[Amps] 8877 Time Delay Query

[Jerry Muller]

Dentron would be suspect, Alpha wouldn't.

73, Jerry K0TV (Not a real zero, I just play one on K0TV)

----- Original Message ----- 
From: "Phil Clements" <philc at texascellnet.com>
To: <w2cqm at juno.com>; <Amps at contesting.com>
Sent: Thursday, July 28, 2005 2:42 PM
Subject: Re: [Amps] 8877 Time Delay Query


> 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 at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of w2cqm at juno.com
> Sent: Thursday, July 28, 2005 7:15 AM
> To: Amps at 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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