This is topic 701 readers in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Steve Anderson (Member # 364) on 08-11-2000, 09:33 AM:
I have quite a few 701 readers I am going to look at tonight.Nearly all are reading 8 or flat line. I checked the optical focus with the scope and it seemed within specs but when I went to adjust the voltage of the led and it was maxed out. Any tips?
Posted by Gordon McLeod (Member # 33) on 08-11-2000, 09:35 AM:
What was the amplitued of the video you may be overdriving it
Also check for jitter on the damper
Posted by Rory Burke (Member # 512) on 08-11-2000, 11:33 AM:
Check LED voltage readings and if I recall properly unlike the CAT 700, the Cat 701 has the led piece glued on to the reader itself. In many cases just with moving the Led bracket slightly it corrects itself. about 50% of the time i find problems with these readers that it ends up being that Glued on piece. YUK!
RORY
Posted by John T. Mellor (Member # 468) on 08-12-2000, 11:57 AM:
If the 701 isnot reading and the voltage is maxed out , sorry but you need to replace the led . When you install the new one set the voltage to 4 volts realign and refocus the LED and lens . make sure you use a good test film when you set the 701 , if not your results will not be as good as you would like . I've replaced about 30 of them and they will degrade in 1 to 2 years
Posted by Gordon McLeod (Member # 33) on 08-12-2000, 01:51 PM:
Most of the cases where the LED has been blamed have really been bad alignment
Often the Led creates an uneven top to the video amplitude. It takes patience to get a flat top line of the open perf vompared to peak performance. Practice makes perfect. A led that was new will get by missaligned better than when it gets older and marginal
Posted by Steve Anderson (Member # 364) on 08-12-2000, 04:52 PM:
I worked on 8 readers last night. I found that most of them were runing around 2.5 to 3V. I also noticed the jagged top line that Gordon pointed out. After bringing up the voltage and setting the focus I had 5 readers hitting about 4 on the readout. Gordon it sure is difficult to get that top line flat. Any suggestions on slowly moving the led head for adjustment? I also found that the LED voltage cable in the unit was not secure and rubbing against the flywheel!
Another one had the tension spring on the damper unhooked. Is there another manual that has a break down of these parts? I have only the instllation manual which tells me nothing. Thanks for everyones help!
Posted by timothy johnson (Member # 83) on 08-13-2000, 11:44 AM:
I have a question, I have a CAT 701 in my home screening room, and I got it brand new, and since I use it only 4 hours a week, can I assume it will last me for a good five years without replacing the LED ?
Posted by Gordon McLeod (Member # 33) on 08-13-2000, 02:08 PM:
should last longer than that
Posted by Ken Jacquart (Member # 369) on 08-13-2000, 08:45 PM:
Steve, When you adjust the 701's led assembly (loosen the 2 screws on the head and it will pivot ever so slightly...)adjust the upper perf trace for minimum sawtooth pattern on the scope. You won't get it perfect because you are literally seeing the droop in video amplitude between each LED segment. The LED array inside the capsule is 12 x 2... that is 2 rows of 12 (one above the other). As Gordon indicated, with patience you can get it pretty smooth. By the way, if you need a new LED assembly for the 701 reader, the Dolby part number is 83308. Also, we finally have a mechanical drawing which includes many part numbers for the 701 reader! I'll try to get a .pdf of it and get it to Brad to post in the manuals section.ken
Posted by Mark Gulbrandsen (Member # 72) on 08-15-2000, 09:35 PM:
One thing I'm wondering about is how many of you are switching the LED on and off in between shows, or are you leaving it on all the time???
Had an interesting phone conversation tonight woth another Film-Tech techie about the red led's. We're wondering if frosting the face of the led slightly and difusing the light output would make it a bit easier to set up??? This might make it more like the Cat 700 light source which was a whole lot more forgiving to set up and was very easy to get looking reel good by a slight coaxing of the light pipe.
Mark
Posted by Bill Purdy (Member # 202) on 08-16-2000, 10:12 AM:
NO! Don't try to frost the LED. It will cost you a whole lot of light and you may not be able to drive them hard enough and you sure will greatly limit their life because of the additional current. Remember that the performance of the LEDs is highly dependent upon their inner temperature. The lower the current the cooler and therefore the longer their life, so don't do anything to cause them to be operated at a higher current.------------------
Bill Purdy
Component Engineering
Posted by John Pytlak (Member # 331) on 08-16-2000, 10:18 AM:
I agree with Bill that "frosting" the lenslet surface of the LED will significantly reduce light output, and raising current to compensate will greatly reduce life expectancy. "Frosting" will also diffuse the light, and probably reduce the ability to sharply focus on the CCD.------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com