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321. Re: [Amps] Heat Dissapating 8877 HV Plate Caps (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Sat, 25 Aug 2007 07:53:22 +0100; Just to emphasise a point here - the cap that covers the pinchoff is thin metal, with barely any contact onto the rest of the anode metalwork. The heatflow into/through it is negligible. It certainly; /archives//html/Amps/2007-08/msg00172.html (8,447 bytes)
322. Re: [Amps] gs-35b bias pb? (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Tue, 28 Aug 2007 12:31:46 +0100; Something is allowing conduction between the anode and grid. Maybe gas inside the tube, maybe cathode material on the grid, maybe a short. Try following the instructions here: http://www.nd2x.net/tub; /archives//html/Amps/2007-08/msg00226.html (7,210 bytes)
323. Re: [Amps] T-R switching (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Thu, 30 Aug 2007 07:58:51 +0100; Sounds very much like rf is getting into things. I can't see how Z1/T17 are being damaged by dc in the circuit if the control input is a switch to ground as you show. I suggest you add 10nF disc cera; /archives//html/Amps/2007-08/msg00256.html (8,626 bytes)
324. Re: [Amps] Shipping Alpha 91b from US to Eu (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Sun, 02 Sep 2007 21:21:23 +0100; Maybe they don't any more. Last conversation I had with them, the amplifier products were not RoHS compliant which means it's illegal to sell them into the EU. Steve ________________________________; /archives//html/Amps/2007-09/msg00017.html (8,365 bytes)
325. Re: [Amps] Shipping Alpha 91b from US to Eu (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Sun, 02 Sep 2007 22:44:33 +0100; The cut off was 1st July 2006. Non compliant goods had to have been already sold or 'on the market' by that date. Items still in production don't count. The stupidity of the legislation means it appl; /archives//html/Amps/2007-09/msg00018.html (8,958 bytes)
326. Re: [Amps] AL1500 cooling mod? (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Thu, 06 Sep 2007 18:55:13 +0100; Yes, that's the number most manufacturers use - but - the starting point is typically 2000 hours of life at 105C ambient and maximum rated ripple simultaneously. If you come back (say) 20 degrees on; /archives//html/Amps/2007-09/msg00053.html (7,944 bytes)
327. Re: [Amps] Zener diode for TL922 (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Sat, 08 Sep 2007 07:45:14 +0100; You could also look at information about the triode control board designed by G3SEK - http://www.ifwtech.co.uk/g3sek/ and also see the addendum at the end of http://www.landfall.net/Radio/8877-1.htm; /archives//html/Amps/2007-09/msg00103.html (8,141 bytes)
328. Re: [Amps] switching power supply for tube amplifier (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Fri, 14 Sep 2007 18:58:37 +0100; Here's a couple of pages where you might find a starting point. http://lea.hamradio.si/~s57uuu/emeconf/eme96.htm http://w3ref.cfn.ist.utl.pt/cupido/twtps.html If you try it, please come back and repo; /archives//html/Amps/2007-09/msg00150.html (7,774 bytes)
329. Re: [Amps] switching power supply for tube amplifier (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Fri, 14 Sep 2007 19:42:07 +0100; Another thought - buy a relatively cheap 28 or 48V switching supply second hand, and put your effort into building a solid state amp to go with it. Steve _____________________________________________; /archives//html/Amps/2007-09/msg00151.html (7,213 bytes)
330. Re: [Amps] switching power supply for tube amplifier (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Fri, 14 Sep 2007 22:27:58 +0100; Down the bottom of the page there's some interesting archive stuff. Can anything as neat and tidy as the 813 amps really work? :-) Steve _______________________________________________ Amps mailing l; /archives//html/Amps/2007-09/msg00158.html (7,999 bytes)
331. Re: [Amps] switching power supply for tube amplifier (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Fri, 14 Sep 2007 22:57:55 +0100; The orange is there - just not for long. Transistors have a bad reputation from their earlier ancestors. With simple protection they can be very rugged these days. Most of the time tubes look better.; /archives//html/Amps/2007-09/msg00159.html (8,766 bytes)
332. Re: [Amps] switching power supply for tube amplifier (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Sun, 16 Sep 2007 22:02:26 +0100; It's important to take all the factors into consideration. There's some brands/designs of tube amps that have a poor reputation here, primarily because of design failings. In 31 years of solid state; /archives//html/Amps/2007-09/msg00172.html (8,899 bytes)
333. Re: [Amps] stability of amps (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Mon, 24 Sep 2007 23:35:12 +0100; How does the instability show - what frequency is any oscillation at? Steve _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/l; /archives//html/Amps/2007-09/msg00231.html (6,868 bytes)
334. Re: [Amps] 6 mtrs: (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Tue, 25 Sep 2007 07:51:39 +0100; I'd add to that list - in a multiband amp the tune C itself contributes vhf resonances because of physical size. I suspect it's the dominant factor. Steve ____________________________________________; /archives//html/Amps/2007-09/msg00249.html (7,107 bytes)
335. Re: [Amps] 6 mtrs: (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Tue, 25 Sep 2007 12:38:03 +0100; For sure - I was going to make the same comments as you about a 10m single bander. Steve _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.; /archives//html/Amps/2007-09/msg00252.html (7,732 bytes)
336. Re: [Amps] New SB-200 owner (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Thu, 27 Sep 2007 14:36:28 +0100; I think they can do better linearity than that - the amps I built have all done so at 250-300W/tube. The STC data sheet for 4CX250B gives IMD figures under the typical operating conditions. At 2kV,; /archives//html/Amps/2007-09/msg00389.html (9,351 bytes)
337. Re: [Amps] New SB-200 owner (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Thu, 27 Sep 2007 14:59:30 +0100; My driver ran around -55dBc IMD3 and I never tried to measure IMD5, it was off the screen. I use dBc to mean referenced to a single tone (assuming that's what you mean by 'method of testing'). Steve; /archives//html/Amps/2007-09/msg00398.html (10,660 bytes)
338. Re: [Amps] New SB-200 owner (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Thu, 27 Sep 2007 15:27:41 +0100; I'm sorry if we ended up at cross purposes. I was talking about 2 tone measurements - just like when I was designing mil gear. Steve _______________________________________________ Amps mailing list; /archives//html/Amps/2007-09/msg00405.html (11,889 bytes)
339. Re: [Amps] New SB-200 owner (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Thu, 27 Sep 2007 15:35:00 +0100; It needn't be. If you stay simple, a dropper from the anode supply with an uncomplicated active shunt regulator costs about a pack of beer. Regulation is more than adequate. I begrudge wasting 30W as; /archives//html/Amps/2007-09/msg00406.html (8,830 bytes)
340. Re: [Amps] New SB-200 owner (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Thu, 27 Sep 2007 16:07:32 +0100; There were no problems with the measurements, and I'm familiar with what Tom was saying. I've not seen any figures from Eimac giving IMD for 4CX250s - the data sheet I referenced was from STC, who ma; /archives//html/Amps/2007-09/msg00409.html (10,212 bytes)

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