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161. [Amps] Alpha 77Dx Replacement Transfomer Options (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Thu, 27 Mar 2008 11:01:57 -0400
It appears that Magcap has begun to offer replacement transformers based on the Peter Dahl specifications. I am considering the purchase of a spare, in-cabinet replacement transformer for my Alpha 77
/archives//html/Amps/2008-03/msg00291.html (7,691 bytes)

162. Re: [Amps] Relays (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Mon, 31 Mar 2008 07:15:36 -0400
Gary, one root-cause of an R.F. vacuum relay's premature demise is related to hot-switching. Oftentimes, the operator doesn't know its occurring. About ten years ago, I downloaded a firmware upgrade
/archives//html/Amps/2008-03/msg00382.html (9,333 bytes)

163. Re: [Amps] Relays (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Wed, 2 Apr 2008 10:32:40 -0400
I can't comment on the failure rate statistics, but I can tell you I have a real love-hate relationship with high-power PIN diodes. I know that they will not hold up as well as a vacuum relay under
/archives//html/Amps/2008-04/msg00036.html (9,369 bytes)

164. Re: [Amps] Relays (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Wed, 2 Apr 2008 13:46:32 -0400
Good suggestion, Vic. Although typically, that's half the solution. Generally, cabling going to the relay's pins contributes much to sound conductivity. For example, RG-213/214, RG-142 and coaxial c
/archives//html/Amps/2008-04/msg00040.html (8,984 bytes)

165. Re: [Amps] Alpha PA-77 (not D or S) Questions (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Tue, 29 Apr 2008 19:20:46 -0400
Bob, I would not run the 77 on 12M unless you update the plate choke. One possibility is to send the existing choke to Dick Byrd, N4UQ who will exchange it with a modified B&W 802 type. His choke us
/archives//html/Amps/2008-04/msg00324.html (7,729 bytes)

166. Re: [Amps] ALPHA DOA... (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Thu, 5 Jun 2008 11:30:08 -0400
I never thought I would live to see the day when the life expectancy of my old Alpha 70V with its extremely scarce 3CV1500A7 tube may actually exceed that of the microprocessor-based 4CX800 amplifie
/archives//html/Amps/2008-06/msg00026.html (7,761 bytes)

167. Re: [Amps] Amps DOA (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Thu, 5 Jun 2008 13:58:27 -0400
Same here. My original GE electric cook-top was only 10 years old and the in-counter mount spacings had changed. I was in search of ANY electric cook-top that would simply drop right into the counter
/archives//html/Amps/2008-06/msg00033.html (8,890 bytes)

168. Re: [Amps] Alpha 77dx (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Fri, 6 Jun 2008 14:49:07 -0400
I never could understand the fascination with running a par of 8877s, except for the bragging rights. My single-tube 77Dx is already capable of far more output power than authorized by U.S. regulati
/archives//html/Amps/2008-06/msg00047.html (7,847 bytes)

169. [Amps] Barker & Williamson (E.F. Johnson) HDVL-HDCL-HDA Coil Sets (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Sat, 17 Jan 2009 22:11:22 -0500
As part of a link-coupled tuner project, I need any of the above B&W "HD" series coil sets (e.g., HDVL, HDCL, HDA, etc.) for all bands, in any condition so long as the ceramic base insulator and jack
/archives//html/Amps/2009-01/msg00146.html (7,081 bytes)

170. [Amps] B&W "HD" Series Jumbo Banana Plug (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Sun, 18 Jan 2009 12:18:42 -0500
After spending a considerable amount of time in trying to determine if someone still, after 60 years, made large banana-style plugs, I discovered that the exact part as used in the high-power B&W coi
/archives//html/Amps/2009-01/msg00151.html (7,639 bytes)

171. [Amps] Alpha 77Dx (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Wed, 21 Jan 2009 15:21:20 -0500
I had an unusual condition today that seems to be the prelude of my Alpha 77Dx's 8877 going bad. Shortly after applying AC power (about 20 sec.), the HV was reduced from what is normally 2600VDC duri
/archives//html/Amps/2009-01/msg00215.html (7,956 bytes)

172. Re: [Amps] Alpha 77Dx (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Thu, 22 Jan 2009 06:51:33 -0500
Carl & Steve, Thanks for your excellent suggestions. My first thought was a cathode-to-filament fault. I'll be swapping tubes to verify. If its not the 8877, I will be investigating Carl's suggestio
/archives//html/Amps/2009-01/msg00235.html (7,237 bytes)

173. [Amps] Alpha 77Dx Filament (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Thu, 22 Jan 2009 13:45:46 -0500
Looking for opinions on the subject of 8877 filament voltage... Due to high AC line voltage here (~ 127/254 VAC), my 8877 filament sees approximately 5.75 Vrms (as measured on a Fluke 189 True RMS DV
/archives//html/Amps/2009-01/msg00240.html (8,189 bytes)

174. Re: [Amps] Alpha 77Dx Filament (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Thu, 22 Jan 2009 14:08:08 -0500
Just thought about another possibility... If I add an RF Parts bifilar filament choke to the 77Dx, there may be just enough series IR loss in the choke to get the 8877 back into the specified filamen
/archives//html/Amps/2009-01/msg00241.html (8,946 bytes)

175. Re: [Amps] Alpha 77Dx Filament (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Fri, 23 Jan 2009 10:47:32 -0500
I bit the bullet and ordered the RF Parts filament choke for the Alpha 77Dx. I've determined that two of my 8877 suffer from an intermittent cathode-to-filament short -- which explains why there's no
/archives//html/Amps/2009-01/msg00268.html (8,360 bytes)

176. [Amps] Alpha 77Dx Filament - No Free Lunch (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Fri, 23 Jan 2009 13:58:32 -0500
Earlier, I had posted a comment about being able to "bring life back" to my 8877 tubes where they had developed an intermittent short between cathode and filament. One astute observer thwarted my thi
/archives//html/Amps/2009-01/msg00272.html (8,773 bytes)

177. [Amps] Alpha 77Dx Filament Mod Update (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Sat, 31 Jan 2009 22:16:18 -0500
For those interested, I've begun to document the filament mods conducted on my Alpha 77Dx. Recall, that I wanted to (1) decrease the filament voltage to the 8877; and (2) float the filament above gro
/archives//html/Amps/2009-01/msg00381.html (9,703 bytes)

178. Re: [Amps] Alpha 77Dx Filament Mod Update (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Sun, 1 Feb 2009 15:39:46 -0500
Gary, I agree with that assessment. And that probably explains why the AL-1500 is tied since (I believe) Tom designed that amp for Ameritron. As to how important this is in real operation, I am not
/archives//html/Amps/2009-02/msg00020.html (10,227 bytes)

179. Re: [Amps] Glitch Resistor (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Mon, 2 Feb 2009 11:33:41 -0500
Bob, For about $3.00 ea., Mouser sells new Dale/Vishay silicone enamel power resistors. The P/N is HL05006Z50R00JJ: http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMuQ5%2fsBR7SoAr9dHZ%2f
/archives//html/Amps/2009-02/msg00024.html (9,223 bytes)

180. Re: [Amps] Alpha 77Dx Filament Mod Update (score: 1)
Author: "Paul Christensen" <w9ac@arrl.net>
Date: Mon, 2 Feb 2009 11:52:11 -0500
Quoting myself: screw from these amps. The chassis and neutral can be un-linked by cutting a jumper at the Cinch-Jones power plug. Then, the three-wire power cord is replaced with a four-wire cord in
/archives//html/Amps/2009-02/msg00027.html (8,121 bytes)

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