rothackerben8 Posted August 23, 2017 Share Posted August 23, 2017 Hi everyone, I'm new to this forum, but I have a big problem on my hands. Our local theatre is having a production that a friend and I are in charge of. It's only a small theatre, and the tech is quite old. The dimmer that we are planning to use is a Strand Lighting Minipak. I'm unsure of the model, but it has 3 separate dimmer banks, each with 4 dimmer channels in each, in one unit, running off 3 phase power. The problem is that only one of the dimmer banks is working, with the other two permanently closed circuit and outputting something around 230v. Someone mentioned that it could be a triac inside the unit, if this is the case, assuming I could replace the triac, would this work? would it have to be the exact same specification? what could've caused it to blow? and will the new one blow if I replace the triac. Any help much appreciated, as the production is in a few days. Thanks. Ben Rothacker. NM Entertainment Boort http://www.blue-room.org.uk/public/style_emoticons/default/rolleyes.gif Link to comment Share on other sites More sharing options...
Don Allen Posted August 24, 2017 Share Posted August 24, 2017 the triacs usually go short circuit if a lamp blows and there is a short circuit on the triac. Sometimes in community theatre, if there is a faulty lamp, a person will keep plugging it into dimmer channels, blowing fuses and sometimes triacs until they run out of channels to try, then suspect the lamp is faulty. This information is for competent technicians. All tests with dimmer unplugged from mains. Is this your dimmer Minipak Check your fuses first. These fuses are shorter than 3AG. Check the high wattage resistors that are in series with the triac gate, if they have gone open circuit or high resistance, the channel won't turn on. If all four channels are not working, check the mains transformer at the back, as it supplies low volts for the trigger circuit and the mains frequency timing. If the channel is hard on, check the triac for short circuits. If the channel does not come on and the resistors are ok, swap the trigger ic. Replacements are hard to find. I get mine from a parts supplier in China. I have circuits of these Minipaks, let us know if this is your dimmer. Link to comment Share on other sites More sharing options...
ianknight Posted August 24, 2017 Share Posted August 24, 2017 The only issue you may find is that the power controllers are not actually triacs but thyristors - Mini 2's and Tempus use the same arrangement until triacs became more obtainable and cheaper to use - if they're thyristors, you may have real issues finding replacements. The thyristor often has a threaded end which is bolted to a heatsink whereas a triac will look like a "conventional" power transistor package. Link to comment Share on other sites More sharing options...
Jivemaster Posted August 24, 2017 Share Posted August 24, 2017 Do you have the right or permission to open the dimmer, and the skills? Consider that a hire dimmer could get your show on the stage for less than a competent repair to a piece of vintage kit. If you go into the old dimmer, be careful there could be live heatsinks -stud SCRs were live body, tab SCRs or triacs may or not be live tab which may or may not be electrically connected to the heatsink. Only replace tings with the right part, especially check the fuses are all FF rating or faster. An FF fuse may blow before the semiconductor others may not! Link to comment Share on other sites More sharing options...
alistermorton Posted August 24, 2017 Share Posted August 24, 2017 +1 for considering a hire. Link to comment Share on other sites More sharing options...
Jivemaster Posted August 24, 2017 Share Posted August 24, 2017 The "minipack" is described as analog so will not likely work with DMX kit, any hired kit now will be DMX. If it is as simple as the dimmer on phase one works and the others don't then look at some upstream phase fuses first. Link to comment Share on other sites More sharing options...
timsabre Posted August 24, 2017 Share Posted August 24, 2017 If it is as simple as the dimmer on phase one works and the others don't then look at some upstream phase fuses first. He says the channels are "permanently closed circuit outputting 230V" which I presume means stuck on at 100% - so not a fuse. Could be a thyristor problem as suggested above, though it is strange that 8 out of 12 dimmers are affected. Could be a control system problem - 0V lost on the analog input maybe or something inside the dimmers. Link to comment Share on other sites More sharing options...
alistermorton Posted August 24, 2017 Share Posted August 24, 2017 Tim's suggestion crossed my mind too. A couple of dimmers and a console hire may still be a cheaper short term solution than repairing. Depends on what's failed and what skills are to hand to investigate. Link to comment Share on other sites More sharing options...
rothackerben8 Posted August 24, 2017 Author Share Posted August 24, 2017 the triacs usually go short circuit if a lamp blows and there is a short circuit on the triac.... ....Is this your dimmer Minipak.... ....I have circuits of these Minipaks, let us know if this is your dimmer.Hi don, This is the dimmer we are using. any schematics would be much appreceiated Okay, so our budget is very small, and the nearest hire venue is 100 kilometres away, so hiring isn't an option. I have been granted access to repair the dimmer, and have many years of soldering experience. I'll be having an experienced person assisting me during the repair, the only thing we can't work out is the difference between a triac and a thyrister, and also does it have to be a certain specification, or can it be above? Cheers. Ben Rothacker. NM Entertainment Boort Link to comment Share on other sites More sharing options...
ImagineerTom Posted August 24, 2017 Share Posted August 24, 2017 if your "experienced person" doesn't know the difference between a triac and a thyristor, doesn't know whether the specification is important and can't find them on such a relatively simple circuit board then I think your definition of "experienced" is very different to the normal definition. I assume this is you? https://www.facebook.com/pg/NMBoort/about/?ref=page_internal You're playing with mains voltages here; tiny mistakes will result in major damage or serious injury. You are out of your league on this one and you should be handing this whole project over to someone who has real-world experience working with these voltages and types of equipment because that is going to cost you a lot less than muddling on yourself and asking complete strangers on the other side of the planet. Link to comment Share on other sites More sharing options...
Brian Posted August 24, 2017 Share Posted August 24, 2017 Post all the numbers on the devices. Someone will identify them for you. Link to comment Share on other sites More sharing options...
rothackerben8 Posted August 25, 2017 Author Share Posted August 25, 2017 Have taken ImagineerTom's advice, I'll be taking it to a professional, and will get them to look at it Link to comment Share on other sites More sharing options...
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