Help identify a component

: :I'm trying to repair an optical encoder from a machine and have :trouble identifying a component. It's two leads, surface mount, :rectangular and as tall as it is wide, and about twice as long. The :length is about the same as a 1/2 watt resistor. : It looks like a plastic case, but isn't, breaking it open shows it's :semiconductor material. I suspect it's a diode. One end was burned :enough to make it hard to see any polarity indicator, but it could :have been there. I was barely able to read the numbers on it: : :A 475V : P3503 : :Unfortunately, none of that seems to cross reference with anything :I've found so far witn NEC, ECG, etc., or even googling the numbers. : :I would appreciate any assistance. If anyone knows what this device :is, with enough specs to make a substitution, I would appreciate it. :The email addy is valid without the ".nospam.invalid" and or I'll :check beck here. : :Thanks

A pic on alt.binaries.schematics.electronic is worth a thousand words.....

Location in the circuit? Length and width in real units?

Not a plastic case - what material is the case or is there only a coating.

Colour.

Are there 'leads' formed for smd or are the ends metalized for surface reflow - shape and extent of either?

Semiconductor material??? Describe it.

Very little of the actual contents of a diode package is actually semiconductor - a small wafer usually dwarfed by the soldering interface and metal lead-out. The same is ~ true of polymer ptc's.

Varistors and some thermistors will be a solid crystaline structure with the consistency of pencil lead-graphite.

The part burnt or solder junction burnt? Burning extends into body or just on surface?

RL