Unison CMd DMX Driver Replacement

Issue

My Unison CMd is not receiving DMX, and I would like to swap it as a troubleshooting measure.

Explanation of Issue

• DMX driver chips may fail when subjected to excessively high voltage, whichcan be caused by a power event such as a lightning strike or transformer failure.

• You may need to replace the DMX driver chip if the CMd is not receiving DMX from a known working control device (i.e. something that is successfully controlling other devices), or if the chip appears to be burnt or damaged.

• If there has been damage to the chip, it is best practice to replace both the DMX driver chip (U16) and the DMX Opto chip (U17) on the dimming engine control card.

Dimmer racks without an accessible power disconnect device cannot be serviced safely. Before removing dimmer or control modules for service, de-energize main feed to dimmer rack and follow appropriate Lockout/Tagout procedures as described in NFPA Standard 70E. It is important to note that electrical equipment such as dimmer racks can present an arc flash safety hazard if improperly serviced. This is due to available large short circuit currents on the feeders of the equipment. Any work on energized equipment must comply with OSHA Electrical Safe Working Practices.

Steps to Solution

Before you begin, set up a clean, well-lit work area and take appropriate ESD (Electro-Static Discharge) precautions (this means either wearing a grounding devire or wearing rubber gloves to prevent static discharge into the circuitry).

Tools Needed:

• #1 Jewelers Phillips Screwdriver
• Dual In-Line (DIL) Chip Puller or needlenose pliers
• DMX Output Transceiver Chip (LTC485) – ETC Part # Z1458-F
• (Optional) DMX Output Opto-Coupler Chip (6N137) – ETC Part # Z423-F

1. Ensure power is turned off to the dimming rack.
2. Open the door and locate the control module.
3. Remove the CMd control processor from the Unison DR rack and place the unit on a clean, stable surface.
4. With your #1 Jewelers Phillips screwdriver, remove the (4) circled screws on the back of the unit and (2) along the short sides (noted below) and gently pull the cover plate away from the processor.

5. Orient the processor so that the LCD display is facing you.
6. Locate the DMX chip at location U16 and the Opto Chip at location U17 of the dimming engine control card (noted below).

7. With your chip puller or pliers, gently remove the DMX and Opto chips.
8. Insert the replacement chips so that pin one is in the correct location.

Please take note of DMX chip orientation by the divot on top of the chip.  U17 should be installed so that pin 1 is closest to the blue components. It is very common to install both U16 and U17 in the same direction when replacing the chips. If one or both of these chips are installed incorrectly, the processor will not receive DMX , which will cause a "No DMX" error.

Replace lid and screws, making sure the ESD buffer strip on the upper portion of the
lid is inside the processor.

9. Slide the CMd back into the DR rack, ensuring to push firmly until you feel the connections slide home.
10. Close and lock the Unison DR rack door before restoring power.

If you have any questions regarding this procure, please contact ETC Technical Services.