[Drake] R-4A 1st oscillator transistor, update

[Dennis Monticelli]

Excellent news, Darryl.

While I see nothing wrong with leaving a 2N3904 in there, I can offer
you a direct replacement.

I stopped by the local electronics surplus store on the way home and
noticed that they carried NOS 2N3393's....in the vintage style plastic
packages no less.  The 2N3393 is just an up-spec'd 2N3394.  All specs
are the same except that the 2N3393 has a high Beta.  If you wish, I
could easily swing by the store early next week and mail a couple of
them to you gratis.

Dennis AE6C

On Jan 3, 2008 11:48 AM, Darryl Trump <kb8bku at woh.rr.com> wrote:
> All,
>
> Just a short update, since I used so much bandwidth already.  Bias
> appeared to still be there.  I replaced the defective 2N3394 with a
> 2N3904 I had on hand.  The R-4A came to life!  As far as I know, all is
> well, but will continue to check out.  Good work men!
>
> KB8BKU, Darryl
>
> On Tuesday, January 1, 2008, at 11:03 AM, Darryl Trump wrote:
>
> > All,
> >
> > Thanks to those who replied promptly, both through the reflector and
> > direct.  I got seven replies all told, some even with offers for a
> > transistor.  Most had very good information for me.  The consensus was
> > that the 2N3394 is readily available, but it's not critical anyway,
> > and most any small signal NPN would work.  Garey's reply regarding the
> > proper interface connections spoke to the heart of the matter.  I am
> > also grateful for Dennis's suggestion to also check the Zener in the
> > PTO that supplies the current to the transistor.   This was my first
> > query to the group, and the response was very gratifying.
> >
> > As I write, it is colder, and new snow is falling here in Dayton, so
> > it will be especially cosy to have another Drake station operable in
> > the shack.  I hope the New Year brings happiness to you and yours, and
> > thanks again for all your help.
> >
> > Since Chris was interested in the answers, I reproduced them here.  As
> > a courtesy to the CIA agents and other paranoids among you, I keep
> > your responses (and e-mail addresses) anonymous.
> >
> > Sincerely,
> >
> > KB8BKU, Darryl
> >
> >
> > I would first check to see that the transistor is receiving bias
> > voltage.  There is a zener in the PTO that is more likely to fail than
> > the transistor.  If it is the transistor, I can track down suitable
> > replacements.  The 2N3394 does not have unusual (ie. hard to
> > duplicate) performance characteristics.
> >
> > Darryl -
> >
> > Yes, it is quite likely that the transistor is blown.  The connector
> > on the cable from the FS-4 should consist of a single pin and a ground
> > lead.  The ground lead is connected to the chassis directly since
> > there is no ground connection on the rear panel crystal sockets.  The
> > pin is then plugged into the accessory crystal socket on the side with
> > all connectors bussed together.  I think that is the lower pins of
> > each row, but check to be sure.  If you plug the ground lead into any
> > of these pins, it shorts out the emitter resistor of the oscillator,
> > zapping the transistor.
> >
> >
> > The 2N3394 is not anything special, and audio type NPN with a 25 volt
> > rating.  I would think that a 2N3904 would work fine probably a 2N3565
> > also.
> > I have 100's of either one.
> >
> > try this :http://webtronics.stores.yahoo.net/mps3394 (they have
> > mps3394 at 0.28 $ )
> > if you search on internet there ary a lot of suppliers , the only
> > problem can be the quantity to be ordered or the minimum price for
> > theorder.
> >
> > 2N3394's are very common and cheap! 7-cents each from Mouser.
> > (www.mouser.com)
> >
> > You can use any small transistor such as a 2N2222 or 2N3904.
> > If you need 2N2222 I could send you some.
> > Have you checked it out to be sure the 2N3394 is shot?
> >
> >
> > On Sunday, December 30, 2007, at 09:28 AM, Darryl Trump wrote:
> >
> >> I think I need a new 2N3394 oscillator transistor for my R-4A.  The
> >> set will receive using the FS-4 synthesizer, but not with the
> >> internal oscillator.  The cable I was using for connection to the
> >> FS-4 has a crystal housing on the R-4 end of a coax cable which plugs
> >> into the crystal socket deck at the rear of the R-4A.  I note that
> >> neither side of the crystal is grounded in the R-4A's schematic, but
> >> it gets grounded when I plug in the FS-4, so perhaps that took out
> >> the transistor.
> >>
> >> Does anyone know of a source for the 2N3394, or a good substitute.
> >> I'm not absolutely sure this is the problem, so any other comments or
> >> suggestions are welcomed.
> >>
> >> Thanks in advance for any help,
> >>
> >> KB8BKU, Darryl
> >>
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