Electro Controls Alpha Dim with Lite scene Electronics

Bart53

Member
Hello All,
I've got a church with the above dimmer system. I've had to replace the firing cards in three of the circuits. I'm using the FC-445 firing cards from Johnson Systems. I've also replaced the SCR's. What I have is some lamps glowing dimly after the lights fade to off. I've checked and adjusted the power supply to 15VDC. The preheater circuit jumper is set to disable. I have various amounts of low voltage over several channels after the lights fade to off. These levels vary from about 1 volt all the way up to about 12 volts. The channels with voltages from about 4.5 volts up glow. When I secure the control power circuit, all of the glowing lamps extinguish. When I remove the control voltage connector on channel 2's firing card all of the glowing lamps extinguish. I replaced the firing card and the SCR in channel 2 today. Is there anyway or anyplace in the dimmer cabinet that I can adjust these voltages down to the point where the lamps are not glowing after the off scene dims down to off?
 
If you have replaced the EC firing card with the Johnson Systems card and you are still getting lamps unable to extinguish with the new card, give Shaun Johnson a call or email. They are great at tech support and have a lot of experience with EC systems. It could be that the Lite Scene unit has components going out of tolerance and outputting a greater than normal control voltage. Have you measured the DC control voltage at the input to the firing card with the controller at zero? The dimmer may just be doing what it's been told to do by the controller.
I assume you've been checking the AC voltages with a true RMS voltmeter?
 
Thanks for the reply Microstar. I did check the input DC control voltage to the firing card with the controller at zero. It was about 1/2 a volt. While not a lot, it certainly seems to be causing the issue that I am seeing. When I unplug the DC control voltage connector the lamps go dark. As for the true RMS voltmeter, I'm using a Fluke 87III.
 
There could be some kind of "trim pot" on the Lite Scene unit that could adjust the output voltage. Would be worth a phone call to Johnson Systems. Another EC specialist that I've had really good luck with is Edwin Jones Company in Richardson, TX. 731-572-4000. Ask for David McElvy. He knows everything. There's always Steve Short at Lite-Trol in New York also a great source of information.
 
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All the "trim pots" on the lite scene cards were set at zero. I have been in touch with Shaun at Johnson Systems and he thinks that the power supply could be causing the ghosting problem that we're seeing. I'm going to have the power supply ordered and will replace it. Thanks for you r help. I'll let you know how it goes after I've replaced the power supply.
 

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