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Ramsey Electronics Model No. MX10
Now here’s the simple easy to use mixer for all of you home
brew DJs out there! This mixer has all of the features you will
ever need to mix audio as the professionals do - in a small
compact size! Perfect for DJing on the desktop transmitter,
making car tapes, mixing for a wedding or anywhere else a
mixer could be needed.
• 2 Line inputs, 1 phono and 2 mic inputs, all most people will
ever need!
• Overload protection on the microphones input to “
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RAMSEY TRANSMITTER KITS • FM10A, FM25B FM Stereo Transmitters • AM1, AM25 AM Transmitters • TV6 Television Transmitter RAMSEY RECEIVER KITS • FR1 FM Broadcast Receiver • AR1 Aircraft Band Receiver • SR2 Short-wave Receiver • AA7 Active Antenna • SC1 Short-wave Converter RAMSEY HOBBY KITS • SP-1 Speakerphone • AVS10 Automatic Sequential Video Switcher • WCT20 Cable Wizard Cable Tracer • L
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Ramsey Publication No. MMX10 Price $5.00 KIT ASSEMBLY AND INSTRUCTION MANUAL FOR MX10 STEREO THREE INPUT MIXER Table of Contents Introduction ....................................4 Circuit Description ...........................5 MX10 Parts List ............................10 Assembly Procedure .....................11 Schematic Diagram ......................16 Initial Testing .................................23 Troubleshooting ............................24 Layout Diagrams ...
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INTRODUCTION TO THE MX10 Seeing the need for a high fidelity low noise mixer to be used with our micropower transmitters, we came up with this easy to build compact mixer. The small size lends to the small size of the transmitter for portability. You can easily fit an entire radio station inside of a briefcase, just try that with electronics of just a few decades ago! While designed to go with our micropower transmitters, the MX10 will work as well, if not better than most commercial mi
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MX10 CIRCUIT DESCRIPTION We will use the schematic diagram to step through the circuit and find out what makes it “tick”. There are plenty of different devices performing different tasks in the MX10. The most common active component is the opamps. These are used in a number of ways in the MX10, one of which is mixing. To perform mixing, an opamp is set up in what is called a summing amplifier. This amplifier does exactly what it says. It takes all of its inputs and adds them together on t
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The next stage of the microphone amplifier has two diodes in the feedback loop. What are these for? you may ask. Well they are called clipping diodes. Diodes have a property of needing about .7 volts across them if the forward bias direction before they turn on. On signals under .7V P/P, the gain of the second stage is determined by Ri of 10K (R28) and Rf of 10K (R27). This gives us a gain of 1. But if our signal becomes greater than .7V P/P, then the diodes D1 and D2 begin to turn on. Thi
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circuits. The earphone amplifiers LM386s have quite a bit of kick to them, which should be more than enough to out power most DJ systems. The peak hold meters serve the function of displaying peak amplitudes in your audio so your eye can see them. Normally a short duration pulse such as a drum beat or strum of a guitar has a very short time duration for the initial higher power sound. If we didn’t use a peak hold circuit, your eye would be hard pressed to see the LEDs blink on the bargraph
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RAMSEY “LEARN-AS-YOU-BUILD” ASSEMBLY STRATEGY Be sure to read through all of the steps, and check the boxes as you go to be sure you didn't miss any important steps. Although you may be in a hurry to see results, before you switch on the power check all wiring and capacitors for proper orientation. Also check the board for any possible solder shorts, and/or cold solder joints. All of these mistakes could have detrimental effects on your kit - not to mention your ego! Kit building tip
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As with all Ramsey kits, we want to mount the parts AS LOW AS POSSIBLE to the board. A 1/4” lead length on a resistor not mounted close to the board can act as an inductor or an antenna, causing all sorts of problems in your circuit. Be aware though that if there are stand up components in your circuit, they don’t need to be squished to the board. Keep the portion of the resistor closest to the board mounted right on the board. For each part, our word "Install" always means these steps:
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RAMSEY MX10 PARTS LIST Semiconductors ❒ 3 LF347 Dual operational amplifiers (U4,5,6) ❒ 2 LM386 Audio power amplifiers (U2,3) ❒ 2 LM3915 LED bargraph drivers (U7,8) ❒ 4 1N4002 type diodes (black epoxy body with white stripe)(D29,31,34,35) ❒ 6 1N4148 type diodes (small glass body with black stripe)(D1,2,5,6,8,19) ❒ 10 Small yellow LEDs (D3,10,11,12,13,14,22,23,24,25) ❒ 6 Small green LEDs (D4,7,9,18,20,21) ❒ 6 Small red LEDs (D15,16,17,26,27,28) ❒ 1 7808 +8 volt regulat
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ASSEMBLY OF THE MX10 Now we are getting to the good stuff-assembling the MX10. We will begin by mounting first the low parts, beginning with the parts on the side of the board labeled as “PARTS” side on the PC board. When we are finished with that side, we will begin to install parts on the “CONTROL” side of the board. This side is where all of the controls go, and will be the side of the board facing the top of the case. In the case of this project we will attempt to go from top to bot
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❒ 18. Install R27, a 10K ohm resistor (brown-black-orange). ❒ 19. Install R28, a 10K ohm resistor (brown-black-orange). ❒ 20. Install D1, a 1N4148 type diode (orange body with black stripe). Make sure that the cathode end (with the stripe) is installed in the same orientation as where the “arrow” is pointing to the stripe of the diode symbol. The stripe of the diode is the same as the stripe on the layout. ❒ 21. Use the same procedure to install D2, another 1N4148 type diode. Make sure th
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ready to continue with the rest of the project. ❒ 39. Install R54, a 10K ohm resistor (brown-black-orange). ❒ 40. Install R52, a 10K ohm resistor (brown-black-orange). ❒ 41. Install R82, a 10K ohm resistor (brown-black-orange). ❒ 42. Install R70, a 100K ohm resistor (brown-black-yellow). ❒ 43. Install D6, a 1N4148 type diode. This diode and U4:A form the “real diode” section of the peak hold circuit. “real diode” means that there is no .7 volt drop across the diode that would normally occ
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❒ 59. Install R89, a 68K ohm resistor (blue-gray-orange). ❒ 60. Install R43, a 100K ohm resistor (brown-black-yellow). ❒ 61. Install R67, a 180 ohm resistor (brown-gray-brown). ❒ 62. Install R76, a 10K ohm resistor (brown-black-orange). ❒ 63. Install R77, another 10K ohm resistor (brown-black-orange). ❒ 64. Install R51, a 10K ohm resistor (brown-black-orange). ❒ 65. Install R49, a 10K ohm resistor (brown-black-orange). ❒ 66. Install R68, a 2.0 ohm resistor (red-black-gold). ❒ 67. Install
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parts, we will quit going from left to right, top to bottom and begin to install parts close to one another. ❒ 81. Install C1, a 10uF electrolytic capacitor. Notice this is the first capacitor of this type. You want to pay close attention to the polarity markings on this part. In most cases the negative (-) side is marked on the capacitor, while the positive side (+) is marked on the parts layout. If you fail to mount this component correctly, the part can fail as well as prevent proper o
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MX10 Page 16
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MX10 Page 17
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❒ 101. Wow, it’s hard to believe we have come 100 steps already! Install C36, a 10uF electrolytic capacitor. Again check the orientation before continuing. ❒ 102. Install C34, a .1uF ceramic capacitor (marked .1 or 104). ❒ 103. Install C8, a .01uF ceramic capacitor (marked 103, 10n or .01). ❒ 104. Install C33, a 220uF electrolytic capacitor (orientation!) ❒ 105. Install C5, a .01uF ceramic capacitor (marked .01, 103 or 10n). ❒ 106. Install C6, a 10uF electrolytic capacitor. Orientation!
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❒ 125. Install J6, a 3.5mm mono microphone jack. (Identified by only three mounting pins instead of five) Note that they don’t fit exactly in the holes since a better jack was ordered that the one the kit was originally designed for. ❒ 126. Install J5, a 3.5mm mono microphone jack. We have just completed this entire side of the PC board and now we are ready to begin working on the other side of the board. Flip the board over and notice where all of the controls are to go. Notice that th
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and S4. ❒ 133. Install the next two yellow LEDs (D11 and D23) Check the long lead side! ❒ 134. Install two more yellow LEDs (D13 and D24). Again check the long lead side. ❒ 135. Install the last of the yellow LEDs to go in the meter (D14 and D25). There should be two left over for the microphone indicators. ❒ 136. Install the first of the red LEDs to go in the meter just to the right of the yellow LEDs (D15 and D26). Make sure the long leads are oriented correctly. ❒ 137. Install the
