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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?
From: Bill Dzurilla <>
Date: Sun, 23 May 2010 06:13:07 -0700 (PDT)
List-post: <">>
Thanks, Lou.  There is little info available about this homebrew amp so I'm 
just trying to be safe.  Have not yet tried it in WSJT mode but tube appears 
normal in color during my testing so far.  The amp has 2 fans so hopefully 
cooling will be adequate.  The spec sheet says max 200C at the base seals and 
225C at the plate seal.  The infrared thermometer is a good idea.

What this amp really needs, I think, is higher plate voltage.  This transformer 
was intended for the tubes in an SB-200, not for a 3-500Z.  It seems to me that 
400w key down is about the best I can hope for with just 1950v on the plate.  
The .52a key down current is higher than the .4a "singletone" on the spec sheet 
and was not sure if that was a concern.

73, Bill 

--- On Sun, 5/23/10, <> wrote:

From: <>
Subject: Re: [Amps] How to read the 3-500Z spec sheet?
Date: Sunday, May 23, 2010, 8:37 AM


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 
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 
someone 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 
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:
  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 
> 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 
> 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 
> --- 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
> > 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
> > 3-500Z can produce 900w or so on 6m, but it has a
> > 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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