Thanks to Garey and to those who replied off-line to my question about the one
ohm resistor. May I trouble you with another question?
I have a homebrew 6m 3-500Z amp with similar circuitry to the L-7 and L-4B.
Unfortunately, its power supply is not that beefy (2000v) and I don't get full
output. So I came up with the idea of trying to connect my L-7 power supply to
the other amp.
To do this, I disconnected the homebrew amp's internal p/s HV connections
(leaving in place the internal p/s's filament, relay, and blower connections)
and attempted to connect the Drake p/s. I connected the Drake p/s's HV cable
to the homebrew amp's B+ connection, and I connected the Drake p/s's B-
connection (pin 6 of the Cinch connector) to ground on the homebrew amp. I
also grounded the chassis' together.
To turn the Drake p/s on, I jumpered pins 1 and 3 of the Cinch connector.
After hooking all this up, I turned everything on and it did not work. There
was no RF output at all from the homebrew amp. The plate current meter showed
some plate current, but much less than usual.
What am I doing wrong? All I can think of is that I'm forgetting to make some
connection, or that I have the Drake p/s AC input wired wrong. Jumpering pins
1 and 3 seems to be the equivalent of turning the Power switch to On and
turning the CW Tune/SSB switch to SSB, but perhaps I'm reading this wrong or
forgetting something.
Any thoughts or ideas would be greatly appreciated.
73, Bill NZ5N
--- On Sat, 5/29/10, Bill Dzurilla <billdz....@yahoo.com> wrote:
> From: Bill Dzurilla <billdz....@yahoo.com>
> Subject: Re: L-4B and L-7 power supply question
> To: drakelist@zerobeat.net
> Cc: k4...@mindspring.com
> Date: Saturday, May 29, 2010, 11:26 AM
> Garey,
> Thanks for the reply. I still don't get why the
> resistor is needed. The ammeter is in series with the
> flow of the current, so what does the resistor do?
> What would happen if B- went directly to ground? I'm
> sure the answer is simple but for some reason it is evading
> me.
> 73, Bill
> ********************************
> Bill -
>
> It's just a relatively safer way (low voltage) to measure
> current of a
> high voltage supply. Any current that goes OUT of the
> supply on the
> positive end MUST come IN via the negative end, or
> vice-versa depending
> upon whether you learned your electronics in the military
> or civilian
> schools!
>
> Anyway, the resistor is near ground, (unless it opens!,)
> and so
> connecting it to a panel meter is much safer than having
> the meter
> connect across a shunt resistor somewhere up in the HV area
> of the supply.
>
> 73, Garey - K4OAH
>
>
> --- On Sat, 5/29/10, Bill Dzurilla <billdz....@yahoo.com>
> wrote:
>
> > From: Bill Dzurilla <billdz....@yahoo.com>
> > Subject: L-4B and L-7 power supply question
> > To: drakelist@zerobeat.net
> > Date: Saturday, May 29, 2010, 9:56 AM
> > Hi,
> >
> > The B- of the power supply for the Drake L-4B and L-7
> goes
> > to pin 6 of the Cinch connector. Inside the amp,
> the
> > B- is floated above ground by a one ohm resistor.
> The
> > one ohm resistor that floats B- above ground is said
> to be
> > for the purpose of plate current metering. I do not
> > quite understand how this resistor is needed for
> plate
> > current meter accuracy. Could someone please tell
> me
> > how that works?
> >
> > I have an L-7 and a homebrew amp that uses a similar
> power
> > supply. However, in the homebrew amp the B- goes
> > directly to ground. I'm trying to understand the
> > difference in the configurations.
> >
> > Thanks and 73,
> > Bill NZ5N
> >
> >
> >
> >
>
>
>
>
_______________________________________________
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist
