Film-Tech Forum ARCHIVE: AW-3 Mut Speed Control Problem

This is topic AW-3 Mut Speed Control Problem in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=007523

Posted by Joshua Waaland (Member # 287) on 10-12-2005, 02:41 PM:

A friend of mine has an AW-3 mut and the speed control does not work. Any advice on where to start looking in it? Common component failures? We tried my mut on his platter and it worked so we know it isn't the platter.

Posted by Mark Gulbrandsen (Member # 72) on 10-12-2005, 10:05 PM:

Typically we rebuiuld the MUT with a small 3 amp variac. You need to rectify the output of it with a full wave bridge rectifier. These are much more durable than the el-cheapo speed control module that costs cinema dealers about 70.00!! These modules blow alot because of various operator errors....

Also check the MUT motor carefully. The brushes wear and the motors fill with carbon dust and can short out, commutators also wear to the extreme. Some times the comutator can be turned down by a motor repair shop but these have to be examined on an individual basis to see if its possible. The original Bodine motor is no longer available and Christie's new motor is much larger and modifications are usually necessary in order to mount it properly... its also dam expensive!! The variac mod is also the last speed control the mut will ever need.... it can withstand shorts and such and is far more durable than its solid state counterpart.

Mark

Posted by Joshua Waaland (Member # 287) on 10-14-2005, 10:14 AM:

We checked the motor and brushes and it worked okay. We definitely traced it to the speed control. Thanks for the advice Mark!

Posted by Mark Gulbrandsen (Member # 72) on 10-14-2005, 06:06 PM:

Thats good because the older motor is no longer available!! Go with the Variac, the Christie speed control card is a joke to say the least.

Mark

Posted by System Notices (Member # 2357) on 10-17-2007, 01:52 PM:

It has been 732 days since the last post.

Posted by Larry Zuverink (Member # 1483) on 10-17-2007, 01:52 PM:

Hey Mark,

We just inherited a theatre with a bunch of blow speed control cards. So you say just a 3 amp variac and I assume a 3 amp bridge rectifier will cure this problem? Also what are the operators doing to cause this?

Posted by Monte L Fullmer (Member # 2797) on 10-17-2007, 04:06 PM:

Big problem that I've encounted with these MUTS is that of the usage of the "BRAKE" switch. It's a good idea, but a weak one.

For what blows these cards out being that when the reversing current that suddenly goes to the motor to brake down the platter.

This causes the rewind motor to be under an extreme load caused by the film tension from the platter motor being activated in reverse. Thus, increase of current is required through the card to keep the rewind motor torque and RPM the same, causing the cards to blow, due to being a weak link in the chain.

Easy trick is to do simply do the rag method to hand brake down the deck and turning down the rewind motor speed at the same time when the splice comes around...and leave the "BRAKE" switch totally alone.

Posted by Mark Gulbrandsen (Member # 72) on 10-17-2007, 07:29 PM:

Again, I will reiterate what I said long ago and is posted above.... If you have the means and are able to convert the speed control to a 3 amp variac with bridge rectifier you will be money ahead. I use the variac that's used on the SPECO platters. It mounts in the sane hole the origial speed control mounts into and all you need do is add the bridge rectifier and you're in buisness. I will post pics of a converted table as soon as I'm back in SLC.

Mark

Posted by Louis Bornwasser (Member # 3063) on 10-18-2007, 06:51 PM:

I have only lost Christie speed controls if:

1. the motor brushes are left to get too short.

2. The 6 pin plug is reversed. One way to stop this is to paint the top of the plug white. Another way is to changed the plug to a "right angle" style plug, such as one mad by Beau or Cinch-Jones. Louis

Posted by Mark Gulbrandsen (Member # 72) on 10-19-2007, 11:56 AM:

Or... if someone stalls either the platter deck or the rewind motor when its running of if the wiring in the plug at the end of the cable shorts out... the latter is the main source of speed controler failures that I see. Burns the foil right off the pcb. The variac route doesn't cost all that much more han that 10 cent speed controller and its the last time it'll ever be replaced.

Mark

Posted by Larry Zuverink (Member # 1483) on 11-19-2007, 01:56 PM:

Hey Mark,
Do you have a schematic for doing this convertion or the rewind table?

Posted by Mark Gulbrandsen (Member # 72) on 11-19-2007, 07:35 PM:

Larry,

Its very easy... no schematic needed. Just get the variac that is used in the SPECO platter. It is small enough to bolt right in place of the existing speed control in the same hole. You will want to locate and drill a small hole for the locating pin on the variac so it can't spin if the nut works loose.

Take the 120 volt feed that went to the speed control card and feed it to the variac input. The terminal when you turn the wiper full clockwise gets this hot wire. The variac tap with the wiper all the way counter-clockwise on the variac is the neutral.

Connect a 2.5 amp push to reset circuit breaker in series with that hot input lead.

Locate and drill a convenient clearance hole for an 8/32 screw and mount the bridge rectifier to the MUT for heatsinking. Find a suitable place where there is room to get at it.

Then connect one end of a wire to the wiper terminal of the variac and take the other end of that wire wire to one of the AC input terminals of a 40 amp 600 volt square cased bridge rectifier.

Connect one end of another wire to the neutral at the variac then connect the other end of that wire to the other ac input of the bridge.

The plus (+) output of the bridge goes to where the output of the old variable speed card connected and the minus (-) goes to the other wire from that card.

Add the 40 watt florescent make up light for a nice touch... they rarely fail.

It takes longer to read this than it takes to do it!! Any questions let me know or call me at CLACO tommrrow. The number is on this site under dealers in the product section.

Mark

Posted by Monte L Fullmer (Member # 2797) on 11-20-2007, 03:04 AM:

what's that big wirewound resistor used for and what is its function in the circuit...like a ballast?

Posted by Larry Zuverink (Member # 1483) on 11-20-2007, 06:45 AM:

Fantastic Mark, thanks.

Posted by Mark Gulbrandsen (Member # 72) on 11-20-2007, 10:27 AM:

quote: Monte L Fullmer
what's that big wirewound resistor used for and what is its function in the circuit...like a ballast?

To pre-warm the film and make it more pliable [Big Grin]

.

Mark

Posted by Mike Blakesley (Member # 26) on 11-20-2007, 05:48 PM:

I like the giant light bulb replacing the standard bulb which burned out so often I finally just started holding the film up to the window.

Posted by Monte L Fullmer (Member # 2797) on 11-21-2007, 12:25 AM:

...(true Mark, Poly film is more stiffer than acetate stock when it just comes out of the cans during the winter being in the delivery trucks all day ...(lol))

-pretty soon, you're gonna see practically all light bulbs being the compact flourscent type ....

Posted by Steve Guttag (Member # 268) on 11-21-2007, 04:44 PM:

Yeah Monte...until they discover the active ingredient in florescent lamps. Mercury...that substance they've been trying to get rid of from thermometers, fillings and most every other substance. It is almost like they don't see what is going to happen to the lamps when they are disposed. There is a time and place for both types of lamps...personally, in the home, I like the tungsten lamps for most things...in a workshop...florescents.

Posted by Mark Gulbrandsen (Member # 72) on 11-21-2007, 08:15 PM:

I agree... I like tungsten at home... Halogen desk lamps are nice too. The florescents will somewhat disappear eventually... probably not totally though. It will be interesting over the next 5 to 7 years as the world shifts more towards LED lighting. The big problem at this point it the cost of a 100 watt medium base lamp equivelent is about 90 bucks.

Mark

Posted by Steve Guttag (Member # 268) on 11-22-2007, 07:07 AM:

What gets me about LED lights (for lighting) is that they tend to put the LED(s) in the middle of a reflector pointing out (like in an LED flashlight). The problem is, most LEDs radiate from its tip mostly...it would be better to point the LED into the reflector so the reflector could collect the light and focus it. As a general rule, I hate LED flashlights...don't like the color and I can't see as well with them.

Note, on clip on work lamps...a plus to flourescents is the lack of heat on the unit when you are done...no cool down time. Then again, I like my "rough service" tungsten lamps because they are not as fragile. You can drop kick those lamps, even when hot, and they keep going.