Film-Tech Forum ARCHIVE: Correct zener diode to use in auto ignitor?

This is topic Correct zener diode to use in auto ignitor? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Brad Allen (Member # 470) on 05-31-2008, 12:33 PM:

Just replaced a Kneisley rectifier with a Xetron (IREM).
Now the lamp auto ignitor in the lamphouse won't fire.
I'm sure what I need is to put in a lower voltage zener diode on the autostart board.
What would be the proper one?
No load voltage measure's 78.5 volts from the rectifier.
Thanks.

Posted by Sean McKinnon (Member # 612) on 05-31-2008, 02:07 PM:

I would go with one around 65-75 Volts DC. The important thing is that you have a value low enough to allow the autostrike to activate with an IREM but not so low that you have trouble lighting the lamp due to inadequate open circuit (no load) voltage.

Posted by Dave Macaulay (Member # 813) on 05-31-2008, 03:14 PM:

It depends on the lamphouse. Usually you want the open circuit to measure about 25 to 30 volts above the zener voltage. So somewhere around a 50V zener would be a good first try.

Posted by Louis Bornwasser (Member # 3063) on 05-31-2008, 08:30 PM:

Brad: use the same value as your other, identical, set up. Louis

Posted by Gordon McLeod (Member # 33) on 05-31-2008, 08:33 PM:

The zenier you use must relate to the voltage rating of the relay as well

Posted by John Walsh (Member # 168) on 05-31-2008, 09:46 PM:

I agree with Dave; 48Vdc is my suggestion.

Posted by Mark Gulbrandsen (Member # 72) on 06-01-2008, 10:28 AM:

I've always used 48 volt with older Irem's. Newer Irems have much higher no-load dc and you will require a higher voltage zener for those...around 60 volts give or take a few volts. Be sure to a zener rated at 5 watts!!!

Mark

Posted by Brad Allen (Member # 470) on 06-01-2008, 07:49 PM:

quote: Louis Bornwasser
Brad: use the same value as your other, identical, set up. Louis

I would, but I don't recall what diode I used and I can no longer read the numbers on that diode. UV is dastardly.

I do recall it took some trial and error to get the right one the last time.

Thanks for the replys.