RF-640 test print problem

[Topimpress]

Hi,
I have made a test print and I have problem with..
any idea what's is the problem

 

[damonCA21]

That is a problem with the on and off signals being sent to the head. This can either be from bad cables ( either the short ones to the head or the long ones from the print carriage board to the mainboard ) a bad mainboard or a partly shorted head

 

[Topimpress]

thx for ur reply..
did the transistor C4131 cause the problem.. I found one with 17ohm on the two outside legs
all other is about 41.7

 

[damonCA21]

OK that can also cause problems as they turn the head on and off. Change that transistor and it may fix it if there are no other problems. If it is reading 17 ohms then it has most likely shorted

 

[Topimpress]

I have replaced the transistor. After power on the fuse F1 and F2 is blowing.. any advise were to locate the fault

 

[Topimpress]

Before i power on i have tested the transistor and i have 41.7ohms and after the power on and the fuse blow. I mesured again and i found 30ohms on the transistor that i changed.
Is motherboard defective i think..??

 

[damonCA21]

If the fuses are blowing when you turn it on either the head is shorting or there is something else on the mainboard causing it

 

[damonCA21]

I do mainboard repairs if you want me to look at it. I am in the UK but do repairs worldwide

 

[Topimpress]

So the only method to confirm that default comes from motherboard is to test printhead in another printer..
But if i test the printhead in other printer and the head is shorted, it blow only the fuse not the transistor ..???