Yellow Color Channel Block Printing on LEC-330

[graphicsphere]

I recently changed printheads in my LEC-330 and now the yellow color channel is constantly firing the print head nozzles also known as block printing.

The printheads are tested and working because when I move the heads to different color channel the block printing stays on the yellow color channel which is head 3 for the LEC-330.

I tested all transistors and none of them appear to be .000. Do you know what else I should try testing besides the transistors?

For the LEC-330 is the head board mostly my problem or could the print carriage board and mainboard also be the problem?

 

[damonCA21]

If it is constantly printing then the head is getting the incorrect signals when to turn on and off. This could be a, bad head cable, print carriage board, cables from carriage board to head board. When you replaced the heads did you unplug the printer from the wall and leave for at least 15 minutes before unplugging any cables?
Check the cable ends for any bent pins. Did all the transistors give the same readings as they don't have to be shorted to be faulty! You need to go through each part of the signal path and check for any obvious problems.

 

[graphicsphere]

It goes back and forth from printing no yellow color channel to printing yellow block printing. Transistors are all within range.

I checked and reinstalled all ribbon cables on the yellow head, print carriage board and head board but still have the problem on the yellow color channel.

 

[Jim Hancock]

The printheads are tested and working because when I move the heads to different color channel the block printing stays on the yellow color channel which is head 3 for the LEC-330.

Which printheads did you change? Who was your printhead supplier? So, if I understand correctly, you moved ribbon sets so that you were firing the yellow head with the ribbons from a different head and the yellow head is still blockprinting?

 

[graphicsphere]

No it's not the head it is a board as far as I can tell that is causing the block printing. I have a few new heads I tried in the same yellow color channel and still did the same block printing then I put that head into a different color channel and was good.

I inspected all ribbon cables from all boards and there are no bent pins and I aligned the pins to the connectors so don't think its any of the ribbon cables.

 

[Jim Hancock]

I'm still not clear if you did the ribbon swap or not. Also, have you tried replacing the head ribbon cables for the yellow head? Block printing is a common rresult of bad head cables. This should be the first thing you replace at this point. Easy, quick and cheap.

You said none of the transistors were reading 0. Were they all reading in the 41-42 ohm range? They usually short, but I have had one instance where one of the transistors was open. It's been so long ago I don't remember the symptoms, but they all need to be in that range. You may also whant to ohm out the trailing cables from the carriage board to the head board.

 

[graphicsphere]

Ribbon head cables are like new. Does the ohm values on the trailing cables from carriage board to head board supposed to be the same as the transistors on the head board? How do you test the trailing cables? Do you touch the probes to the ribbon cable pins or something else?

I think it has to be the yellow color channel transistors. The range of the transistors are not all the same. There are some that are definitely above normal like 45-46 ohm. Most of the transistors are testing 42-43 ohm.

 

[dreko]

You mean 'block firing?' Roland uses the word 'blocks' to describe sections of it's nozzle test pattern, not continous nozzle firing.
The firing signals could be coming from the print carriage board, or the main board/head driving circuitry

 

[graphicsphere]

The LEC-330 has a separate head board and mainboard for the head driving circuitry. I’m not sure if the LEC-330 mainboard also has head driving circuitry which I also need to know???

The LEC-330 print carriage board could be bad too but I have to repair the LEC-330 head board first before I know the print carriage board is bad???

 

[cornholio]

The carriage board is only routing the signals from the wide flat cables to the head cables with no active components.(except a sensor signal amplifier or so)
This changed with the Truevis series.

 

[dreko]

Since you've swapped out different print heads... and the firing happens only in the yellow (printhead , to printhead, to printhead)
If you can swap ribbon cables this will eliminate that from the problem.

Finally, I would pull all cables/connectors off the carriage board first and reseat. That board was exposed when doing the head swap
The main mother board is not exposed. Possible droplet of ink landed somewhere??

I'd then move the main board... remove all connectors/cables, etc... reseat.

 

[damonCA21]

45-46 ohm resistance won't cause it. The measurement isn't actually reading the transistor, it is reading the resistor across it. Resistors are generally 5% or 10% tolerance, so that won't be the cause. You need to diode test the transistors to make sure they are working. They should give a reading around 480 to 500.
To test the cables you need to do a continuity test for each pin from end to end.
The long cables can fail but read continuity when the head is in one position, but as the cable folds it can disconnect so you need to check this a well