[GreenKeys] ST6 questions

[Eugene Hertz]

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 
> 
>_______________________________________________ 
>GreenKeys mailing list 
>GreenKeys at mailman.qth.net 
>http://mailman.qth.net/mailman/listinfo/greenkeys 
>