FSL 8w EOL on HF Matchbox - Cathodes Melts

[Oliver]

The FSL tube reached EOL. The cathode melted down.


https://www.youtube.com/watch?v=5nA51zX ... e=youtu.be

[Oliver]

This is what the ballast looks like. Quite impressed with it and it's done some good burnouts.

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[Danny]

Damn! Mine dont do that to them

[Oliver]

It's great for finishing off tubes. This FSL never worked again after that. These HF matchbox ballasts seem quite good. Mine continues to work perfectly even after all the abuse - loads of EOL tubes and I used to have it 15 min on 15 min off, for a test I did once.

[dor123]

Hey!
I think that the Philips HF Matchbox, is just a CFL like ballast with an electrode fusing mechanism, so when the lamp reaches EOL, the ballast overloading the bad electrode to fuse it, and have a circuit that opens when the electrodes blowing up, rendering the lamp non-working.

[FrontSideBus]

Matchbox Blue is just basic instant start. The Matchbox Red has all the fancy toys like warm start ect.

[BC5-80]

I'm surprised the EOL protection didn't kick in before it reached vacuum loss. I've had four Matchbox blue ballasts in daily use for years (3 x 13W T5 and 1 x 15W T8). They've gone through countless tubes and all have been shut down at EOL still with their cathodes intact.
I have a theory. The protection is activated by lamp rectification causing a DC offset in the load current. If the lamp is cheap with thin lead-in wires and surrounding structure that can sustain electron emission at orange heat without excessive rectification, vacuum loss will be the result without activating the protection. I saw it about to happen recently with a cheap 15W tube at EOL on 50Hz choke when the lead-in wire suddenly glowed bright orange. It was hardly flickering at the time. I switched it off just before vacuum loss and the bright orange glow slowly died down. A better quality lamp is not able to sustain electron emission from the cathode structure at normal operating current and voltage, probably because it's too substantial / thermal mass too high so can't get hot enough to incandesce / made from better materials. (That's my theory and I'm sticking to it. )

[dor123]

The electrode fusing is the ballast EOL protection here.

[Oliver]

The HF Matchbox blue is instant start and the EOL protection is similar to a CFL where it will cut out when the cathode blows. With the cathodes shorted, it will run most EOL tubes and often give quite impressive EOLs.

Considering the amount use mine gets (and abuse) it's been reliable.

[dor123]

You meaning: When only one wire connected to each end of the lamp, it will run most EOL lamps to vacuum loss?