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Total 13 documents matching your query.

1. [Amps] HF amp output power dropping (score: 1): Author: jordan moser <henry8877amp@hotmail.com>; Date: Sat, 29 Sep 2007 14:26:14 +0000; I have an old Henry 3000d RF heater that was converted to HAM use by someone else. It runs a 3CX3000A7 tube in grounded grid. Recently the output power has begun falling off rapidly whenever I apply; /archives//html/Amps/2007-09/msg00477.html (7,470 bytes)
2. Re: [Amps] HF amp output power dropping (score: 1): Author: "Tom Rauch" <w8ji@contesting.com>; Date: Sat, 29 Sep 2007 10:34:42 -0400; Assuming the drive is constant and the meters are good, it sounds like a bad tube. It could be a capacitor or inductor drifting off value and making something get mismatched, it could be the bias is; /archives//html/Amps/2007-09/msg00478.html (7,671 bytes)
3. Re: [Amps] HF amp output power dropping (score: 1): Author: "jeremy-ca" <km1h@jeremy.mv.com>; Date: Sat, 29 Sep 2007 13:56:46 -0400; It could very well be the plate blocking cap, especially if it is undersized for that power or not even rated for RF use such as the TV doorknobs. Also check the filament voltage, filament choke and; /archives//html/Amps/2007-09/msg00491.html (9,075 bytes)
4. Re: [Amps] HF amp output power dropping (score: 1): Author: "Tom Rauch" <w8ji@contesting.com>; Date: Sat, 29 Sep 2007 14:11:05 -0400; Not much chance of that. It is a self-testing component. If the plate blocking cap is dissipating hundreds of watts it would explode or go up in flames in a matter of seconds. It is not value critic; /archives//html/Amps/2007-09/msg00493.html (8,670 bytes)
5. Re: [Amps] HF amp output power dropping (score: 1): Author: Mike Willis <m.j.willis@rl.ac.uk>; Date: Sat, 29 Sep 2007 22:06:48 +0100; Last time I had this happen it was the antenna. I think something was getting hot and changing the match. I am sure you are tuning it into a dummy load, so it can't be that. However, it was possibly; /archives//html/Amps/2007-09/msg00497.html (7,913 bytes)
6. Re: [Amps] HF amp output power dropping (score: 1): Author: Pat Barthelow <aa6eg@hotmail.com>; Date: Sat, 29 Sep 2007 14:23:19 -0700; Last time I had this happen it was the antenna. I think something was getting hot and changing the match. I am sure you are tuning it into a dummy load, so it can't be that. However, it was possibly; /archives//html/Amps/2007-09/msg00498.html (8,982 bytes)
7. Re: [Amps] HF amp output power dropping (score: 1): Author: "jeremy-ca" <km1h@jeremy.mv.com>; Date: Sat, 29 Sep 2007 22:33:27 -0400; Try and have it your way as usual. Ive seen plenty of plate blocking caps heat up and change the output tuning and still not be at the point of failure. I'll mail the next one I find to somone that c; /archives//html/Amps/2007-09/msg00500.html (8,776 bytes)
8. Re: [Amps] HF amp output power dropping (score: 1): Author: jordan moser <henry8877amp@hotmail.com>; Date: Sat, 6 Oct 2007 14:03:32 +0000; I'm not sure how to respond to my first thread. Sorry if this is a duplicate. I have been trying to find the cause of my amplifier's output power falling off. Last night I checked it by transmitting; /archives//html/Amps/2007-10/msg00062.html (7,026 bytes)
9. Re: [Amps] HF amp output power dropping (score: 1): Author: Mike Willis <m.j.willis@rl.ac.uk>; Date: Sat, 06 Oct 2007 17:52:29 +0100; OK - That is interesting. While you have it set up, check that the power does not come back when you tune the input circuit. If you can not tune the input circuit, this might be your problem. If it d; /archives//html/Amps/2007-10/msg00063.html (9,655 bytes)
10. Re: [Amps] HF amp output power dropping (score: 1): Author: "EP Swynar" <gswynar@durham.net>; Date: Sat, 6 Oct 2007 15:52:30 -0400; On 6th October, Jordan wrote... "...After 1 minute output dropped by about 50 watts. At higher wattages the loss is more pronounced, at 600 watts it may drop to 400 over a minute time..." ** Hi Jorda; /archives//html/Amps/2007-10/msg00064.html (8,223 bytes)
11. Re: [Amps] HF amp output power dropping (score: 1): Author: "Tom Rauch" <w8ji@contesting.com>; Date: Sat, 6 Oct 2007 21:27:59 -0400; I'm not sure how to respond to my first thread. Sorry if this is a duplicate. I have been trying to find the cause of my amplifier's output power falling off. Last night I checked it by transmitting; /archives//html/Amps/2007-10/msg00065.html (7,884 bytes)
12. Re: [Amps] HF amp output power dropping (score: 1): Author: "Tom Rauch" <w8ji@contesting.com>; Date: Sun, 7 Oct 2007 20:01:17 -0400; Sorry about that, I posted last week and and didn't know how to do a follow up on the thread. The amp is a homebrew 3CX3000a7. I did not build it myself. Plate current and plate voltage behave as alw; /archives//html/Amps/2007-10/msg00077.html (8,950 bytes)
13. [Amps] HF amp output power dropping (score: 1): Author: Peter Chadwick <g3rzp@g3rzp.wanadoo.co.uk>; Date: Mon, 8 Oct 2007 06:25:33 +0200 (CEST); rises. Used to always drop under load.< Presumably measured in the same way with the same meter - and not a DVM affected by RF? How does the input SWR of the amp change while this is going on? Which; /archives//html/Amps/2007-10/msg00080.html (8,443 bytes)

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