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World of Ham Radio 1997
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==============================================================================
K E N W O O D
>>> A M A T E U R R A D I O S E R V I C E B U L L E T I N <<<
==============================================================================
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
==============================================================================
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