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 ..???

 

[damonCA21]

If the print head is shorted it can blow various components on the mainboard, this is why you need to check it properly to find out what is causing the fuses to blow. If you put a bad head onto another printer you could completely fry the mainboard on it. If testing a mainboard fully is beyond your skills then you need to get someone who knows how to do it for you

 

[Topimpress]

Thank u very much for reply… but how to test the printhead..???
My printhead is new and the first test print i made with it is the photo result in 1st post
Please can u advise me..

 

[damonCA21]

The easiest way is to check the mainboard is working correctly. If it is then the problem is with the head. There is no easy way to check a damaged printhead, you would just have to replace it.
How new is the head and where did you buy it from? If it came from China or was cheap, then 99% it is faulty. Nearly all heads from China are scams and either sold as refurbished ( all they do is clean the outside, there is no way to refurbish a Roland head ) or sold as new when they are used faulty ones.
If it is a brand new head bought from a legitimate seller or Roland dealer, then chances are the head is OK and the fault is elsewhere

 

[Topimpress]

It’s original and from roland seller.. so the short can be from cable maybe
I saw if i put the printhead in mimake printer.. it can give me a error with shorted printhead.. is it true…???

 

[damonCA21]

Ok the head should have been ok then. It could also be from a cable so those are worth testing for continuity with your multimeter. I dont know about the Mimaki as I dont work on those sorry

 

[Topimpress]

Thx for reply sir..
After the second blowing fuse.. i have this test print.. I'm disoriented

 

[damonCA21]

Is that from a nozzle test ?

 

[Topimpress]

Is that from a nozzle test ?

Yes