Need fuse current value for Metrologic ML-868 laser...

[The_LED_Museum]

The fuse in my Metrologic ML-868 helium neon laser blew, and I can't really read the rating on it.
The replacements I obtained were 750mA fast-blow, and they "go" within 50-100mS. I'm not certain these are the correct rating, or if the laser is blown and I'm SOL.

Does anybody know the correct fuse value for this laser?

 

[The_LED_Museum]

I just sent an email to Metrologic with the following content:

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Hi,

I have a Metrologic ML-868 Neon Laser that I purchased on the used market several months ago.
I have it on my website at http://ledmuseum.candlepower.us/eighth/ml868.htm

Yesterday, the HV section of another HeNe PSU arced on the Metrologic laser's case, and the fuse on the ML-868 laser blew.

What is the fuse value for the ML-868?
I was not able to read the value of the blown fuse, which is why I'm asking.
The replacement fuses I got this morning are rated at 750mA "fast acting", but they blow almost immediately.

Thank you, and have a fantastic week - or what's left of it anyway. 🙂
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[PhotonWrangler]

Craig, if you think that the Metrologic's power supply might have been damaged from that arc, one way to find out is to put in a bigger fuse and look for smoke. If it works and none of the magic smoke escapes, you just need a bigger and/or slo-blo fuse. if it smokes, you can stop looking for fuses for the moment.

 

[The_LED_Museum]

The arc was to the outer case; one would have "thunk" that the charge would have been dissipated to ground (the laser has a 3-prong grounded plug). That's why I don't understand this.
The next opportunity that I'll have to obtain more fuses will be tomorrow afternoon (~3:00pm PDT); I'll give your suggestion a try and see what happens. :twothumbs

 

[Handlobraesing]

What does the blown fuse look like? If you it's simply melted, it could be from secondary side short or using too small of a fuse.

If the glass turned dark grey/black, it's a dead short in primary side components.

 

[The_LED_Museum]

The fuse looks like the element inside fried pretty quickly; however there is no noticeable deposition/burns on the glass barrel. So it looks like an overload, rather than a direct short in any of the primary components.

 

[Rubycon]

Try putting a light bulb in series with the laser. A 40W incandescent lamp should work. This will help to prevent excessive damage should a major overcurrent situation develop.

 

[The_LED_Museum]

I'd need a special jig to do that...the laser's power cord is terminated in a standard three-prong male grounded plug, and I do not have any receptacles that can be wired up in that fashion (to put a load of any type in series with it). :shakehead

 

[The_LED_Museum]

I heard from Metrologic a short time ago today, and the 750mA fast-blow fuses I tried were indeed the correct ones. It could be a relatively inexpensive fix - but I'll know more when I obtain an RMA # and send them the laser.

 

[Kenom]

Crap. too bad it wasn't just the wrong fuse. Sorry for yur news

 

[The_LED_Museum]

If the repair is inexpensive, I'll spring for it.
But if not, the cute and loveable little laser will be a total loss. :shakehead