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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 # 1008
MODEL: TH-78A
SUBJECT: Call Channel Tone Frequency Error (Revised)

Symptom:

When the TSU-7 CTCSS unit is installed the tone frequency of the CALL CH is
overwritten under the following circumstances:

1. Program the Call Channel with a tone between 67.0 Hz and 114.8 Hz. For
   example 100.0 Hz
2. Program any memory channel with any frequency and tone frequency.  For
   example: 118.8 Hz
3. Recall the memory channel to the VFO.
4. Recall the CALL  channel.  

The tone frequency of the call channel changes to that of the memory channel.
    (Changes from the programmed 100.0 Hz in the example to 118.8 Hz.)

Parts Required:

IC-5: Original part....75517GF-155-3B9

IC-5: Change to:.......75517GF-170-3B9

Procedure:

This symptom is caused by a microprocessor programming error.  The cure is to
replace the microprocessor (Control Unit X53-3420-00, IC-5) with the part
listed above.   

Note: Units with serial numbers 404xxxxx - 406xxxxx have a limited production
microprocessor installed.  This microprocessor incorporates the correction for 
this error. The part is labeled 75P518GF-JDF3. You do not need to replace this
IC.  Units with serial number 407xxxxx and after will have the 75517GF-170-3B9 
microprocessor installed at the factory.

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 1 hour or less.                          
Service Code:  A:98 B:X53-3420-00 C:IC-5 D:91