Panasonic SAHT730 Technical Guide - Page 17

Subwoofer Unit Repair (SB-WA730 / SA-WA930) Overview - Refer to figure 11. The SC-HT930 consists of a Subwoofer and Control unit. The units are connected by a 25 pin round umbilical cord that carries power from the Subwoofer to the control unit and audio from the control unit back to the subwoofer. When connected together and plugged in to AC, the Subwoofer provides standby (SYS6V) voltage to the micro in the control unit. The SC-HT730 model is similar but has less front channel wattage. That model does not have a Subwoofer front Amp Board. Its front channel power amplifier is part of IC501 in the subwoofer's Power Board. Figure 11 - Protection - Refer to figure 11. The protection monitoring circuitry in both of the subwoofer (left) and control unit (right) feed the microprocessor IC2018 in the control unit. If shutdown is triggered, the micro via the 25 pin umbilical cable opens the subwoofer AC relay power relay, shutting off the power for both the control & subwoofer [but standby voltage (SYS 6V) is still present]. Error code F61 may be displayed just before power is lost. In the subwoofer, the lines monitored for shutdown are: • Speaker Balance - All 6 channels to the speaker must average 0Vdc +0.6Vdc with or without audio or the unit will shut down. • + 9Vdc balance - Both the positive and negative 9V power supplies must be within 1.2V of each other or the unit will shut down. • + 9Vdc loss - Missing 9V or excessive 9V load that brings the 9V line below 5Vdc will shut down the unit. Subwoofer Repair Strategy - Start by isolating the problem SA-HT730 / SAHT930 17