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This topic comprises 2 pages: 1 2
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Author
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Topic: Xetrol Dimmer Delayed "UP"
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Steve Kraus
Film God
Posts: 4094
From: Chicago, IL, USA
Registered: May 2000
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posted 03-24-2017 10:43 AM
Mark, that would be at full tilt: 6 and 12 lamps, each with 100W bulbs. The main dimmer (the problematic one right now) has the panic button feature that brings them instantly up full. There are no work lights so smaller bulbs would not be effective. Our normal "UP" is a little below max. I have one critic who routinely hits the panic button when entering the room just for those few added lumens. When I see this I always take it back to normal. It's a little game.
Anyway....
And the winner is...
(If you're dying to know skip to the last graph.)
I pulled the control card to get proper readings of the two motherboard resistors. They checked out though the bottom one seemed like it might be open but I put that off to poor contact of the meter probes.
So I opened the good dimmer and proceeded to swap the triac power cubes. As expected, no change. But curiously, the lower resistor on that one looked discolored. I wonder if the unit overloads it or maybe aging control card characteristics (both of them) was responsible.
So the next step was to replace that resistor. A big job since these dimmers are 7' up on the wall of the electric closet so it takes at least 20 minutes to disconnect all wires and pull out the chassis.
So got it in the booth, hooked up a power cord and a 100W bulb. As I did not have a higher rated 220 ohm resistor I decided to spread the load over 3 in series adding up to the same amount.
Along the way I noted that no resistor in that spot produced the same result: Minutes would go by but eventually the lights would rise. Odd because I thought that resistor provided the gate power to one of the triacs. Any, replacement with the correct value did not solve the delay issue. Nor did experiments with higher or lower values. I left it with a single resistor as built.
Hmmm....running out of potential faults.
At this time I noted a curious thing. If you are in bright mode and hit the dim button, the dim relay clicks and electrically latches in. But if dim and you it the bright button the bright relay (which I had replaced) continues to respond momentarily. It clicks in with subsequent button pushes. (I checked if holding the button brings the lights up faster but it does not.) Something seemed wrong about that.
However this proved to be a red herring. I checked the good dimmer and it works the same way. Oh well.
But thinking about the relays drew my attention to the DIM relay which was still original. I replaced it. Problem solved. So, the delay on bright was caused by a faulty DIM relay. With a good relay in there and controls back to how they were there is still an 8-9 second delay before the ramp up starts but I think that's how it always was. Before posting I felt compelled to go back and recheck that I had not been spacing about which relay is which but, yeah, the dim relay caused the problem.
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