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                             K E N W O O D
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                        Kenwood Service Centers

   Kenwood Service Corporation             Kenwood Service Center, East
   2201 East Dominguez Street              829 Lynnhaven Parkway, Suite 130
   Long Beach, California 90801            Virginia Beach, Virginia 23452
   Telephone 1-310-639-5300                Telephone 1-804-340-1702

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BULLETIN # 1048
MODEL: TH-78A
SUBJECT: IMD Improvements 

Symptom:

When the transceiver is subjected to a strong electric field, such as might
be encountered near an FM Broadcast Station, TV Transmitter or near Land
Mobile sites, the sensitivity might be lowered, scanning operation may 
become difficult or impossible, distortion of the desired signal may be
encountered or problems with the S-Meter circuit may become apparent.

Corrective Action:

Change of the components indicated in the chart on the TX-RX Unit 
(X57-4090-XX B/4) will reduce mixer currents and reduce the bandpass of 
the Band Pass Filter (BPF) circuit.
 
Parts Required:
Qty   Description              Kenwood Part No.        Circuit Description
1     1 k ohm chip resistor    RK73GB1J391J            R80
1     3.3 k ohm chip resistor  RK73GB1J332J            R81
1     3 pF chip capacitor      CC73GCH1H030C           C100
1     18 pF chip capacitor     CC73GCH1H180C           C116
1     10 pF chip capacitor     CC73GCH1H100D           C155

Procedure:

1. Change R80 from 390 ohm to 1 k ohm.
2. Change R81 from 3.9 k ohm to 3.3 k ohm.
3. Change C100 from 1 pF to 3pF.
4. Change C118 from 33 pF to 18 pF.
5. Change C155 from 1000pF to 10 pF.

This modification required advanced surface mount soldering equipment that is
rated for CMOS circuits. It also requires familiarity with advanced surface 
mount soldering techniques. If you do not have the proper equipment or
knowledge do not attemt this modification youself. See qualfied assistance
from your nearest Kenwood Service Center (Long Beach, Ca. or Virginia
Beach, Virginia)

Time required for this modification is 60 minutes or less.
Service Code A: 18  B: X57-4090B/4 C: R80 D: 91