EDI Scrimmer II dimmer pack repair?

[Keith Herron]

I'm working with a school in NYC that has an EDI Scrimmer II dimmer pack with 24 2k dimmers. The Overtemp light on the controller card is lit and so it is not working. This is the state when it is just powered on after having been off for years, probably.

So, if the overtemp light isn't lit because of an actual over temperature condition, what could be the problem and is there any chance of me getting this dimmer pack to work?

Anyone out there with EDI experience?

Many thanks!

 

[theatricalmatt]

I used several in a school setting (north of Boston), though it's been years since I've set foot in that space.

Check airflow; bad ventilation means heat gets trapped in the unit, which puts it into overtemp. If you're willing / able to open up the unit, see if the temperature sensor itself hasn't gotten covered in theater dust over the years, and consider giving it a cleaning. Temp sensors don't look like much but you might be able to trace the circuit on the logic board. (Should go without saying, but unplug it from the mains before servicing!)

 

[brucek]

https://www.theatrecrafts.com/archive/documents/scrimmer2_rev411pgs.pdf

Theatrecrafts - Equipment - SCRimmer II Power Pack

I would check that the Multi-link card is properly seated and all internal connectors are good.
If I recall, EDI used pin5 on the DMX line as an over-temp signal back to the board - I dont know if that pin could cause the whole pack to go into over temp if it is shorted, etc. Does it go into over-temp without the control cable plugged in?

Bruce

 

[Keith Herron]

https://www.theatrecrafts.com/archive/documents/scrimmer2_rev411pgs.pdf

Theatrecrafts - Equipment - SCRimmer II Power Pack

I would check that the Multi-link card is properly seated and all internal connectors are good.
If I recall, EDI used pin5 on the DMX line as an over-temp signal back to the board - I dont know if that pin could cause the whole pack to go into over temp if it is shorted, etc. Does it go into over-temp without the control cable plugged in?

Bruce

Right you are. And thanks for the links to the manuals - I found those, too. Very helpful.

OT condition remains with no MUX/console connected. I'm asking the teacher to remove/reseat all dimmer modules to see what that does. It's not clear to me from the manual, but I assume the dimmer pack will function with less than a full set of dimmer modules installed - ie. if one of the modules has a bad temp sensor and I just leave it out, perhaps we'll be in business. I think only 17 dimmers are in use, not the full compliment of 24.

FWIW, when I removed the Multi-link card to check/reseat it, it was remarkably clean and dust free. I'm hopeful we can get them functioning.

Thank you for your help, brucek and theatricalmatt!

 

[Jay Ashworth]

One more question: does the OT light come on *immediately*, even if you start it up from dead cold, say, overnight? With the master disconnect opened, even?

 

[derekleffew]

It's not clear to me from the manual, but I assume the dimmer pack will function with less than a full set of dimmer modules installed - ie. if one of the modules has a bad temp sensor and I just leave it out, perhaps we'll be in business. I think only 17 dimmers are in use, not the full compliment of 24.

Pretty sure each module doesn't have its own otemp sensors. That wiring and associated is in the rack and often may only indicate whether or not the fan is running. We've all seen it, 60°F room, turn the dimmer rack on. Otemp lights up. But it's a cold room and we just turned it on! O-temp error. Give the fan a spin, otemp clears.

 

[Keith Herron]

One more question: does the OT light come on *immediately*, even if you start it up from dead cold, say, overnight? With the master disconnect opened, even?

Comes on immediately. The unit hasn't been powered for years.

Not sure what you mean by "master disconnect opened"?

 

[Keith Herron]

Pretty sure each module doesn't have its own otemp sensors. That wiring and associated is in the rack and often may only indicate whether or not the fan is running. We've all seen it, 60°F room, turn the dimmer rack on. Otemp lights up. But it's a cold room and we just turned it on! O-temp error. Give the fan a spin, otemp clears.

This is a great suggestion - I'm not hearing any fan spinning, so maybe it just needs a "gentle" shove!

 

[derekleffew]

So, if the overtemp light isn't lit because of an actual over temperature condition, what could be the problem and is there any chance of me getting this dimmer pack to work?

Anyone out there with EDI experience?

Lite-Trol.

 

[Keith Herron]

Pretty sure each module doesn't have its own otemp sensors. That wiring and associated is in the rack and often may only indicate whether or not the fan is running. We've all seen it, 60°F room, turn the dimmer rack on. Otemp lights up. But it's a cold room and we just turned it on! O-temp error. Give the fan a spin, otemp clears.

btw - I'm just going by the diagram here, where #4 indicates a "thermal sensor" - but maybe that doesn't feed into the OT sensor of the entire rack.

 

[Jay Ashworth]

Comes on immediately. The unit hasn't been powered for years.

Not sure what you mean by "master disconnect opened"?

The power to your dimmer rack comes from a non-fused master disconnect switch, required to be positioned "within sight of" the rack, a phrase occasionally subject to ... creative interpretation.

But yes, "for years" is enough cooldown time.

 

[Gage]

I'm thinking it's very likely that muti link control card will need repair. Out of all 5 scrimmer IIs I have worked on all have had shorted tantalums that have resulted in odd behavior (and in 3 cases some magic smoke). Very similar symptoms to what you describe, most of them wouldn't get through power up and would just sit there with an overtemp light illuminated.

Other EDI products I've worked on had similar problems down to aging tantalums. It seems the longer they sit the more likely they are to short.

It's possible you could have also had a "smokey moment" without catching it, I would pull the card out and look for burned or "vaporized" tantalums for a start.

 

[Keith Herron]

I'm thinking it's very likely that muti link control card will need repair. Out of all 5 scrimmer IIs I have worked on all have had shorted tantalums that have resulted in odd behavior (and in 3 cases some magic smoke). Very similar symptoms to what you describe, most of them wouldn't get through power up and would just sit there with an overtemp light illuminated.

Other EDI products I've worked on had similar problems down to aging tantalums. It seems the longer they sit the more likely they are to short.

It's possible you could have also had a "smokey moment" without catching it, I would pull the card out and look for burned or "vaporized" tantalums for a start.

I pulled the card and didn't see any obvious smoke trails - tho I wouldn't swear I knew exactly what a burned out tantalum (capacitor, I assume?) looks like.
Thanks for another area to check.
dkh

 

[TimMc]

I pulled the card and didn't see any obvious smoke trails - tho I wouldn't swear I knew exactly what a burned out tantalum (capacitor, I assume?) looks like.
Thanks for another area to check.
dkh

Bad caps: puffy (domed end), leaking anything. Many digital multi-meters now measure uF capacitance.

 

[EdSavoie]

Bad caps: puffy (domed end), leaking anything. Many digital multi-meters now measure uF capacitance.

This works for most liquid electrolyte type caps. (Which are generally the big bulky ones that do the heavy lifting on power supply rails)

While I wouldn't go sticking your hands in there, excessive heat coming from a cap is also a decent indicator, a FLIR or even a simple temperature gun would be your friend in looking for bad caps (or other components)

 

[Gage]

I've pulled a multi-link card and attached a photo below to possibly make things easier. The cards only have two liquid electrolyte metal cans, used for power filtering, I personally have never seen them go bad but even the newest of these cards are old enough to make it a possibility. The ones that constantly fail shorted are the tiny little tan-yellow (sometimes orange depending on the age of the card) epoxy drops. I've got a pencil pointing at one in the picture. If in a circuit capable of supplying high enough current they will explode violently when they short, but in this application, I've found there are several caps that will never get enough current across them to explode even if they are bad. This still results in a non-working card but with no obvious component damage. The only real fix is to replace all of the tantalums, if you only replace the offenders, it causes cascade failures and you are right back on the bench.

I've seen it so much in EDI products that any of them not going in the personal collection get a blanket tantalum recap for reliability concerns.

I would second contacting steve at lite-trol, hes got a wealth of knowledge and is more than happy to help just about anyone.