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Author Topic: 4 channel dimmer repair help.  (Read 1874 times)

Matt Harris

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4 channel dimmer repair help.
« on: January 22, 2007, 05:13:27 PM »

Hey guys, i have been running about 6 of the standard 4 channel digital dimx dimm er packs you can find everywhere. It seems like the same company makes them and they are all branded differently. They are this model found here:
http://www.chauvetlighting.com/system/pics/DMX4_big.jpg

Any how, everytime i blow a bulb, a fuse will blow and then that channel will not work anymore. What happens is that after i replace the fuse, that specific channel on the dimmer will turn full on even if the dimmer pack itself is off. No DMX response or anything. the other  channels will act fine. The reason i am asking is that i would like to repair these myself if possible. I have about 6 of these and dont want to keep buying new ones everytime one goes down. Anyone know what it could be? thanks in advance.   -Matt
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Al Whale

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Re: 4 channel dimmer repair help.
« Reply #1 on: January 22, 2007, 10:41:59 PM »

Hi Matthew,
Dimmer modules use dual SCR (Silicon Control Rectifiers) or Triacs to do the dimming. These are Solid State devices, and as such react far quicker than fuses. The normal reaction of Solid State devices to overload is to "short". If the overload continues, the next reaction is to burn out to an open circuit.

The first situation is happening in your case (a short is equivalent to full illumination). To prevent this, most reliable companies highly overrate the current carrying capacities of the device. Your controller specified 10 amps/channel. You will probably find that the SCR/Triac is rated @ 20 amps. Probably you should replace it with 40-60 amp devices. This is because of the transient nature of the spike (due to the bulb blowing).

Also check the voltage rating of the devices. They should be at least 400 Volts (the next lowest rating is 200 v and that is too low for 220 v operation and can be marginal with power spikes for 120 volt operation). Anyways, you will probably find little difference in the price for 400V or 600V models as compared to 200V models.

Usually the driver circuit will be OK.

When replacing the parts, keep in mind that this is the line voltage part of the circuit (120V or 240V). Insure that any Mica insulators are reused, and insure that if the original devices had insulated tabs, that the replacements do also.

If you are not use to working with this type of circuit, for safety sake it is better to get a professional.

Hope this helps
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Matt Harris

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Re: 4 channel dimmer repair help.
« Reply #2 on: January 24, 2007, 07:08:56 AM »

hey, thanks for the info. i spoke with ADJ today and they are sending me some triacs. 8$ each though. im sure i could get the same thing alot cheaper somehwere else but im not sure of the part number. Ill try to find out and let you guys know. it does not look like there are anything covering the triacs legs etc. Just looks like a little chip. should be easy to replace right?  
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Tony "T" Tissot

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Re: 4 channel dimmer repair help.
« Reply #3 on: January 24, 2007, 04:17:03 PM »

Don't know if it is the case today - but find out if a heat sink on the leads when soldering will save some grief.

In the "old days" there were some fried components (SCRs) from the act of soldering.
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MNGS
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