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Total 39 documents matching your query.

21. Re: [Amps] Fwd: rx noise? (score: 1)
Author: "David Robbins K1TTT" <k1ttt@arrl.net>
Date: Tue, 09 Dec 2008 23:38:39 +0000
It's an LM7812 on a decent size heat sink standing up on the board. David Robbins K1TTT e-mail: mailto:k1ttt@arrl.net web: http://www.k1ttt.net AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net __
/archives//html/Amps/2008-12/msg00185.html (12,648 bytes)

22. Re: [Amps] Fwd: rx noise? (score: 1)
Author: "David Robbins K1TTT" <k1ttt@arrl.net>
Date: Thu, 11 Dec 2008 00:19:41 +0000
Well, its not an epidemic anyway. Just finished checking the other 6 of those amps in the shack and none of them had any oscillation, at least when first turned on cold. Perhaps as someone suggested
/archives//html/Amps/2008-12/msg00194.html (15,195 bytes)

23. Re: [Amps] Cleaning Cigarette tar....? (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Fri, 31 Jul 2009 23:10:08 +0000
A flame thrower comes to mind... or maybe an ultrasonic cleaner full of gasoline. That is tough stuff and you can be sure it is down in every nook and cranny of the amp. David Robbins K1TTT e-mail: m
/archives//html/Amps/2009-07/msg00451.html (8,752 bytes)

24. Re: [Amps] Help With Command Technologies HF2500 (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Sat, 05 Dec 2009 22:09:44 +0000
Check the 1.5a fuse on the control board. David Robbins K1TTT e-mail: mailto:k1ttt@arrl.net web: http://www.k1ttt.net AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net ____________________________
/archives//html/Amps/2009-12/msg00134.html (8,565 bytes)

25. Re: [Amps] Conservation of Energy! (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Sun, 06 Dec 2009 15:33:21 +0000
Well, actually you could make some argument that running on 120v instead of 240v increases the I^2R losses in both the transformer and power line to the amp. But I doubt that you would notice that in
/archives//html/Amps/2009-12/msg00161.html (7,691 bytes)

26. Re: [Amps] QRO Questions (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Fri, 05 Feb 2010 22:43:05 +0000
My neighbor has lights that come ON when I transmit... some kind of a touch lamp. David Robbins K1TTT e-mail: mailto:k1ttt@arrl.net web: http://www.k1ttt.net AR-Cluster node: 145.69MHz or telnet://d
/archives//html/Amps/2010-02/msg00133.html (8,277 bytes)

27. Re: [Amps] placement of RF choke bypass cap. (Results of experiment) (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Sat, 20 Mar 2010 16:52:40 +0000
Sounds reasonable. But it doesn't show that current flows through the center of the disk. There are capacitive paths between the wire on each side and the disk surface that provides a shorter path th
/archives//html/Amps/2010-03/msg00416.html (11,003 bytes)

28. [Amps] hf-2500 (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Thu, 13 Dec 2012 17:26:09 +0000
I have an older Commander HF-2500 that needs a new transformer. Anyone have a source for good ones?? Or does anyone want an RF deck and doorstop? _______________________________________________ Amps
/archives//html/Amps/2012-12/msg00076.html (6,809 bytes)

29. Re: [Amps] hf-2500 (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Sat, 15 Dec 2012 13:32:51 +0000
Thanks for all the suggestions, for what the deck is worth I think I'll keep it and try the rewinding path. For anyone needing to work on these amps, here are a few links to my repair and modificatio
/archives//html/Amps/2012-12/msg00087.html (9,560 bytes)

30. Re: [Amps] hf-2500 (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Wed, 19 Dec 2012 17:15:03 +0000
Agreed, that is why I have modified one to do only 40-10m... removing the 80m and 160m coils from the toroid removes the shorted turns problem and makes it run very nicely doing rtty on 40m. also the
/archives//html/Amps/2012-12/msg00106.html (8,894 bytes)

31. Re: [Amps] hf-2500 (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Tue, 25 Dec 2012 12:45:56 +0000
In the HF-2500 the ONLY failures I have had were on 40m and 80m contest RTTY. On these amps half or three quarters of the turns are shorted on the toroid on 80m and 40m respectively. To make it worse
/archives//html/Amps/2012-12/msg00176.html (15,536 bytes)

32. [Amps] commander hf-2500 schematic (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Wed, 03 Apr 2013 23:43:17 +0000
Has anyone actually traced out the real schematic from an older commander hf-2500, around s/n 435??? The one in the book is not complete (parts list missing stuff) nor correct. there appears to be lo
/archives//html/Amps/2013-04/msg00018.html (8,526 bytes)

33. Re: [Amps] commander hf-2500 schematic (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Sat, 06 Apr 2013 14:04:59 +0000
What would you expect the voltage to be from Cathode to Ground when keyed and when idle on this thing?? David Robbins K1TTT e-mail: mailto:k1ttt@arrl.net web: http://wiki.k1ttt.net AR-Cluster node: 1
/archives//html/Amps/2013-04/msg00024.html (9,184 bytes)

34. Re: [Amps] commander hf-2500 schematic (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Sun, 07 Apr 2013 13:33:31 +0000
Ok, now I'm making some progress... thanks for some of the tips in here. Yesterday I traced out the circuits for the rf deck, hv power supply, and meter board, and was able to connect up the whole lo
/archives//html/Amps/2013-04/msg00025.html (11,773 bytes)

35. [Amps] hf-2500 again (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Sat, 20 Apr 2013 14:33:08 +0000
Ok, got parts in and replaced most of the bias circuit. Now I have 9.7v on the cathode on rx and 8.7v on tx. Would those be reasonable for bias when cutoff and tx in ab2 operation for the pair of 3cx
/archives//html/Amps/2013-04/msg00182.html (6,884 bytes)

36. Re: [Amps] hf-2500 again (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Sat, 20 Apr 2013 16:41:07 +0000
That is essentially correct on how this one works. I did replace the transistor that shorts out the 330k resistor and that seems to be working now, the last thing I found was a capacitor across that
/archives//html/Amps/2013-04/msg00184.html (9,116 bytes)

37. Re: [Amps] hf-2500 again (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Sun, 21 Apr 2013 13:48:21 +0000
Another advantage of having more than one of these. besides not being in a rush to fix it, is that I can put another one side by side and compare measurements. Yes, the cutoff bias is too low. A good
/archives//html/Amps/2013-04/msg00186.html (10,564 bytes)

38. [Amps] command tech hf-2500 schematics (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Tue, 07 May 2013 23:24:14 +0000
I have scanned some of my manuals (at least the ones that looked like they were different) and have some donations from others. I have not heard from the latest owners of the product line regarding c
/archives//html/Amps/2013-05/msg00118.html (8,818 bytes)

39. Re: [Amps] Experiences shipping a Commander II with the XFMR installed (score: 1)
Author: "K1TTT" <K1TTT@ARRL.NET>
Date: Sat, 25 May 2013 21:40:11 +0000
Remove the transformer and the tube(s)... if the construction of that is similar to other commander amps the base that the transformer is on is not strong enough to handle much shock, or even a long
/archives//html/Amps/2013-05/msg00180.html (8,998 bytes)

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