[GreenKeys] ST6 questions

[Ralph Mowery]

----- Original Message ----- 
From: "Eugene Hertz" <ehertz at tcaf.org>
To: "Don and Diana Cunningham" <wb5hak at duracom.net>; "Eugene Hertz" 
<ehertz at tcaf.org>; <greenkeys at mailman.qth.net>
Sent: Sunday, July 16, 2006 7:03 PM
Subject: Re: [GreenKeys] ST6 questions


Thanks, Don. I do have that article. I wasn't sure, however, if it would be 
worth the effort to tune the torroids or whether I'm "close enough"...
The transistor in question appears to be Q402 on board #4. The manual says 
it should be MPS3708. The working board has this transistor. One of the 
non-working has Q402 in place facing the opposite way than depicted in the 
manual. To the best I can see, the markings on the Q are AT2907

Anyone know if this is/was a substitute for the 3708? And can anyone tell if 
this should be inserted in the opposite direction? EBC/CBE?
Thanks, Don!
Eugene

>-----Original Message-----
>From: Don and Diana Cunningham [mailto:wb5hak at duracom.net]
>Sent: Sunday, July 16, 2006 05:51 PM
>To: 'Eugene Hertz', greenkeys at mailman.qth.net
>Subject: Re: [GreenKeys] ST6 questions
>
>Eugene,
>I'll take a stab at some of these. For copying RTTY, the shift is the most
>important of these variables, as you won't know the difference when you 
>tune
>the signal in properly. ST6 #1 is very close, and probably would work fine.
>Where you could run into trouble is on transmit where your transmitted 
>tones
>should match. You will always be off frequency to those that copy you just
>a little, but likely no one would notice except a few of the "particular"
>gentlemen that notice such things, hi. It is not hard to tune the toroid
>filters to put them very close on to the 2125/2295 pair that is common. I
>think someone posted the tuning info that Irv Hoff, W6FFC, put out in a QST
>article a few weeks ago. I think he might have posted that to RTTY.com, but
>not sure. I might be able to find a copy of that if you needed it. His
>method is very easy, and if you remove turns from the toroid, you can learn
>to get VERY close to perfect tone pairs on the ST-6. Wiring errors are VERY
>common on kit ST-6's. I have RARELY found one that was perfect, hi. I
>don't remember what the autoprint transistor was, but there could be two
>different basings very easily. Good luck with your TU's. The ST-6 was one
>of the best!!
>73,
>Don, WB5HAK
>
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Most of the transistors are not critical.  Just use the same general type. 
I built one using the 2n2222 transistors for most of  the npn types.  The 
2n3904 series should be a good subistute for most of the transistors.  It 
does seem that some transistors have the leads for the EBC in differant 
order.  You have to match them up.  The high voltage one that keys the loop 
and the ones in the power supply are about the only ones you really need to 
be careful about .

As to the other question about the receiver with a product detector.  You 
just adjust the frequency on the dial so the tone comming out of the 
receiver is what you want.  It does not have to match the listed frequency 
of the transmitting station.