TS-940S FAN MODS K0ZL 11/08/2006 PARTS NEEDED: 1/4w
Contents
1. nor encouraged by the author or by B amp B TECHNICAL SERVICES In case of error omission or correction contact the AUTHOR directly do not contact the distributor of this information All rights reserved This document in original unedited condition may be distributed freely for personal use only COPYRIGHT 2006 B amp B TECHNICAL SERVICES IC 101 Diol TH101 pPC7805 H S15VB10 STP 41L 2N5885 2SD1266 P Q 2S014061Y Q101 102 0103 Q104 101 01 lon Joa cower THM 7 5 COD 12 5V HOT J toz Heros 13 6 tornon V cro3 croz lf TH 101 298861 C ua a re G2 4 25024581Y aro 470 AVR UNIT ge D os OCI ae lt i X43 1500 00 5 394 AP io Pelee Pu 37a 470s p gt Er T e lg w a e ee 38 U irm 4 a oe ak ew lt iu piar 01 2 10 13 UOSB MTZ 18UC er u WA 1 2 10 13 4 18UC or 03 82 320 MTZ 20a E D4 MTZI2JC or 09 MTZ9 1JA or L e MTZ13JA MTZB 2UC a 05 7 155133 016 MTZ22JD or 06 svo3ys MTZ24JA Service manual reprint courtesy Kenwood USA All rights reserved COPYRIGHT 2006 2007 B amp B TECHNICAL SERVICES Neither the author nor B amp B TECHNICAL SERVICES is responsible for damage to any electronic equipment from use of this information Static control procedures and tools must be used in the execution of this work If in doubt please enlist the help of a competent2. technician Illegal operation of Amateur Radios is neither condoned nor encouraged by the author or by B amp B TECHNICAL SERVICES In case of error omission or correction contact the AUTHOR directly do not contact the distributor of this information All rights reserved This document in original unedited condition may be distributed freely for personal use only COPYRIGHT 2006 B amp B TECHNICAL SERVICES TS 940S PC BOARD VIEWS MAIN ENCODER ASS Y W02 0328 10 Co nt side view DC DC UNIT X46 1030 00 Component side view RIT ENCODER UNIT X54 1690 01 Component side view AVR unit Attachment method of F1 and R9 Fuse or resistor 1 5 m 4 15 152 44 04 SW unit Attachment method of display tube Packing SW unit Attachment direction of 1B1 DC DC unit Attachment method of T1 amp 2SA1015 2SC1959 2 C2235 2SC2274K Be ec 25A1048 xX 9 Ware 2SC2458 2SB861 pnNi26s W X uPC78L05A DTA143ES 102 Qa SS AS aA E 8 C OUTPUT ce Service manual reprint courtesy Kenwood USA All rights reserved COPYRIGHT 2006 2007 B amp B TECHNICAL SERVICES Neither the author nor B amp B TECHNICAL SERVICES is responsible for damage to any electronic equipment from use of this information Static control procedures and tools must be used in the execution of this work If in doubt please enlist the help of a competent technician Illegal operati
3. TS 940S FAN MODS KOZL 11 08 2006 Note Static control procedures and tools must be used in the execution of this work If in doubt please enlist the help of a competent technician PARTS NEEDED 1 4w resistors 4 7K and 470 ohm 1 each Synthetic motor oil one drop The life of the TS 940 can be greatly increased with better cooling especially of the 29 volt regulator transistors and their heat sink Also on some older 940s the fan may not even turn on due to wear or thickened lubricant on the fan bearings This will lead to catastrophic failure of the 29 volt pass transistors Q101 and Q102 and subsequent destruction of the expensive and hard to find driver transistors and zener diodes on the PA unit This mod will cause the power supply fan the one towards the left side rear of the radio as the rig faces the operator to turn on at a lower temp and to run slightly faster when it does turn on Fan noise may be increased this can be ignored or the fan motor can be lubricated or replaced as desired Note lowering the fan turn on temperature of the PA fan has not been noted to be of benefit as most of the heat problem is generated by the regulator pass transistors At any rate this change is much more difficult Procedure Allow the rig to remain unplugged and discharging for at least one hour prior to performing this mod Remove the connectors one at a time along the back and right edges of the AVR unit prior to loosening the AVR uni
4. on of Amateur Radios is neither condoned nor encouraged by the author or by B amp B TECHNICAL SERVICES In case of error omission or correction contact the AUTHOR directly do not contact the distributor of this information All rights reserved This document in original unedited condition may be distributed freely for personal use only COPYRIGHT 2006 B amp B TECHNICAL SERVICES
5. t Remove all four screws on the AVR unit and fold out so that the solder pads are accessible On the AVR unit change R11 from 390 to 470 ohms 1 8 or 4 watt This will make the fan come on at a lower heat sink temperature Also change R17 from 10K to 4 7K 1 8 or 4 watt This will allow Q5 to drive the fan motor with a slightly higher voltage While the AVR unit is exposed re solder all suspicious solder joints particularly on the power rectifier diodes and larger pass transistors where heat is an issue Be very careful of solder bridges as these can destroy the AVR unit which is NO LONGER AVAILABLE After the mod and resoldering job remove the rear fan and remove the fan on it s bracket Put one drop of synthetic motor oil SW 30 or 10W 30 either one on the motor shaft where it enters the bearing This will quiet the motor and help the anti rattle spring last longer Side note If replacement of the 29 volt pass transistors is necessary for some reason it has been our experience that substituting for these will not be a good thing Use the original 2N5885 qty 2 COPYRIGHT 2006 2007 B amp B TECHNICAL SERVICES Neither the author nor B amp B TECHNICAL SERVICES is responsible for damage to any electronic equipment from use of this information Static control procedures and tools must be used in the execution of this work If in doubt please enlist the help of a competent technician Illegal operation of Amateur Radios is neither condoned
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