Symptoms of Dying tube?

[jeaves]

I have a 40-watt CO2 hobby laser that I bought new at the end of October from FSLaser. I used it heavily for about 2 months, but since then have hardly used it. Yesterday, I noticed that it would not cut through 1/8" poplar ply, (which it usually cuts) and the engraving was really light and inconsistent. I checked the alignment and cleaned the mirrors and lens, but no improvement.
I have tested the beam all around the table, and have noticed that it starts out strong, but then loses its power within 5 seconds. If it sits for a few minutes, it regains its power, but then it dissipates again (like a dying cordless drill). I am trying to figure out if I have a bad tube or a bad power supply, before I spend any money on parts. The laser company tech says that it's odd for such a new laser to go bad, but they probably only deal with new lasers. Anyone familiar with these symptoms? Any advice that you have would be greatly appreciated. Thanks.
-jeaves

[Bec Weir]

The laser on my 40W started acting up after about 60-70 hours of occasional cutting. It would start to cut, and then stop cutting (I pretty much only vector cut). Turning down the 10-turn pot dial would trigger the laser to again switch on and start to (poorly) cut. Turn it back up to the 15mA and it would stop cutting again.

FSE was contacted and I was told it was either the laser tube or the power supply.

I still had the machine that was originally borked (details in another couple of threads here), and took the laser tube out and the power supply, which was an easy job.

I put the near-new laser tube from the "old" machine into my new machine first, in the hope that this would be the easy fix, as I was unsure whether it was the power supply that was the original problem for my first machine.

It has worked beautifully ever since.

FSE gave me some lark about only guaranteing the laser tube for two months and the manufacturers warranty only being good for two weeks on their 40W tubes, and said I'd have to get another tube from them. Luckily I still have the first machine that I'm slowly striping for parts for the faulty second machine that they sent.

I'd be looking on eBay for a 40W tube from a China supplier for a MUCH cheaper source of tubes than FSE.

[jeaves]

Wow. So it was a bad tube, not your power supply? Interesting. Have you bought one of these cheaper ebay tubes before? I'm just curious to know if they are the same diameter and length as the FSLaser tubes. I know that they all originate in China, so I suspect that they might be a standard size.
-Jon

[Bec Weir]

Yeah, it was the tube. I don't know whether it is the power supply burning out the tube however, I guess I'll find out in a few months time. It is, working better than it has ever worked befor for me - though that isn't saying much.

I have ordered another 40W tube from an eBay seller, and it looks exactly the same as the one from FSE. Same length, diameter, sticker and a similar serial number; just a couple of hundred bucks cheaper than FSE.

it was well packaged and came with a "no break on transport guarantee".

[jeaves]

Thanks for the tip. I'll keep that in mind. I am going to check the voltage on my supply first, then. - Jon

[rayscott]

Be CAREFUL...

I know this posting is a bit old to respond to.. My answer is more for people that might develop similar questions and then think, "hey, I'll check the laser power supply output?"

The laser power supply on a 40 watt system can be as near 20,000 volts. This is far too high for most volt meters. It actually takes a special probe to get a test meter to work correctly and safely.

The laser tech support company can tell a customer to try to see some effects, change this device, look at the laser color, listen for sparks... The tech support should NEVER ask the customer to measure the voltage coming out of the laser power supply wires.

Please be careful in whatever you do.

Ray Scott
Owner / Engineer
Rabbit Laser USA
513-217-5707