Dead Rudia Controller RDC6442S

I have a 3 year old Chinese laser that has a rudia RDC6442S-B(EC). The machine stopped in the middle of a job , the screen was off (no display, no backlight) , and the light under the gantry was off. No LED lights were lit on the controller.

I thought the 24v power supply died. I measured the voltage going into the controller and did not get a stable reading (controller was connected at the time) I replaced the power supply, checked it’s output before connecting the controller since it was an adjustable power supply. tuned it to 24.0v.

When I connect the power supply the voltage reading at the ps terminal drops and is not stable. the light under the gantry turns off. (If the controller is disconnected the light works). So I assume there is a short in the controller. (again no LED lights on the controller when it’s connected)

is swapping out the controller with one off ebay straight forward? anything I need to know about programing machine parameters? can I switch to a RDC6445 from the RDC6442S?

Try disconnecting the other other connectors on the controller and see if it powers up? There was another thread that looks to be the stepper drivers being the problem. If not hopefully you have a backup of the original settings.

I’d be suspicious of a variable voltage power supply. Why not a 24v out of the box?

How is the gantry light powered? Most are 5v, but mine turned out to be powered by the mains :frowning: Sounds like it’s 24v, but they are not consistent. Be aware if you deal with it.

As @micrololin pointed out you will have to isolate the controller to ensure that is the issue.

The controller doesn’t really use much current and what the controller switches is low current, it’s possible it’s a peripheral, such as a limit switch or something.

Follow Jeffs lead and unplug the connectors, but keep track of them. If it powers up ok, then start adding a connector at a time until it fails.

Probably, why would you want to?

Your main problem will be the configuration that the manufacturer set in the controller.

I hope you made a backup of the Machine Settings before it died, you’re probably fine. If not you’ll probably have to contact the manufacturer for the proper configuration data.


it was a 24V power supply but has an adjustment screw for fine tuning. (out of the box it was 23.2v)

I did unplug everything and the control panel lit up. I added back connections one by one and the machine did boot up each time. (I did not leave it on for very long before shutting down and adding the next terminal group) eventually had everything plugged back in and it started up but but died / or reset itself after a minute or two.

Currently the machine is running with the CN2 terminal unplugged, and the lightbar off. On my machine this had a single wire connected to CN2-pin6 witch is labeled 24v. I am finishing off the job that was in the machine when it died, just to see if it actually completes.

Another thing I thought of, was the gantry LED lightbar has been flickering some (has been doing this for months) it’s possible there is a short in the light bar that was messing with the 24v supply to the controller. Will try anther job with CN2 connected and the light off.

Make a backup of the controller while its operational.

well that was inconclusive. The machine finished off the job that was interrupted (about 30 minutes) . I shut it down and plugged CN2 back in, left the light on. and did a small 5 minute job and it ran fine. So now the machine has every plug back in place and the new power supply and it ran fine.

I did backup my vendor settings. will try a few more jobs later in the day to see if it holds up.

Does the CN2 connector power the lights? Does that wire travel in a wire chain? Maybe an intermittent short.
Glad its working again.

CN2 does not power the lights. (they worked when controller was unplugged, and also when CN2 is disconnected) Looking at the controller manual CN2 would be for a foot switch or other protection circuit but more pins would need to be populated rather than just the 24V.

I am guessing it is a intermittent short somewhere , but because it is intermittent it will be difficult to trace. hopefully doesn’t return

The 24v is powering something. I would trace the wire when you get a chance.

It actually has that information labeled on the controller.

You have the lightbar powered by another supply?

Most of these machines have plastic or non conductive drag chains and the wiring used in these are usually very flexible which would limit the chances of a ‘short’ in the drag chain. The Y on my machine has everything that the Y and X axis needs, with the exception of the Y limit switch. That is frame mounted.

They come apart easily. My machine had an ‘led’ pointer on the head. When I removed that, I had to pull the wiring out of the drag chain. Took out the link at the ‘curve’ and pulled it right out. Snapped the link back and was good to go.

Or ‘is not powering something’. It would almost sound as if you have an intermittent ‘open’ on the 24v supply line somewhere. Maybe a bad connection or connector itself.

We’re always glad it’s fixed. It is always better to fix the problem then to have it ‘fix itself’…:frowning:

Good luck…


I think that’s where my limit switches gets its power I’ll need to look. I was thinking something is overloading that power output causing the controller shutdown.

That’s where mine get their power also.

You are worried about a short. I’m starting to think he has a connection that is opening up.


An open doesn’t overload anything. It’s just like no wire connected at all. But a high resistance short would cause the 24v to drop to something the controller will not run on.

The controller won’t run on zero voltage from and intermittent open 24v line either…


True, I was focused on the CN2 connector wire having a short. That doesn’t power the controller.

Just trying to hit all the bases. It could be either as the symptoms are power goes out throughout when it fails.

Having fixed this junk for many years (decades) I try not to focus on anything in particular until I have enough information to think about it.

Wasted lots of time ‘assuming’. Sometimes that’s all you got :frowning:


I think it may be a short in the drag chain and be possibly unrelated to CN2. unplugging everything form the controller and resetting the machine caused the head to re-home and moved the drag chain and possibly the short.

my X drag chain would contain wires for the autofocus pen (which i don’t use) and the red dot pointer (also don’t use) and air assist tube. the Y portion would add in power for the light under the gantry.

Y chain has stepper motor and X limit switches also. I really doubt it’s in the chain…

The controller controls the heads and everything. If it were ‘unplugged’ it wouldn’t move anything.??

Good luck


Just the process of unplugging everything and adding them back one by one allowed the head to move again. Most likely the short was somewhere where that was movement which brings us to the chain

starting to think we have our short candidate

moving the head over and poking it a bit more

I will have to look up where the focus pen connects to the controller. I believe the red dot just connects directly to the 24v/5v power supply. I am concerned about the quality of the wire insulation in the whole machine. I am fine with loosing the focus pen and red dot. the Y chain does have critical wires, but also much less motion than the x chain. Did not see any fraying from an initial inspection but need to break down the chain to get a clear view.

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I think I would have seen this without a bunch of debugging. Anything mechanical or moving is the first thing on the list.

I’ve seen lots of wear from these environments, but some of those wires actually look like they were cut…

Is there any debris in the chain to cause this? Seems very unlikely without some kind of obstruction or maybe just ‘Chinese wire :(’.

Assume this was on the X chain?

Generally anything used on the X axis needs to go through the Y chain to get there. Any movement with wires, including connectors are always on the top of the list.

This is generally just a ‘pull down’ to ground and is an input to the Ruida.

It must be a short, so whatever is carrying power is a likely suspect. Do you have anything on the head that requires power, aside from the LED pointer?

Glad you found it… You can ‘snap’ the links out and back in. Small screwdriver to break them apart and hand pressure to put them back…