[Drake] R-4A 1st oscillator transistor

[Darryl Trump]

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 
the order. 

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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