Film-Tech Forum ARCHIVE: Christie AW3R Problem

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Posted by Matthew McBride (Member # 6598) on 06-02-2014, 06:15 PM:

I searched the forums but couldn't find an answer for this particular type of problem. I am having an issue with my lower platter. When it is switched to normal operating mode, there is a constant audible hum coming from the column, near the control harness, and when it is switched to makeup/breakdown mode there is no more hum. These are the toggle type switches, the vintage of the AW3R is 2007. I noticed this when my bottom platter stopped functioning in normal mode, however it worked just fine for makeup/breakdown, so the motor is ok.

I have checked all of the motor cards and the LED card and those are fine too. I have also tested the LED/sensor assembly and it is ok too. I replaced the entire column control assembly from a spare of the same model/vintage and the bottom platter works again however there is still the hum. I thought it was the toggle switch but I replaced that and still the hum is present. I did notice that when the motor is unplugged the hum also goes away. I have run out ideas on what to check. I thought maybe there is a bad connection between the normal mode to the motor but not for the makeup/breakdown mode? Another reason why thought this is I detached the led/sensor assembly from the connectors and still the hum in normal mode. Any ideas. Thanks.

Posted by Brad Miller (Member # 2) on 06-02-2014, 09:14 PM:

Turn the LO pot on the speed control card down just a touch.

Posted by Matthew McBride (Member # 6598) on 06-02-2014, 10:39 PM:

I did just that and voila gone. Thanks Brad. Here's another question. What exactly then is causing the hum? Is there just enough current being set to the LO pot allowing electricity to flow to the motor but not enough to make it run?

Posted by Justin Hamaker (Member # 2165) on 06-03-2014, 12:02 AM:

Matt, that is exactly correct. If the LO pot was turned up just a little more then you would probably get a very slow creep. It might be a good idea to pull out your manual and check the for all three decks.

Posted by Monte L Fullmer (Member # 2797) on 06-03-2014, 11:45 AM:

One needs to do the mechanical and electronic alignment on these things.

Manual section to find the manual for these AW3R units and follow the alignment instructions. A VOM and a Platter Tach are your best friends.

Might have a bad photosensor under the deck arm. Take it out to see if any burnt traces can be seen under the glass. If so, this sensor is gone and needs to be replaced, for a bad sensor will cause some of this issue.

Also, the filter plate could be out of adjustment.

(Dang, haven't worked on a AW3R for a couple of years now since digital took all that away...but glad I can still remember how to work on these things..)

-Monte

Posted by Matthew McBride (Member # 6598) on 06-03-2014, 07:20 PM:

I have a multimeter and I used it and the tape/stopwatch method to time/align it. I also timed/aligned per the instructions in the warehouse section in platter tips. Though I probably should redo the whole alignment procedure anyways. It's not terribly hard with the AW3's which is a great thing. BTW, I did check the photosensor when I was trying to rule things out and it is A-Ok.