Date: 12 Aug 90 03:05:48 GMT

From: portal!cup.portal.com!Steve_M_Kile
Subject: Kenwood TS-680 mods

To: info-hams


The following mods appeared on a local ham radio BBS.  This is the first I

have seen of these mods, has anyone tried them?  Do they also apply to the

TS-140?



TS680s Squelch modificatios - adds squelch to all modes



Parts required



1 each 100 uF 20 v capacitor

1 each 10k ohm 5% 1/4W resistor

2 each 1N914 small signal diodes



Modification:



All modifications are to the signal board.  Remove the signal board

to gain access to the bottom of the board.



Remove R178 100 ohm resistor. (I cut the land between C177 and R178)

(Removes FM chip control voltage) R178 is on the bottom of the

board.



Add jumper with a diode in series between IC6 pin 14 and the base of

Q57.  Cathode of the diode goes to the base.  (This is the squelch

trigger control voltage)  Q57 is on the bottom of the board.



Connect a diode between the 8V line (very near IC6) and pin 4 of

IC6. This activates the FM chip (IC6) all of the time.  Cathode goes

to pin 4, anode to the 8 volt line.



Connect a 10 k ohm resistor between IC6 pin 4 and IC6 pin 14.



Connect a 100 uF 25 volt capacitor between IC6 pin 14 and ground.

(This slows this quick squelch down a little bit)

Tests have shown (using commercial communications monitor) that

activating FM chip IC6 does not degrade IF strip performance at all.



I have had this mod in my 680 for a bout year and a half and is

still working great!





TS-680 6 METER POWER OUTPUT INCREASE



Adjust VR15 (50M) control on the SIGNAL UNIT board while monitoring

6 meter transmit power out put into a 50 ohm dummy load.  I adjusted

mine while also monitoring the ALC level to insure that I still had

some ALC action.  Using this method I have increased my 6 meter

power output to appx. 25 watts.





Broadcast Sensitivity Modification for the TS680S / 140S



Between .500 and 1.6 MHz attenuation is added to reduce? front-end

overload on the Broadcast band. Some of us BCB DXers find this a

HIGHLY undesirable feature. If I want attenuation I will use the

front panel switch. The following mod will restore the sensitivity -

Cut the land between IC1 pin 11 and R7 (SIGNAL UNIT, M54581P)



Cut the trace between IC1 pin 12 and R10



Add a small signal diode (1N914, 1N4148) between IC1 pin 11 and R7

(Cathode towards R7)

Add a small signal diode between IC1 pin 12 and R7 (Cathode towards

R7)



Trace the lands from pin 11 and 12 of IC1 and you will find a good

place (to the left of connector CN5) to cut these traces as well as

pad to solder the diodes to.



WOW WHAT A DIFFERENCE!!!!!





If any new mods come up or enchancements of this one please contact

me!!



73, WB5HJV



David A. Underwood

9705 Caffrey

Houston, Texas 77075



==========

Steve - N0FBL



steve_m_kile


------------------------------