- - A change in VOX delay after operating for a period of time can be caused by
leakage in diode D201. The other possibility is a change in value of capacitor
C213. Either component could experience a change in operation characteristics
due to heat.
ah.4.7. SB-102-7: SB & HW Series Instability & Corrective Information.
May 23, 1974
SB-102 Bulletin No:SSB Transceiver SB-102-7
We suggest you check for each of the following possible causes:
1. Intermittent, rosin or cold solder joints.
Loose hardware at the tube sockets, terminal strips, circuit boards, shields and rear panel
sockets.
Poor lead dress at tube sockets V8 & V9. The component leads must be short as possible.
Check C925 (Final tune capacitor) to be sure it is isolated from the tuning shaft. This is to
prevent RF from traveling on the shaft to the front panel.
Check all edges of the final enclosures for proper grounding to the main chassis.
Check the hardware for the side rails to be sure a good ground is being provided.
Be sure that all the ground clips on the coil cover are making good contact with the switch
shields.
Check the soldering of the switch shields to the center pins of tube sockets V6, V7, V10 & V11.
Check the ground leads from the switch board & shields, to be sure they are going to ground foil
& not to the preselector capacitor foil pods on the RF driver board.
Check for broken or shorted pigtails on each of the shielded cables in the unit.
Check RFC801 & L901 for any signs of deterioration or physical damage, (burn spots). If
apparent replace the part.
Improper adjustment of the Het. Osc. coils could cause improper mixing action, resulting in the
final operating at a different frequency appearing as instability.
Change driver & final tubes then re-neutralize per manual instructions.
Check driver tube shield to be sure that it has a good ground contact with the socket spring clip.
Check for a good ground between the front panel & chassis.
Check the SWR of the antenna system at the frequency of opertion. Should be below 2:1.
Check the antenna coax for leakage, poor connectors & broken shield connections.
Is the transmitter properly grounded?
Be sure all shields & tube shields are installed.
Realign using a properly terminated 50 ohm non-reactive dummy load.
SB-102 Service Bulletins Page 178
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