No, Alphas with 8877's all have 3-minute timers. They won't key up until the
time-out occurs. Others have already posted that the Eimac sheet on this
tube says nothing about delaying HV application. That is correct, for the
reasons already given.
Since my main interest is 160 meters, I chose a single-bander amp. dedicated
to that band, using the old indestructible 3CX3000A7. Brief band openings
occur often, with no warning, and last a few minutes, especially at
gray-line times. This set-up allows instant pouncing. I have worked a lot of
rare DX that had come and gone in 3 minutes. Switch back to off, and all the
blower noise and heat are gone until the amp. is needed again. I do have a
3-minute timer, but it is for the blower. It runs after the mains switch is
turned off. An 8-inch muffin fan is mounted on the lid of the RF deck for
use in the winter to heat the ham shack nicely!
(((73)))
Phil, K5PC
Subject: Re: [Amps] 8877 Time Delay Query
I imagine that Alpha figured if you bought one of their amps, you'd already
know to let a tube warm up? That kind of reminds me of an instruction manual
that came with a VCR I had bought. The very first page showed Superman
reading the manual and scratching his head. Anyhow, I always let any of them
warm up at least 3-5 minutes. A lot of people complain about warm up time
but to be honest, it don't take that long if you remember to fire up the amp
as soon as your in the shack, and not wait until you need it. Trading off a
little warm up time for life expectancy means a lot. And I'll still about
bet a tube will outlast solid state 2:1 in rough conditions.
Best,
Will
*********** REPLY SEPARATOR ***********
On 7/28/05 at 1:42 PM Phil Clements wrote:
>Another to add to the list; Alpha never bothered to delay HV on any of
>their
>8877 amps.
>
>(((73)))
>Phil, K5PC
>
>
>-----Original Message-----
>From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
>Behalf Of w2cqm@juno.com
>Sent: Thursday, July 28, 2005 7:15 AM
>To: Amps@contesting.com
>Subject: [Amps] 8877 Time Delay Query
>
>Can anyone help with specific knowledge about the 3 minute time delay and
>the application of HV on the Eimac 3CX1500A7/8877? The 8877 tube data
>sheet only specifies a 3 minute filament warmup. However it does not
>mention whether HV can be applied when the tube is turned on (no
>excitation of course) and filament voltage applied. Ameritron (AL1500)
>holds off application of HV for the full delay period. Dentron did not
>in their 8877 amp with no apparent problems! I hasten to mention that I'm
>not too confident about the general level of Dentron circuitry and that
>testimonial. The 3CX800A7, smaller version of the 8877, date sheet
>specifically admonishes the ham not to apply either RF excitation or
>high voltage "...for a minimum of three minutes (of filament warmup)...to
>allow for proper conditioning of the cathode surface". At this point, I'm
>not certain if the 8877 is materially different from the smaller, yet
>similar tube. If the application of HV makes no difference with the 8877
>during the warmup period, it saves a lot of control circuitry and a
>separate filament transformer; especially when both windings are from
>the same xmfr. Consequently, the delay can be incorporated in the antenna
>relay circuit only. In the 8877 amps I've built, I've always delayed the
>application of HV just to make certain there'd be no damage. Any
>comments based on first hand engineering data would be appreciated. Ron
>W2CQM/3
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