Roland SP-300 Print Problem

[extreme-graphics]

Hope somebody can help having a few problems with an SP 300 that's been stood for some time. Thank you, soup thank you.
The yellow and magenta PrintHead print okay however the black and cyan nothing is printing.
I have removed the printHeads and swapped them over however I'm getting an odd print. We have changed the ribbon cables. We have checked the fuses on the main board both are okay and we have also replaced the print carriage board just because it was cheap enough to try. We have also had the transistors checked and they're all oka, still have the same problem. Any suggestions?

 

[damonCA21]

That is a signal problem to the head. As you have eliminated the head itself as the cause, then the next thing would be to change the long cables from the print carriage board to the mainboard. I would lean more towards a mainboard problem though. When you say the transistors were tested, how was this done? There is also more to the printing circuit than just the transistors needs to be checked.

 

[Solventinkjet]

I agree with damon. Your black / cyan head is probably fried since you moved it to a known working signal and it still didn't fire as long as you've ruled out any ink flow issues. The magenta / yellow head firing like that in the black / cyan spot indicates what damon said. Most likely, whatever blew the black / cyan head also blew a component on the main board or the long trailing cables are damaged.

 

[extreme-graphics]

That is a signal problem to the head. As you have eliminated the head itself as the cause, then the next thing would be to change the long cables from the print carriage board to the mainboard. I would lean more towards a mainboard problem though. When you say the transistors were tested, how was this done? There is also more to the printing circuit than just the transistors needs to be checked.

I followed a video on YouTube testing the transistors on a Roland,SP board with the multi meter the A1746 got 17.8 kho on all 4
And the A4131 got 0.5mho on my second printer. I don't really want to mess around with it too much as it's working, but I did get a different reading. On the A4131's 1.7mho

 

[damonCA21]

What are you testing on them as those amounts are all wrong. Between two of the legs you should get around 42 ohms and Between the other two 480 to 500 on the diode test setting. Note you need to test different readings on the A and C type transistors as they are different types ( PNP and NPN ) so you don't test them in the same way. You also need to test all the legs to make sure there are no shorts.

If the transistors do test OK you also need to test the other components in the head circuit