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Modifications for the CB for my Rife machine |
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Author: Email |
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Background. I “purchased this “kit” machine from my father in January 2003. Finally, I got this machine assembled and working in September. If you look at the pictures you will notice it’s assembled on a small computer desk. Neat, but I got shocks from everywhere and an RF burn when I touched the case of the Linear (which had been running for 30 seconds). Tuning the SWR was impossible because my hand changed the settings every time I touched anything. Not to mention the fan blowing on the tube stopped whenever the tube lit. |
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The Fix I figured that the system needed some decent bonding. I used 8G car-audio power cable, and tied all the equipment cases to the common negative terminal block. That fixed some of the tuning problems, but I still have to do something about the wires to the tube. I can’t watch TV with it running (see below for why). |
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The Faults The system ran for a total of about 20 minutes, then the power supply made a loud crack and…. Dead. It took a few days to find a suitable similar circuit on the net, and a few more days to get some parts to fix it. Then it was time to tune the tube. I got about 110W out of the linear but then the power slowly dropped away. So I started looking at the Semoia generator and RF outputs with a CRO. What I saw wasn’t good. The generator has parasitic’s everywhere. I got inside and repaired some badly corroded tracks, changed the power filter caps and the output transistor that had gone leaky. Next I looked at the CB. Not good either. The audio drive IC was overheating even with a fan to cool it. And the output had a frequency range from about 500hz to about 2500hz (3db points). This wouldn’t do at all. I found a circuit and some layouts of the top of the board. I bought a new TDA1905 and that didn’t improve things. Time to look for those mods that I had read about, but the web pages had been removed. It was also time to learn about AM and transmitters generally. I found the “Young and Wormus”
mod's on a news-server, but no matter how hard I tried, I couldn’t make sense
of it without pictures. I think he was changing the circuit to use a basic
emitter-follower to drive the modulator. I tried his suggested circuit,
but the transistor he specified just cooked itself in about 10 minutes. There is just no way that a
200mW transistor can survive 250mA at 1.0V (=250mW). So I thought about it for a few
days and bread boarded some circuits. I ran
simulations on some more until I thought I had something that fulfilled all
the needs except the voltage boost that the original circuit achieved by
driving that 1:2 transformer. I built the circuit and tested
it. It worked exactly as predicted. Pulse rise and
fall times less than 1uS. So theoretical frequency limit
is about 500Khz and it runs to DC. It should also square up the
output from a PC sound card. But what of the power output……
Still 100-120W with DC input and 100W with 100Hz 50% duty-cycle I thought about using the audio amp to run a charge-pump voltage doubler, but decided it didn't have the grunt. So I’m leaving the output as it is. I also checked the RF spectrum of the tube output with an
Anaritsu 100khz-23G spectrum analyser - |
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The Modification Circuit for a Uniden 510xl/520e |
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I am publishing the project for
anyone reasonably handy with a soldering iron, to install in their CB. |
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Circuit Description The circuit is assembled on a piece of perforated strip board measuring 1.6inch x 1inch. It uses 2 transistors and directly drives the modulator with 13.8V switched. With no signal the output is high, so the RF output is on, and the tube can be lit. The input is AC coupled by C1. The value has been chosen to give good coupling down to 1Hz.
Parts list Resistors all 1/4w 5% metal film. Values as shown. Capacitors – Radial leaded (leads at one end) C1 RB 2mm lead space x 5mm dia, 22uF 16V C2 RB 5mm lead space x 10mm dia, 470uF 16V low ESR. V1 Generic signal diode. 1N914 or equivalent. V2 Generic PNP signal transistor 40V 200mA TO-92 package. V3 Generic PNP Power transistor >3A 40V 20W TO-220 package. |
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Circuit board. |
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Dimensions are in mils (1000th inch) = 1 inch by 1.6 inch. Board outline is blue. Tracks required are in green. Tracks that need to be cut are indicated by the blue crosses. Note the polarised components (C1, V1, V2, V3 and C2). A pad with a black circle around it indicates where the body of the part goes. Most resistors are standing up. |
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Construction method. |
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1. Print out the UNIDEN 510-520 Mod Board pcb.pdf file for the board layout. Note the board must be printed at 1:1 scale so uncheck the “expand to fit page” checkbox. 2. Take the print and cut it out 6-10mm larger than the outline. 3. Stick some invisible tape along one edge and place it over the board. Make sure the tracks run the same orientation as the green lines on the artwork. 4. With a light shining from underneath the board, line the pads on the artwork to the holes in the board. Roll the tape down. 5. Recheck alignments then fold the paper back over and use a “glue stic” to coat the back. 6. Fold the paper back and rub it down. 7. Push a point through the 2 locations marked by the X, then turn the board over and use a 1/8” (2mm) drill to cut the 2 tracks (use your hand, not a power drill). 8. Proceed to fit all the components. Bend the leads on the upright components so that the lead from the top goes straight down the side of the body. Bend the extra lead length out and then down where it passes through the second hole. 9. All components must fit hard down on the board. 10. Solder all the leads and trim them to about 1mm long. Solder wires into the input/output and power/ground holes. Leave the leads at least 8” (200mm) long. 11. Use a fine bladed hacksaw to cut the rectangular board from the larger panel. (I did it that way because I find it easier to hold a larger board when fitting parts etc, but it makes the cutting a delicate process – don’t break the board).Make sure that the board edges are clean – file the edge back at 45degress if necessary 12. It should look like this
13. Stick double sided tape strips to the rear
14. Trim the corners off with side cutters along the blue outline 15. Check the fit in the CB. See picture step 12 16. Make a heatsink for the power transistor.
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Fitted heatsink. |
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17. Remove the double-sided tape backing and place it into the CB. See the picture at step 12. |
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CB Modifications |
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Remove the drive to the modulator circuit. To the left of the large transformer you will find D7, D14 and C22 (0.47uf 22v). Remove the parts. The wire marked o/p goes into the Cathode of D7 as shown. |
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Copper traces side of the view above. D7 was in the middle and C22 just to the right. |
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Now remove the 470uF capacitor that drives the transformer. I drilled a 2mm hole through the board to get the power leads to the back of the board. Soldering the wires on the pads of the psu smoothing cap (grey cylinder on the right hand side of this pic). If you drill the hole from underneath you can miss the tracks. See the picture below. |
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Feed the power wires through the hold and solder them to the pads shown. Red is positive and green is ground. (The Power amplifier IC is at the bottom-left of this photo). |
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Now comes the fun. To remove the audio from the input to the power amp you need to remove R89 (8.2K) and R93 (1.0K). They are the 2 resistors closest to the blue electrolytic in the photo above. The input wire goes into R89 hole closest to the front of the CB. |
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My Setup |
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Uniden Pro 510e - no fans needed now. |
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