Re: [DIYbio] Help Fix an Invitrogen Blue Light Transilluminator

On Wednesday, August 10, 2016 at 7:49:10 PM UTC-7, wrote:
I have identified the problem :)

I poked around and didn't find any components that were improperly soldered.  All the connections looked good.  So I pulled out my multimeter and found that there was no continuity across the fuse.  When I bypass the fuse with a wire the device works great.

Unfortunately it's a surface mount fuse with nothing identifying the current rating.
It connects directly to the +24V DC input.  Is there any way to identify the current rating for the fuse without talking to the manufacturer?

Marking might be on the bottom of the component. Remove it since it's no good anyway and flip it over.
Fuses dont blow by their own. Maybe someone in the past connected up a wrong power supply to it. Otherwise maybe it was liquid spill caused it to blow so double check that ie might be good to wash the board with iso.   Check any nearby cap's to see they dont have any visible damage.  Check nearby diode, there will be a reverse polarity protection diode in there somewhere near the connector, if someone connected a wrong supply with backwards polarity, that diode might have shorted and then caused the fuse to blow, so, replace it too (very common 1n4001 will do but make sure to connect it in as reversed in circuit).

I agree it is easy to rate the fuse based on the power supply connector or power supply rating.  Take that number convert it to amps and round up to the nearest fuse and/or add 30% to round up.  It is not super critical because it is only lighting LED's with 24v probably 2A switching supply limited so probably an automotive fuse holder + common automotive fuse would do.   You could also probably replace it with 24v lamp bulb if you wanted but that wouldnt fit in the case and it would get warm (it would be a nice hack, very retro looking).

To avoid the "oops connected wrong power supply" since you have it apart already, consider removing the power supply connector, putting on your own water resistant molex connector, and putting the matching connector on the power supply, so, some random power supply that only fits the jack while being the wrong rating or wrong polarity, isnt accidentally connected.   If that seems like too much trouble then at least get happy with the label maker, label the connector and the plug on the power supply and the supply itself etc, it is pretty much "all incoming equip gets the label maker treatment no matter what" in my labs.

## Jonathan Cline
## Mobile: +1-805-617-0223

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