1 Press "fine" button for about 5 seconds , until issued five times tweet press "start" button, not self .

 

2 boot and press "start" button is not activated.

 

(3) sending and receiving faxes , press "start" button , the called user can not hear the sound signal (9600bps), do not take the paper ; When sent, the user signal (9600bps) after issuing press "start" button is not responding.

 

Analysis and Maintenance : Because no ready-made drawings , and more problems , which made ​​it difficult for maintenance work. Based on past experience in the maintenance , available from the following three aspects:

 

1 assembly quality inspection machine , with or without plug- open, exposed, components Weld phenomenon.

 

2 in the presence or absence of the various components observed machine overheating , smoke, burned phenomenon .

 

3 detects the DC output voltage is normal .

 

Upon closer inspection , found that the circuit board welding solid, reliable , good assembly quality , no burned components. Check the unit's power working within the state , the projected supply requirements based on the known components of the supply voltage requirements . Such as: 74 series ttl circuit chip requires +5 v supply voltage .

 

Test with a multimeter , found on the motherboard ± 5v,-12v, ± 24v power supply voltage , etc. , but no +12 v power supply voltage. Cut off the power supply , motherboard +12 v voltage measurement terminal to ground resistance r11 is 90ω, apparently not due to a short circuit caused no +12 v power supply voltage. Open the cover, directly measured with a multimeter DC voltage output switching power supply , still no +12 v power supply voltage.

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