Printheads problem sc540

[johnci]

Hi,
i have a Roland SC-540 . The Light Cyan printhead got damaged and during its replacement with a new one I had forgotten to connect one of the print heads wires. While openning the machine this wire was touching a metallic part and then it produced a spark. Later on during the print test and from then and on it completely stopped printing the Group C of the print heads (LIGHT CYAN, LIGHT MAGENTA) and the following day it also stopped printing Group B as well (MAGENTA & YELLOW). And now the SC-540 no longer prints or gives the commad to print any of the above mentioned 4 colours.

I would appreciate if you could let me know which part is at fault and what I should replace in order for the SC-540 to function properly again.

Thank you in advance.

 

[Gabriel]

You should try..

To measure the fuses F1,F2 and F3 placed on the Head Board. Replace those fuses and if it still doesn't work, you should replace the C4131 transistor TR 2SC4131 GB on the Head Board coresponding to B and C group. It's 15 Euros per piece. Then the printer will work for sure. And be carefull next time when you remove the flat cables coresponding to the print heads :Oops:.

 

[Jim Hancock]

There are 2 types of transistors that control the print head, the C4131 and an A1746. These can be measured in the board with an ohm meter. If they are bad, you will read 0 ohms on at least one pair of leads. In addition, there is a 43 ohm chip resistor that goes between the base and emitter of both of these transistors that may increase in value or open up. I've replaced 2 of these resistors that increased in value to 1000 ohms. I don't know what impact that will have on the operation of the print head if they are not changed, but it will certainly have some impact. These resistors are about this big ( O ) so you will need to have surface mount soldering capability to replace these.