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Total 14 documents matching your query.

1. [Amps] Fwd: rx noise? (score: 1): Author: "Patrick Egloff" <pegloff@gmail.com>; Date: Sun, 7 Dec 2008 07:35:34 +0100; Hi All, I also have an HF2500 amplifier i got second hand years ago. During the last CQWW CW i had problem with the antenna switching relay. I had to open the amp an try to clean this nasty relay....; /archives//html/Amps/2008-12/msg00134.html (16,167 bytes)
2. Re: [Amps] Fwd: rx noise? (score: 1): Author: "David Robbins K1TTT" <k1ttt@arrl.net>; Date: Sun, 07 Dec 2008 12:21:15 +0000; There were several vintages of the commander hf-2500 and along the line he raised the plate voltage. The older ones I have only start at about 2kv on the plate, the new ones are about 2.7kv. And yes; /archives//html/Amps/2008-12/msg00140.html (19,255 bytes)
3. Re: [Amps] Fwd: rx noise? (score: 1): Author: "David Robbins K1TTT" <k1ttt@arrl.net>; Date: Sun, 07 Dec 2008 12:27:46 +0000; p.s. with practice you can clean those relays in about 10 minutes. Leave the top and bottom covers on, take off the back plate and tilt it back and you can reach in with medical forceps to clean the; /archives//html/Amps/2008-12/msg00141.html (19,453 bytes)
4. Re: [Amps] Fwd: rx noise? (score: 1): Author: "David Robbins K1TTT" <k1ttt@arrl.net>; Date: Mon, 08 Dec 2008 23:28:36 +0000; I think the noise in that one is solved... take a look at the scope pic for a 12v regulator with a 2v p-p oscillation on it at: http://wiki.k1ttt.net/2008%20Maintenance%20and%20Upgrade%20Blog.ashx?No; /archives//html/Amps/2008-12/msg00160.html (8,978 bytes)
5. Re: [Amps] Fwd: rx noise? (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Tue, 9 Dec 2008 08:39:07 +0000; Glad you found the problem, Dave. By coincidence(?) someone recently found a similar problem with a 78xx in a GaAsFET preamp that had been OK for years, but then decided to become unstable. Any thoug; /archives//html/Amps/2008-12/msg00164.html (9,417 bytes)
6. Re: [Amps] Fwd: rx noise? (score: 1): Author: <d.cutter@ntlworld.com>; Date: Tue, 9 Dec 2008 10:32:41 +0000; Did the regulator have proper bypass in the first place or was this a problem just waiting to pop out? Capacitor-to-regulator distance is critical. I've never known a regulator go funny if it was pro; /archives//html/Amps/2008-12/msg00165.html (8,430 bytes)
7. Re: [Amps] Fwd: rx noise? (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Tue, 9 Dec 2008 14:31:51 +0000; This came from a source I would trust - an experienced moonbouncer who keeps a very close watch on his noise level, and immediately noticed when that level increased. The e-mail exchange was only cop; /archives//html/Amps/2008-12/msg00170.html (9,302 bytes)
8. Re: [Amps] Fwd: rx noise? (score: 1): Author: "David Robbins K1TTT" <k1ttt@arrl.net>; Date: Tue, 09 Dec 2008 22:45:22 +0000; According to the schematic there is a .1uf on the input, I didn't try to follow the tracks to see where it was though. There is no output side cap at all. David Robbins K1TTT e-mail: mailto:k1ttt@arr; /archives//html/Amps/2008-12/msg00181.html (10,608 bytes)
9. Re: [Amps] Fwd: rx noise? (score: 1): Author: "David Robbins K1TTT" <k1ttt@arrl.net>; Date: Tue, 09 Dec 2008 22:50:46 +0000; p.s. as I noted in my blog I have heard similar wandering birdies before but never had them land on a band like that one did during cqww. I have been doing other repairs on those amps so they have mo; /archives//html/Amps/2008-12/msg00182.html (10,884 bytes)
10. Re: [Amps] Fwd: rx noise? (score: 1): Author: "David Cutter" <d.cutter@ntlworld.com>; Date: Tue, 09 Dec 2008 15:05:02 -0800; Fascinating stuff. I couldn't find a reference to exactly what regulator is used. 7812 or variable regulator? David G3UNA _______________________________________________ Amps mailing list Amps@contes; /archives//html/Amps/2008-12/msg00184.html (11,245 bytes)
11. 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)
12. Re: [Amps] Fwd: rx noise? (score: 1): Author: "David Cutter" <d.cutter@ntlworld.com>; Date: Tue, 09 Dec 2008 23:41:47 -0800; That makes it even more curious. The LM7812 is less susceptible to instability compared to some others and according to a NS application note does not need an output cap for stability, though I would; /archives//html/Amps/2008-12/msg00187.html (13,387 bytes)
13. 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)
14. Re: [Amps] Fwd: rx noise? (score: 1): Author: Pete Smith <n4zr@contesting.com>; Date: Mon, 29 Dec 2008 11:09:04 -0500; Hi Dave - you and others might want to look into the small HiG d'Italia RF-switching relays that Allen Bond sells at mgs4u.com on the President's Page. They are rated 75 watts RF hot switching and I'; /archives//html/Amps/2008-12/msg00364.html (21,876 bytes)

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