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Author Topic: CE LS-40 LED issue Tom Wienholt Master Film Handler Posts: 371 From: Towson, MD, USA Registered: Dec 2002 posted 06-28-2015 01:19 PM                     I am having trouble achieving dolby tone. I have boosted the pre-amp gain controls of my CP65 and the gain control on the LS-40 power supply all the way up. Aside from replacing the LED itself, is there any other way of boosting the gain? Thanks!  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 06-28-2015 05:48 PM                       I believe I answered this question. Look on the PC board of the reader and there should be gain jumpers either soldered in or with links, one for left and another for right. They were mandated by Dolby Labs. If you can't find them call Component Engineering in Seattle. They will know exactly where they are located.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-28-2015 06:14 PM                     For the 40 system...the locations are there but no wires were ever put in.  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 06-28-2015 09:12 PM                     EDITED to add: Apologies to Sam, I did not see the previous thread where he pointed out the LED bracket alignment... Tom, the most important first step is to make sure the LED is physically adjusted to the distance from the film AND most critically, the vertical alignment must be spot-on. Depending on the soundhead involved (Simplex, Century, RCA and Christie all come to mind), you need to loosen the screw(s) supporting the LED bracket slightly, and while running your Dolby tone loop, SLOWLY work the LED bracket up and down (being careful to NOT allow the LED itself to touch the film) till you get maximum output. After you get max output, turn the gain controls in the processor to get Dolby Level. You will find there is a "sweet spot" (and it's a VERY narrow one) where you will get enough output to overdrive the processor. Even a slight misalignment will drop the gain a lot or give you no output at all. (I got tripped up by this on a service call once...thought I had a dead reader but in reality in the heat of the moment I neglected to check the LED alignment...which was the real problem. I ended up with a brand new at my expense Kelmar reader and LED set for my spares. )  |  IP: Logged

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