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[[File:Kenwoodts940-brhrimg.jpg]]'''Features'''{|| 160-10 meters IF Notch CW Reverse 40 Memories Automatic Tuner | | CW VBT SSB Slope Tuning Memory Keyer Variable AGC Sub-display |}== Known Issues ====Operation=====controls===[[File:Kenwood-TR940S_controlsP1900x740.jpg]]FUNCTION switches* T-FSET switch - Depress this switch to "SPOT", or momentarily interchange reception frequency with transmission frequency. Frequency "SPOTTING" is possible only in receive and is ineffective during transmission* A/B - Selects the VFO or VFO B.* SPLIT - For split frequency operations A-R, B-T OR B-R,A-T.* A=B - During VFO operation, press this switch to equalize the frequency and mode of the idle VFO to that of the active VFO.* F.LOCK - Press this switch to lock the VFO and BAND switches.* VOICE - Announces the frequency when an optional VS-1 is installed inside the cabinet.[[File:Kenwood-TR940S_controlsP2900x400.jpg]]==Review=====some of the known issues======production run improvements===[https://forums.hamisland.net/showthread.php/10730-Kenwood-TS-940S Quoted from N8YX], "''any folks opine that any serial number above 7 million is "safe", while others swear that the magic number is 8 or even 9 million+.''"===power supply==="''The later version's IF board can be swapped into an earlier unit and this will cure many'' (problems). Also ''look into upgrading the power supply cooling arrangement''. Citation [https://forums.hamisland.net/showthread.php/10730-Kenwood-TS-940S from N8YX]The power supply fan operates on 12VDC. Sometimes when the OEM fan tests good on external power, it could be that under load the fan is not getting sufficient voltage from inside the unit. Under load it has been reported that the voltage measured on a meter dropps from 17v down to 3v. This relates to a problem with the AVR board. Modern computer fans can serve as excellent replacements in the fan is bad.===PLL Unlock===From a Kenwood TS-940S Service Bulletin 10/18/1985 - Some users of the TS-940S have reported a blanking of the display accompanied by a loss of transmit and receive. Readjustment of the PLL unit will correct this tendency. Procedure:On the PLL Unit #Set the dial frequency for approximately 1.8Mhz (inside the band).#Using an RF probe at TP #5 adjust L22, L23 and L24 for a maximum reading on the meter. You should see approximately 250mV.#Adjustment of L24 will produce the greatest change, which may be up to 90 degrees from its present position.[[File:Kenwood-TS940S_ASB0900.JPG|thumb|none|100px]]===Sub LCD Display Blank or Boxes===On the bottom right of the LCD Board thereis a black plastic momentary switch. I justpuched it once and it reset all the LCD parameters.VFO display, Clock, etc. That was it!reference: http://www.eham.net/ehamforum/smf/index.php?topic=68286.0Procedure verified. ===Vacuum Fluorescent Display problems======maintenance===''A semi-skilled tech should have no problem keeping one on the air. Pay close attention to the AVR pass-transistor cooling fan (or replace it). Most problems of an intermittent nature with a rig this old can be traced to questionable connectors on the various circuit boards. Resoldering them is a tedious job but aside from replacing memory batteries (or re-peaking the VCO tuning coils, if necessary) is usually all that's required in the way of maintenance'' (for the TS-940S transceiver.) Citation [https://forums.hamisland.net/showthread.php/10730-Kenwood-TS-940S from N8YX]See the list of Kenwood Service Bulletins * http://www.qsl.net/bg4aaf/book/kenpic/kenwood.htm [atunit.pdf]<big>'''Service Manual, Individual Board Schematic Diagrams, and other Product Literature from Kenwood.'''</big> controlunit.pdf digitalunit.pdf*[http://www.ke0etz.com/files/atunit.pdf AT Unit schematic] ifunit.pdf*[http://www.ke0etz.com/files/controlunit.pdf Control Unit schematic] kenwood-ts-940-sat-service-manual.pdf*[http://www.ke0etz.com/files/digitalunit.pdf Digital Unit, Switch Unit, RIT Encoder Unit schematics] mpdf.pdf*[http://www.ke0etz.com/files/ifunit.pdf IF Unit schematic] pllunit.pdf*[http://www.ke0etz.com/files/pllunit.pdf PLL Unit, CAR Unit schematics] ts940_brochure.pdf*[http://www.ke0etz.com/files/rffinalunit.pdf RF Unit, LPF Unit, Final Unit schematics] ts940s_manual.pdf*[http://www.ke0etz.com/files/schematic.pdf 2 page schematic TS-940S (scanned)] TS-940S_Service_manual.pdf*[http://www.ke0etz.com/files/ts940_brochure.pdf TS-940S HF Transceiver brochure] ts940technical.pdf*[http://www.ke0etz.com/files/ts940s_manual.pdf Original Service Manual (scanned)]*[http://www.ke0etz.com/files/TS-940S_Service_manual.pdf New Revised Service Manual]*[http://www.ke0etz.com/files/ts940technical.pdf TS-940S Technical Information (scanned)][[File:kenwoodts940s.jpg]]The cooling fan on the back is temperature sensor based rather than timer based, according to a HAM radio source online. This needs confirmation.The cooling fan on the back is temperature sensor based rather than timer based, according to a HAM radio source online. It is a recommended modification to make it so the fan runs all the time, which is accomplished by jumping connector #13. ===SSB slope tuning===In SSB slope tuning, one filter passband can be shifted up in frequency and the other filter passband can be shifted down in frequency, effectively narrowing the bandwidth of the combined filters. Basically you can narrow from either end and to what degree best helps to eliminate noise and near frequency interference. An excellent article on [http://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/2001/02/page42/index.html How to maximize your receiver's effective selectivity] written by ham radio operator Rob Kalmeijer covers the use of slope tuning. ===compatible microphones===Microphones recommended in literature for the TS-940S.*Kenwood MC-60A - upright desktop microphone*Kenwood MC-42S - hand microphone with up/down*Kenwood MC-80 and MC-85 - upright desktop amplified microphones [[File:KenwoodMicrophonePins01.jpg]]<BR>source: [http://homepage.ntlworld.com/rg4wpw/date.html rg4wpw Microphone Connections] The Kenwood MC-42S is an 8-pin 600 ohm dynamic mic with up/down buttons on the top. Kenwood mic pin-out:*Pin 1 - Mic audio*Pin 2 - PTT*Pin 7 - Mic audio ground*Pin 8 - PTT ground ==Service=====cooling fans===There are two of them. One for the voltage control and one on the finals. Both are in back of the unit but only one is visible without removal of case.Cooling fan: The cooling fan is connected to the AVR board. There is a thermister on the back panel inside. It can be removed so that the fans run continuous. This will burn up the OEM fans if ran continuous. Computer fans can run continuous. If the fan stops you will loose the AVR unit, very hard to find and now you have a door stop. The OEM fans are still around, but getting somewhat rare. It is better to replace them with computer fans, which are a lot less of a problem. ===LCD Sub Display===If the LCD sub display starts to show garbage you can attempt a reset. The reset is a momentary button inside the unit, you will have to remove the case. So take off the top case and look at the board with a battery on it directly behind the LCD. Right of the battery and in the bottom corner of the board is the black reset button. Use a nonconductive tool to press it and reset the sub display.K3TEN Electronics [http://www.k3ten.com/discuss.htm Technical Information-Kenwood TS-940s] - many pictures of boards and components.* NORTH CAROLINA* TEXAS[http://www.k3ten.com/index.htm K3TEN Electronics] (unverified) Amateur Radio Repair & Restoration* NEW JERSEY[[Category:Electronics]][[Category:Radio]][[Category:Ham Radio]][[Category:2-Way Radio]][[Category:Tangible Product]]