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1. [Amps] QRO HF2000 bias board fix (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Thu, 7 Jun 2018 13:38:21 +0000; Looking for info on possible fixes to a QRO HF2000 Rev 5 bias board. There are layout mistakes on the board and various component problems. I suspect a few folks have figured this out long ago. Tryin; /archives//html/Amps/2018-06/msg00018.html (7,010 bytes)
2. Re: [Amps] Big HV Supply (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Fri, 3 Aug 2018 14:54:22 +0000; Possibly a Peter W Dahl transformer? He made some monsters. Company was acquired recently by Hammond Mfg. Sounds like Amp Supply. They were famous for that... Does it have a jones plug on the cables?; /archives//html/Amps/2018-08/msg00015.html (8,706 bytes)
3. Re: [Amps] Big HV Supply (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Sun, 5 Aug 2018 23:03:25 +0000; I have one in my QRO Technologies amp. All the big Amp Supply transformers were Dahl, some had a tapped HV winding for the LK-550 and LK-800 and others were custom non advertised for the 3CPX800A7 LK; /archives//html/Amps/2018-08/msg00021.html (11,128 bytes)
4. [Amps] setting trimmer caps on amp RF in/out (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Fri, 21 Feb 2020 04:26:37 +0000; I'm looking for a procedure/recommendation on proper setting of the trimmer caps on the RF input and output of a QO HF 2000 amp. They are located right at the SO-239s. The input cap is in circuit (to; /archives//html/Amps/2020-02/msg00109.html (7,145 bytes)
5. [Amps] FL2100B bias (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Sat, 14 Nov 2020 03:35:38 +0000; Does anyone on the list know what the voltage across the R3 shunt (in the FL2100B plate current meter circuit) should be at a 90mA bias current? I trust my DMM but not the Yaesu meter. 73, John AI6LY; /archives//html/Amps/2020-11/msg00000.html (5,989 bytes)
6. [Amps] QRO / Commander power switch (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Tue, 26 Jan 2021 15:24:19 +0000; Does anyone know the part number for a replacement rocker-style mains power switch used on the QRO Technologies and Commander HF linears? 73, John AI6LY ______________________________________________; /archives//html/Amps/2021-01/msg00014.html (6,519 bytes)
7. [Amps] QRO HF2000 input SWR adjustments (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Mon, 15 Mar 2021 00:14:06 +0000; The input SWR at 160m is below 1.5:1 from 1800 to 1925 khz, then rises rapidly to >3:1 at 200 khz. Similarly, at 80m it's below 1.5:1 from 3600 to 3880 khz then rises to 2.2:1 at 4000 khz. Those are; /archives//html/Amps/2021-03/msg00004.html (7,361 bytes)
8. [Amps] tank coil Q question (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Thu, 18 Mar 2021 00:32:29 +0000; I had to replace the iron power low band tank coil when bringing a QRO HF2000 back to life, by replicating what appeared to be the original. It works, but it appears to be Q = 7 to 8 at 160 and 80m,; /archives//html/Amps/2021-03/msg00024.html (6,788 bytes)
9. [Amps] QRO HF2000 tank coil Q question (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Mon, 22 Mar 2021 16:22:43 +0000; Wondering if anyone can provide the specs on the low band tank coil for a QRO HF2000. It appears to be a stack of two red-mix T225A-2 iron powder toroids, with a total of 25 turns, and taps for 40M a; /archives//html/Amps/2021-03/msg00025.html (6,675 bytes)
10. Re: [Amps] QRO HF2000 tank coil Q question (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Mon, 22 Mar 2021 18:05:34 +0000; Thanks Peter. I calculate a Q of 7 to 8 for the stock design mentioned in the previous email. There are still a fair number of these amps in use, I wondered if others had similar experience. I consid; /archives//html/Amps/2021-03/msg00027.html (9,349 bytes)
11. Re: [Amps] QRO HF2000 tank coil Q question (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Tue, 23 Mar 2021 01:28:30 +0000; yes I took that into consideration for the calculations. Have you guys taken into consideration that the tank circuit in these amps only transform down to 200 ohms, not 50 ohms from the plate impedan; /archives//html/Amps/2021-03/msg00031.html (11,272 bytes)
12. [Amps] adjusting trimmers on amp input/output (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Sat, 27 Mar 2021 17:06:31 +0000; The QRO HF2000 amp has 25-150pF trimmers to ground on both the RF input and RF output. How would one optimize the settings on those? Are those intended to tune out the reactance of external cabling,; /archives//html/Amps/2021-03/msg00044.html (6,592 bytes)
13. Re: [Amps] Swan Mark 1 on 160 meters (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Tue, 29 Jun 2021 23:29:10 +0000; I have a stack of two T-225A-2 as the low band tank coil in my QRO HF2000 (2 x 3-500z). It does get quite warm on extended key down but so far no failure. John AI6LY Get Outlook for Android<https://a; /archives//html/Amps/2021-06/msg00016.html (8,210 bytes)
14. [Amps] toroid tank coil heating up (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Sun, 26 Sep 2021 15:54:03 +0000; My 2 x 3-500Z amp uses a two-stack T-225A-2 red mix iron powder toroid for 160-80-40. It gets hot, especially on 160, changing the loading and causing the grid current to drift up on extended transmi; /archives//html/Amps/2021-09/msg00018.html (6,727 bytes)
15. [Amps] QRO HF2000 plate choke (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Tue, 2 Nov 2021 02:24:53 +0000; Looking for a photo of the stock plate choke for a QRO Technologies HF2000 amp. Wondering about number of turns, spacing etc. Archived photos from the old QRO website don't show enough detail to copy; /archives//html/Amps/2021-11/msg00000.html (6,143 bytes)
16. Re: [Amps] QRO HF2000 plate choke (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Tue, 2 Nov 2021 13:53:31 +0000; Apparently a resonance. There is a burn mark in the center coil section after keying down on 28.425. It did not fry the coil but you could smell it immediately. Please tell us what these problems are; /archives//html/Amps/2021-11/msg00003.html (7,660 bytes)
17. [Amps] QRO Technologies HF2000 plate choke, cont. (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Mon, 8 Nov 2021 02:16:27 +0000; Hello again list, I received a few responses to my last post including and some photos of the plate choke from the original QRO HR2000 amps. They seem to be close wound with something like 120 turns; /archives//html/Amps/2021-11/msg00010.html (7,097 bytes)
18. [Amps] tuning a linear for AM operation (score: 1): Author: John Keating <john.keating@outlook.com>; Date: Mon, 31 Jan 2022 04:09:32 +0000; Looking for suggestions as to a quick way to tune a linear for AM operation. Amp will be undercoupled if tuned using an unmodulated carrier. I don't have an easy way tune at high modulation percentag; /archives//html/Amps/2022-01/msg00116.html (6,736 bytes)
19. [Amps] EIMAC vs Amperex 3-500 (score: 1): Author: "john.keating@outlook.com" <john.keating@outlook.com>; Date: Sat, 22 Oct 2022 01:30:38 +0000; Spec sheets for these tubes appear identical. Yet they behave differently in my dual 3-500 amp. I can drive the Amperex at 90w for near-legal limit out (power gain of about 16x) without exceeding 200; /archives//html/Amps/2022-10/msg00029.html (7,288 bytes)
20. Re: [Amps] EIMAC vs Amperex 3-500 (score: 1): Author: "john.keating@outlook.com" <john.keating@outlook.com>; Date: Sat, 22 Oct 2022 15:06:35 +0000; 200mA is the total for two tubes, that's in the amp tune condition, single tone key down. My question is more about why the Amperex and Eimacs draw such different grid current under identical operati; /archives//html/Amps/2022-10/msg00035.html (11,449 bytes)

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