[Central-Electronics] 10A crystal location

[Tom Elmore]

After reading about all this drift I had a thought. I own both a 10B and 20A and can't recall how the crystall is mounted. Is it possible to isolate the crystal with say a piece of 3/4 or 1" PVC that is open on either end.




-Tom / KA1NVZ 

-----Original Message-----
From: k6jek [mailto:k6jek at comcast.net]
Sent: Friday, September 9, 2011 10:07 AM
To: central-electronics at mailman.qth.net
Subject: Re: [Central-Electronics] 10A crystal location

That is very interesting. Moving the crystal to the top of the chassis is probably a bad idea since CE went to some trouble to move it underneath.I have a first-three-months-of-production 20A. They completely junked the oscillator I have, switched tubes, changed the circuit entirely after three months. It was the first product change they made. I need to rebuild to the later circuit before I do much else.But let me give you an idea of just what drifter this thing is. I did several long tests with controlled room temperature and regulated AC supply. I gave it a five minute warm-up then started measuring every 10 minutesTime	Drift in last ten minutes10	-9	20	-4630	-4660	-2690	-12120	-5Cabinet off, chassis raised off tableTime	Drift in last ten minutes10	-1620	-1130	-560	-190	0120	1	Dramatically better. I think rather than install a crystal oven it might be good enough just to get some air to the circuit. First though, I'm going to rebuild to the later versionThanks,JonOn Sep 9, 2011, at 10:01 AM, Merv Schweigert wrote:> Had an early 10A and the Xtal was on top of the chassis, just about right over the> position it is in the 20 a underneath.> Merv K9FD/KH6> > Have a 20A I need to start working on and your xtal problems have me wondering ...> > >> Where is the 9 MHz crystal on the 10A, above the chassis or below?>> >> I notice a huge difference in drift of the 20A oscillator when I give the rock a little air. Out of the cabinet with circulation under the chassis, the drift just stops dead after a few minutes. Rock solid. With the cabinet on it drifts like leaf in a stream.>> >> I also noticed the mounting holes for the bracket holding the crystal are spaced just about right for a crystal holder, maybe exactly right. I wonder. Would moving the crystal above the chassis (where it is in the 100V) make things a lot better? But maybe that's where it was in the 10A and they moved it underneath for a reason.>> >> Which brings me to my question. Was it up top in the 10A?>> >> Thanks>> >> Jon>> ______________________________________________________________>> Central-Electronics mailing list>> Home: http://mailman.qth.net/mailman/listinfo/central-electronics>> Help: http://mailman.qth.net/mmfaq.htm>> Post: mailto:Central-Electronics at mailman.qth.net>> >> This list hosted by: http://www.qsl.net>> Please help support this email list: http://www.qsl.net/donate.html>> >> > ______________________________________________________________Central-Electronics mailing listHome: http://mailman.qth.net/mailman/listinfo/central-electronicsHelp: http://mailman.qth.net/mmfaq.htmPost: mailto:Central-Electronics at mailman.qth.netThis list hosted by: http://www.qsl.netPlease help support this email list: http://www.qsl.net/donate.html