ELECRAFT K3 HIGH-PERFORMANCE 160 – 6 METER TRANSCEIVER KPA3 100-WATT AMPLIFIER OPTION INSTALLATION INSTRUCTIONS Rev G, July 25, 2011 Copyright © 2011, Elecraft, Inc.
Contents Introduction............................................................................................................................................... 3 Customer Service and Support ............................................................................................................................ 3 Technical Assistance ....................................................................................................................................... 3 Repair / Alignment Service ...
Introduction This manual covers the installation of the KPA3 100-watt amplifier option in your K3 transceiver. Only a few basic hand tools are needed (see page 5) to perform the installation. No soldering or wiring is required. The KPA3 option consists of three subassemblies: the KPA3 power amplifier, a fan panel, and the KPAIO3 interface module. More details about the KPA3 are provided under Circuit Description on page 21.
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.
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.
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 Customer Service and Support, page 3). CAUTION In addition to taking ESD precautions, be careful not to damage components on either side of the circuit boards when handling them. This is especially true of the KPA3 module because of the weight of the heat sink. QTY. ELECRAFT PART NO.
QTY. ELECRAFT PART NO. Rear Shield 1 E100217 Screw, 4-40, 1/4” (6.4 mm) Zinc, Pan Head 9 E700005 Screw, 4-40, 1/4” (6.4 mm) Black, Pan Head 1 E700009 Screw, 4-40, 3/8” (9.5 mm) Black, Flat Head 1 E700131 Screw, 4-40, 7/8” (22 mm ) Black, Flat Head 8 E700159 Acorn Nut, 4-40 8 E700160 Standoff, 4-40, 5/16” (7.
Remove the nine screws to free the top cover as shown in Figure 1. After the cover is open, lift it gently to reach the speaker wire connector. Unplug the speaker and set the top cover aside in a safe place. Figure 1. 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 4 for more information. On the rear of the K3, remove the large blank panel above the GND screw.
K3 KIT BUILDERS: If you are installing the KPA3 as part of the initial K3 kit assembly, skip the following steps and resume with Installing the KPAIO3 Interface Module on page 12 Remove the stiffener bar that runs from side to side across the top of the K3 chassis. This is the bar the center three screws in the top cover thread into. The bar is held in place by a single screw at each side.
Hold the KRX3 module by the two brass knurled nuts on the top, and lift it straight up to gain access to the small TMP coaxial connectors plugged into the module. There are two along the front. There may be one at the back as well, depending upon the options installed. As you lift the KRX3 module, it will unplug from two small interface circuit boards. One is at the front and the other is at the rear. These small boards may come out with the module or they may remain attached to the K3 main RF board.
Installing the KPA3 Shield Remove the three screws, washers and standoffs (on the bottom of the RF) board shown in Figure 6. Save the lock washers and standoffs. The screws will not be reused. Figure 6. Rear Shield Mounting Screw Locations. Set the rear shield in place as shown in Figure 7. Figure 7. Positioning the Rear Shield. Loosely secure the rear shield with three 1/4” (6.4 mm) zinc pan head screws, the lock washers and standoffs you removed earlier as shown in Figure 8.
Place a black 4-40 3/8” (9.5 mm) flat head screw through the hole in the back panel and the tab at the top edge of the shield as shown in Figure 8. Secure it with a #4 inside tooth lock washer and 4-40 nut. Figure 8. Rear Shield Installed. Tighten the three screws holding the bottom of the shield and the screw at the top on the back panel. Do not over-tighten but be sure all four screws are tight. Don’t overlook one! Good contact is essential for the shield to perform correctly.
On the KPAI03 board, install a 5/16” (7.9 mm) 4-40 standoff near K1 as shown in Figure 10. Use the exact hardware shown. This is important so that the height of the standoff is correct when it is mounted in the K3. Figure 10. Installing Standoff on the KPAIO3 Board. As you install components and reassemble your K3, be sure all the screws are in place and secure, but do not over tighten them.
Assembling the Fan Panel Locate the fan panel and mount the fans as shown in Figures 12 and 13 using 4-40 7/8” black flat head screws and acorn nuts. Note that the appearance of the fans in your kit may differ slightly from those shown. If you purchased the optional Stainless Steel screw kit, use the 4-40, 7/8” black flat had screws and acorn nuts from the kit to mount the fans on the panel as described below. Include a stainless steel interior tooth lock washer from the kit under each acorn nut. 1.
Install the 20A circuit breaker in the small hole with the pushbutton on the same side as the fans as shown in Figure 13. Position the fan panel near the rear opening and plug the fan leads into the connectors in the upper right corner of the KPAIO3 board as shown in Figure 14. Be sure to orient the connectors so the red lead is to the left as indicated on the board. If the connectors don’t want to slide onto the pins, check to see if there is any extra plastic on the side facing the board.
Installing the KPA3 Amplifier Module Your KPA3 module may produce a rattling sound when shaken. This is normal. It is caused by ferrite beads sliding along wire leads in the module. Place the KPA3 module inside the shield from the top. Mate the two connectors fully with the KPAIO3 board as shown in Figure 15. Like the KPAIO3 to RF board connectors, these connectors may require some force to mate them fully. Do not place undue pressure on the RF board without supporting it.
Position the fan panel you assembled earlier behind the opening at the rear of the K3 and connect the leads as shown in Figure 16. Figure 16. Connecting Fan Panel to K3. Mount the fan panel on the K3 using four 3/16” (4.8 mm) black pan head screws as shown in Figure 17. These are the screws you that originally held the blank panel. If you haven’t installed the blank panel, the screws are included with basic K3 parts. Do not use washers. Figure 17. Fan Panel Installed on K3.
Dress the fan leads so they are well clear of the fan blades. Check to ensure both fans turn freely. Figure 18. Positioning the Fan Leads. K3 KIT BUILDERS: Skip the following steps. Resume with Replacing the Covers on page 19 Replacing the KNB3 Module Replace the standoff and the KNB3 module you removed earlier (see Figure 5).
Replacing the Covers REPLACE ALL THE SCREWS! The K3's chassis has excellent rigidity despite its light weight. The screws that hold the top cover in place are an important part of the structural design. Please be sure to replace all the screws and verify they are tight whenever you replace the cover or other panels Replace the bottom cover(s) using the 4-40 black pan head screws you removed earlier. Note that three locations take the 4-40 1/4” (6.
Hold the top cover above the K3, route the speaker wire under the stiffener bar and plug it into P25 on the KIO3 board at the left rear of the K3 as shown in Figure 20. Figure 20. Connecting Speaker Cable. Position the top cover on the K3. Note that the tab on the back center goes under the rear lip of the K3 rear panel. Secure the top cover with the nine 4-40 3/16” (4.8 mm) black flat head screws you removed earlier.
Circuit Description The KPA3 option consists of three subassemblies: the KPA3 power amplifier, a fan panel to provide cooling, and the KPAIO3 interface module. KPAIO3 The KPAIO3 acts as an interface between the RF board and the KPA3 power amplifier. It includes a relay that allows the KPA3 to be bypassed when it is not needed during low power operation. The cooling fans are also controlled by circuitry on the KPAIO3.
