Control/Dimming Leviton D4DMX - DMX doesn't work

goats

Member
I have a Leviton D4DMX with 3-pin connectors and no matter what I try, it is unresponsive to DMX. Also, sometimes the LED display leaves off some of the segments.

I've verified that I'm using the DMX input with actual DMX cables. I tried it on two different working DMX sources with no luck. I checked the cables and they appear to be correct. The dimmer powers on and the chases and manual controls work. All channels appear to be normal. The DMX input and the corresponding LED, however, are not doing anything. I have no way to test the Microplex input. I took the cover off and nothing appears out of the ordinary.

Is this repairable? I found mention in another thread that the DMX chip could be bad? Is that possible here? Does this sound like something that could be repaired easily? Other thoughts?

Thanks!
 
Good Morning

When I see these dimmers with a 3pin it's usually MicroPlex.

Is this a new dimmer or has it been working with DMX in the past?

You say you popped the top, the older NSI boxes added a chip to make it DMX. Is there a chip missing?
Yes the chip could be bad.
Yes it is repairable.
 
It is not new, and it has DMX and MicroPlex connections. Nothing appears to be missing inside. I was hoping for something simple, like the connector disconnected, but no luck. Inside there is one large chip, which I assume is the main controller for the unit. There are smaller, surface mount chips as well. If one of those were dead, I could probably replace it if I knew which one, or how to verify the issue.
 
If it has both 3 pin and 5 pin XLR connections, the 5 pin will be DMX and the 3 pin Microplex.

Yea, the manual is very vague on that making it sound like you can use the 3 pin for DMX, but on microplex, one of the pins is used for 12 volts DC, so I agree. Use the 5 pin.

proxy.php


More on Microplex: Microplex (MPX) Project by Infidigm
 
It has 3 pin connecters for both systems. Here's a picture. Considering the LED won't light and it is completely unresponsive over DMX, yet otherwise works fine, I'm suspecting maybe someone connected something which burned out the DMX input... Does that sound likely? If so, what would the likely point of failure be?


d4dmx.png

Yea, the manual is very vague on that making it sound like you can use the 3 pin for DMX, but on microplex, one of the pins is used for 12 volts DC, so I agree. Use the 5 pin.



More on Microplex: Microplex (MPX) Project by Infidigm
 
Those dimmers ship with either 3 pin dmx (and let's skip the debate on that one) or 5 pin dmx, plus microplex jacks. I have some of each. The extension on the model # will define it, and the connectors are fairly well marked.

Regardless, the display is pretty cheap. Some of mine fail too. Overall, depending on your skill level and access to test equipment they may be repairable by you, or you may have to send them in. I have sent them in through Bill at Entertainment Systems, and repair time usually takes about 10 days.
 
It has 3 pin connecters for both systems. Here's a picture. Considering the LED won't light and it is completely unresponsive over DMX, yet otherwise works fine, I'm suspecting maybe someone connected something which burned out the DMX input... Does that sound likely? If so, what would the likely point of failure be?
View attachment 9465

So, Leviton gave in and started building with 3 pin DMX... (Sad, but save for another day.)

It is possible that someone plugged microplex into the DMX connector, the chip is not designed to take 12 volts. Still, I would have thought that they would have taken precautions in the design to prevent something this easy to do from causing damage.

If you are not getting the DMX led, and you have already tried reversing the polarity of the DMX signal (swapping pins 2 & 3) then it is time to send it in for repair. Unlike some of the "shoebox" dimmers out there, this one is definitely worth repair.

Older style:
proxy.php
 
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I have yet to try swapping the polarity. I'll do that tonight and see what happens. Assuming that's not it, any idea what the repair cost would be? I may poke around and see what I can do. Considering it's price, I don't want to pay more to fix it than I did to buy it...
 
Many DMX devices use a 75176 or MAX485 chip as the RS485 receiver. It's usually an 8-pin DIP or SOIC IC.
/mike
 
This one appears to use an 81847 SOIC IC. Considering how cheap they are, I might try replacing it, even though soldering a surface mount chip doesn't sound too fun. That being said, is the RS485 chip the likely failure point, or do other parts of the input section usually fail at the same time? Such as what tells the DMX signal LED to light. I'd like to order whatever I need, since the shipping will probably exceed the cost of the parts.
 
This one appears to use an 81847 SOIC IC. Considering how cheap they are, I might try replacing it, even though soldering a surface mount chip doesn't sound too fun. That being said, is the RS485 chip the likely failure point, or do other parts of the input section usually fail at the same time? Such as what tells the DMX signal LED to light. I'd like to order whatever I need, since the shipping will probably exceed the cost of the parts.

Conceptual overview:

DMX hits the jack, goes to the RS485 chip via some interface components. The 485 chip does not try to figure out if the signal is valid, it simply converts it to a standard serial data signal that is fed to the processor. If the processor sees that it is a valid data-stream, it then flags the DMX indicator.

My hunch is that something popped the interface and that the problem lies between the jack and the 485 chip (inclusive.)

My only advice on smd component replacement is that if you don't have a hot-air soldering station, then have plenty of very fine gauge silver-solder and plenty of very fine wick (not the junk from Radio Shack.) In most cases, the components are not epoxied to the board, although a few manufacturers liked to do that. Slipping some back-plane wire under the leads and "unzipping" them as you melt them works nice. Once the old chip is cleared, spend some time prepping the pads by wicking off all excess solder and cleaning all flux off. If and when you get solder bridging on the new chip, use the wick to draw out (from the chip outwards) excess until all bridging is clear.
 
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That sounds like an adventure for sure. It also seems to be the next step in the saga if I want this thing to work. I haven't taken the board out to trace where the signal goes, but the chip seems to be the most likely failure point.
 
81847 doesn't show up on Octopart. It's either a house number or some sort of date code. Any other info on the chip?
/mike
 
Good Morning Goats

If this unit is out of warranty, leviton has a flat fate on their repairs.
Call your local dealer & get an RMA.
If you try to swap a SMD without experience you may damage the PCB beyond repair.
Practice on something before you dig into your dimmer.
 
Looking at the specs for that chip, I doubt it is the failure point. It is designed to handle a 12 V input without harm, and it is heavily static protected. While some of the earlier input chips are common failure items, this one isn't likely to be.
 
These are good points. I'll do a little more investigating before trying anything drastic. I contacted Leviton and they will do some basic troubleshooting over the phone. I'll try that next. I might look closer at the circuit board to see what components are in the input section and what else could be wrong.
 
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Also, sometimes the LED display leaves off some of the segments.

Are you sure it is not trying to tell you something? Sometimes those crude words done on a numeric display can really be a trip!

In any case, if it is truly leaving off segments, then I would go with the "send it in for re-firb" route, because there really could be a processor problem.
 
I wouldn't rule it out. With the display, sometimes when it is turned on, part of the 'A' in the address display is off. There could be others. Seems to do it every once in a while. Usually, powering it off and on will fix it. I read somewhere about a test feature, which I tried and it said 'pass', though I don't know what it was testing...

Are you sure it is not trying to tell you something? Sometimes those crude words done on a numeric display can really be a trip!

In any case, if it is truly leaving off segments, then I would go with the "send it in for re-firb" route, because there really could be a processor problem.
 

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