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Author Topic: Installing Kelmar AT-1200 reverse scan Tom Wienholt Master Film Handler Posts: 371 From: Towson, MD, USA Registered: Dec 2002 posted 09-29-2003 07:41 PM                     When installing a Kelmar AT-1200 reverse scan reader, can the existing exciter power supply be used as a power source or is it necessary to use a different power supply? Any help would be appreciated.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 09-29-2003 09:35 PM                     The Kelmar scanners are fine scanners and my 2nd choice for reverse scanners. All of them that I've installed had a seperate powersupply. There is the LED supply, and then plus and minus DC voltage for the preamp thats mounted on the pickup. I'm not aware of any other version of the Kelmar scanners than this. The BACP scanners can be powered by the old exciter supply if desired, whoever many of them are getting old and may give problems in the not too distant future. I usually opt for the wall wart that comes with it. The BACP scanners are available through Ultra Stereo Labs dealers. A quick call to Kelmar in the morning should answer your question. Ask for Thomas. Mark @ CLACO  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 09-29-2003 10:21 PM                     Why would one want to use the old supply The LED is a current source and needs current limiting and the preamp is bipolar in effect  |  IP: Logged Tom Wienholt Master Film Handler Posts: 371 From: Towson, MD, USA Registered: Dec 2002 posted 09-30-2003 03:01 PM                     On the installation drawings, it shows that an exciter supply should be hooked up to the power module which then distributes power to the preamp and the LED. Am i missing something?  |  IP: Logged Matt Zeiner Expert Film Handler Posts: 146 From: Windsor, CT USA Registered: Sep 2003 posted 09-30-2003 03:09 PM                     Not if the unit you are installing has the letters "DCPM" after the model number - That unit uses the existing supply with a box containing 2 add-on switchers - one for the LED and one for the bi-polar supply for the preamp. They work great as long as you are not using a USL exciter supply - The Kelmar switchers will not function unless they see at least 10 volts, and the USLs are limited to 8V. Changing R3 in the USL exciter supply to 3.9k will allow you to get the necessary 10V out of it.  |  IP: Logged Tom Wienholt Master Film Handler Posts: 371 From: Towson, MD, USA Registered: Dec 2002 posted 09-30-2003 08:08 PM                     So now im being told that the existing exciter supply is used for installation.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 09-30-2003 10:01 PM                     I checked and Kelmar now does supply an invertor PCB so one can power the sanner fomr an existing exciter supply. One would assume this is in response to the BACP design of being able to run the scanner off of just about anything except a can of beer. C.E has yet to take this approach...thankfully. On the BACP one has to be very careful of the no-load DC level as if its over 14 volts it'll blow the preamp/inverter card out instantly. Why anyone would want to power a modern device like this off of a sooner or later to fail DC power supply I'll never understand. Using a wall wort not only eliminates a very unreliable and possibly old power supply from the chain, but it also makes repairs easier and safer to perform. Mark @ CLACO  |  IP: Logged Tom Wienholt Master Film Handler Posts: 371 From: Towson, MD, USA Registered: Dec 2002 posted 09-30-2003 10:15 PM                     quote: Using a wall wort not only eliminates a very unreliable and possibly old power supply from the chain, but it also makes repairs easier and safer to perform. What is a wall wort?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 09-30-2003 10:34 PM                     Its one of those little square plug in the wall transformers. Its also an easy way to UL listing if ya get a good one. Mark  |  IP: Logged Tom Wienholt Master Film Handler Posts: 371 From: Towson, MD, USA Registered: Dec 2002 posted 09-30-2003 10:38 PM                     Where do you buy these plug-in transformers and what type is needed?  |  IP: Logged Matt Zeiner Expert Film Handler Posts: 146 From: Windsor, CT USA Registered: Sep 2003 posted 10-01-2003 07:38 AM                     I've used Radio Shack's units in the past when the customer's existing supply is garbage - they sell a 12V 1A wall wort that will work fine. The DCPM units don't really care what you feed into them as long as you provide at least 10VDC. As for the use of existing exciter suppiles in general, I don't really see the problem here unless the customer has some REALLY old kneisley or something. The Kelmar supplies fron the AS-7200 series units are extremely reliable and common - there is really nothing in them that can go. As a matter of course we change out the 3055 transistor and capacitors before installation of the reverse scan - costs about the same as the wall wort, and will still provide AC backup power (yes - the DCPM does work nicely on AC backup) so if the wall wort goes, the whole thing has to be replaced. If you use an existing supply, at least you have backup in case of failure. The simplicity of installation can't be beat - your exciter switching is alredy in place. Also - a lot of our customers have the newer USL Supplies built into their monitors/processors - although they require slight modification, they are pretty robust units and good for 50W dissipation.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 10-01-2003 08:23 AM                     I once had ALOT of problem with Kelmar Exciter supplies. That was when the new switching version first came out though. Personally in my experience its far better to keep things simple, thats why I prefer the wall wort. Mark  |  IP: Logged Tom Wienholt Master Film Handler Posts: 371 From: Towson, MD, USA Registered: Dec 2002 posted 10-01-2003 09:50 AM                     Thanks for your help.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 10-12-2003 11:03 PM                     I'm not a big fan of wall-warts and don't plan to start using them! The Kelmar converter unit will work off of AC or DC so even if your old supply craps out in DC mode...AC-emergency should still keep you going. I also have a thing against DC-DC converters so I'd rather use a nice well-designed power supply...like the CE 30 or 40 series units. Steve  |  IP: Logged Matt Zeiner Expert Film Handler Posts: 146 From: Windsor, CT USA Registered: Sep 2003 posted 10-13-2003 03:08 PM                     I hear ya, Steve - I just don't trust those inverter circuits. For the most part, they seem to work reasonably reliably... Are you certain that the CE supplies don't use switchers? I think they do, but could be wrong.  |  IP: Logged

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