"Sammy" wrote in message
...
I have a 12v halogen dimmer light - a 'mother and child'
uplighter (240v). The diac is faulty. I don't need to have
the dimmer function working.
It would be ok if I could just have it at full brightness
all the time. Could I substitute 2 diodes in parallel, one
in either direction, to achieve full
brightness?. Any particular diodes?. == Sammy ==



Diac? Are you sure it's a diac you mean? Can you describe the circuit and
the component in question, and how you tested it? The answer is no, if the
diac is faulty it should be replaced with a diac, it's not as simple as two
standard diodes back to back.

I've repaired stacks of dimmers and rarely had to change a diac. They tend
to fail only when the triac they drive shorts out, which often results in
other burnt out components.

Where is the 12V derived from? Does it come from an isolating 240V-12V
transformer then go through the dimmer? If so then *theoretically* you'd
just wire the 12V straight to the bulb bypassing the dimmer circuit, no
faffing with diodes is necessary. If the dimmer is on the mains side then
bypass the dimmer and take mains straight to the transformer primary.

However, without knowing exactly what you have I couldn't recommend the
above procedures as they may raise important safety issues.

If the 12V is derived by dropping 240V to 12V by a triac chopper (not likely
legal in the EU) then it's strongly recommended you get it professionally
repaired or bin it.

I've seen halogen lights with 'electronic transformers', which are
switchmode power supplies designed to be dimmed. I wouldn't recommend
delving inside these as they provide isolation from the mains as well as
240v-12v conversion and can't just be bypassed.

Morse