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Author Topic: Getting the most out of your RED LED. Ian Bailey Master Film Handler Posts: 317 From: Nambucca Heads, Australia Registered: Jun 2003 posted 03-07-2006 06:44 PM                     I'm told that the RED LED in a Component Engineering reader should last around two years! Well I'm getting less than one year out of mine when it gets to the point of not being able to reach "DOLBY LEVEL". I need to clarify the following points: 1: When an A-Chain alignment is done does this optimise the strength of the output signal from the reader to the processor input.so initially you get the largest signal to the processor leaving a lot of "headroom" for future Dolby level adjustments? 2:The power supplies I am using to drive the CE readers do not have o/p voltage adjustment but do have o/p current adjustment(I think!) via a strap on the PCBd,which I think all of mine have been "CUT" so I think I'm feeding maximum current to my Leds all the time.I never seem to have much adjustment left at the processor to set Dolby Level when I install a new LED.Which means it doesn;t seem to take long before Dolby level cannot be reached. 3:Don't know how much you guys pay for RED LEDS but down here they cost $180-200 AUD each.(approx $260 US each)For what it is this is INSANE!! Just to double check it is the CAT-69T dolby loop that is used to set Dolby level???? Any other information you guys could give me on this topic would be greatly appreciated. THX Ian  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 03-07-2006 06:47 PM                     Yes the cat69T is used to set Dolby level. Make sure the processor is in MONO though, as many require that. The trick is when doing the A-chain alignment to adjust the position of the led (which may require moving the entire bracket) around until you get the highest output. THEN perform your A-chain. Finally I set the Dolby level to approximately 80% of it's capability, then trim the led's power supply down until Dolby level is reached, and do a fine tuning job (mostly for balancing between the channels) back on the processor. This way your leds are running as low as possible. As time goes on and you lose the capability to achieve Dolby level using the top 20% of the processor's range, you simply lower it back down to about 80% and up the led's power supply until you achieve Dolby level again. Sooner or later you will run out of headroom on the led's power supply, but you will easily more than double your led's life handling the setup in this manner. Another good trick is to wire your system such that the leds switch on and off with the motor.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 03-07-2006 08:29 PM                       Several comments. I agree with Brad as far as he goes. There is also a 6 dB gain jumper on the line amp. of all readers certified by Dolby. This link increases the gain of the system and can be used to reach Dolby level instead of and/or in addition to adjusting the LED current. As to the price of genuine Dolby LED part # DPN 32075; Dealer price for the raw LED without heatsink is $60 US. Even with a reasonable markup it should not be anything like you are quoting. I will be happy to sell you all you want at a price you will like.  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 03-07-2006 08:58 PM                     $180-200 AUD is only about $130-145 USD (XE.com just now). Considering shipping, duty, profit... $180-200 still sounds quite steep but not insane.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 03-08-2006 12:18 AM                     Ask Mark G, for some LED's if your good at soldering. Claco has a wad of LED's by themselves for the do-it-yourselfers who want to do their own LED changeout. -Monte  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 03-08-2006 08:13 AM                        But won't Brad's method increase noise (since it requires raising the preamp gain above what it would normally be)? Or is that a non-issue with modern (SR) noise-reduction systems? Would it be an issue when playing older (mono or Dolby A) prints?  |  IP: Logged Ian Bailey Master Film Handler Posts: 317 From: Nambucca Heads, Australia Registered: Jun 2003 posted 03-08-2006 08:17 AM                     Thanks guys. Brad-How do you "trim the Led's power supply down?" Sam-I think I'll take you up on that offer,I hate paying that much for a Led.I'm not sure what you mean "without a heatsink"-I'm not aware that the Leds i use have a heatsink,or I'm buying Leds with the heatsink which i thought was part of the whole package not knowing the two can be separated.And I'm also confused at Monte talking about soldering.The leds I use in my C.E. readers you have to trim the length of the legs and push the legs into a small socket,like a socket for a transistor-there's no soldering involved.I've always thought this socket arrangement lends itself to poor contact to the Led. Ian  |  IP: Logged Pete Naples Phenomenal Film Handler Posts: 1565 From: Dunfermline, Scotland Registered: Feb 2001 posted 03-08-2006 09:17 AM                     On the back of the LS30 PSU is a small pot, there's one for each module installed. You turn it clockwise to increase, anti-clock to decrease the current. I've onyl ever seen CE reverse scan with an LED that pushes into the sockets, and is secured by a small punched plate.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 03-08-2006 11:18 AM                        The question not asked is: "What current should I start with?" With the Dolby at 80% (per Brad) you should be able to use 225ma. and get Dolby tone. (On CP-500 I can get dolby tone at 225ma on led and 60% on meter.) This is for "normal installations like Simplex, RCA, Century/ Westrex.Louis  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 03-08-2006 01:47 PM                       BACP uses a non adjustable 150 mA LED current and achieves Dolby level with 8 dB to spare on the Dolby preamp controls even with the reader line amps set to low gain. The reason is we use the highest MTF and fastest lenses in this market. Our lenses were specificallty designed for us for this application. The lower the current the longer the LED life. We average 3 years before needing to change the gain to high, which then typically yields another two years.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 03-08-2006 04:03 PM                     An additional way to prolong the LED aside from the method that Brad gives is to place the AC side of the Scanner power supply on either the Exciter contacts or across the motor terminals so its off when film is not running. This alone can add another 3 years of life to an LED. USL also supplies an LED that is as good and a bit less expensive then Dolby's is. The only dofference is that the polarity of the leads are reversed.... no big deal. In some locations we have seen power supply failure(Kelmar) long before the LED needs replacement. Mark  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 03-08-2006 05:25 PM                        In some cases the Kelmar had current set as high as 790 ma. Many of the old gray cases suffered from bad connections on the internal board plug. In doing upgrades (new box, old board, new led, new lens) I did find 2 or 3 cases out of 400. Never had a board fail, however. Louis  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 03-08-2006 05:48 PM                     quote: Louis Bornwasser In doing upgrades (new box, old board, new led, new lens) On the Gray box Kelmars board there is an inductor near the output molex that runs blazingly hot if the LED current is cranked and still fairly hot even at normal 250 ma setting. Its very clear that this inductors heat output which travels through the copper foil to the Molex connector is what causes the Molex to dis-color and then eventually causes the Molex's contacts to fail. I've seen one that had disintegrated the foil for that distance, damaged the heated inductor, and burnt a nearby resistor to a crisp. Replacing that old junk really doesn't make sense nor is it cost effective, nor are you doing your customer any favor. Replacing it all with a new BACP makes a ton more sense since it runs at the lowest LED current in the industry. If the customer doesn't want to do a complete change-out of scanner we generally just replace the Kelmar supply as a whole with the LS-40 C.E. supply. Its built far far better than even the new Kelmar supply. Have yet to have one fail since they first appeared close to ten years ago. On first generation scanners if you have to go beyond just the supply you might as well just replace the whole dam thing.... lens, led, and supply and you're already 95% of the way there Mark  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 03-08-2006 06:15 PM                     Maybe it's just me but 2 years out of the LED doesnt sound right. I have easily gotten 5 years from all the units from Componenet while maintaining proper levels from both the LED and Preamps.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 03-08-2006 06:24 PM                     If the power supply switches on and off then more like 7 is common. The BACP if switched should last even longer than that. Mark  |  IP: Logged

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