Customer Service and Support ............................................................................................................................ 4
Preparing for Installation .......................................................................................................................... 6
Tools and Supplies Required ............................................................................................................................... 6
Parts Included ...................................................................................................................................................... 7
Circuit Boards and Enclosure .......................................................................................................................... 7
KRX3 Hardware Bag E850334 ....................................................................................................................... 8
E850344 TMP-BNC Cable Bag ...................................................................................................................... 9
E850249 I.F. Crystal Filter Bag (or Box) ...................................................................................................... 10
E850249 I.F. Crystal Filter Bag (or Box) ...................................................................................................... 10
Installing the Auxiliary KRX3 Antenna Input via the KAT3 ....................................................................... 26
Installing the Auxiliary KRX3 Antenna Input Via the Rear Panel BNC Connector .................................... 27
Assembling the KRX3 Subreceiver Module ..................................................................................................... 31
Installing the KRX3 Subreceiver Module ......................................................................................................... 36
Final Assembly .................................................................................................................................................. 43
Removing the KRX3 Module ................................................................................................................. 44
Preparing for Operation ..................................................................................................................................... 45
Using the Sub Receiver ..................................................................................................................................... 46
Dedicated Sub Receiver Controls ................................................................................................................. 46
BSET: Additional Sub Receiver Controls ..................................................................................................... 46
Sub Receiver Antenna Selection ................................................................................................................... 46
Sub Receiver Band Independence ................................................................................................................. 46
Sub Receiver Crystal Filter Considerations .................................................................................................. 47
SPLIT Mode with the Sub Receiver ............................................................................................................. 47
Appendix A: Installing Crystal Filters in the KRX3 Subreceiver………..……………………………A1
Elecraft manuals with color images may be downloaded from
www.elecraft.com
2
.
Introduction
If your KRX3 is already installed in your K3, turn to Using the Sub Receiver on page 46 for operating
instructions.
The KRX3 subreceiver features specifications identical to the main K3 receiver including up to five roofing
filters and an independent, dedicated DSP system. The subreceiver can tune the same range of frequencies as the
main receiver, including frequencies outside of the Amateur bands when it is equipped with the optional KBPF3
general coverage filter board.
The KRX3 has three major components as shown installed in a K3 in Figure 1. The shielded enclosure contains
the main KRX3 board, mixer and noise blanker pony boards, optional KBPF3 general coverage filter board and
roofing filters that you will assemble and mount in the enclosure.
Only a few basic tools are required to assemble the components and install them in the K3 (see page 6).
Figure 1. KRX3 Subreceiver Installed in K3.
3
Customer Service and Support
Technical Assistance
You can send e-mail to k3support@elecraft.com and we will respond quickly - typically the same day Monday
through Friday. Telephone assistance is available from 9 A.M. to 5 P.M. Pacific time (weekdays only) at
831-763-4211. Please use e-mail rather than calling when possible since this gives us a written record of the
details of your problem and allows us to handle a larger number of requests each day
.
Repair / Alignment Service(We want to make sure everyone succeeds!)
If necessary, you may return your Elecraft product to us for repair or alignment. (Note: We offer unlimited email
and phone support to get your kit running, so please try that route first as we can usually help you find the
problem quickly.)
IMPORTANT: You must contact Elecraft before mailing your product to obtain authorization for the
return, what address to ship it to and current information on repair fees and turn-around times. (Frequently we
can determine the cause of your problem and save you the trouble of shipping it back to us.) Our repair location
is different from our factory location in Aptos. We will give you the address to ship your kit to at the time of
repair authorization. Packages shipped to Aptos without authorization will incur an additional shipping charge
for reshipment from Aptos to our repair depot
.
Elecraft 1-Year Limited Warranty
This warranty is effective as of the date of first consumer purchase. It covers both our kits and fully assembled
products. For kits, before requesting warranty service, you should fully complete the assembly, carefully following all
instructions in the manual.
What is covered: During the first year after date of purchase (or if shipped from factory, date product is shipped to
customer), Elecraft will replace defective or missing parts free of charge (post-paid). We will also correct any
malfunction to kits or assembled units caused by defective parts and materials. Purchaser pays inbound shipping to us
for warranty repair, we pay shipping to return the repaired equipment to you by UPS ground service or equivalent to
the continental USA and Canada. Alaska, Hawaii and outside U.S. and Canada actual return shipping cost paid by
owner.
What is not covered: This warranty does not cover correction of kit assembly errors. It also does not cover
misalignment; repair of damage caused by misuse, negligence, or builder modifications; or any performance
malfunctions involving non-Elecraft accessory equipment. The use of acid-core solder, water-soluble flux solder, or
any corrosive or conductive flux or solvent will void this warranty in its entirety. Also not covered is reimbursement
for loss of use, inconvenience, customer assembly or alignment time, or cost of unauthorized service.
Limitation of incidental or consequential damages: This warranty does not extend to non-Elecraft equipment or
components used in conjunction with our products. Any such repair or replacement is the responsibility of the
customer. Elecraft will not be liable for any special, indirect, incidental or consequential damages, including but not
limited to any loss of business or profits.
4
Preventing Electrostatic Discharge Damage
There is no climate or work location where the components of your K3 are safe from Electrostatic Discharge
(ESD) unless you take specific steps to prevent such damage. Many of the components in your K3 can be
damaged by static discharges of only a few volts: far too little for you to notice. Those low-voltage but
destructive discharges easily happen anywhere and in almost any environment.
ESD damage may not be apparent at first. The damaged components may not fail completely. Instead, the
damage may result in below-normal performance for an extended period of time before you experience a total
failure.
How ESD Damage Occurs
Whenever an object containing a static charge touches a circuit in your K3, current will rush into the circuit until
the components reach the same voltage as the source of the static charge. If the voltage or current that passes
through a component during that brief period exceeds its normal operating specifications, it may be damaged or
destroyed.
Preventing ESD Damage
ESD damage cannot occur if there is no voltage difference between the components in your K3 and any object
that touches them. That is how anti-static packaging works. Anti-static bags allow the static charge to flow over
their surface, so that any part of the bag that touches the components inside are all at the same potential at all
times. Anti-static foam keeps the leads of sensitive components at the same potential.
At your work bench, avoiding a dangerous voltage is achieved most easily by tying everything together and
connecting them to a common mains safety ground. This includes your K3, individual boards or other sensitive
components as well as everything they may touch at the work table.
Inexpensive static dissipating work mats are readily-available that will steadily and safely drain off any charges
built up on parts or circuit boards placed on them. They are supplied with a lead that connects the mat to the
common workbench ground. Also, metal cabinets on test equipment used on the bench should be tied together
and connected to the common ground.
Most importantly, you must have a way of continuously draining off any static charges that occur on your body.
Such charges are easy to create, even while sitting quietly at the work bench. Moving your feet on the floor,
shifting position in your chair or even moving your arms so that clothing rubs against itself can produce
destructive static charges. You can discharge yourself by touching an unpainted metal ground, but that will last
only until you move in a way that produces a new static charge. The safest technique is to wear a grounded wrist
strap with a series 1-megohm resistor that continuously drains off any charges. Such wrist straps are readilyavailable and inexpensive.
WARNING
DO NOT attach a ground directly to yourself without a current-limiting resistor as this poses
a serious shock hazard. A wrist strap must include a 1-megohm resistor to limit the current
flow. If you choose to touch an unpainted, metal ground to discharge yourself, do it only
when you are not touching any live circuits with your other hand or any part of your body.
5
We strongly recommend you take the following anti-static precautions (listed in order of importance) to avoid
trouble:
Leave ESD-sensitive parts in their anti-static packaging until you install them. The packaging may be a
special plastic bag or the component’s leads may be inserted in conductive foam. Parts which are
especially ESD-sensitive are identified in the parts list and in the assembly procedures.
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.
Use a grounded anti-static mat on your work bench.
If you choose to use a soldering iron to work on your K3 for any reason, be sure your iron has an ESD-
safe grounded tip tied to the same common ground used by your mat or wrist strap.
Preparing for Installation
Tools and Supplies Required
1. #0 and #1 size Phillips screwdrivers. To avoid damaging screws and nuts, a power screwdriver is not
recommended. Use the screwdriver that best fits the screw in each step.
2. Small pliers or a 1/4” nut driver.
3. Side (diagonal) cutters.
4. Long nose pliers.
5. Soft cloth or clean, soft static dissipating pad to lay cabinet panels on to avoid scratching.
TM
6. Approximately 2.5” (6.4 cm) of transparent tape such as Scotch Magic
as shown in Figure 44 on page 37).
The following tools are strongly recommended:
1. ESD wrist strap.
2. Static dissipating work pad.
You may need the following in order to install a single resistor on the main RF board (See Checking and Modifying Resistor R91 and DAC Input Circuits on page 21 to determine if you will need to install this part.)
1. Digital multimeter capable of measuring in resistance values.
2. Fine-tip temperature-controlled ESD-safe soldering station with 700 to 800F tip (370-430C).
Recommend a spade tip approx. 0.05” (1.3 mm) wide. Do not use a high-wattage iron or soldering gun
since this can damage pads, traces, or the parts themselves.
3. IC-grade, small-diameter (.031”) solder (Kester #44 or equivalent).
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.
mending tape (will be used
6
Parts Included
The following parts should be included in your kit. Check to ensure you have them all. If any parts are damaged
or missing, contact Elecraft for replacements (see page 4).
Circuit Boards and Enclosure
Note: Some pins on the male connectors may have been removed and some holes in the female connectors may
have been plugged. This is intentional to help you align the connectors properly during assembly.
ILLUSTRATION DESCRIPTION QTY.
ELECRAFT
PART NO.
Auxiliary DSP Printed Circuit Board
Assembly
1 E850234
ESD Sensitive. Follow ESD safe handling
procedures. Keep in ESD-safe bag until installed.
KSYN3 Printed Circuit Board Assembly
ESD Sensitive. Follow ESD safe handling
procedures. Keep in ESD-safe bag until installed.
1 E850402
KRX3 Main Printed Circuit Board
Assembly
ESD Sensitive. Follow ESD safe handling
procedures. Keep in ESD-safe bag until installed.
1 E850276
K3 Mixer Board
1 E850257
ESD Sensitive.
KNB3 Noise Blanker Board
1 E850280
ESD Sensitive.
7
ILLUSTRATION DESCRIPTION QTY.
KNB3 SUBIN Board
ESD Sensitive.
KNB3 SUBOUT Board 1 E850332
KRX3 Enclosure, Top (with tall standoffs) 1 E100334
Screw, Zinc, Pan Head 4-40 1/4” (6.8mm) 8 E700005
Screw, Zinc, Pan Head 4-40 1/2” (13 mm) 2 E700196
Screw, Black, Pan Head, 4-40, 1/2” (13 mm) 2 E700030
Screw, Black, Pan Head, 4-40, 3/16” (4.8 mm) 4 E700015
Screw, Zinc, Pan Head, 4-40, 1-1/2” (38 mm) 4 E700157
Screw, Nylon, Pan Head 4-40, 1/4” (6.8 mm)
Note: 1/2” (13mm) long screws (E700022)
may be supplied instead.
Lock Washer, 4-40, Split 33 E700004
3 E700166
Lock Washer, #4, Inside Tooth 4 E700010
E850344 TMP-BNC Cable Bag
ILLUSTRATION DESCRIPTION QTY
Knurled Nut, 4-40 2 E700158
ELECRAFT
PART NO.
TMP Cable 14” (36 cm) with BNC
Connector with nut and lock washer
Screw, Black, Pan head 4-40, 3/8” (9.5 mm) 1 E700008
Lock Washer, #4, Inside Tooth 1 E700010
Nut, 4-40 1 E700011
1 E850342
9
E850249 I.F. Crystal Filter Bag (or Box)
NOTE: If the optional 8-pole 2.8K filter is purchased instead (see next item) this filter is not supplied.
ILLUSTRATION DESCRIPTION QTY
KFL3A-2.7K Filter
Note: This filter is not supplied if you
purchased the optional 8-pole 2.8 kHz
filter with your K3 kit.
1 E850249
ELECRAFT
PART NO.
Screw, 4-40, either 1/4” (6.4 mm) Zinc,
or
or
Pan Head or 3/16” (4.8 mm) Black Pan
Head screw.
Lock Washer, #4, Inside Tooth or Split
Ring
1
1
E850249 I.F. Crystal Filter Bag (or Box)
OPTION: Not supplied unless ordered. Otherwise the standard 5-pole filter (above) is supplied.
ILLUSTRATION DESCRIPTION QTY
KFL3A-2.8K Filter (optional, see above) 1 E850249
Screw, 4-40, either 1/4” (6.4 mm) Zinc,
or
Pan Head or 3/16” (4.8 mm), Black Pan
Head screw.
1
E700005 or
E700015
E700010 or
E700004
ELECRAFT
PART NO.
E700005 or
E700015
or
Lock Washer, #4, Inside Tooth or Split
Ring
1
E700010 or
E700004
10
Installation Procedure
K3 KIT BUILDERS: If you were directed here to install the KRX3 Subreceiver as part of the
initial K3 assembly, remove the top cover as shown below, and then go directly to Checking and Modifying
Resistor R91 on page 21 since you have already installed the Auxiliary DSP board.
Disconnect power and all cables from your K3.
Remove the nine screws to free the top cover as shown in Figure 2. After the cover is open, lift it
gently to reach the speaker wire connector. Unplug the speaker then set the top cover aside in a safe
place. If you have the K144XV 2-meter option installed, slip the speaker wire under the chassis stiffener
bar that runs across the top of the K3 along the depression in the top of the K144XV module.
Figure 2. Removing K3 Top Cover.
CAUTION
Touch an unpainted metal ground or wear a grounded wrist strap before touching
components or circuit boards inside the K3. See Preventing ESD Damage on page 5 for
more information.
Remove the chassis stiffener bar that runs across the top of the K3 (see Figure 3)
Figure 3. Removing the Chassis Stiffener Bar.
11
If your K3 has the K144XV 2-meter option installed, remove the three 6-32 black flat head screws holding
it to the left side panel (see Figure 4). Unplug the cables going to the K144XV module. The red power wire
plugs into the K3’s main RF board. Unplug it and set it aside with the module.
Figure 4. Removing the K144XV Module.
Installing the Auxiliary DSP Board
If the auxiliary DSP board is already installed in your K3, skip the following steps and go directly to Checking
and Modifying Resistor R91 and DAC Input Circuits on page 20.
Stand the K3 on its side feet, remove the six screws shown in Figure 5 and lift the left side panel off. Set the
side panel aside in a safe place to avoid scratches.
Figure 5. Removing the Left Side Panel.
12
Remove the screw shown in Figure 6. It is located directly behind the front panel microphone connector.
There may be a lock washer under the screw. If so, save it with the screw. Removing the screw ensures the pc
boards on the front panel assembly will have adequate clearance when the front panel assembly is removed in a
later step. Remove only the screw shown. Leave the other screw in place as shown in the figure.
Figure 6. Removing the 2D Screw.
Remove the three screws securing the top of the front panel assembly as shown in Figure 7.
Figure 7. Removing Front Panel Mounting Screws.
Turn the K3 upside down. Place it on a clean, soft surface to avoid scratching the top of the front or rear
panels.
it in a safe place to avoid scratches.
Refer to Figure 8 and remove screws 1 through 7, then lift the forward section of the bottom cover off. Put
Figure 8. Removing Bottom Cover and Front Panel Screws.
Refer to Figure 8 and remove screws 8 and 9.
13
CAUTION
Before continuing on with the next step, be sure you have removed the three top Front
Panel Assembly screws shown in Figure 7. You may bend and damage the front panel or
shield assemblies if the screws are not removed!
Use a screwdriver in the pry tool openings to press back against the circuit board while pushing the lip on
the front panel assembly toward the front as shown in Figure 9. Do not insert the screwdriver any farther than necessary to avoid damaging components! When you have the front panel assembly free, set the main
chassis aside in a safe place.
Figure 9. Separating the Front Panel Assembly from the Chassis.
On the front panel, remove the knurled nut from the
PHONES jack directly above the MIC connector. Be
very careful not to scratch the paint on the front panel.
Place the front panel assembly face down on a
smooth, clean soft surface to avoid scratches to the LCD
cover or front panel paint
Remove the three screws and split lock washers shown in Figure 11.
Figure 10. Phones Jack Knurled Nut.
Figure 11. Removing Main DSP Board.
14
With the three screws removed, the main DSP board is held on to the front panel board by two multi-pin
connectors. Slip your finger tips between the boards and pull the main DSP board away from the front panel
board to unplug it.
A large, thick spacer washer should be
lying on the front panel near the hole for the
phones jack (see Figure 12). This spacer fits
between the phones jack and the back of the
front panel board to provide a solid mechanical
ground connection when the boards are in place.
Remove the washer and set it aside. If it’s lying
on the inside of the front panel you can tip the
panel so it will slide out at the end.
Figure 12. Phones Jack Washer.
If your kit was supplied with 1/4”
6.4mm) long nylon screws, skip this step. If
you have 1/2” (13mm) nylon screws, cut all
three of them to length as follows:
Screw three 4-40 nuts onto the 1/2”
(13 mm) 4-40 nylon screw as
shown in Figure 13.
Cut off the nylon screw flush with
the last nut. Sharp diagonal cutters
or a knife will cut the nylon.
After cutting, remove all three nuts.
(The nuts establish the correct
length for the screw and “clean up”
the thread where you cut the
screw.)
The boards are especially vulnerable to ESD damage when unplugged. Wear a
wrist strap or touch an unpainted metal ground frequently when handling the
boards to avoid ESD damage. See Preventing Electrostatic Discharge Damage on page 5
for more information.
Figure 13. Cutting 1/2” (13mm) Nylon Screws.
CAUTION
15
Mount the three standoffs on the component side of the main DSP board as shown in Figure 14. Be sure
that:
The standoffs are on the component side of the board as shown.
No lock washer is used between the standoff and the board.
One lock washer is used between the nut and the board.
Figure 14. Installing Standoffs on the main DSP Board.
Check to see if the nylon standoff shown below near J51 is mounted on the main DSP board. If not, install
the nylon standoff supplied with your KRX3 parts as shown below. Be sure you place it in the correct hole near
the corner of the board.
CAUTION
To avoid damaging a circuit trace very close to the metal ring around the screw hole,
position the lock washer under the screw so the split faces away from the trace. Tighten the
hardware by turning the standoff while holding the screw and lock washer stationary. Do
not over-tighten the screw. It is easy to strip the threads in the nylon standoff.
Figure 15. Installing Nylon Standoff on Main DSP Board.
16
Locate resistor R3 on the front panel board (the board still mounted on the front panel assembly). If R3 is
positioned above the board on its leads as shown in Figure 16, push it over to one side of the outline as shown.
Be sure you don’t push it so far its leads might touch the solder pads for other components on the board.
Figure 16. Positioning R3 on the Front Panel Board.
Check the VFO B encoder and trim the pins as shown below if they haven’t been trimmed already to ensure
they cannot short against the main DSP board. If trimming is needed, remove the encoder to ensure clipped ends
don’t get lost in the front panel assembly. To remove the encoder, loosen the set screws and remove the knob,
then remove the felt washer and nut and lift the encoder out. You need trim only the five pins shown close to the
back of the pc board. Replace the encoder by reversing the process. Be sure the spacer nut on the inside is tight
against the shoulder of the ferrule.
Figure 17. Checking and Trimming the VFO B Encoder Pins.
17
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