[Amps] 3-400Z zsac tspa

[Gary Schafer]

Hi John,

Thanks for the info. I finally found the data sheet online. It shows 100 ma
each at 3kv with zero bias and 73 ma at 2500 volts. I had gotten a few
replies with various amounts of current. Bob said that they would draw
around 250 ma at 3 kv and no bias. The amp I have shows right around 250 ma
at 3 kv so I guess it is in the ball park.
The amp is an old TMC unit that has auto presets for the tuning. Had it
laying around for some years and just now dragging it out and getting it
going.

The next question is how much should I run the ZSAC at with 3 kv on the
plates. At 250 ma that is dissipating 750 watts which seems awfully high.
At 75 ma each at 2500 volts is about 375 watts dissipation.
Is there a general rule of thumb for idle dissipation compared to plate
dissipation capability?

This amp was originally shipped with 8163's in it. I see in some of the
handbooks they show the 8163 as having an upper frequency limit of 30 MHz
and slightly higher plate current than the 3-400Z. The 3-400Z has an upper
frequency limit of 110 MHz.

On the eimac spec sheet that I found the sheet lists it as 8163/3-400Z which
would indicate that they are the same tube??

I can't clearly read the printing on the tubes in the amp so I am not sure
exactly what they are.

73
Gary  K4FMX

> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of John T. M. Lyles
> Sent: Friday, March 16, 2007 3:02 PM
> To: amps at contesting.com
> Subject: [Amps] 3-400Z zsac tspa
> 
> Hi Gary
> You can look it up on the tube constant current curves in the
> datasheet. That should be available online somewhere.
> 
> Depending on your Grid or Cathode Bias voltage, pick off the closed
> anode current estimate, above 3 kV anode voltage. Not sure if you are
> talking zero bias or with a slight bias of 10-20 volts there?
> 
> john
> K5PRO
> 
> >
> >Date: Thu, 15 Mar 2007 21:26:09 -0400
> >From: "Gary Schafer" <garyschafer at comcast.net>
> >Subject: [Amps] 3-400Z ZSAC
> >To: "'amps'" <amps at contesting.com>
> >Message-ID: <20070316012550.E593F319B34 at dayton.contesting.com>
> >Content-Type: text/plain;	charset="US-ASCII"
> >
> >Can anyone tell me what the ZSAC should be on a pair of 3-400Z tubes at
> 3000
> >volts?
> >
> >
> >
> >Thanks
> >
> >Gary  K4FMX
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