[600MRG] RAKs and such - ballast tube.

[Todd Roberts]

Hi Ken,
The RAK receivers are a lot of fun to work on.

You actually do have to remove the #876 ballast tube in the RAK original power supply
if you want to remove it from the circuit and let everything run cooler.


When the ballast tube is switched "in" using the internal switch, it is placed in series
with a transformer winding. The ballast tube is also connected in series with a giant 80 ohm/200 watt
 wire-wound power resistor R201 across
part of the transformer windings. It is this combination that causes the power supply to draw
approx 200 watts. The ballast tube is always in series with this big power resistor.

When the internal switch is switched "out" the ballast tube is actually still in circuit - this time it
is connected in parallel with more transformer primary windings but still connected in series with the large
wire-wound power resistor. This stops the regulation but the power supply is still drawing
nearly 200 watts.


You have to physically remove and unscrew the ballast tube from the mogul socket to
remove the tube completely from the circuit and position the internal switch to "out".
This removes the large wire-wound resistor R201 from the circuit also. Doing this
drops the power supply input draw to approx 60 watts.


Look at the power supply schematic and this action should be clear. A lot of the excess heat
and power draw when using the ballast tube is drawn by the large power resistor R201 always in
series with the ballast tube. 


So it is always best to completely remove the ballast tube and remember to set the internal power supply
switch to "out" to save on excess heat and power draw, if someone wants to use the original unit.


73 Todd WD4NGG


http://www.navy-radio.com/rcvrs/ral-ps.htm


-----Original Message-----
From: Kenneth G. Gordon <kgordon2006 at frontier.com>
To: 600mrg <600mrg at w7ekb.com>
Sent: Mon, Nov 3, 2014 3:26 pm
Subject: Re: [600MRG] RAKs and such - ballast tube.


On 3 Nov 2014 at 14:59, Bill Cromwell wrote:

> Hi Rudy,
> 
> My RAK is all original AND I use the original power supply. We can pull 
> the ballast tube out of those (unless we are going into naval combat). 
> That leaves a pretty much standard B+ with a voltage regulator - two of 
> the three original tubes. You just unplug that ballast tube pull it and store 
it 
> someplace 'safe'.

Ha! Youse guys... (shakes head...)

You don't have to remove that ballast tube: there is a switch down at the 
bottom, inside, that simply turns it off. That way you can "store" the ballast 
tube in the power supply.

Ken W7EKB

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