Roland VS-540 - Only Magenta Printing test, other colors missing. (Photo Included)

[Alex C]

Hi everyone,
I'm working on a Roland Vs-540 and running into an issue I haven't seen before. When doing a test print, i'm getting only two magenta channels printing - No Cyan, yellow or black at all.

Here's what i've tried so far:

- Replaced print head No change.
- Replaced Head Cables No Change.
- New dampers installed
- New Captop installed
Confirmed ink presence - cyan, yellow and black are visible under the head and even on captop.
- Mainboard fuses tested and OK

Here's a photo of the test print output:

I'm starting to think this may be an electronic issue - possibly the mainboard's firing transistors or IC's for the non-magenta channels. Has anyone seen something similar or can suggest a next step?


Appreciate any advice

Thanks in advance


AleX

 

[Zoogee World]

2 things I might suggest, 1. Did you test the big transistors on the head to see if they are all good? 2. Did you try pulling ink through the head with a syringe attached to the line after the cap top?

 

[netsol]

it is always possible that the fuse can test ok, when doing a continuity test, but, the 41VDC is missing

are you sure one of the ribbon cables doesn't have one foil lifted and bent over touching another connector

 

[Alex C]

2 things I might suggest, 1. Did you test the big transistors on the head to see if they are all good? 2. Did you try pulling ink through the head with a syringe attached to the line after the cap top?

1. Big transistors tested .. Desoldered from board.
2. Didn't find it useful to use a syringe cause the ink flow when doing cleaning is present.( Captop full )

 

[netsol]

(1) buy a service manual.
(2) do A simple voltage check comparing the working channel to the bad ones
there are 4 pairs of transistors. From collector of the npn to emitter of the pnp is approx 41 Vdc.
on each pair there is 41 volts from center pin to center pin.
IS IT PRESENT ON ALL 4?
IF YES, look carefully at those ribbon cables. Isa foil bent over on one end?