A bit puzzled but think that I know wher the problem is. Run our lighting with an early model EDI Mark VII dimmer rack with 140 dimmers and a Multi Link. Getting ready to start a show this weekend and all of the lights on the top half of the Multi Link started to flash on and off randomly with either an ETC Express 24/48 or a Leprecon 1500 board in control. Lights worked fine when being run off of architectural control. As near as I can figure only top half of the multi link was common to the flashing lights ( lights on the bottom half of the Multilink functioned fine off either board.) Any suggestions on what I might check or tweek to make this work right. Waiting to hear back form our nearby service folks. Thanks
Control/Dimming EDI Mark VII
- Thread starterStagetech
- Start date
JD
Well-Known Member
DMX frame rate problem? Odd that only one half of them are doing that, but if they work on the other board, I would start by dropping the frame rate. There is something else going on, such as noise or something else effecting the DMX. Too many firing cards doing the same thing to blame them. (70 channels, right?) I am assuming the system was working before and this problem just popped up out of nowhere.
I considered that and tried slowing DMX down on the Express with no difference. Had a similar problem a few years back when using the EDI board that came in with the dimmers and it was an issue with the Multilink. Was hoping there were some user things to try. And yes it was working fine then went wacky.
Are you sure that your EDI MKVII doesn't have 120 dimmers, as this was the standard for that rack? The multilink has two circuit boards a top and a bottom. Each board controls 60 dimmers. It is very common for one board to fail without the other board being affected. The most common failure is the communication chip.
The MKVII multilink was introduced when AMX and CMX were still very popular and DMX was just coming into play. Because of this the board uses a communication chip that was meant for RS422 instead of RS485. As both are a balanced signal, RS422 is also suppose to work with DMX as well as AMX and CMX. My MKVII was losing one of the communication chips almost monthly, probably because of ground loops in a building built in 1975. Also the RS422 chip does not like to see a signal when it is not powered. So if you have the console sending DMX/RS485 when the rack is not powered, you can damage the chip. When the chip is damaged, it will very often work off of a console or controller that is DC powered or has enough isolation as to keep the building ground from getting into the DMX output. such as a Battery operated DMX tester. It will not work with an express series console and many others. It took me 2 years and many tries to solve this problem. I tried several corrections, and therefore, I am not sure which ones resolved the problem. But here they are in no particular order:
1) Installed line protection on all three phases of power that go into the multilink.
2) Installed a double pole relay on the DMX in wiring that was only closed when the multilink was powered.
3) Had the DMX signal go through a Optoisolated splitter from the console to the rack.
4) Modified the multilink boards to use an RS485 communication chip (75176 transceiver) This is in my mind is the most important step. I did this by removing the RS422 chip and inserting an 8 pin Dip socket in it's place. I then built a small circuit board that holds the 75176 chip and a few resistors for better isolation and plugged it into the socket I placed on the multilink board. I then put a connector on my small piggy back board, that would accept the DMX connector that previously plugged into the multilink board. In this way, there is no permanent modification to the multilink board in case that it would have to be sent back to EDI for service.
Since all of this has been done, there hasn't been a failure in the rack in over five years. Building the piggy back board will require somebody with a good knowlege of pin assignments on transceiver chips and a schematic of the multilink.
Tom Johnson
Master electrician Theater Winter Haven
[email protected]
The MKVII multilink was introduced when AMX and CMX were still very popular and DMX was just coming into play. Because of this the board uses a communication chip that was meant for RS422 instead of RS485. As both are a balanced signal, RS422 is also suppose to work with DMX as well as AMX and CMX. My MKVII was losing one of the communication chips almost monthly, probably because of ground loops in a building built in 1975. Also the RS422 chip does not like to see a signal when it is not powered. So if you have the console sending DMX/RS485 when the rack is not powered, you can damage the chip. When the chip is damaged, it will very often work off of a console or controller that is DC powered or has enough isolation as to keep the building ground from getting into the DMX output. such as a Battery operated DMX tester. It will not work with an express series console and many others. It took me 2 years and many tries to solve this problem. I tried several corrections, and therefore, I am not sure which ones resolved the problem. But here they are in no particular order:
1) Installed line protection on all three phases of power that go into the multilink.
2) Installed a double pole relay on the DMX in wiring that was only closed when the multilink was powered.
3) Had the DMX signal go through a Optoisolated splitter from the console to the rack.
4) Modified the multilink boards to use an RS485 communication chip (75176 transceiver) This is in my mind is the most important step. I did this by removing the RS422 chip and inserting an 8 pin Dip socket in it's place. I then built a small circuit board that holds the 75176 chip and a few resistors for better isolation and plugged it into the socket I placed on the multilink board. I then put a connector on my small piggy back board, that would accept the DMX connector that previously plugged into the multilink board. In this way, there is no permanent modification to the multilink board in case that it would have to be sent back to EDI for service.
Since all of this has been done, there hasn't been a failure in the rack in over five years. Building the piggy back board will require somebody with a good knowlege of pin assignments on transceiver chips and a schematic of the multilink.
Tom Johnson
Master electrician Theater Winter Haven
[email protected]
Try getting an Fleenor single Opto Isolator. MKVII is an RS422 input. Your consoles don't have an isolated DMX out.
I want to thank everyone for all the suggestions. At this point I think I am ready to call someone in to work on the system. Does anyone know who in the Baltimore Maryland area does service for EDI? I tried reaching the company we used in the past but they do no return calls over two weeks with several calls in that time period. Also is there anyway to directly contact someone at Cooper that is an EDI serrvice expert. I am hoping that we could get them to send a working multilink and then send them back our bad one in return. Or at least talk with them and see what they might suggest. Thanks again to everyone.
Try ELS at 301-953-3679. Either Ken or Dan should be able to help you out locally. You can contact EDI directly at 503-645-5533.
Tracy
JMusumeci
Member
OK. I am having a similar problem. Appears to be the top board as well. ELS is history. parlights has been named the newest "authorized" repair site for EDI gear in our region, and I spoke with the owner and the manager, and it seems the road is growing dim for EDI users. Alan, the tech at EDI has been very helpful, but: does anyone out there locally have any spare Multi-Link boards? I have a busy rental schedule and a lot fo events coming up, and can't really make due without 60 dimmers.
JMusumeci
Member
No, the ELS cited above was in Laurel Md. Coincidentally, they were right next to a theatre where I design. Trying to get contact info for Dan, but Parlights says that they really can't help me much and have been loathe to send the whole ML unti off to the "factory" without something to replace it. Got Alan to build us a spare board out fo parts EDI had lying around, but now IT is fried. At wit's end.
