Portable dimmer power switch off- lights stay on

theatre4jc

Active Member
Joined
Nov 14, 2008
Location
Woodstock, GA
What are some possible causes of a Chauvet portable "shoebox" dimmer pack staying live, even when the power switch is switched off? Circuits 1 and 2 have become constant on, which I first thought was a blown triac. It worked great yesterday and today, poof, constant on. Well it was time to leave for the day, so I thought I would just flip the power switch off for the night and tech it tomorrow, but when I flipped the switch circuits 1 and 2 stayed live, while 3 and 4 were dead as they should be.

Any ideas why and how the power switch could be bypassed for half the circuits but not all of them?
 

danhr

Active Member
Joined
Feb 28, 2011
Location
Syracuse NY
I believe your triac diagnosis is correct. On most shoebox packs the power switch only turns off the control circuits. The mains are always connected (look at the size of the switch and you can see that it couldn't carry the full load). I blew a channel in one myself last week with a shorted fixture. It's basically now a straight-through circuit. I have found that sometimes replacing the inexpensive wire fuses with ceramic ones helps save the triacs; the best is to upgrade them to 25 amp ones if you have the nerve.....
 

JD

Well-Known Member
Joined
Jan 1, 2005
Location
North Wales PA
If you are experienced with service work, there are several threads on here that deal with the triacs used on such units. The stock triacs are 15 amp, which is not enough headroom in some cases to deal with the inrush current. As stated above, changing them to 25 amp (same package) has worked for many of us.
 

artdeco18

Member
Joined
Dec 14, 2012
Location
Ontario
I am in Canada so am having problems finding the STM 25amp triacs. However, Littlefuse makes a part Q6030LH5 which is a 30 amp triac that is available. Is this a suitable replacement?
 

FMEng

Well-Known Member
Fight Leukemia
Joined
Mar 31, 2008
Location
Tacoma, WA
They may be triacs or SCRs. Look up the specs of the original part to find out. As long as the pinout and mechanical characteristics are the same, any device of the same type with the same or higher current rating (better) should do the job.
 

R45glasses

Member
Joined
Sep 12, 2014
Location
Washington, DC
Hey all,

I'm working in a space with a bunch of Leviton D4DMX-MD5 packs. They're the sort with breaker switches instead of fuses. Yesterday, a lamp blew and it tripped the breaker on the pack. I replaced the lamp, reset the breaker, and plugged the unit back it. Now it's just on all the time and I can't regain control of it. Any suggestions, or am i just down another dimmer?
 

florentinian

Member
Joined
Sep 13, 2014
Location
Florence, OR
Hey all,

I'm working in a space with a bunch of Leviton D4DMX-MD5 packs. They're the sort with breaker switches instead of fuses. Yesterday, a lamp blew and it tripped the breaker on the pack. I replaced the lamp, reset the breaker, and plugged the unit back it. Now it's just on all the time and I can't regain control of it. Any suggestions, or am i just down another dimmer?
Almost certainly the 16 amp triac on the channel with the blown lamp died just as the breaker opened -- that's a "feature" of the D4DMX [sarcasm intended]. They're rated for 110V / 220V operation, but I think the "design" is adequate only in a 220V environment [like China] where the channel amperage is half of the requirement for the same lamp at 110V. A 16a triac has a 2X+ safety margin in a 220V setting, but the margin is barely greater than 1X here in the USA . Breakers are intended to protect the circuitry behind them; unfortunately, the breaker and the triac both fail at perilously close to the same amperage in the D4DMX. If you, or someone you know, has moderate soldering skills, you can easily replace/upgrade the four 16A triacs with 24A units. They're available at Mouser Electronics (BTA24-600BWRG, 24A, 600V, $1.15/ea, as of this date). It takes about an hour. While you're at it, replace the four, cheesy, stab-lock outlet receptacles with commercial, back-wired receptacles; the factory receptacles generate quite a bit of resistance themselves (which adds to the amperage load on the triacs and produces a lot of extra heat). With those two changes you'll have the dimmer pack that Leviton should have sold you. They'll likely run cooler and be more robust when exposed to transient load spikes.