Chunwang:
I have decided to push back on the re-lableing of the figures---too
much work and will not improve, in my opinion.
I will look at the other things after I get to the office in a couple
of hours. Have to get going because fereezing rain is arriving soon.
Have been working at home up to now today. I might call later.
Bill
At 02:00 PM 1/16/2011, you wrote:
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>Today's Topics:
>
> 1. Restoring DX100 (John Lyles)
> 2. Re: Restoring DX-100 (Glen Zook)
> 3. Re: Restoring DX-100 (Bill, W6WRT)
> 4. DX-100 Restoratiom (Bob Good)
>
>
>----------------------------------------------------------------------
>
>Message: 1
>Date: Sat, 15 Jan 2011 14:04:17 -0700
>From: John Lyles <jtml@losalamos.com>
>Subject: [Amps] Restoring DX100
>To: amps@contesting.com
>Message-ID: <4D320BD1.1040900@losalamos.com>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>900 volts on pair of 6146, 6146A, 6146B is exceeding max ratings for the
>tube. Not only is there overdissipation risk but also arc over. The
>socket for the rectifier tube will also be close to breaking down. Mine
>was definitely arced there, and I eventually solid-stated the HV
>entirely. eliminating those tube sockets from the failure chain. This
>did provide nearly 800 volts before key down. It dropped with carrier.
>I don't remember whether the 1625s liked it, as they were quite rosy. I
>replaced them with 6CA7/EL34s with a screen regulator.
>
>125 - 130 watts output was typical in mine. Its pushing the tubes a bit,
>but that's a personal thing.
>
>The two series electrolytics and their bleeder are weaknesses in the
>DX100, esp. given the vintage. Recommended to replace them up front and
>don't take the risk of leakage in one causing the other to be
>overvoltaged. Check the mid point voltage to make sure that this doesn't
>happen, esp since the bleeder is tapped there to provide screen voltage
>I believe (memory doesn't always serve me).
>
>73
>John
>K5PRO
>
>
>------------------------------
>
>Message: 2
>Date: Sat, 15 Jan 2011 13:16:11 -0800 (PST)
>From: Glen Zook <gzook@yahoo.com>
>Subject: Re: [Amps] Restoring DX-100
>To: Roger D Johnson <n1rj@roadrunner.com>
>Cc: amps <amps@contesting.com>
>Message-ID: <745881.52750.qm@web121706.mail.ne1.yahoo.com>
>Content-Type: text/plain; charset=us-ascii
>
>I know what the RCA transmitting tube manual and the specification
>sheets show for the output. However, those are outputs which do not
>take into consideration things like losses in matching networks,
>etc. In the "real world", at 3.5 MHz you are going to be lucky to
>see anything more than around 70% efficiency rather than the 77%
>theoretical efficiency shown in the tube manual. Efficiencies
>between 60% to 65% are much more realistic in the long
>run. However, with brand new tubes you may see efficiencies
>approaching 70% on the 80-meter band, but, as the tubes age, the
>efficiency is going to drop.
>
>Also, as the frequency of operation increases the efficiency decreases.
>
>The 6293, which is basically the same tube as the 6146A/8298 except
>that it has a more robust plate construction, is definitely a good
>choice and those tubes, generally, last a considerably longer period
>when run in the same operating parameters as the 6146.
>
>Glen, K9STH
>
>Website: http://k9sth.com
>
>
>--- On Sat, 1/15/11, Roger D Johnson <n1rj@roadrunner.com> wrote:
>
>My RCA tube manual says (for 2 tubes ICAS) 600 volts Vp, 214 ma Ip,
>Po 104 watts! As you state in your article on 6146 series tubes,
>the 6293 is mo better in this application.
>
>
>
>
>
>------------------------------
>
>Message: 3
>Date: Sat, 15 Jan 2011 15:15:58 -0800
>From: "Bill, W6WRT" <dezrat1242@yahoo.com>
>Subject: Re: [Amps] Restoring DX-100
>To: Amps reflector <amps@contesting.com>
>Message-ID: <cq34j618c03tp85p3o1bsoccjj8hv6398m@4ax.com>
>Content-Type: text/plain; charset=us-ascii
>
>ORIGINAL MESSAGE:
>
>On Sat, 15 Jan 2011 10:56:21 -0500, "Bob Good" <k4bg@planters.net>
>wrote:
>
> > Since it is a common transformer supplying both filament and LV,
> I do not know how I am going to slowly bring up the voltage to the
> electrolytic since I have to have full filament voltage...
>
>REPLY:
>
>Go ahead and use the variac on both filaments and HV. The filaments will
>begin to conduct well before they reach max temperature and no harm will
>be done. In a way, it might even be better because the current will be
>limited by the low filament temperature.
>
>73, Bill W6WRT
>
>
>------------------------------
>
>Message: 4
>Date: Sat, 15 Jan 2011 18:45:56 -0500
>From: "Bob Good" <k4bg@planters.net>
>Subject: [Amps] DX-100 Restoratiom
>To: <Amps@contesting.com>
>Message-ID: <99C350A256AB42ED8B064CFD4E44BC7E@Laptop>
>Content-Type: text/plain; charset="iso-8859-1"
>
>Thanks to the large group who responded to my previous post
>concerning my DX-100 Restoration project. Excellent advice was
>offered and I now feel comfortable continuing with the
>project. Your contributions are greatly appreciated. "73, Bob K4BG
>
>------------------------------
>
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>
>End of Amps Digest, Vol 97, Issue 26
>************************************
William Q. Meeker
Department of Statistics
2109 Snedecor Hall
Iowa State University
Ames, Iowa 50011
Phone: 515-294-5336
Fax: 515-294-4040
Home Fax: 515-232-1323
www.public.iastate.edu/~wqmeeker
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