Elecraft KXB3080 User Manual

ELECRAFT KXB3080 30 and 80 METER ADAPTER
Assembly and Operating Instructions
Revision B, May 16, 2012
Copyright © 2012, Elecraft; All Rights Reserved
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Your KX1 must have an 18-turn inductor installed at L3 before using it on 80 meters. If L3 in your KX1 has only 6 turns, see “KX1 Builder’s Alert, Modifying Final Amplifier Choke L3” for instructions on how to rewind the inductor.
Introduction
The KXB3080 adds 30 and 80-meter capability to the Elecraft KX1 transceiver. It also improves the receiver sensitivity on the other bands. High-performance PIN-diode switches are used to minimize insertion loss and ensure good sensitivity.
The KXB3080 consists of two printed-circu i t boa rds (PCBs). The main PCB sits between the main KX1 PCB and the front panel, directly below the encoder shaft. It is held securely in place by the leads attaching it to the main PCB. If your KX1 is currently equipped with the KXB30 adapter, the KXB3080 will replace it. A smaller PCB contains two toroidal inductors and a relay that replaces existing toroidal inductors L1 and L2 in the KX1. Because it must be extremely compact to fit in the space available, the main PCB uses a number of surface mounted devices (SMDs). All of the SMDs are pre-installed for easy assembly.
Specifications
30-m coverage Transmit/receive: 10100-10150 kHz; receive only: 8000-12500 kHz. 80-m coverage Transmit/receive: 3500-4000 kHz; receive only: 1000 – 5500 kHz Added current drain Approx. 3 mA except approx. 18 mA on 80 meters. Size KXB3080 main PCB: 1-9/16” x 1-1/32” (40 mm x 26 mm)
LPF1 PCB: 13/16” x 13/32” (20 mm x 10 mm)
Tools Required
Desoldering tool: An effective desoldering tool is essential. You will need to remove or replace
several parts on the KX1 PCB. A good vacuum desoldering tool such as the Soldapullt® model DS017LS is strongly recommended to avoid damaging the PCB.
Fine-tip temperature-controlled ESD-safe soldering station with 700 to 800F tip (370-430C).
Recommend a spade tip approx. 0.05” (0.13 mm ) wide. Do not use a high-wattage iron or soldering gun since this can damage pads, traces, or the parts themselves.
Solder: IC-grade, small-diameter (.031”) (Kester #44 or equivalent) is recommended.
DO NOT use acid-core solder, water-soluble flux solder, additional flux or solvents of any kind. Use of any of these will void your warranty.
Elecraft • www.elecraft.com • 831-763-4211
Screwdrivers: A small #2 Phillips, a small flat-blade for slotted screws and a very small flat-
blade (about 0.1” or 2.5 mm wide) with an insulated handle to adjust the trimmer caps.
Needle-nose pliers. Small-point diagonal cutters. Flush-cutting type is required (Xcelite MS54-5J or equivalent). Hobby knife or similar tool to cut a PCB trace. 50-ohm dummy load capable of handling 5 watts, minimum. Digital Multimeter (DMM) for voltage checks and confirming resistor values. A DMM with
capacitance measurement capability is desirable, but not required.
Magnifying glass or visor.
Preventing Electrostatic Discharge Damage
The KXB8030 main PCB is sensitive to electrostatic discharge (ESD) damage. Also, the individual PCBs in your KX1 may be vulnerable when they are unplugged.
Keep parts in their ESD-safe packaging until called for in the assembly instructions. Do not place
individual PCBs in Styrofoam™ or similar containers. If possible, place loose PCBs inside ESD­safe bags when you are not working on them.
Wear a conductive wrist strap with a series 1 megohm resistor. If you do not have a wrist strap,
touch a ground briefly before touching any sensitive parts to discharge your body. Do this frequently while you are working. You can collect a destructive static charge on your body just sitting at the work bench. DO NOT attach a ground directly to yourself as this poses a serious shock hazard.
Make sure your soldering iron is ESD-safe and has a grounded tip Use a grounded antistatic mat on your work bench.
Parts Inventory
The table below lists the leaded parts to be installed, the pc boards, toroid cores, wire and
miscellaneous hardware required. The KX1 Owner's manual has photographs of similar parts.
Ref. Description Qty Part No.
C1, C4 Capacitor, 1-40 pF trimmer 2 E540002 C1 (see Note 1) Capacitor, 0.1 µF (104), 0.1” lead spacing 1 E530020 C26 Capacitor, 56 pF, (56) disc ceramic 1 E530146 C1 (see Note 1) Capacitor, 15 pF, (150) disc ceramic 1 E530140 C9 Capacitor, Electrolytic, 10 µF, 35V (10) 1 E530045 K1 Relay, DPDT (G6K-2P) 1 E640029 L6 RF choke, 6.8 µH (blu-gry-gld) 1 E690044 L1, L2, T1 Toroidal core, T37-2 3 E680006
KXB3080 PCB with SMD devices pre-mounted.
MISC (See Note 2) MISC (see Note 2) LPF1 PCB 1 E120001
MISC Kynar® wire, white, #24 solid 1 ft. E760032 MISC Solid, insulated hookup wire, green, #24 6” E760008
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Caution: ESD sensitive! See page 2.
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1 E120000
MISC Toroid wire, green #26 2 ft. E760004 MISC Toroid wire, red, #26 4 ft. E760002 MISC Toroid wire, red, #28 4 ft. E760003 MISC Rubber bumper, .04" thick x 0 .3" square 2 E980017
Note 1 : Duplicate reference designators are for parts on different PCBs. The parts are clearly identified in the text. Note 2: The PCBs may have rough places along the edges. This is a normal result of the manufacturing process and will not
interfere with installation.
For reference, the table below lists the pre-mounted surface-mounted devices.
Ref. Description Qty Part No.
C3, C6, C7, C8, C10 Capacitor, 0.1 µF 5 E530222 C9 Capacitor, 10 uF,10V, 20% 1 E530223 C2, C5 Capacitor, 300 pF 5% NPO 2 E530221 D1, D2 PIN diode, dual, common cathode 2 E560026 D3 Small Signal Diode 1 E560027 L1, L2, L3, L4, L5 RF choke, 47 µH 5 E690063 Q1 Transistor, PNP, 2N3906 1 E580030 R1, R2, R6, R7 Resistor, 470 ohms 1/10 W, 5% 4 E500187 R3, R4, R5 Resistor, 240 ohms, 1/10 W, 5% 3 E500188 R8 Resistor, 15 k-ohm, 1/10W, 5% 1 E500189
Assembly and Installation
There are four major steps in the procedure. Follow them carefully and in the order given.
1. Modify the KXB1 PCB to install a new receiver input circuit.
2. Assemble and install the KXB3080 option PCB. Install new firmware if needed.
3. Assemble and install Low-Pass Filter LPF1.
4. Reassemble, test and align the KX1 with the KXB3080 module.
Part I: Modify the KX1 PCB
Disassemble your KX1 and remove the main PCB from the enclosure. If you have the KXAT1 antenna tuner option, remove it and place it in a safe place where it will be free from ESD damage. Use an ESD-safe bag if you have one available.
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Very important:
1. Be careful to avoid accidentally touching components w i th you r sol dering iron. Relays
and potentiometer shafts are especially vulnerable to heat damage.
2. Clear pads of all solder before attempting to install new parts.
3. As you install new components, clip all leads flush with the PCB on the reverse side.
Bend C15 (near the crystals on the KX1 board) up to gain access to solder pad G under it.
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If present, remove the KXB30 module. Remove the KXB30 wires from the KX1 main PCB and clear the pads on the KX1 main PCB of all solder.
Replace C26 on the KX1 PCB (see Figure 1) as follows:
Remove the existing 120 pF (121) capacitor. It will no longer be used. Clear all the solder from the pad holes.
Install the 56 pF (56) capacitor supplied with the KXB3080 kit. Form the leads of the new capacitor as needed to fit. Be sure the capacitor stands no higher than 5/16” (7.9 mm) above the board. After soldering, trim the leads flush. Save the leads for use as jumpers later.
Replace C1 on the KX1 PCB (see Figure 1) as follows:
Remove the existing 4.7 pF (4.7) capacitor. It will no longer be used. Clear all the solder from the pad holes.
Install the 15 pF (150) capacitor supplied. Form the leads of the new capacitor as needed to fit. Be sure the capacitor stands no higher than 5/16” (7.9 mm) above the board. After soldering, trim the leads flush.
C26
C27
C1
L7
L6 (Partially hidden behind po t)
Figure 1. KX1 PCB Original Component Locations.
Remove molded inductor L7, 4.7 µH (yel-vio-gold) (see Figure 1). It will no longer be used. Clear all the solder from the pad holes.
Remove capacitor C27, 150 pf (151) (see Figure 1). It will no longer be used. Clear all the solder from the pad holes.
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Turn the KX1 PCB over and cut the trace from CB to C27/R1 as shown in Figure 2. Use a sharp hobby knife and cut across the trace several times as needed to cut through the metal.
Cut Circuit Trace Here
Jumper from Trace to Grounded Pad of Trimmer Capacitor CC
Figure 2. Modifying Trace From Capacitor CB.
Use your DMM to confirm that the cut trace is an open circuit. Check the resistance between a solder pad on one part of the cut trace and a solder pad on the other part. It should be greater than 1 megohm.
Scrape off the green coating and tin a short length of the trace adjacent to the pad for trimmer capacitor CC. Use a cut lead to form a short jumper between the trace and the grounded end of CC as shown in Figure 2.
Remove molded inductor L6 from the top side of the PCB (see Figure 1) and reinstall it on the bottom of the PCB as shown in Figure 3. Be sure you place the leads in the same solder pads L6 originally occupied. In case you damage the inductor while removing it, a replacement is provided: 6.8 µH (blu-gry­gld). When soldering L6 in place, do not fill the pad for connection A. This pad will be needed later to attach the KXB3080 module. Trim L6’s leads flush with the top of the PCB.
L6
Figure 3. L6 Relocated on Bottom of KX1 PCB.
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Keep Pad "A" Clear.
Rotate potentiometer R1 fully clockwise and check the resistance between ground and the part of the cut trace that goes to the open solder pad for C27 and the center terminal of potentiometer R1. The resistance must be greater than 800 ohms. If the resistance is low, check for a solder bridge between the pad for capacitor CC and solder pad A or the adjacent pad for L6.
Cut a 20” (51 cm) length of the #28 red toroid wire. (The #28 is the smaller red wire.)
“Sew” the long end of the wire through the hole in one of the T37-2 toroid cores (red) for a total of 33 turns exactly as shown in Figure 4. Be sure you wind the turns the direction shown in the figure. Count one turn for each time the wire passes through the center of the core. There are no half or quarter turns when winding a toroid. The turns should fill about 90% of the toroid core as shown in the figure.
Cut a 3” (7.6 cm) length of the #26 green toroid wire. Strip the insulation from 1/2” (13mm) at one end of the green wire (you’ll strip the insulation from the other end later). Use one of the following methods to remove the insulation and tin the lead:
1. Heat Stripping: a. Place a small amount of solder (a.k.a. a “blob” of solder) on your soldering iron. b. Insert the clipped end of the wire into the hot solder so it touches the bare end of the wire. If
the iron is hot enough, you should see the insulation bubble and vaporize after 4 to 6 seconds.
c. Add solder and feed more wire into the solder as the enamel melts. After reaching the point
where you want the tinning to stop, slowly pull the wire out of the solder.
d. If any burnt enamel remains on the lead, scrape it away using your thumbnail or sharp tool.
2. Burning: The insulation can be burned off by heating it with a butane lighter for a few seconds. Use sandpaper to remove the residue, then tin the bare wires.
3. Scraping: Use a sharp tool to scrape the insulation away. Work carefully and gently: do not nick the wire. Remove all the enamel around the circumference of the wire, then tin the bare wire.
The stripped end of the green wire is end 2 as shown in Figure 4. Position the green wire so the stripped end extends right up to the point where the wire passes into the center of the core, then wrap the long end of the wire around the toroid and through the center one more time to make two turn s.
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