Film-Tech Forum ARCHIVE: Getting the most out of your RED LED.

This is topic Getting the most out of your RED LED. in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Ian Bailey (Member # 1752) on 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

Posted by Brad Miller (Member # 2) on 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.

Posted by Sam D. Chavez (Member # 1841) on 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.

Posted by Dave Macaulay (Member # 813) on 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.

Posted by Monte L Fullmer (Member # 2797) on 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

Posted by Scott Norwood (Member # 30) on 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?

Posted by Ian Bailey (Member # 1752) on 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

Posted by Pete Naples (Member # 761) on 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.

Posted by Louis Bornwasser (Member # 3063) on 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

Posted by Sam D. Chavez (Member # 1841) on 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.

Posted by Mark Gulbrandsen (Member # 72) on 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

Posted by Louis Bornwasser (Member # 3063) on 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

Posted by Mark Gulbrandsen (Member # 72) on 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

Posted by Richard May (Member # 2627) on 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. [Confused]

Posted by Mark Gulbrandsen (Member # 72) on 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

Posted by Brad Miller (Member # 2) on 03-08-2006, 07:38 PM:

quote: Mark Gulbrandsen
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.

Aside from the method I recommended? I gave two. Go 9 posts up above yours. [Razz]

Posted by Ian Bailey (Member # 1752) on 03-08-2006, 09:52 PM:

Ok I can see where I'm getting confused here!
When I said I had Component Engineering readers the assumption was made that I had C.E. power supplies.That is not the case.
the power supplies I have connected to my readers are:
Brand Name PROTEK
Model PX53-31-9A
Input 240 volt A.C. @ 0.8 amps
Output +5volt D.C. @ 6 amps
+12 volt D.C. @ 2 amps
-12 volt D.C. @ 0.5 amps
Looks awfully much like a power supply for a P.C. to me!!
There is no current adjustment and I think there is a dropping resistor in series with the LED.
Is this my problem why my LEDS don't last and I never have much headroom adjustment for setting Dolby levels at the processor?
If so would it solve my problems getting CE power supplies?
Do I have any other options regarding power supplies?
THX
Ian

Posted by Mark Gulbrandsen (Member # 72) on 03-08-2006, 10:01 PM:

quote: Brad Miller
Aside from the method I recommended? I gave two. Go 9 posts up above yours.

I did see your post but no where in it did I see that you mention it can add 3 years of longevity to the LED. Do the math... it does.
Mark

Posted by Robert Burtcher (Member # 3227) on 03-08-2006, 11:12 PM:

Just what kind of LEDs do these things use? For the price you guys are saying, it sounds like a Luxeon 5 Emitter on steroids or something.

[ 03-09-2006, 04:09 PM: Message edited by: Robert Burtcher ]

Posted by Brad Miller (Member # 2) on 03-09-2006, 01:02 AM:

I figured the math would've been obvious by turning it off when the projector was not running, but then again perhaps not.

Posted by Sam D. Chavez (Member # 1841) on 03-09-2006, 10:35 AM:

Ian,

It is possible you have a copy or knockoff of the CE reader. Such were made by a Don Howard from your country with some help from Ray Derrick. This might explain why you have readers with no power supply. One way to tell is to see if the ring or fixture that holds the LED is made of copper or aluminum. CE's were made of Copper which is very diicult to machine.

The CE LS-40 power supply is a good general purpose supply for this application.

Posted by Ian Bailey (Member # 1752) on 03-10-2006, 01:53 AM:

Hi Sam
No it's not one of Don's readers and yes it is a CE reader with the fixture that holds the led being copper.Just not a CE power supply.
Any idea what a CE LS-40 power supply costs?
And are there any alternatives?
ian

Posted by Mark Gulbrandsen (Member # 72) on 03-10-2006, 08:25 AM:

quote: Ian Bailey
Any idea what a CE LS-40 power supply costs?
And are there any alternatives?

Well under 100.00 U.S. unless a dealer is ripping you off. Uoi could also build one or have a local electronics guru build one for you. They're very simple.

MArk

Posted by Mark Gulbrandsen (Member # 72) on 03-10-2006, 08:25 AM:

quote: Ian Bailey
Any idea what a CE LS-40 power supply costs?
And are there any alternatives?

Well under 100.00 U.S. unless a dealer is ripping you off. You could also build one or have a local electronics guru build one for you. They're very simple.

MArk

Posted by Sam D. Chavez (Member # 1841) on 03-10-2006, 10:40 AM:

I would go with the LS-40 as it works perfectly for this application and has a built in shutoff for the LED current.

Even I, as a competing company to CE uses them for specific applictions.