Film-Tech Forum ARCHIVE: Smart Tri-Level 3K Dimmer Voltage

This is topic Smart Tri-Level 3K Dimmer Voltage in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Jeremy Weigel (Member # 4208) on 06-24-2010, 07:01 PM:

Is there any way to adjust the load voltage other than the trim pots? I have a pair of these on a screen. One controls stage lighting and the other house lighting. On both, the voltage for "full dim" will only go down to 24.5v on one and 27v on the other leaving the bulbs with too much glow that is quite distracting (especially for the stage lighting). There are 4 stage and 10 house bulbs. All bulbs are R40 120watt.

Posted by Louis Bornwasser (Member # 3063) on 06-25-2010, 01:37 AM:

Contact Sonic in Iola Kansas. They purchased the Smart dimmer line (along with Kneisley.) Louis

Posted by Jeremy Weigel (Member # 4208) on 06-25-2010, 02:02 AM:

Yeah they actually installed them last year with our digital conversion. They couldn't figure it out either. I have the same set up on another screen and don't have this problem. The voltage on those will go down to 17-18v. It still has a glow, but its much less noticable. It has the same number of bulbs and type as well.

I seem to remember reading a post on here some time ago where the guy that designed these dimmers made mention of this fact. Maybe he'll chime in. [Big Grin]

Posted by Catalin Balaceanu (Member # 3712) on 06-25-2010, 03:14 AM:

Hey Jeremy,
I was in the same situation as you, with this dimmer. Not having an official service provider for Smart devices here in Romania, I just took the problem in my own hands and started fiddling around with it.
Look for a green multi-turn trim pot on the board. Apparently, this trimmer, that tweaks the transition time between off and on status of the lights, has something to do with this.
Here's what I did:
I switched the dimmer to "off" position (ofcourse, the bulbs still had a minor glow) and started to sloooowly rotate the multi-turn pot until the lights were completely off. Just pay attention to the evolution of the glow as you rotate; if the glow will increase, just start rotating the other way.
I also noticed that the glow will vary according to the size of the load. The dimmer will behave totally different if it will have a 50W lamp on it, compared to...say 2000W load.
Now, this was MY experience with it. If you want to try this out, I don't want to be held responsible if something goes wrong. [Smile]

If you want to wait for Oscar Neundorfer's advice, he's the one who should be asked about this dimmer.

Good luck!

Posted by Oscar Neundorfer (Member # 458) on 06-25-2010, 04:50 AM:

Jeremy,

It has been way too long since I designed this dimmer, so I am going on faded memories here. I believe Catalin is correct. The multi-turm trimpot was there to limit the minimum load voltage to solve problems in some cases where the load would interact with the triggering of the SCR's and cause some flickering or other anomalies. Ususally this problem occured with magnetic low voltage lighting that uses a transformer.

The earlier units did not have this trimpot, but it sounds like you have a late model. You cannot hurt anything by adjusting this. It may solve your problem easily.

Catalin mentions a green trimpot, but I seem to recall it as being light blue in the units made by SMART. You need a thin flat screwdriver blade to adjust it. Usually a processor alignment tool will work fine.

Oscar

Posted by Jeremy Weigel (Member # 4208) on 06-25-2010, 05:15 PM:

Thanks for the replies. Are you referencing the R2 trim next to the C2 capacitor?

Posted by Gordon McLeod (Member # 33) on 06-25-2010, 10:44 PM:

I have forwarded the schematic and test procedure to brad to upload to the site