Young-Wormus CB Mods
The following are the Young and Wormus mods. They work very well.
"Subj: Young & Wormus mods
Date: 98-02-03 00:10:25 EST
From: firstname.lastname@example.org (Gerard Bechard)
Can anyone tell me what the Young and the Wormus modifications to the
510xl are, or point me into the right direction in the archives?
Rife-List posting from Sept 14:
Hi to all...; I have finally finished testing of a new modification to
the Uniden which replaces the audio modulation method with a direct RF
modulation method.; This method offers many advantages over the former,
such as an excellent square wave response from DC to 250 kHz and is
still very good up to 1 MHz.; Also, the pulse width, or duty cycle, is
precisely controllable. The only disadvantage is a peak output power
reduction from 16 watts to4 watts, so you will probably want to set
your linear amplifier switches to maximum.
The circuit is very simple (only 4 parts) and costs next to nothing
($3or less).; If you are not at all handy with a solder gun, though,
you might want to seek the help of someone who is.; My web page is no
completed and I have no graphics to go with this, but I will try to
convey all information that is required in a concise written format.
; 2N3904; NPN small-signal transistor; (get one that has leads1/2" long
; 1N4148 or 1N914; silicon switching diode
; 10K resistor; (or try a 3.3K if your freq. generator can't putout at
least 3 volts)
; 470uF 16V; electrolytic capacitor; (you may substitute higher value
and/or voltage, just be sure it fits inside the radio!)
Step 1:; Remove top and bottom covers.
Step 2:; Remove the internal speaker from the bottom cover
(4screws/nuts) and cut its wires close to the circuit board.; We have
no need of it and it takes up valuable space.
Step 3: Place the radio upside-down with front facing you.; For all
descriptions to follow, left is YOUR left, right is YOUR right.
Whenever I say "from the left/right/rear edge", I mean from the edge of
the radio's metal chassis.; For clarity, I have capitalized the
functional name of the component leads.; Good luck!
Step 4:; Find the 27-ohm 5% resistor (red-violet-black-gold) which is
located 42mm (1 5/8") from the rear edge and 14mm (9/16") from the left
edge.; It is lying flat on the board.; Cut the resistor's right-side
lead as flush with the board as you can (or de solder it from the
bottom), then lift the resistor up on its left lead at a 45-degree
Step 5:; Find the metal RF transformer labeled L2. It is 56mm (2
3/16") from the rear edge and 33mm (1 5/16") from the left edge.; Using
your solder gun, heat the top side front-left corner of L2's shield and
place bead of solder there.
Step 6:; Spread the leads of the 2N3904 so Emitter and Collector point
away at 45-degree angles.; Hold the 2N3904 horizontal in your left hand
with the flat side (printed side) facing up and the leads facing to the
right.; Solder the Emitter lead of the 2N3904 to L2's solder bead that
you just made.
Step 7:; Stretch the 2N3904 Collector lead over to the free-floating
27-ohm resistor lead and solder them together.
Step 8:; Cut both leads of the 1N4148 diode to a length of about 1/4".
Solder the Anode of the diode to the solder bead on L2 and solder the
Cathode (band end) to the Base lead of the 2N3904.
Step 8:; Cut both leads of our 10K resistor (or 3.3K or whatever size
you picked) to about 1/4". Solder one lead to the Base lead of the
2N3904,Solder a 6" length of 20 or 22 gauge stranded hookup wire to the
other side of the 10K resistor.; If you have some, slip 2 or 3 ferrite
beads over; this wire to prevent RF from feeding back into the
Step 9:; Remove the audio output transformer.; It is located 30mm (1
3/16") from the rear edge and 48mm (1 7/8") from the right edge.; It is
labeled "TF-375".; I recommend using de soldering braid to do this
(Radio Shack #64-2090).; You must de solder all 5 leads plus the two
metal tabs that extend from the metal frame.
Step 10:; Construct a jumper wire of 18 to 22 gauge solid wire and make
it 18mm (11/16") between the bends.; Again, place the radio upside-
down facing you.; Insert one side of the jumper wire into the left-rear
transformer hole and the other side into the middle hole of the 3 front
transformer holes.; Solder the jumper wire in place.
Step 11:; Position the 470uF capacitor inside the radio where the audio
transformer used to be.; Solder the positive lead of the capacitor to
the jumper wire you just installed, and push the negative lead through
one of the transformer holes where the metal tabs were.; Solder the
negative lead to the ground foil on the bottom side.
Step 12:; Flip the radio right-side up, facing you.; Notice the 4
Philips-head screws holding the circuit board to the chassis.; Look
closely at the 2 screws on the right side.; There is copper foil
completely around these screws and also a gap and more foil to the rear
of both screws.; Using a small flat-tip screwdriver or wood chisel,
scrape away the coating on the copper foil to the rear of both screws
and on both sides of the gap.; Solder a short straight jumper wire
across each gap.; Do it for both screws. This modification connects the
circuit common to the actual chassis, which provides better grounding
for the audio generator and can prevent certain types of feedback.
Step 13:; (Optional); This is a component replacement that provides for
slightly sharper square waves when modulating above 200 kHz.; Find the
.01uF ceramic disc capacitor just behind the 27-ohm resistor we've been
working with.; It is about 7mm diameter and labeled "103M". De
solder and replace this with a 470pF disc capacitor.; This reduces the
square wave rise/fall time from 125nS to about 50nS.
Step 14:; Re-assemble the radio.; When placing the bottom cover, run
the 6" piece of hookup wire through one of the holes of the speaker
grill. Connect your audio/function generator to this wire and chassis
That's it!; BTW, the reason for yanking the audio output transformer
and installing the 470uF is to smooth out RF envelope fluctuations that
were occurring below about 200 Hz.; You can now enjoy experimentation
all the way from DC to over 1 MHz and I will be very interested to see
what we can all discover with some of the Hulda Clark frequencies and
very low frequencies!; One thing I have found is that the tube does not
want to light if you use a duty cycle less than about 20%. Sure hope I
didn't leave anything out here.; Feel free to forward any questions
regarding this mod. I will be happy to answer them.
To get the power back the collector of the output transistor needs to
be run at 24 volts. This can be accompolished by either using two
power supplys for the CB as I did. I got a surplus 24V supply (mine is
3.6amp but 2amp should be enough) and regulated the 24 to 12 in the CB
to power the front end.
I hooked in the 24V by lifting out the front leg of the jumper
described in Tom's instructions (connected to 470mf Cap) and attaching
the +24 to this jumper. Note this results in the back end of the
jumper being at 24v it is left unconnected to the front. ie its no
longer a jumper. The 24v supply takes the place of the step up from
the removed transformer.
If you have questions let me know.
The neg. goes to gnd. I used one of the attachment holes left by
removing the transformer.