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

[Darryl Trump]

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 
> 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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