#### Clifford

##### Active Member
Hello all,

One of our high school's has an EDI Mark VII rack with a Multilink 120 controller and SPI-2 2.4kW dimmers. For a long while ten of the dimmers haven't functioned properly, and unfortunately with the way the system was designed, that's the entire second electric. And we only have two electrics. Naturally, this makes any sort of show with complicated lighting a challenge. Having done some research I've learned that the controller is made up of two boards, each controlling 60 channels, and that these sometimes fail. My question is why then are only 10 circuits dead, and not 60?

My plan is to call EDI Service and Repair who were mentioned in another thread. I just wanted to see if anyone else had any input or information on the system that might be useful, or if anyone had run into a similar issue.

Thanks,

#### dramatech

##### Well-Known Member
On the multilink, there is a small patchpanel on the front of it. The patch is performed with what appear as very small staples. These patches assign various dimmers to 10 channels of analog. In some installations this is for emergency lighting, in others, it is so that there can be control backstage for selected dimmers. In a school environment, this so that the chorus teacher can turn on selected channels for over stage lighting without having to go to the booth. I would suggest making a note of where each of these little staples are patched so that you can put them back if necessary. Then remove all of them. Then see if your problem dimmers start working. If so, you might encounter some controls throughout the theatre, that are not in the booth. If these controls are then dead. It might be because of the removal of the staples. Then it would be a matter of determening which ones need to be replaced. The analog controls might be overriding your booth control. If the analog unit has gone bad, you may want to really evaluate how badly you need it. I have helped two of our local high schools plus my own theatre, with Mark VII racks with similar problems and each case just removed the staples and did away with the analog control.

Tom Johnson

#### Clifford

##### Active Member
We have analog control panels backstage and in the booth, but as far as I know, they're only for houselights. The one backstage doesn't get power unless the one in the booth is plugged in. Also the district has changed some of the circuits out of the rack after the original houselight controller was thrown out with the original board (another whole story in itself). In all of this messing around, they may have done something with the controller I suppose.

Is the patch panel within the controller unit? Ours is just a flat front with phase status indicator lights.

#### dramatech

##### Well-Known Member
The four units that I have worked on all had the patch panel on the front of the unit. It looks like like a black plastic surface with 1200 very tiny holes. The spacing of the holes is about the distance between pins on an integrated circuit, but in every axis. If it isn't there, it would be the first time I have seen one without the patch.
Parts are not available for the Multilink, but from the schematics, only the PROM with the software and possibly the microprocessor are not available to repair it. Having said that, there are chips on the board, that If they fail, would take out multiple dimmers.
There are a couple of folks that really know those units. I think one of the best would be dimmer.com. I don't know if he is on this forum or the lightnetwork. In any case, you have a dimmer rack that was put into many schools in the late 80s and early 90s. There are ways to rebuild it, with contol circuitry from several sources, but none of them are easy and can vary in expense a great deal depending on who upgrades them. The project is labor and knowlege intensive enough that in most cases, the recomendation will to replace it. The real problem in replacing it, is that is one of the only dimmer racks built that has 120 dimmers. Most others are 96 or some lesser multiple of 96.
The schematics that I have, are drawn like architectural blue prints and very large. I have no way of scanning or putting them on a digital media, that could be shared.
I believe that EDI was purchased by Cooper controls, but I think the support for the Mark VI is less than outstanding. I am sure that there are many on this and various lighting forums that have a better knowlege than I do.

Tom Johnson

Senior Team

#### Clifford

##### Active Member
I'll take a look at the unit again next week. If the front of the unit you're describing is so different from the one I've seen, it's possible that it's not a Multilink 120. The front says Multi-something, and the system drawings only label it as "120 Channel Controller" so I assumed it would be the Multilink 120. Other than that, there is a small panel held on by two screws which I haven't opened, and 3 LEDs that indicate status for the 3 phase power. I have pictures of it somewhere that I can probably drag up. I want to know what I'm dealing with before taking up peoples' time by calling them.

Edit: Found the pictures. It is a MultiLink, but I'm still not sure where the patch is supposed to be, unless it's behind that panel I mentioned (on the left).

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#### dramatech

##### Well-Known Member
I'll take a look at the unit again next week. If the front of the unit you're describing is so different from the one I've seen, it's possible that it's not a Multilink 120. The front says Multi-something, and the system drawings only label it as "120 Channel Controller" so I assumed it would be the Multilink 120. Other than that, there is a small panel held on by two screws which I haven't opened, and 3 LEDs that indicate status for the 3 phase power. I have pictures of it somewhere that I can probably drag up. I want to know what I'm dealing with before taking up peoples' time by calling them.

Edit: Found the pictures. It is a MultiLink, but I'm still not sure where the patch is supposed to be, unless it's behind that panel I mentioned (on the left).

You are very much correct. I do not see the patch panel. Your multilink appears to be a newer version than mine. Mine does not have the "overtemp" LED. The little cover that you mentioned and is secured with a few screws, covers some dip switches for setting the addresses of the two boards, and some switches for selection of the data input protocal. The dip switch addresses are very confusing compared to what most of the industry uses.
If you can you tell me which dimmer channels are not working, I will look at the schematics that I have, and see if I can find a chip or combination of chips that if bad, would kill those dimmers. I wouldn't reccomend changing them yourself, but it might be handy in telling some repair person where to start.

Tom Johnson

#### Clifford

##### Active Member
It's either 60 or 61 through 69. Is it possible the patch got moved into the unit somewhere?

#### dramatech

##### Well-Known Member
It's either 60 or 61 through 69. Is it possible the patch got moved into the unit somewhere?

I just got home from the theatre, and thought that I had those schematics at home. A search of my totally unorganized shelves turned up just about everything on the Mark VII rack and the Omega controller, except the Multilink. I have "Tech" at the theatre tomorrow and I will check for the schematic when I am there.
I can say from memory, That one of the boards controls dimmers 1-60 and the other 61-120. While the ribbon cables in the multiliknk, can allow either board to be on the top, It is usually the top board that is 1-60 and the bottom board is 61-120. As almost all of the digital chips on the board are used to demux the incoming data signal for control, they do it in groups of 8. So if you have lost dimmers 61-69 that would very likely be one of those digital chips. I will be able to say much better, when I can view the schematic. If it truly starts with 60 for your bad dimmers, then that would not follow that logic. Most of the rest of the chips on the board are opamps being used as comparators and combiners for the analog control and for analog AMX192.
The Multilink boards have SIP connectors for their ouput to ribbon connectors that eventually go to the dimmer modules. The dimmer modules are the typical Solid State Relay (SSR), choke and breakers. On the front edge of the multilink boards are SIP connectors for ribbon cables that go to the patch panel. It is completely feasible that the ten analog inputs on the back to be connected through a custom cable to just ten or less dimmers through these connectors. This would be for a permanent installation where selected channels would not have to be changed or patched. If this is the case there wouldn't be a patch panel.
Sometimes the dimmer modules will have some of the connections from the ribbon connectors cut at the back of the dimmer rack, and several modules used as house lights on a separate control circuity, which will be mounted on the rear of the rack, inside and behind the multilink. Mine was that way. When I put in a new separate house dimmer in, I went back and restored that wiring so that I could use it for stage lighting.
My multilink boards, did not have the usual RS485 transceiver chips. Mine were For RS422, which will work with DMX, but is not the best choice. I modified my boards by removing the RS422 chips, and replacing them with an 8 pin DIP socket. I then built a small circuit board to accept the RS485 chip, that would in turn plug into the socket where the RS422 chip had been located. The reliabilty improved by an unbelievable amount.
Because the Multilink boards were developed at the time DMX was just coming into existence, They were made to accept AMX192, 10 channels of analog, CMX and eventually DMX. There is so much circuitry on the boards that is unnecesary when using DMX only, that the board could be reduced to 1/4 of the size. Also because the boards are using demultiplexing of binary multiples. Each board is built to and contains the components to handle 64 dimmers (a binary number), but only use 60. I have yet to figure what the other four channels could do or how you would address them.
Well, enough brain rambling, I will check the schematics and let you know. In the meantime, if you can confirm the actual dimmer numbers that are not working, it would help.

Tom Johnson

#### Clifford

##### Active Member
It is just 61-69 that aren't functioning properly. The problem with 60 was an erroneous soft patch at the board. Also, our copy of the drawings for the system only show a fan behind the MultiLink, no other controller, and none are listed on the Bill of Materials.

#### dramatech

##### Well-Known Member
It is just 61-69 that aren't functioning properly. The problem with 60 was an erroneous soft patch at the board. Also, our copy of the drawings for the system only show a fan behind the MultiLink, no other controller, and none are listed on the Bill of Materials.

Clifford, I found the schematics yesterday at the theatre.
Just a little prelim info, that you probably already know. There are two circuit boards in the multilink. One controls dimmers 1-60 and the other controls dimmers 61-120. The boards are identical and the only difference is the setting of the address with dip switches. The top board usually controls the dimmers 1-60 and the lower board dims 61-120, but it is possible to be reversed if some one working on them connected the wrong cables.
The critical thing about working on a multilink, is to document every cable you disconnect, as there are many that have the same connectors.
If your multilink is assembled correctly, the most likely problem is an integrated circuit on the lower board. The data coming to each board is multiplexed. In order for the data to be demultiplexed and control individual dimmers. There are eight data switches that each break out eight channels. The integrated circuit that is labelled "U33" controls the first eight dimmers on each board. Therefore on the lower board it controls Dims 61-69. This is the only component in the multilink that is common to those eight channels. U33 is a 4051 logic chip or IC. It might have other numbers or letters with the 4051 depending on manafacture, and age of fabrication. The fact that the first number is a "4" indicates that it is CMOS. CMOS ICs require carefull handling during installation, as they can be damaged with static electricity. There are newer versions of the Chip that are TTL and aren't as sensetive to damage. I would still replace it with one of the true CMOS cips and keep yourself or whoever does the repair grounded. You can google and find out how tha is done.
The ICs are soldered into the board, and the board is a multilayer board. This means that it is very easy to damage the board during desoldering. I would purchase spare chips, and remove the old one by snipping the leads of the IC as close to the chip as possible, with really small cutters. Then I clamp a hemostat (devices used by paramedics) to each lead at a time tip the board over and then touch the pad where the lead is soldered with a soldering iron, while jiggling the board very gently. The weight of the hemostat should pull the lead from the solder pad. If it doesn't fall immediately, pull the soldering iron away, let it cool and then try it again. The trick is not to apply more heat than necessary. Once all of the leads are free from the board, use a solder sucker or solder wick to remove all of the solder from the through holes that the leads were in. Then I would put a 16 pin DIP socket where the IC came out. This will facilitate putting the new IC in with less heat involved. The socket will have a slight indentation on one end, and the Circuit board will have a silked screened image of the IC with the same indentation, or a dot at pin 1 or the number 1 at pin 1. The indentation indicates the end that pin 1 is located. When inserting the IC into the socket, make sure that you have placed pin one at the end with the indentation. Pin one on the IC will either have the indentation, or a dot at pin 1. Most circuit boards are laid out so that ICs of the same model are laid out in the same direction.

The components that you need are available from many sources, but I did look up the part on Mouser.com for you. The IC is Mouser part number 595-CD4051BEE4 and is $0.54. The integrated socket is 649-DILB16P-223TLF and is$0.20. That is for a pressed pin socket. If you want a Machined pin socket, then it is 855-D2816-42 and is $1.18. I personally would go with a machined pin socket considering the high speed switching and importance of having it work during a show. The shipping is going to cost you about$6.00 for approximately a five day delivery. Considering the cost of the shipping in comparison to the products, I would Purchase several of each part. Also, If you are in need of XLR connectors for either audio or DMX, you might want to consider purchasing some at the same time. Neutrik connectors can be found with a search for audio connectorsl There are some XLRs that at are considerably less expensive than the Neutriks, that are very close in quality, that I use all of the time. The catch is that they are manufactured by Pomona, a long time test connector manufacture, and therefore they don't show up under audio connector search. They can be found under test connectors, or Pomona.
I hope that this helps, and if you need to contact me direct with any more questions. [email protected]

Tom Johnson

#### Clifford

##### Active Member
Wow, thanks for the information. I'm not sure when I'll be able to do this, but I'll try to have a look at the unit soon to see if I can confirm that controller is the problem.