[pure-silver] Re: ELC bulbs failing in D2 Dichro Head
- From: "J Stewart" <jrstewart8@xxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Wed, 16 Jan 2008 20:31:04 -0500
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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