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Re: [Amps] How to read the 3-500Z spec sheet?

Subject: Re: [Amps] How to read the 3-500Z spec sheet?
Date: Sun, 23 May 2010 08:37:41 EDT
List-post: <">>
Bill, Any tube run within its specified limits is OK, however with ham  
radio the limiting factor is cooling.  You have to take into account that  tube 
specs are listed for CCS operation.  This assumes that the tube is  
receiving the specified amount of cooling which is ALSO a spec on the tube data 
chart.  So the question to your question is this.  Does your amp  provide a 
CCS rated amount of cooling?  This is not an answer to your  question but 
rather the information you really want to know.  If you could  find the 
operating temperature of the glass envelope of the 3-500, you can buy a  rather 
inexpensive infra red thermometer and shoot the temperature of the  envelope 
when you are running WSJT at the end of the transmission and see what  the 
temperature is and if it is in the ballpark.  On the other hand perhaps  
knows for sure what the level of cooling is in your amp and if it is  100% 
up to the CCS rating of the tube.  If you are savvy about the anode  color 
of a 3-500 under normal CCS operation you can probably tell if the tube is  
within limits.  I don't know if this helped you, but I think this is the  
information you are after.  Lou
In a message dated 5/23/2010 8:25:43 A.M. Eastern Daylight Time, writes:

Does  anyone have any further thoughts or comments on this?  Is it OK to 
put  the amp into WSJT service at 400 watts?

73, Bill NZ5N

--- On  Sat, 5/22/10, Bill Dzurilla <> wrote:

>  From: Bill Dzurilla <>
> Subject: Re: How to  read the 3-500Z spec sheet?
> To:
> Date:  Saturday, May 22, 2010, 5:54 PM
> Thanks for the reply, but I  don't
> think I follow.
> Guess I had interpreted the  spec sheet as meaning that, if
> you configure the tube in class B  grounded grid and apply HV
> of 2000v, you should expect to see 400ma of  plate current
> and 500 watts of peak "useful" output.
>  I am just trying to figure out if this homebrew amp, which
> does not  have any manual or detailed info, is working as it
> should.  If  the spec sheet means what I think it means,
> it seems the amp is in the  ballpark.
> 73, Bill NZ5N
> >Spec sheets don't know  anything about load or no load.
> If it says for
> >example,  3000 volts at 500 mA, that's what it means. 
> >73, Bill  W6WRT
> --- On Sat, 5/22/10, Bill Dzurilla  <>
> wrote:
> > From: Bill  Dzurilla <>
> > Subject: How to read the  3-500Z spec sheet?
> > To:
> > Date:  Saturday, May 22, 2010, 10:39 AM
> > Hi,
> > 
> >  I'm looking at the spec sheet for the 3-500Z at
> >
> > 
>  > At the top of the second pages, it gives numbers for
> > various  parameters at different levels of high
> voltage
> > (3000,  2500, 2000, and 1500).  Are these voltages at
> > load or  no-load?  And how do Single-Tone DC Plate
> > Current and Peak  Envelope Useful Output Power
> correlate with
> > key down  plate current and output?
> > 
> > The reason I ask is  because I picked up a homebrew 6m
> amp
> > with a single  3-500Z, which uses a power transformer
> from an
> >  SB-200.  Key down power output is 400w.  Assuming
> > the  amp's meters are accurate, no-load plate voltage
> is
> >  2300v, and plate voltage under full load is 1950v. 
> > Plate  current with no drive is 100ma and plate current
> with
> >  full drive is .52a.  About 40 watts of drive
> produces
>  > the full 400w out.  Further increases in drive, up
>  to
> > 100w, do not increase output.
> > 
> >  Judging from the spec sheet's 2000v table, my guess is
> that
>  > the amp is performing as well as it can with this
> power
>  > supply.  I know that a converted AL-80B with a
>  single
> > 3-500Z can produce 900w or so on 6m, but it has a
>  3000v
> > p/s.
> > 
> > Do you think it would be OK  to run this amp at the
> full
> > 400w in WSJT (continuous  carrier) modes?
> > 
> > 73, Bill NZ5N 
> >  
> > 
> >       
> > 

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