Circuit Details - Varicap Tuned Bandpass Filters
before building this section.
This section uses all the T50-6 (Bag 4) cores in the kit. The wire length will give you plenty of extra on each end. Start with 1" of wire on the end you begin winding.
After winding, scrape the enamel off the wire as close to the toroid as possible and tin with solder. Pre-tinned wires make a good connection on the board.
Wind the coils as follows:
____2 - 8 Turns, wire length 7"
____4 - Blue Relays (Bag 4), Be very careful with the part as the pins are fragile. Do not bend the pins when mounting/soldering to the PCB. Orientation does not matter, inner pins are the coil, outer pins are the relay.
1. Clean and tin the pins with solder before mounting to ensure a good solder joint. The pins can be difficult to solder without pre-tinning.
After tinning, remove any excess solder. Wipe the excess solder to the top of the pin so the pins will fit in the holes. When soldering on the board, the heat will melt the excess solder and the relay will fall against the board.
2. Be sure to mount the relays flush with the board. If mounted slightly off the board, the relay will flex back and forth while handling the board, and break the pins between the relay and PCB.
Solder one pin to the PCB, then hold the relay against the top side of the PCB and remelt the soldered pin to set the relay against the board. Then solder the other pins.
____5 - 100K resistors (Bag 3) (brown, black, yellow)
____9 - .01 capacitors (Bag 3)Note: There is one capacitor next to the text "40/30" that is marked "10". Do not put a .01 in that spot by mistake.
____2 - .001 caps (Bag 5)
____3 - 1N914 diodes (Bag 4), Black band, be sure to match the band on the diode to the band on the footprint, one on each end of the filters near the middle of the board.
____2 - IREDs (Bag 4), Smoky colored, on a cardboard strip, do not cut the leads off the strip, tear the IR LEDs off the strip and clean the bottom of the leads. Mount as high as possible, then aim to the appropriate photo receiver. They are located to the right of the output relays on the left.
____1 - 100K Panel Mount Potentiometer (Bag 6), The three holes labeled "Filter Tune" should accept the pins of the potentiometer supplied with the kit.
____2 - 1K (Bag 3), On both sides of the Filter Tune pot. Do not solder at this time.
Push the Filter Tune Pot through the holes, bend the end tabs over, pull the resistor almost out of their holes, and run the leads through the hole in the tabs. Then bend the resistor wires over to secure pot against the bottom of PCB.
Solder and clip the leads. On the left hand tab, solder will flow into the hole of the tab, but not so much that it flows onto the ground plane. Then clip the end of the tab to prevent a short to ground. Solder other 1K resistor leads.
Install Filter Tune Wire from Filter Tune Pot to Filter Tune Circle and 12 Volt Wire to Tune Pot
____1 - SPDT Miniature PC Mount switch (Bag 5), There is a switch footprint in front of the Bandpass Filter. There are two hole patterns. Mount the switch in the holes that fit the switch in Bag 5.
Install BPF Wire from switch to BPF Tune
The wire can be run either below the board or on top the Board. Shown in the next picture is how the run the wire below the board.
Running the wire on top of the Board is shown in the following two pictures.
Installing the Bandpass Coils
Make sure that the wires of the coils are clean of insulation where they are soldered underneath the board. If not, raise the coil enough to get clean wire for a good solder connection.
Aim the Photo Devices
When bending the Photodiodes forward, as shown in the picture, keep the face (with the bubble) vertical.
TV & FM Filter and RF Amplifier
The 4.5 MHz High Pass Filter is optional. The parts for the High Pass Filter are not included in the kit. If you live in a large metropolitan area where several high power AM stations or nearby amateur radio stations are present, you might consider installing the parts. Check out TV & FM, Broadcast Filters for information.
____6 - .01 capacitors (Bag 3)
____1 - 100 ohm resistors (brown, black, brown) (Bag 3)
____2 - 100pf NPO (Bag 3), Next to the 8 turn coils. Orange color, short leads flared out, labeled "101".
____1 - 2N5109 Transistor and Heatsink (Bag 6), Put the heat sink on the transistor first before soldering to the PCB.
____Place the PCB in front of a bright light. If you see light shining through any of the soldering holes, you missed a solder connection.
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