[pure-silver] Re: ELC bulbs failing in D2 Dichro Head

I'd check the sockets. My ELC were burning out fast although not quite right
away, and I replaced the sockets and the problem went away. A crack socket
will allow the juice to flow in unintended paths. POP!

Eric 

Eric Neilsen Photography
4101 Commerce Street
Suite 9
Dallas, TX 75226
http://e.neilsen.home.att.net
http://ericneilsenphotography.com
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> -----Original Message-----
> From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver-
> bounce@xxxxxxxxxxxxx] On Behalf Of J Stewart
> Sent: Wednesday, January 16, 2008 7:31 PM
> To: pure-silver@xxxxxxxxxxxxx
> Subject: [pure-silver] Re: ELC bulbs failing in D2 Dichro Head
> 
> Thanks, All.
> I checked the voltage at the lamp socket. It read 26 VAC and 8 VDC = 34
> total. Is this enough to blow the bulbs as described?
> 
> My power source (Super Chromega Dichroic Lamphouse Cat. No. 412-021) does
> not appear to have a triac. I.e., all wires are connected either to plugs
> (i.e. to timer, to source, to stabilizer)or to/from the transformer coils
> and various voltage connectors: this supply has voltage connectors labeled
> 117V 110V 100V and others for a total of 8 pairs of connectors. All
> connections "look" sound. No wires are going to anything that looks like a
> triac examples sent by Nicholas.
> 
> My stabilizer (Solid State Voltage Stabilizer CAT NO 404-841)- all
> connections look sound. There is one 3-way connector not labeled that
> could
> be a triac I guess.. In no case is the resistance between any two of the
> terminals greater than 22 ohms.
> 
> Does this sound like the triac (or some equivalent circuit)has failed? If
> I
> replaced something, would it be the power supply unit or the stabilizer or
> both?
> 
> Again, thank you very much everyone.
> 
> Jim
> 
> 
> 
> -----Original Message-----
> From: pure-silver-bounce@xxxxxxxxxxxxx
> [mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Nicholas O. Lindan
> Sent: Wednesday, January 16, 2008 11:57 AM
> To: pure-silver@xxxxxxxxxxxxx
> Subject: [pure-silver] Re: ELC bulbs failing in D2 Dichro Head
> 
> From: "J Stewart" <jrstewart8@xxxxxxxxxxx>
> 
> > Folks, can anyone help me troubleshoot reasons why my lamps are
> > blowing out within a few seconds of turning on my Dichro II color head
> > (on a D2).
> 
> The power supply is busted.  Most likely the triac regulator.  I am
> guessing
> how the supply works by extrapolation from other vendor's supplies, so
> take
> this with a grain of salt as it may be quite wrong.
> 
> ELCs are 250W 24V bulbs, running at about 10A.  The voltage is converted
> to
> 24V by a transformer in the power supply.
> 
> If the power supply is regulated then odds are it uses a triac (a sort of
> transistor-like thingy) to do the regulation with the transformer
> producing
> 28 volts or so.  The system is sort of an inside-out lamp dimmer:
> it keeps the lamp from dimming by always keeping it slightly dim.  It
> adjusts itself if the AC power fluctuates so the dimness/light output
> stays
> the same and the lamp always sees the 24V it wants.
> 
> When a lamp fails naturally it produces an arc for a fraction of a second
> -
> the bright flash and pop when a bulb goes.  The arc is pretty much a dead
> short-circuit and the current spike from the short circuit destroys the
> triac, leaving the fuse that is supposed to protect the triac intact.
> 
> This is the common failure mode of household lamp dimmers.
> 
> Triacs short-out when they fail.  For a lamp dimmer this means the lamp is
> always at full brightness.  For your power supply this means the lamp is
> not
> dimmed and is driven with 28V instead of 24V.  The higher makes the lamp
> burn brighter for a short period and then fail.
> 
> If it is only the triac that has failed then it is fixable and replacement
> triacs are generally available - Radio Shack even.
> 
> ==
> Nicholas O. Lindan
> Cleveland Engineering Design, LLC
> Cleveland, Ohio 44121
> 
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