Symptom:
Attempting to tune the AT-50 when it is connected to an antenna with a relatively high SWR value might cause the ACCY fuse to open in the TS-50S. This change will correct this tendency.

Parts required:
.047 µF disc ceramic capacitors, CK45B1H473Z, QTY. 2

Procedure:

1. Remove the top cover from the antenna tuner.
   
   
2. Locate X53-3470-00 D/4 (It is attached to the top left side of the chassis with the foil side up).
   
   
3. Add the two .047 µF capacitors as shown in the drawing below.
   
   
4. Replace the top cover.

No additional adjustment or modification will be required. Caution: This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance.

Time required for this modification is 30 minutes or less.



23-04-2000 AT-50 Blows ACCY fuse in TS-50S (Part 2)
Author: Kenwood Communication, inc.

Symptom:
Attempting to tune the AT-50 when it is connected to an antenna with a relatively high SWR value, especially on the 3.5 MHz band might cause the ACCY fuse to open in the TS-50S.

Parts required:

Qty   Description                          Kenwood Part No.  Circuit description
 2    Toroidal coil                        L33-0699-05       NA

Procedure:

1. Remove the top and bottom covers from the antenna tuner.
   
   
2. Locate X53-3470-00 D/4 (it is attached to the top left side of the chassis with the foil side up).
   
   
3. Remove the two .047 µF capacitors shown in figure 1 if they are present.
   
   
4. Cut the foil and add one of the toroidal inductors as shown in figure 2.
   
   
5. Turn the tuner over and locate capacitor C123 and C124, as shown in figure 3.
   
   
6. Move the capacitors (or add new capacitors) to the locations shown in figure 3.
   
   
7. Cut the foil path and add the remaining totoidal inductor as shown in figure 3.
   
   
8. Remove jumper W106 as shown in figure 3. (Note: remove the jumper from the component side of the board).
   
   
9. Add a jumper from the ATG foil to W104 as shown in figure 3.
   
   
10. Replace the top and bottom covers.

Caution: This modification requires soldering equipment rated for CMOS type circuits. It also requires familiarity with surface mount soldering techniques. If you do not have the proper equipment or knowledge do not attempt this modification yourself. Seek qualified assistance.

Time required for this modification is 30 minutes or less.



23-04-2000 AT-50 Mechanical stability
Author: Kenwood Communication, inc.

Symptom:
When the unit is placed on a flat surface it appears to be slightly unstable, i.e. rocks back and forth when pressing down on the left front corner of the unit.

Procedure:
Add a flat spacer at the location shown between the chassis and the bottom cover.

Parts required:

Qty   Description                          New Part No.      Circuit Description
 1    Spacer                               J30-0597-04       NA

Time required for this modification is 15 minutes or less.