 transmitters have
> become golden idols to the AudioPhoolery cult,
> so many of these interesting transmitters stay cold.
> I've been experimenting with the idea of alternate, inexpensive
> tubes.  So far, I've subbed a pair 1626s in the RF stages.
> Jumper 7-8 together fil to cathode and connected that to
> the fil pin nearest the outside of the set.
> These tuned right up, neutralized and put out power
> without a hitch.  They are rated for 250 volts at 25 mils in
> this type of service and the PA puts out
> about 2+ watts at 220 VDC.
> Only trouble- the 1626 is a 12-volt fil tube.  If you have
> a BC-230 and you sub all four tubes, you'll need 24 volts fil.
> If you have a BC-430, it would take 48 volts.
>
> So.... is there a 6.3 volt equiv. to the 1626, that isn't
> an object of cult worship?  6J5 is no-go... too little current
> capacity.  How about triode-connecting an inexpensive
> power pentode, like 6K6 or the like?
>
> What are your ideas?  They will be applicable to other
> rigs that are suffering from cult-inspired amputations.
>
> 73 Dave AB5S.
>
> p.s.  If you decide to work on one of these:
> The 25 mFd filter cap is open.... No.. Really.
> They make them the size of a pencil eraser now.
> The .1 bypasses leak a little, but are still serviceable
> at this B+ in the two sets I've fired-up so far-
> .1 at 350 volts is still big and looks clunky ;-).
> In one set, the hand-made 120 pFd A.R.C. silver mica
> "sandwich" cap with the 30 K-Ohm across it was diseased.
> In the other, it was fine.  In both, the 30-K resistors had
> drifted 15-20% high. Parallelling a 220K across brought
> them down to spec.  Other resistors were within spec,
> except the One Megger (of course).  Lifted one end
> and subbed a new one.
> If you're on 80-75 meters, put a good 1KV NPO 75 pFd
> cap in series with the roller-coil contact output.
> Put the roller about half-way up the coil.
> It will tune right up into 50-ohms.
> Haven't tried 40 yet.
> Move the roller up and down a turn at a time
> and re-tune the tank cap each time for max.  out.
> Keep your power, control and antenna leads short- bypassed
> if possible- or mount the set over a ground plane (thanks Mike H)
> if you have the control boxes.  Otherwise RF will get back into
> the audio leads and you'll FM.  I used aluminum tape (with contact
> tabs, of course) on my wooden base and it works great.
> Neutralize, then "tweek" to min. FMing, just like a BC-375.
> Fun rig.
> Oh... and De-Ox-Id is your friend.
> More later... work calls.
>
>
>
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-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/