Principles of Operation

Repairing the C094 MAIN Board Assembly

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This section gives instructions for repairing the C094 MAIN board and describes various problems, symptoms, likely causes, checkpoints, and solutions. The checkpoint column shows proper waveforms, resistance values, and other information for each component of the C094 MAIN board.

Table 6-8. Repairing- the C094 MAIN Board Assembly
Problem Symptom

Cause

Checkpoint

Solution

 

 

 

 

4bnormalThe CPUThe resetCheck the voltage waveforms of the VDD (+5 V) Replace Ic4
(IC4 pin 41) and ROUT (IC4 pin 15) when the

 

weration atdoes notcircuit is

 

power is turned on.

 

rower on.operatedefective.

 

 

 

 

properly.

 

 

 

The controlCheck HIGH/LOW alternation for the

Replace

ROM is notsignal (IC4 pin 4).IC4.
selected.

 

 

Either theReplace IC2
ROM or theor IC3.
RAM is

 

defective.

 

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Epson PX-870/1170