Film-Tech Forum ARCHIVE: CP500 Fader Knob Not Working

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Posted by Jason Setzer (Member # 3949) on 10-08-2006, 09:13 AM:

In one our theatres the cp500 Fader Knob is turning the volume down no matter which way you turn the knob. This just started happening this weekend. I am sure this is a simple fix but it has been racking my brain.

Posted by Cody Martin (Member # 2523) on 10-08-2006, 10:10 AM:

Had this happen recently. Our front panel fader died and had to be replaced. A simple TEMPORARY fix if you have another cp500 is to

take the motherboard out of the broken cp500
put it into another with a good panel
set the volume
and then put the motherboard back into the broken unit

Hope this helps,
Cody

Posted by Demetris Thoupis (Member # 833) on 10-08-2006, 02:57 PM:

You need a replacement Front Panel. Happened to one of our theaters down in Cyprus and we replaced it with an exchanged one from Dolby. Not a hard replacement that you can't do by yourself if you have the part.
D

Posted by Brad Miller (Member # 2) on 10-08-2006, 03:19 PM:

Just run down to Radio Shack and purchase a 100K linear potentiometer for $2 and hook into the back of the unit. Then set it to "auditorium fader". It may not be pretty, but it will work for awhile until you can get the part from Dolby.

Instructions are in the manual you can download here.

Posted by Steve Guttag (Member # 268) on 10-08-2006, 04:59 PM:

Or..hook up your computer and send it the proper fader commands...or buy the Bourns rotary encoder and solder it in...or...

I like Brad's solution best.

Posted by Mark Gulbrandsen (Member # 72) on 10-08-2006, 05:03 PM:

I'll second Brad's idea too. Replacing the whole front panel for the sake of a bad rotary encoder is as rediclous as replacing a power supply board because of a burn't Molex pin. Use the 100K till you can get a new encoder from Dolby or another source.

Mark

Posted by Louis Bornwasser (Member # 3063) on 10-09-2006, 03:41 PM:

Mark: not every tech has the ability to solder on a board. This is why we ship modules around. While I would never personally replace a front panel when the encoder (which we stock) is bad; it is a fact of life that we must make peace with the fact that good techs are not universally available. Louis

Posted by Steve Guttag (Member # 268) on 10-09-2006, 04:51 PM:

As luck would have it...I just encountered this problem...the fader would only go down.

Here is the rub...how do you tell the CP500 to go to auditorium fader mode? You have to rotate the volume UP...can't do it!

Changing the rotary encoder seems particularly goolish on the CP500 front panel...it is sandwiched in such that one remove stuff to get to it....what a pain for a part that is likely to wear out (it is mechanical).

Steve

Posted by Sam D. Chavez (Member # 1841) on 10-09-2006, 09:50 PM:

According to Lonny, replacing the encoder is not for the faint of heart and he is adamantly against doing it in the field.

This from a guy who climbs 16 ft. security fences to get into a locked area.

Posted by Mark Gulbrandsen (Member # 72) on 10-09-2006, 11:09 PM:

quote: Steve Guttag
what a pain for a part that is likely to wear out (it is mechanical).

That depends on if its a mechanical or optical encoder... hopefully they used an optical unit. I agree that not all techs might want to attempt to do it.... I can remember repairing pocket cassette tape recorders when I worked as a bench tech at Panasonic that were far more difficult just to get inside of than it is to replace that encoder!

quote: Louis Bornwasser
it is a fact of life that we must make peace with the fact that good techs are not universally available. Louis

Probably bcause all the good techs are too busy making posts on F-T!

Mark

Posted by Steve Guttag (Member # 268) on 10-10-2006, 05:51 PM:

It is a mechanical encoder Mark.

I only looked at it briefly since I had another front panel with me (a long story there)...but it looked like one really should have a "rework station" with them. there is a double row header that needs to be unsoldered (around 24 connections) in order to remove the daughterboard that has the encoder.

Alternatively, it might be possible to remove the whole front panel board from its face plate to free up just the encoder...odds are one will have to contend with the buttons and such at that point. The fit through the front panel board sure looked tight! That would probably be my first plan of attack since reworking the 24-pin header has the potential for harm.

In any event, this is not to be casually entered into. Good luck...then again, the potential savings are pretty big...the part is not expensive at all.

Posted by Sam D. Chavez (Member # 1841) on 10-10-2006, 07:10 PM:

I disagree. The cost from Dolby of a hacked up board when it is returned will shiver your timbers. And If you damage the front panel you will be running in bypass until Dolby gets you another front door, something in very short supply and long lead time.

fugedaboudit.

Posted by Steve Guttag (Member # 268) on 10-10-2006, 08:47 PM:

The RXO cost (list) of the CP500 front panel is $600.00. Nothing to sneeze at there. The price of the encoder is around $5.00 from typical electronic suppliers. So the potential savings are very much there.

Compare that to a CP500-FP new (Dolby still lists them) $800.00

No doubt a big part of the cost is that screen...which several of mine are getting lines in them.

I still don't advise anyone to attempt the encoder replacement since it really does seem to be tucked in there but there is something that just rubs one the wrong way to know that the cost of the repair far exceeds the cost of the part. I would definately have the right tools and experience on hand before doing such a thing. As Sam noted...if you screw up...your CP500 is down and will likely be paying for a new front panel to get things back going.

Posted by Sam D. Chavez (Member # 1841) on 10-10-2006, 09:49 PM:

It chaps my hide too to have to get an exchange for such a simple reason, but thats life in the big city.

Posted by Kenneth Wuepper (Member # 1174) on 10-11-2006, 06:42 AM:

The "MODULAR" system of construction is becoming the standard in the digital world. It is no longer practical to field service equipment at the component level. The field technician is not able to carry the equipment to test and repair (surface mounted ) devices in the field.

If the service company equips the technician with the necessary boards to swap out in the field, the system is very fast, efficient and cost effective for the customer. While servicing digital church organs, I had to own all of the boards necessary to service what we sold. If the new organ had a new board, it came with the instrument and we were billed by the company for the "spare". In 33 years as their dealer, we never had one church that was without an operating organ on Sunday.

There are fewer theatre booths than churches so the cost of stocking processor parts is being left to the manufacturers. With DCinema, that practice may have to change and, like the organ company, the field service technician will be required to carry the necessary boards to service the customer immediately.

KEN

Posted by Mark Gulbrandsen (Member # 72) on 10-12-2006, 08:52 PM:

I took a look at one today while I had removed a display board to clean the face of the LCD and although I would not reccomend an inexperienced tech attempt it I didn't see it as being a big deal for an experienced tech. Having the correct tools at hand will also help make it easy.

Mark