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Total 640 documents matching your query.

361. [Amps] 5V @ 30A Filament Transformer Wanted (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Wed, 12 Sep 2012 21:49:25 -0400
Looking for a 5V/30A filament transformer with a 240 VAC primary. Hammond and Stancor types are available but only with a 120V primary. Finally getting around to converting a 77Dx to a 3CX1500D7 for
/archives//html/Amps/2012-09/msg00241.html (6,709 bytes)

362. Re: [Amps] 5V @ 30A Filament Transformer Wanted (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Thu, 13 Sep 2012 21:02:32 -0400
What a good source for an all original 77 filter cap Paul? I got one coming in after I fix the customers HF-2500. Carl, Condenser Products in Brooksville, FL can make oil caps in most any size you wa
/archives//html/Amps/2012-09/msg00242.html (9,677 bytes)

363. Re: [Amps] Sad News for Eimac Users (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Sun, 23 Sep 2012 14:22:31 -0400
BTW, I had never heard of the 3CX1500D7 until recently. It's a fast warm-up (Thoriated Tungsten Cathode) variation of the 3CX1500A7 with a 50 watt grid dissipation rating. It seems preferable to the
/archives//html/Amps/2012-09/msg00274.html (9,345 bytes)

364. Re: [Amps] Novel Screen Grid Regulator (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Thu, 27 Sep 2012 12:52:18 -0400
Jim, Very interesting circuit since the MOSFETs function like a high-power, active voltage divider. I did note that the non-inverting input to U1a may be susceptible to the effects of both the normal
/archives//html/Amps/2012-09/msg00307.html (7,902 bytes)

365. Re: [Amps] QSK on the cheap AND Parasitic (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Sat, 6 Oct 2012 21:25:06 -0400
The only way to know is measure it. And timing measurements are easy with an oscilloscope, triggered by the key line. As you point out, some transceivers add delay through a menu parameter to ensure
/archives//html/Amps/2012-10/msg00043.html (8,598 bytes)

366. Re: [Amps] Question re GU-74B grid current (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Mon, 22 Oct 2012 15:18:14 -0400
Val, For the sake of completeness, I believe the typical "three state" bias voltages for the ACOM 2000A (GU74B) are as follows: -124V on standby; -75V during plate idling with PTT key line enabled; a
/archives//html/Amps/2012-10/msg00111.html (10,114 bytes)

367. Re: [Amps] The GU84B and GU78B tubes / some brief history (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Mon, 29 Oct 2012 11:38:29 -0400
Ian, If you could list the top few important parameters to low distortion tetrode sign, what are they? I think most of us know the importance of well-regulated screen voltage. Other top factors? Paul
/archives//html/Amps/2012-10/msg00205.html (10,502 bytes)

368. Re: [Amps] The GU84B and GU78B tubes / some brief history (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Tue, 30 Oct 2012 07:22:48 -0400
Ian, Great information and thanks for sharing it. Paul, W9AC If you could list the top few important parameters to low distortion tetrode sign, what are they? I think most of us know the importance o
/archives//html/Amps/2012-10/msg00214.html (14,888 bytes)

369. Re: [Amps] Best Alpha amp (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Mon, 19 Nov 2012 12:16:10 -0500
It sounds like it was a defective drive. These are common Jackson Brothers' drives with two mounting forks. Two tapped/threaded holes on the outer drive are used to mount the dial legends. Changing t
/archives//html/Amps/2012-11/msg00134.html (9,075 bytes)

370. Re: [Amps] Vacuum Relay (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Thu, 13 Dec 2012 14:15:57 -0500
A scope isn't going to tell all but it tells a lot about a signal. They're not difficult to use and don't have to cost a lot. It doesn't take long to find some incredibly good buys on used Tektronix
/archives//html/Amps/2012-12/msg00078.html (9,357 bytes)

371. Re: [Amps] Vacuum Relay (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Fri, 14 Dec 2012 15:06:14 -0500
The dual trace function isn't required to determine if hot-switching occurs, but is required to measure system timing. Sheesh, did I write that? My mind was stuck looking at the current trigger confi
/archives//html/Amps/2012-12/msg00081.html (9,400 bytes)

372. Re: [Amps] Vacuum Relay (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Fri, 14 Dec 2012 16:07:45 -0500
With a 100 MHz Tek 465 analog scope now under $100 with at least one probe its a shame not to have one on hand for all sorts of uses. You also get more triggering and display combinations than the mo
/archives//html/Amps/2012-12/msg00083.html (9,531 bytes)

373. Re: [Amps] Vacuum Relay (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Mon, 17 Dec 2012 17:46:49 -0500
Pete, On a single or multi channel scope, connect an RF sample from a loop, sense wire, or capacitive bridge to the vertical input (or Channel A on a multi-channel scope). However, don't be tempted t
/archives//html/Amps/2012-12/msg00094.html (14,071 bytes)

374. Re: [Amps] List of Upgrades or Mods for Alpha 77DX / SX? (score: 1)
Author: Paul Christensen <w9ac@arrl.net>
Date: Sun, 30 Dec 2012 16:03:08 -0500
Rich, On my 77Dx, the only changes have been to 1) balance the 8877 filament, taking all filament current off the chassis; 2) adding a filament choke; 3) adding Siemens GDTs; and 4) ensuring the 8877
/archives//html/Amps/2012-12/msg00195.html (8,431 bytes)

375. Re: [Amps] List of Upgrades or Mods for Alpha 77DX / SX? (score: 1)
Author: Paul Christensen <w9ac@arrl.net>
Date: Sun, 30 Dec 2012 16:10:26 -0500
I suppose (5) would include an upgrade of the PS filter cap. Several of us are now using oil caps rated at 35uF @ 5KV. Paul, W9AC Sent from my iPhone5 _______________________________________________
/archives//html/Amps/2012-12/msg00197.html (8,692 bytes)

376. Re: [Amps] Panel Lettering (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Mon, 31 Dec 2012 12:13:17 -0500
In place of dry transfer letters, I started using a Brother P-Touch PT-2430PC printer. Black on clear matte finish can be purchased in various tape widths. There's no special software loaded on the P
/archives//html/Amps/2012-12/msg00205.html (8,930 bytes)

377. Re: [Amps] Group Purchase - Alpha 77Dx-Sx Oil Filter Cap (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Mon, 31 Dec 2012 12:26:02 -0500
The caps Rich is referring to are made by the same OEM going back to the original ETO ALPHA SEVENTY series some 42 years ago. They are exact drop-in replacements and no additional re-work is required
/archives//html/Amps/2012-12/msg00207.html (10,228 bytes)

378. Re: [Amps] Peter Dahl transformers (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Mon, 11 Feb 2013 14:03:39 -0500
A few months ago, EPD was highly recommended to me by Reid Brandon when he was still with Eimac. Paul, W9AC Have no fear about Harbach not making transformers. My friend Peter Eggimann has been makin
/archives//html/Amps/2013-02/msg00082.html (8,246 bytes)

379. [Amps] Universal Sequential QSK Board (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Mon, 11 Feb 2013 15:07:37 -0500
with the QSK circuit on LZ500ZB and/or have words of wisdom? I wonder if the QSK circuit has been played with and I can't operate it like this. (I'm really knew to "QRO" stuff). Anyone wishing to eit
/archives//html/Amps/2013-02/msg00085.html (13,477 bytes)

380. Re: [Amps] hot keying the amp? (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Wed, 13 Feb 2013 14:28:26 -0500
Apart from the K2, notice that T6 is less than T3, resulting in so-called "dit shortening." Adding back the right amount of lead time to the RF envelope through either hardware or software pulse-stre
/archives//html/Amps/2013-02/msg00104.html (11,022 bytes)

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