Film-Tech Forum ARCHIVE: Diode Change

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Topic: Diode Change

Dennis Burns
Film Handler

Posts: 2
From: Midland, TX, USA
Registered: Jul 2002

posted 08-16-2002 10:44 PM

But then again i am a Christie over loaded engineer...

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Manny Knowles
"What are these things and WHY are they BLUE???"

Posts: 4247
From: Bloomington, IN, USA
Registered: Feb 2002

posted 08-17-2002 12:00 AM

Welcome, Dennis!

I can sense that Brad wants somebody to tell you that you can edit any of your posts by clicking on the "edit" button above them. You don't have to post again just to add something that you left out.

True about getting a spark with a bad diode...but what happens if you've got a diode that's the wrong type? Either wrong voltage (amperage?) or polarity?

~Manny (squeeze your way to shapely hips & thighs.)

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Steve Kraus
Film God

Posts: 4094
From: Chicago, IL, USA
Registered: May 2000

posted 08-17-2002 07:35 AM

Wrong voltage (PIV): Depends "how" wrong. Either immediate failure or failure at some future point probably in response to a voltage spike.

Wrong polarity: Short circuit upon application of power.

Or, if we take this to the limit and have them all be exactly backwards (2 one way, 2 the other) you would have reverse polarity output of the rectifier and explode the electrolytic capacitors. And major damage to the xenon bulb if it managed to ignite.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 08-17-2002 09:50 AM

Denis since it doesn't try to strike it is more of an indication of a problem with the noload voltage.
Cinemecanica consoles have two different styles of ignitors one is a long open assembly usually mounted along the non operating side
The newer ones have a Irem ignitor in the reflector plenum box with a Brass rod comming forward for the lamp to connect to

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Antonio Marcheselli
Phenomenal Film Handler

Posts: 1260
From: Florence, Italy
Registered: Mar 2000

posted 08-17-2002 10:37 AM

I found it!

I connected the probes to the rectifier output and I wasn' able to measure anything (just few AC current). So I decided to check again the diode array.

One diode support (lead side) didn't have the cork insulating. This is causing the array's chassis to be electrically connected with the diode's output (lead) and so (correct me if I'm wrong) feed AC power to the lamp.
The great thing is that I didn't touch that support! So the cork insulating was not there before! I've just thightened it (removing the thin layer of paint that has insulated it during these years)...

I've keept on the rectifier in this configuration only few seconds for each test. Can something be damaged?

Bye
Antonio

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 08-21-2002 09:54 PM

If the lamp didn't light and the filter cap didn't go bang all should be fine
Is it working satisfactorly now?

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Antonio Marcheselli
Phenomenal Film Handler

Posts: 1260
From: Florence, Italy
Registered: Mar 2000

posted 08-22-2002 03:54 AM

Gordon,

Yes, it works perfectly now! I can't explain myself how can has worked since now without that thing...

Thanks to all for the help!
Antonio

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Jean-Michel Grin
Expert Film Handler

Posts: 222
From: Geneva & Lausanne, Switzerland
Registered: Jul 2002

posted 08-22-2002 05:27 AM

Congratulations !

------------------
Jean-Michel Grin - Europlex Cinemas (Switzerland)

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Manny Knowles
"What are these things and WHY are they BLUE???"

Posts: 4247
From: Bloomington, IN, USA
Registered: Feb 2002

posted 08-22-2002 06:57 AM

Antonio:

I have a projector that had a random jumper wire in place and it worked for three years and then -- nothing. It took a short while to isolate the area where the problem existed and then when we came across that wire it was hard to believe that it ever could have worked. Sure enough, removing that jumper solved the problem.

Like yourself, I have no idea how it ever worked in the first place.

~Manny (a taste of the islands.)

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 08-22-2002 07:38 AM

Antonio,
Heatsinks are not painted, but anodized black, clear, gold,or what ever color, This is very common, Anodizing is a very good insulator itself if thick enough, just the anodizing itself probably afforded you the insulation for that duration till you tightened it up and pricked through it.
Mark

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