[Amps] How to read the 3-500Z spec sheet?
Gudguyham at aol.com
Gudguyham at aol.com
Sun May 23 06:30:48 PDT 2010
Bill, considering you can run up to 3500 volts on the 3-500, the 1950v you
have is low. When you raise the plate voltage you lower the amount of
plate current and grid current you need for a given output which is a good
thing, However the bottom line still comes down to plate dissipation. I
would say that 520 mills at CCS for the 3-500 is high, however not for SSB.
I'd like to see you up the plate voltage in that amp. It might be difficult
to read the seal temperature of a tube in the socket. I wonder if there is
a envelope temperature you can read which would be easier, although I
suppose that could be good and the seal temp could be bad depending on how the
air distributes around the tube. My guess would be that seal temperature
would be best managed by a pressurized plenum using chimneys for CCS
operation. Seems like some other types of amps with fan cooling do not keep the
seals cool enough during CCS operation. Some 3-500 tube pins melt the
solder on the pins they get so hot when run in CCS operation.
In a message dated 5/23/2010 9:13:07 A.M. Eastern Daylight Time,
billdz.geo at yahoo.com writes:
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, Gudguyham at aol.com <Gudguyham at aol.com> wrote:
From: Gudguyham at aol.com <Gudguyham at aol.com>
Subject: Re: [Amps] How to read the 3-500Z spec sheet?
To: billdz.geo at yahoo.com, amps at contesting.com
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 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
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 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,
billdz.geo at yahoo.com 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 <billdz.geo at yahoo.com> wrote:
> From: Bill Dzurilla <billdz.geo at yahoo.com>
> Subject: Re: How to read the 3-500Z spec sheet?
> To: amps at contesting.com
> 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 <billdz.geo at yahoo.com>
> wrote:
>
> > From: Bill Dzurilla <billdz.geo at yahoo.com>
> > Subject: How to read the 3-500Z spec sheet?
> > To: amps at contesting.com
> > Date: Saturday, May 22, 2010, 10:39 AM
> > Hi,
> >
> > I'm looking at the spec sheet for the 3-500Z at
> > http://www.scottbecker.net/tube/sheets/088/3/3-500Z.pdf
> >
> > 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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