SC-HM910/SC-HM810
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1 Safety Precaution
1. Before Servicing, unplug the power cord to prevent an electric shock.
2. When replacing parts, use only manufacture’s recommended components for safety.
3. Check the condition of the power cord. Replace if wear or damage is evident.
4- After servicing, be sure to restore the lead dress, insulation barriers, insulation papers, shields, etc.
5. Before returning the serviced equipment to the customer, be sure to make the following insulation resistance test to prevent the
customer from being exposed to a shock hazard.
1.1 Insulation Resistance Test
1. Unplug the power cord and short the two prongs of the plug with a
jumper wire.
2. Turn on the power switch.
3. Measure the resistance value with ohmmeter between the jumper
AC plug and each exposed metal cabinet part, such as screwheads,
antenna, control shafts, handle brackets, etc.
Equipment with antenna terminals should read between 2.7MΩ
and 3.9MΩ to all exposed parts* (Fig.1).
Equipment without antenna terminals should read approximately
infinity to all exposed parts. (Fig.2).
*Note: Some exposed parts may be isolated from the chassis by
design. These will read infinity.
4. If the measurement is outside the specified limits, there is a possi-
bility of a shock hazard. The equipment should be repaired and
rechecked before it is returned to the customer.
Antenna
terminal
Exposed
metal part
Ohmmeter
Fig. 1
Resistance = 2.7 MΩ - 3.9 M Ω
Exposed
metal part
Ohmmeter
Fig. 2
Resistance = Approx
2 Before Repair and Adjustment
Disconnect AC power, discharge Power Supply Capacitors POWER PCB SC-HM910 C556, C557, C558, C559, C561, POWER PCB
SC-HM810 C531, C532, C533, C534 and TRANSFORMER PCB SC-HM910 C705, TRANSFORMER PCB SC-HM810 C402 through
a 10 Ω, 5W resistor to ground.
DO NOT SHORT-CIRCUIT DIRECTLY (with a screwdriver blade, for instance), as this way destroy solid state devices.
After repairs are completed, restore power gradually using a variac, to avoid overcurrent.
Current consumption at AC 127V, 60Hz in NO SIGNAL mode should be ~800mA.
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