SB-896 TS-940S LCD Clock Display Erratic Operation 9-14-85 We have received a few reports concerning erratic operation of teh LCD clock display when the Main dial is rotated, or the VBT or SLOPE TUNE controls are operated. This appears as if you had pressed the SET, SCROLL, or GRAPH switches. This erratic operation may be caused by improper timing of the input pulses applied to the auxiliary display microprocessor, IC1. 1. This symptom is easily corrected by replacing IC2 MBM2764-30T1 with MBM2764-30T2, on Digital Unit A. Early models of the improved IC will carry the old nomenclature but will be distinguished by a white dot on the top of the chip. 2. After the IC has been changed reset the main microprocessor by pressing and holding the A=B key, and then turning the power switch OFF and then back ON. Then release the A=B key. 3. After this change is made the sub-display will not immediately track the main display. A slight delay has been introduced int he new IC to prevent any timing errors. It may take approximately 0.5 seconds for the LCD to track the main display. 4. Please return the old IC2 to the Service Department along with the WSR for Credit. Perform this modification only if the symptom occurs, as a repair. This change is not required otherwise. Time required for this modification is 1 hour or less. CLM (c) 121589TKC SB-900 TS-940S PLL Unlock 10-18-85 Some users of the TS-940S have reported a blanking of the display accompanied by a loss of transmit and receive. Re-adjustment of the PLL unit will correct this tendency. PROCEDURE: On the PLL unit 1. Set the dial frequency for approximately 1.8 MHz (inside the band) 2. Using an RF probe at TP5 adjust L22, L23, and L24 for a maximum reading on the meter. You should see approximately 250mv. 3. Adjustment of L24 will produce the greatest change, which may be up to a 90 degree adjustment from its present position. Time required for this modification is 1/2 hour or less. CLM (c) 121589TKC SB-908 TS-940S PLL Unlock 4-8-86 Reports of a PLL unlock on the lower frequencies may be due to low VCO levels. The following change will increase the VCO level and should prevent reoccurrance of this symptom. Part Required C168 change to 15 pF 50v (CC45SL1H150J) Procedure: 1. On the RF Unit (X44-1660-00) change C168 from a 33 pF capacitor to a 15pf 50v capacitor. 2. Readjust the VCO BPF (RF unit L74-76) according to the instructions contained in the TS-940S Service Manual. This change is applicable to serial numbers prior to 606XXXX. Time required for this modification is 1 hour or less. (c) 121589TKC SB-909 TS-940S AVR Unit Capacitor Change 4-8-86 In those areas of the country that are subject to large poer line voltage fluctuations, excessive voltage may be applied to capacitor C12 on the AVR Unit (X43-1500-00). These voltage fluctuations might exceed the capacitor breakdown voltage. Replacing capacitor C12 with a capacitor having a higher breakdown voltage will help prevent this potential problem. Procedure: On the AVR Unit change C12 from a 6800 uF capacitor to a 5600 uF 25V capacitor (C90-2037-05). Time required for this modification is 1 hour or less. (c) 121589TKC SB-913 TS-940S Signal to Noise Ratio Improvement 8-26-86 The following changes will reduce the tendency of the Zener Diode in the Noise Blanker circuit to cause an increase in the ambient noise level. This change ensures that no current flows thru this diode in the normal receive position. Parts Required: 560 ohm 1/4 watt resistor Procedure: On the IF UNIT X48-1430-00 change R23 from 330 ohms to 560 ohms. This change will be incorporated in all models beginning with serial number 603XXXX. Time required for this modification is 1 hour or less. (c) 121589TKC SB-921 TS-940S SSB Talk Power Improvement 7-22-87 TS-940S's in the serial number range of 601XXXX through 708XXXX may be limited n SSB peak power as compared to full CW output. The level may be increased by changing the value of capacitors C182 and C183 in the ALC circuit on the Control board. The recommended replacement value for each capacitor is 0.0022 uF, 50v (CK45B1H222K). Procedure: 1. Disconnect the power cord and antenna from the transceiver. 2. Remove the top and bottom covers (16 screws). 3. Locate the Control board on the bottom of the transceiver. 4. Locate transistor Q37 on the board (toward the back right hand side.) The two capacitors are mounted on the foil side of the board underneath Q37. 5. To access the bottom of the board remove the 8 screws that mount the board and heat sink to the chassis (See figure 1.) 6. Carefully lift the board/heat sink fomr the right hand side and pivot it toward the front of the transceiver. 7. Replace C182 and C183 with 0.0022 uf, 50v capacitors. 8. Lower the board back into its original position (don't pinch any wires!) and re-install the 8 mounting screws. 9. Put the covers back on the TS-940S and secure them with the 16 case screws. 10. Connect the antenna and power cord then test the transceiver for normal operation. This is an optional change and may not be performed under warranty. Time required for this change is 1 hour or less. (c) 121589TKC SB-951 TS-940S ERRATIC DISPLAY 01/20/89 Intermittent control or display problems that are difficult to correct with the reset procedure may be caused by a faulty ROM socket. The socket should be checked to insure that it makes good electrical contact with each pin of the ROM. If it is found to be intermittent, remove the socket and solder the ROM directly to the board. It should be noted that units between serial numbers 701XXXX to 811XXXX and from 903XXXX to 909XXXX are not likely to have this failure. In addition, units with a serial number of 909XXXX and above do not incorporate a socket. CAUTION Removing the socket requires good soldering skills. The ROM is mounted on the Digital A unit and is designated as IC2. The board, being double sided, has solder connections on both component and foil sides. When the socket is removed, it is very important to insure that each pin is completely solder free. Having to pry up on the socket means that it is not completely desoldered and will cause the circuit foils to tear. When performing any work on the Digital A board, CMOS handling techniques must be observed. Such techniques include using a grounded or isolated soldering tip, avoid touching the pins of IC chips with your fingers, and ground yourself with a wrist ground strap. To remove the socket: 1. Disconnect the power cord and antenna coax. 2. Remove the top and bottom covers from the transceiver. 3. Remove the 2 flat head screws from each side of the front panel chassis. 4. Loosen the round head screw on each side of the front panel chassis. 5. Carefully rotate the front panel forward. It will be necessary to unplug the VS-1 cable from the transceiver. 6. Remove the 4 screws from the speaker mount. 7. Carefully pull up on the mount and rotate it toward the front panel. Swing the mount toward the right side of the transceiver and allow it to rest on the Digital B unit shield. 8. Remove the 8 screws from the Digital A unit shield plate. 9. Lift the plate and rotate it to the left side of the transceiver. 10. While avoiding contact with the pins, remove the ROM (IC2) and set it aside on anti-static foam. 11. Remove the 6 screws that mount the Digital A board. Rotate the board toward the front panel to expose the bottom side of the board. 12. Carefully desolder the socket and remove it from the board. Do not pry up on the socket. If it does not easily pull off the board, the top foils are still soldered to the socket. 13. Install the ROM in the board and solder it in place. 14. Assemble the transceiver by reversing steps 1 - 11. Do not pinch the power switch cables between the front panel and the body of the transceiver. Time required for this modification is 1.5 hrs or less. (C) 011189TKC