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Laser Power Supply

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scrat:

--- Quote from: tecman on April 28, 2011, 02:59:15 pm ---
--- Quote from: scrat on April 27, 2011, 02:18:25 pm ---Is there anyone that can be almost sure about those resistors not being real resistors? They are marked as resistors, so why should they be something else?
IMHO, this seems like a bad patch (not even a little plastic/rubber packing) on a power supply not requiring high efficiency, so could be resistors.
Anyway, since now it doesn't work, I'd try with resistors of the same size, I doubt it would break anything.

--- End quote ---

Usually you can not tell by looking.  For example:  http://www.tokenonline.net/resistor/fusible-resistor.htm

They are in more things than you might think.

paul


--- End quote ---

Interesting... Somewhere it appears like fusible havea fifth white stripe, while here http://www.epanorama.net/documents/markings/resistor_colorcodes.html] [url]http://www.epanorama.net/documents/markings/resistor_colorcodes.html[/url ] they say all white or blue resistors are flame resistant or fusible.

Is it white the color in the posted pic? Light it quite weak there...

mechelec:

--- Quote ---Interesting... Somewhere it appears like fusible havea fifth white stripe, while here http://www.epanorama.net/documents/markings/resistor_colorcodes.html] they say all white or blue resistors are flame resistant or fusible.
--- End quote ---

No, the resistors are a grey colour.

However as paul mentions you can't tell by looking, and I'd hazard that the colour is arbitrary as well.

This application note gives a good overview of the use of fusible resistors and as far as I can tell the resistor bodies are grey.

http://www.welwyn-tt.co.uk/pdf/application_notes/EMC2_AN_A.pdf

I guess I will try and get hold of a fusible resistor and replace it with that.

But I still can't figure out why they would have fusible resistors on both the active and neutral side.

Surely if the idea is to limit the inrush current you would just use a 22R on the active side.

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