March 23, 1976 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-30 Spurious Responses on Ten Meters Some of the high level spurious responses found on ten meters is due to the high VFO injection which occurs when the VFO attenuator pad is bypassed on transmit. This should be corrected in all SB-104's received for service by clipping out the 1000 ohm resistor at R1251. This change keeps the attenuator pad and VFO filter in the circuit at all band switch settings by disabling switch transistor Q1251. In addition to this change, put four large ferrite beads [PN 475-12] on the grey lead from chassis connector pin K5 to lug 8 of the relay. Glue ferrite beads to chassis with PN 350-12. ----------------------------------------------------------------------------- -------------------------------------- March 24, 1976 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-31 Improved Sensitivity The following change should be made to all SB-104's received for service: Remove and discard L733 Remove and discard C787 This change eliminates the series resonant circuit from the colector of Q703 to ground, and improves the performance of the PN 40-1875 coil at L734. ----------------------------------------------------------------------------- --------------------------------------- March 24, 1976 SB-104 Bulletin No: Solid State Transceiver SB-104-32 Improved +11 Volt Regulation The 680 oh, 5% resistor at R254 [See Bulletin No. SB-104-12] may not work well in all cases. When the +11 volt buss is found to be low, R254 should be replaced with a 750 ohm, 5% resistor [PN 1-96]. This bulletin does not apply to the HW-104, since all production units have the 750 ohm resistor installed at R254. ----------------------------------------------------------------------------- --------------------------------------- April 9, 1976 SB-104/HW-104 Bulletin No: Solid State Transceiver SB-104-33 Product Improvements Low Power On All Bands Select R-332 with a D.V.M. to 1.2K 1% or slightly higher. Future runs will use a 1% resistor. The part when speced in will be assigned a new number. Keep in mind, the power spec is 80-125 watts. Too much power can cause additional problems. An ideal performance would be 100 W on all bands. Carrier Suppression Carrier suppression can be improved, if there's ample power on all bands, by lowering the value of R314[1K] to as low as 390 ohm. The carrier balance adjustment can be accurately made by watching the "S" meter on another receiver tune to frequency and adjusting for minimum reading. Couple the receive antenna to the SB-104 to provide an adequate reading. Also, see Bulletin No. SB-104-19. Unstable And Excessive Harmonic And Spurs 15 & 10 Meters ALC Board If the SB-104 has been oscillating for some reason, theres a possibility coils L801, L802 and L803 have been overheating. There will be no physical sign of this now. Direct replacement cures the problem. Driver Board The Driver Board mounting holes (3) do not have the solder resist cleared for secure grounding when the hardware is installed. Each board must be disassembled, solder resist cleaned from around the holes, tinned and reassembled. If the transistors have been oscillating on this board they will probably be getting hot as a sign now. They must be replaced. C Board When first keyed a spur occurs due to late ALC action. Remove C322 on ALL SB-104's serviced. If one band has more output than others and you suspect spurs, change any one [or more] of the corresponding output resistors R337, R339, R343 or R345 to 100 ohms [PN1-1-12]. The most likely one is 40 meter R343. Chassis The four ferrite beads in Bulletin No. SB3-104-30 should be cemented down with the same cement used for the coils [PN 350-12]. This is for mechanical reason only. Low Sensitivity G Board To improve the 80 meter sensitivity, change L734 to PN 40-1726. Remove 2 turns before installing this coil. Future runs will have a coil for this location with its own part number. When it's available, you will be advised. In the first 3 runs, the coils were not color coded. We also find, many of these coils in the B,P,F,S, are below Q spec. If you have a sensitivity problem change to the new number. 80 to 10 meters is usually the more difficult ones to meet spec. New 10 M coil [PN 40-1875 (Red)] New 80 and 40 M coils [PN 40-1882 (White)] The new numbers are found in the most recent manuals. Also a cross reference is in the HW-104 service data book. Also suspect the (3) 8.65 MHz B.P.F. coils [PN 40-1805]. E Board Remove R613 Change R619 from 560 ohms to 100 ohm [PN 1-1-12]. ----------------------------------------------------------------------------- ---------------------------------------- April 21, 1976 SB-104/HW-104 Bulletin No: Solid State Transceiver SB-104-34 Trimmer Capacitors Tune Full Open The 40M and 15M bandpass filter trimmers C718 and C741 usually trim fully open, preventing proper tuning of the filter and reducing sensitivity. Make the following changes in all SB-104/HW-104's received for service. Change: C719 30 pF s.m. to 24 pF s.m. [PN 20-77] Remove and Discard C742 3.9 pF disc. The capacitor plates in the square black trimmers are indicated by the indented and raised spots on the capacitor body -- the capacitor is fully meshed when the indented and raised spots are closest to each other. ----------------------------------------------------------------------------- ------------------------------------- April 21, 1976 SB-104/HW-104 Bulletin No: Solid State Transceiver SB-104-35 Low Sensitivity On 10M and 15M, Other Bands OK In cases of reduced sensitivity, bypassing the 8.65 MHz band reject filter located under the chassis should result in an increase of not more than 1 db on 10M and 15M. Check the series and shunt torroids by pulling them slightly away from the terminal strip and re-checking the filter attenuation. A noticeable improvement in signal-to-noise ratio indicates the insulating formvar on the torroid windings had been broken at point of contact. ----------------------------------------------------------------------------- ------------------------------------- April 22, 1976 SB-104 Bulletin No: Solid State Transceiver SB-104-36 Incorrect Wires In Harness Wiring Harness [PN 134-887] should have a WH/BR/BR wire and a WH/BR wire coming from BO#1 and BO#4. In kits with series number 05551 harnesses were found with two WH/BR/BR wires or two WH/BR wires at these breakouts causing the unit to be wired incorrectly. SB-104 store stock with this series number should be checked for the correct wires in this harness. Factory stock is being corrected. ----------------------------------------------------------------------------- --------------------------------------- April 22, 1976 SB-104/HW-104 Bulletin No: Solid State Transceiver SB-104-37 Low Sensitivity On All Bands The following performance checks will help to isolate specific problem areas in receivers with low sensitivity: 1. Set the SB-104 fron panel controls as follows to prevent damage to the signal generator if the transmitter is accidentally keyed: MIC/CW Level ------------------------- full CCW HI ----------------------------------------- out TUNE ------------------------------------ out 2. Turn the receiver RF gain full CW. With no signal applied, set the volume control for a noise reference level that is high enough to mask the receiver's own hum and noise. If an IM-38 is being used to read the audio output, set the meter to the 0.3 volt range, and then set the noise reference level at -10 db. [Some of the following steps may require a resetting of the reference level before measurement due to changes in receiver noise level]. NOTE: In the follow two steps it will be necessary to isolate input leads during signal injection. This can be done by unsoldering input leads, or, by using the extender card with the pin 1 through 6 extender block shifted over one space to isolate pin 1 on the circuit board. 3. Isolate pin F1 on the F board and inject a 3395 kHz, .6 microvolt signal through a .01 mfd capacitor to the pin. The output should increase by 10 db or more. If not, the problem is probably in the IF strip or AGC. 4. Isolate pin E1 and inject a 3395 kHz, .18 to .2 microvolt signal to the pin. Tune the signal generator across the filter passband; the output should peak at least 10 db or better. If not, the problem is the crystal filter or its input and output circuits. 5. Install the extender block properly on the extender card, and put the G board on the extender card [pin 1 no longer has to be isolated]. With an RF probe, check the voltage at pin G6. This voltage should be approximately .5 to .6 volts on 80M and 40M, and .4 volts on all other bands. If the voltages are significantly lower, the problem is with HFO output amplifier Q405 or the appropriate HFO oscillator on the D board. 6. With an RF probe, check the VFO voltage at pin G4. This voltage can be as low as .4 volts without seriously affecting receiver sensitivity, and should be around .45 to .50 volts. If the voltage exceeds .5 volts, reset the VFO output level to .48 volts at the MIDDLE of the VFO range. 7. Set the bandswitch to 80M and turn off the 80M HFO oscillator by rotating the oscillator slug until the display shows 66XX.X. Remove the filter end of the jumper wire connecting C762 with the filter output bus, and inject an 8.6 MHz, .8 microvolt signal to the jumper wire. The output should increase by 10 db or more. If not, there is a problem in the 8.395 to 8.896 MHz bandpass filter. If it is difficult to keep the bandpass characteristic flat over its 500 kHz passband when tuning C764 and C769, the Q of the [PN 40-1805] coils is probably too low, and they should be changed. Normally C764 will set the low end response and C769 will set the high end, and the passband will be relatively flat. The following components make up the 8.395 MHz to 8.895 MHz bandpass filter: L725 C764 C774 C771 L726 C766 R721 C767 L727 C773 C769 C772 If the output of this step is acceptable, reconnect the jumper wire to the filter output bus, and re-set the 80M HFO slug to start the oscillator. Tune through the oscillator range slowly, noting the output noise response [adjust the VFO as necessary to avoid "birdies" and other spurious responses]. A slight decrease in receive noise will be noticed at one point as the slug is turned through the oscillator range. Using this minimum noise point as the final oscillator setting will give the best signal-to-noise ratio on 80M. The other bands can be tuned the same way, but the effect will be less noticeable. 8. Reset the noise reference level, and tune the receiver to 3750 kHz. Inject a 1 microvolt, 3750 kHz signal through a .01 mfd capacitor to pin G24. There should be a 10 to 12 db increase in output. Check all other bands at mid-band; the output should also be at least 10 db to 12 db better. If not, the problem is most likely in the Q of the bandpass filter toroids, or, the bandpass filters have not been properly tuned. 9. If the output in the preceeding step is accepable, insert the G board into the chassis and watch for an INCREASE in the reference noise level. If this increase is 3 db or more, and the signal-to-noise ratio is equally degraded, coil L729 is no longer self-shielding and must be replaced. 10. If the output in the preceeding step is acceptable, connect the signal generator to the receiver antenna jack and switch the antenna switch to "SEP'. The output may decrease as much as 2 db on 40M due to the attenuation of the 8.65 MHz band reject filter. If the attenuation is greater than 2 db on 40M, or more than 1 db or all other bands, there is a problem with the 8.65 MHz band reject filter. [See Bulletin No: SB-104-35]. 11. Connect the signal generator to the RF output antenna jack, switch the antenna switch to "COM", and repeat step 7. The difference in output should be negligible. Any additional attenuation of output indicates problems with the filters on the ALC board, or with the antenna relay. ----------------------------------------------------------------------------- -------------------------------------- May 11, 1976 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-38 Improved ALC Meter Action The drive voltage developed at the base of Q302 is often insufficient to swing the meter to full scale. Change R322 from 10K to 6800 ohm [PN 1-27-12] to increase the drive voltage. This change is being made in the next production run. ----------------------------------------------------------------------------- ------------------------------------- May 11, 1976 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-39 R11 Overheats The 15 ohm current limiter R11 on lug 1 of the band switch is being change from 15 ohm 1/2 watt to 15 ohm 1 watt [PN 1-12-1] to correct for an overheating problem with the resistor. ----------------------------------------------------------------------------- -------------------------------------- -------------------------------------- May 19, 1976 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-40 SB-104 Modifications The following list is a circuit board and chassis breakdown of modifications that have been done to the SB-104 since introduction. CIRCUIT BOARD A - -NO CHANGES- - CIRCUIT BOARD B [PN 85-1580-3] CHANGE PART NO REASON ----------- ------------ ----------- Change R-254 to 750 ohm 1-96 Increase 11 volts Change C-227 to 47 mfd 25-223 Stabilize 11 volts Change C-208 to .1 mfd 27-47 Reduce Leakage Change C-222 to .1 mfd 27-47 Reduce Leakage Change R-207 to 1.5 meg 1-36 Reduce mic gain CIRCUIT BOARD C [PN 85-1420-6] CHANGE PART NO REASON ----------- ------------ ------------- Add ground clip to 10 mtr coil cover 258-95 Eliminate 10M osc Add 39 pF capacitor C-373 across R-314 21-167 Lower 40M spurious Change C-332 to 50 pF 20-97 Increase 15M bandpass Change R-329 to 12K ohm 1-14-12 Lower 40M spurious Remove and discard C-322 Better keying Remove and discard L-321 & C-348 Replace by attached procedure 20-149 Reduce 3.395 spurious 40-1877 on 80 meter 31-76 Change R314 to 390 ohm 1-23-12 Reduce noise on XMT Change R332 to 1210 ohm 1% 2-68-11 Constant pwr output Change C369 to 390 pF 20-106 Improve 80M passband Change R322 to 6800 ohm 1-27-12 Improve ALC/meter NEW 3.395 MHz TRAP ON C BOARD A high level sput at 3395 kHz may be present in some units due to incorrect tuning of the 3.395 MHz trap on the transmit IF board. This problem can be avoided by removing the old 3.395 trap on the transmit IF "C" board, and installing a new trap as follows: 1. Remove and discard L321 and C348. 2. In the L321 circuit board holes near the top edge of the board install an 8-40 pF [PN 31-76] with the slotted side toward the top end of the board. 3. In the next lower set of holds, install a 150 pF [PN 20-149] capacitor. Do NOT use the holes screend for C348. 4. Next, install a 13.25 uH [PN 40-1877] coil at C348. 5. Remove circuit board D, and pre-set the front panel controls to the 3.5 mHz band, MIC/CW level control full counterclockwise. 6. Put the meter in the POWER position, depress the HI and TUNE pushbuttons. 7. Turn the MIC/CW Level control full clockwise. Adjust the 8-40 pF trimmer for a minimum [null] on the power meter. 8. Turn off the unit, and reinstall circuit board "D". CIRCUIT BOARD D [PN 85-1418-2] CHANGE PART NO. REASON ----------- ------------- ------------- Change C-414 to 18 pF 21-60 Reliable 20M HFO starting CIRCUIT BOARD E [PN 85-1581-5] CHANGE PART NO. REASON ----------- -------------- ------------- Change R-625 to 22K ohm 1-45-12 Better BFO Switching Change C-622 to 22 mfd 25-212 Better BFO Switching Change 6-21 to 100 ohms 1-1-12 Reduce Transmit Gain Remove and discard R-613 Improve 80M Sensitivity Change R-619 to 100 ohm 1-1-12 Decrease background noise VFO FILTER BOARD CHANGE PART NO REASON ----------- ------------ ------------ Remove and discard R-1251 Lower 10M spurs CIRCUIT BOARD F [PN 85-1462-4] CHANGE PART NO REASON ----------- ------------ ------------ Remove and discard R-569 Lower background noise Change R-564 to 330K ohm 1-31 Better Muting Change R-532 to .82 ohm 3-1-2 Stabilize audio output CIRCUIT BOARD G [PN 85-1708-2] CHANGE PART NO REASON ----------- ------------ ------------ Change C-703 to 105 pF 20-162 Better 80M sensitivity Change C-707 to 105 pF 20-162 Better 80M sensitivity Change C-764 to 8-40 pF 31-76 Better IF bandpass Change C-769 to 8-40 pF 31-76 Better IF bandpass Remove C-763 and discard Change Q-701 to this------------ 417-274 Increase sensitivity Change Q-704 to this------------ 417-274 Increase sensitivity Change R-719 to 2.2 mfd choke 45-73 Increase sensitivity Change L-734 to 4.5 mfd coil 40-1875 Increase sensitivity Remove L-733 and C787 and discard Remove and discard C-742 Improve peaking Change C-714 to 24pF 20-77 Improve peaking CIRCUIT BOARD H [PN 85-1422-2] CHANGE PART NO REASON ----------- ------------ ------------ Change R-954 to ferrite bead and wire 475-12 Reduce Harmonics Change R-956 to ferrite bead and wire 475-12 Reduce Harmonics Change L-952 to 4 turns Reduce Harmonics Change L-953 to 4 turns Reduce Harmonics Refer to Pictorial 11-5 for PA Board CIRCUIT BOARD J CHANGE PART NO REASON ----------- ------------ ------------ Change R-903 to 220 ohm 2 watt 1-13-2 Reduce Driver Temperature Change RFC 902 with 390 ohms 1-48 Reduce Oscillations CIRCUIT BOARD K Remove and discard L814 Reduce Oscillations DISPLAY BOARD No Change DC UP CONVERTER No Change VFO BUFFER BOARD CHANGE PART NO REASON ----------- ------------ ------------- Change R-1201 to 1200 ohms 1-10 Eliminate FM Change R-1202 to 350 mfd RFC 45-82 Eliminate FM Change R-1203 to 470 ohms 1-6 Eliminate FM Change R-1206 to 150 ohms 1-66 Eliminate FM Change D-1201 to 1N458 56-24 Eliminate FM Change ZD-1201 to 7.5V Zener 56-97 Eliminate FM CHASSIS CHANGES CHANGE PART NO REASON ----------- ------------- ------------- Change R5 to 0.15 ohm 3-14-2 Stabilize 5V regulation Install 4 ferrite beads on wire connected to K5 475-12 Eliminate Oscillation Install .001 mfd capacitor from F13 to F15 21-14 Reduce "talkback" Install a wire from F7 to asscess. socket lug 3 SB-644 Compatability Install a 10 mfd from C7 to Ground [+side to C-7] 25-54 Reduce T/R "pop" Install 390 ohm from G5 to ground 1-48 Noise Blanker Compatability Install 500 mfd from J1 to Ground 25-157 Improve B+ decoupling Install .001 mfd capacitor from pin 10 of relay to ground [C15] 21-140 Eliminate Oscillation Remove and discard C4 Increase power on 15 & 10 M Install .1/100V from pin C4 to ground Install a .01 ufd from pin C5 to ground Install .1 mfd cap. from C4 to ground 21-195 Eliminate Oscillation Install .01 mfd cap. from C5 to ground 21-176 Eliminate Oscillation Remove wire between G2 and G3. Cut Orange 13.8 V wire running past G board. Install both ends of this wire onto G2 and [S2]. Increase Sensitivity IMPROVING CW KEYING CHARACTERISTICS 1. Remove two gray wires from lug 6 of R2. 2. Connect this 6 1/2" gray wire from S4 lug 1 [R2] to the GND lug. 3. Discard short gray wire going to R2 ground lug. 4. Connect a gray wire from R2 lug 6 to terminal strip BE lug 3. 5. Connect a 5 uF electrolytic [PN 25-149] between lug 3 and GND lug of terminal strip BE; [+] lead to lug 3. ----------------------------------------------------------------------------- ------------------------------------- June 4, 1976 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-41 Low Power On All Bands Change: R-332 from 1.2K to 1210 ohm 1% [PN 2-68-11]. This change will be in -02 level HW-104's and the -06 level SB-104's. ----------------------------------------------------------------------------- -------------------------------------- June 4, 1976 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-42 Improved Passband On 80 Meters The 80 meter transmitter passband response is being improved by changing C369 to 390pF [PN 20-106]. This change is being made in the next production run, and should be made in all SB-104's received for service. ----------------------------------------------------------------------------- ---------------------------------------- June 18, 1976 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-43 ALC Meter Reads Above "3" On Transmit With No Modulation Variations in characteristics due to parts tolerances of ZD301 and Q302 will cause the ALC meter to read between zero and 3 when the transmitter is keyed without modulation, Change ZD301 and/or Q302 until a combination is found that brings the meter reading below 3 on the scale. ----------------------------------------------------------------------------- ---------------------------------------- June 18, 1976 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-44 Stabilizing 80/40 Meters The 80/40 output should be stabilized in all units received for service by making the following change: Change R345 from 1000 ohms to 100 ohms [PN 1-1-12] Change R343 from 1000 ohms to 100 ohms [PN 1-1-12] ----------------------------------------------------------------------------- ---------------------------------------- June 18, 1976 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-45 Improving The 40M Transmit Passband The 40 meter transmit passband can be significantly improved by making the following change in all units received for service: Change C-342 from 75pF to 62PF [PN 20-109]. ----------------------------------------------------------------------------- ---------------------------------------- June 18, 1976 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-46 Eliminating Transmit Chirp Chirp may be experienced during CW keying; the following change should be made in all SB-104's received for service: Change C6 from 500 ufd to 1000 ufd [PN 25-219]. ----------------------------------------------------------------------------- -------------------------------------- June 18, 1976 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-47 VFO Filter Board A change in screening is being made on the VFO filter board, changing the board from PN 85-1516-1 to PN 85-1516-2. Components will be deleted from the new board and the remaining components are being re-numbered, as follows: 85-1516-1 [Old Board] 85-1516-2 [New Board] Value ------------------------------- -------------------------------- -------- FROM: R-1255 TO:R-1252 150 ohms R-1254 R-1251 68 ohms R-1266 R-1253 68 ohms C-1254 C-1252 105 pf C-1256 C-1254 105 pf C-1253 C-1251 .01 uf C-1255 C-1253 620 pf The new board will be incorporated in all future productions runs. ----------------------------------------------------------------------------- --------------------------------------- June 22, 1976 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-48 Change Capacitors To Higher Voltage Caps Make the follow changes in all SB-104/HW-104's received for service: Change: C-321 from PN 21-95 TO .1 ufd mylar [PN 27-47] C-309 from PN 21-95 TO .1 ufd mylar [PN 27-47] C-906 from PN 21-95 TO .1 ufd mylar [PN 21-47] This changes the capacitors to ones with higher breakdown voltage ratings, and increases the RF bypassing. ((((NOTE: PN for the .1 ufd mylar replacement of C-906 is as shown on fiche)))) ----------------------------------------------------------------------------- ----------------------------------- June 22, 1976 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-49 Erratic Display On 10 Meters Erratic display on 10 meters can be caused by R-1252 loading the VFO line. Clip and remove R-1252 [470 ohms] on all SB-104/HW-104's received for service with the PN 85-1516-1 board installed. ----------------------------------------------------------------------------- -------------------------------------- August 3, 1976 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-50 Better Carrier Null A null should be obtainable at two different settings of capacitor C-648; either setting can be used. If there is only one setting that gives a null, remove C-645 [33 pF] and repeat the null setting adjustment. If there is still only one setting that gives a null, install a 62 pF mica [PN 70-109] capacitor at C-645 and repeat the above step. ----------------------------------------------------------------------------- ---------------------------------------------------- January 12, 1977 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-51 Low Output Power on 15 Meters ++++Information not available at this time++++ ----------------------------------------------------------------------------- ----------------------------------------------------- February 4, 1977 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-52 VFO Drift ++++Information not available at this time++++ ----------------------------------------------------------------------------- ----------------------------------------------------- February 4, 1977 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-53 Driver Transistor [PN 417-820] Installation at Q901 and Q902 ++++Information not available at this time++++ ----------------------------------------------------------------------------- ----------------------------------------------------- March 17, 1977 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-54 Circuit Changes ++++Information not available at this time++++ ----------------------------------------------------------------------------- ----------------------------------------------------- May 27, 1977 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-55 Low Gain in HFO Amplifiers ++++Information not available at this time++++ ----------------------------------------------------------------------------- ----------------------------------------------------- October 10, 1977 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-56 Audio Level Control of Receiver Does Not Completely Reduce Volume ++++Information not available at this time++++ ----------------------------------------------------------------------------- ----------------------------------------------------- November 10, 1977 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-57 Drivers Overheats in Standby ++++Information not available at this time++++ ----------------------------------------------------------------------------- ----------------------------------------------------- November 10, 1977 SB/HW-104 Bulletin No: Solid State Transceiver SB-104-58 20-Meter Power Roll-Off ++++Information not available at this time++++ ----------------------------------------------------------------------------- ----------------------------------------------------- February 2, 1978 SB/HW-104(A) Bulletin No: Solid State Transmitter SB-104-59 VFO Dead Check the solder pads at each corner of the PN 85-1205-3 circuit board to confirm that all solder resist has been scraped away. If the solder resist is not removed at these points, the oscillator will not run since the board is not grounded. ----------------------------------------------------------------------------- ----------------------------------------------------- March 31, 1978 SB/HW-104(A) Bulletin No: Solid State Transmitter SB-104-60 PA Board Cracks Or Transistors Break When installing the four 360 pF capacitors in the SB-104 "mod kits" on the foil side of the PA circuit board, mount them as close as possible to the circuit board to prevent breaking the board or the power transistors when the heat sink is installed. These capacitors were added so the PA would be more stable if used with an antenna tuner on 10 M. Production SB-104A's will have these capacitors mounted on the component side of the PA board. Since the vendor is unable to supply us with 360 pF capacitors which are thin enough to be mounted between the circuit board and heat sink, the PN 830-24 "mod" kits are being inserted to instruct the customer not to install these capacitors. ----------------------------------------------------------------------------- --------------------------------------