Mike Audleman
12-04-2015, 6:31 PM
Ok, so last weekend I was working on my Christmas lights display. I needed to whip up a quick plywood support for an LED mega tree. So I draft up the design in Corel and ship it to the laser.
I switch on all the power switches (pump, HV, air, etc). I check the frame, all good. I hit the run button. And.."beep!", it reports no water flow. I am like WTH? I check the bucket. Its a little low but not worth cracking open another jug of water for. The pump is running, I can feel it.
I hit run again. Same, "Beep!". So I tip the bucket, tap the pump. I pinch the hose and I can feel ample flow. So I reach in and tap the flow sensor thinking its stuck. I haven't used the laser in several months. I switch off the HV and try a run. Its happy and pretends to run job. So I reset it, flick on the HV and hit run.
SQAAAAAALLLL! And I hit the kill switch under the shelf within a second or two. It was the sound of a scalded cat! I immediately recognize that sound as an HV arc. Years as a broadcast engineer has taught me to fear that sound. I wasn't about to touch the cabinet! I grabbed a length of 1/4" dowel. I fashioned a shepards crook out of some #12 solid copper and ran a piece of 12ga wire to a conduit ground from the hook.
I flick on kill switch underneath and it happily fires up and homes. I start tapping the chassis with the crook. I hit the pop latches on the panels, the lift handle, etc. It all seems rather content so I hang the hook on the lift handle and kill the power again. I lean around the back and re-verify the ground strap is secure and solid. I am confident the chassis is well grounded. I hit the latches again with the crook and pop open the electronics panel. I probe the HV box and HV leads. And just to CYA I probe the PSU and AC feed lines with the crook. Nothing hot.
I search around for obvious arcing. None to be found. Ok so I hang the crook on the handle again and re-power it. I reach up to pulse the laser with the access panel open so I can see. I briefly press the pulse and instead of hearing the calming tick of it firing a brief pulse, again SQUALLL! Only brief. There is no arcing happening in that end pane thats visible. So I hit the kill again. I take the crook around and tap the latches on the laser box and open it. I was starting to investigate to see if I could see any pitting on paint where the HV leads come through the wall to the laser box. Didn't see anything. Not sure what made me look but I did. And what I saw felt like I had just been sucker punched by Mike Tyson.
On the emitter end of the tube, there was a crack all the way round the outside chamber. WTH? How did this happen? How does the outer chamber crack like that? Inner tube still sealed. Water jacket still sealed and not leaking. But, the end result is I have a +100# paper weight at this point. Its big, blue and sexy with all kinds of fiddly bits but its about as useful as ice cubes in an Alaskan winter.
I am at a loss. I don't know what caused it. It worked fine last time I ran it which was to cut out some disks from a poster board several months ago. Been sitting in the basement since. And no, the basement never gets cold enough to freeze. That I know of, nobody has opened any panel on it.
I am just kinda stunned in disbelief at this point. I was expecting substantially longer service life out of this thing. There is not that much actual run time on it. It spends most of its life turned off, especially lately. It wasn't showing any signs of power loss at all prior to this. What causes it to just crack? Even with no water flow, it should be capable of firing several seconds at least with the reserve water in the tube. The initial squall was immediate the moment the carriage had moved to the initial cut point. I was testing on poster board and there were zero marks on it so it never fired. Or if it did, it was such a brief pulse as to not leave a mark on poster board.
So now what? How much are tubes for this thing and is it worth buying a tube for? If so, who sells them? And whats involved in replacing the tube? It looks like its a simple matter of removing the cooling connections and the HV connections. Not sure if its soldered or not, its covered by RTV silicone. I feel like a lost puppy right now. I had so many plans for Christmas decorations (3 4'x8' sheets of coroplast sitting in the garage to be laser cut). Now I got nothing.
I switch on all the power switches (pump, HV, air, etc). I check the frame, all good. I hit the run button. And.."beep!", it reports no water flow. I am like WTH? I check the bucket. Its a little low but not worth cracking open another jug of water for. The pump is running, I can feel it.
I hit run again. Same, "Beep!". So I tip the bucket, tap the pump. I pinch the hose and I can feel ample flow. So I reach in and tap the flow sensor thinking its stuck. I haven't used the laser in several months. I switch off the HV and try a run. Its happy and pretends to run job. So I reset it, flick on the HV and hit run.
SQAAAAAALLLL! And I hit the kill switch under the shelf within a second or two. It was the sound of a scalded cat! I immediately recognize that sound as an HV arc. Years as a broadcast engineer has taught me to fear that sound. I wasn't about to touch the cabinet! I grabbed a length of 1/4" dowel. I fashioned a shepards crook out of some #12 solid copper and ran a piece of 12ga wire to a conduit ground from the hook.
I flick on kill switch underneath and it happily fires up and homes. I start tapping the chassis with the crook. I hit the pop latches on the panels, the lift handle, etc. It all seems rather content so I hang the hook on the lift handle and kill the power again. I lean around the back and re-verify the ground strap is secure and solid. I am confident the chassis is well grounded. I hit the latches again with the crook and pop open the electronics panel. I probe the HV box and HV leads. And just to CYA I probe the PSU and AC feed lines with the crook. Nothing hot.
I search around for obvious arcing. None to be found. Ok so I hang the crook on the handle again and re-power it. I reach up to pulse the laser with the access panel open so I can see. I briefly press the pulse and instead of hearing the calming tick of it firing a brief pulse, again SQUALLL! Only brief. There is no arcing happening in that end pane thats visible. So I hit the kill again. I take the crook around and tap the latches on the laser box and open it. I was starting to investigate to see if I could see any pitting on paint where the HV leads come through the wall to the laser box. Didn't see anything. Not sure what made me look but I did. And what I saw felt like I had just been sucker punched by Mike Tyson.
On the emitter end of the tube, there was a crack all the way round the outside chamber. WTH? How did this happen? How does the outer chamber crack like that? Inner tube still sealed. Water jacket still sealed and not leaking. But, the end result is I have a +100# paper weight at this point. Its big, blue and sexy with all kinds of fiddly bits but its about as useful as ice cubes in an Alaskan winter.
I am at a loss. I don't know what caused it. It worked fine last time I ran it which was to cut out some disks from a poster board several months ago. Been sitting in the basement since. And no, the basement never gets cold enough to freeze. That I know of, nobody has opened any panel on it.
I am just kinda stunned in disbelief at this point. I was expecting substantially longer service life out of this thing. There is not that much actual run time on it. It spends most of its life turned off, especially lately. It wasn't showing any signs of power loss at all prior to this. What causes it to just crack? Even with no water flow, it should be capable of firing several seconds at least with the reserve water in the tube. The initial squall was immediate the moment the carriage had moved to the initial cut point. I was testing on poster board and there were zero marks on it so it never fired. Or if it did, it was such a brief pulse as to not leave a mark on poster board.
So now what? How much are tubes for this thing and is it worth buying a tube for? If so, who sells them? And whats involved in replacing the tube? It looks like its a simple matter of removing the cooling connections and the HV connections. Not sure if its soldered or not, its covered by RTV silicone. I feel like a lost puppy right now. I had so many plans for Christmas decorations (3 4'x8' sheets of coroplast sitting in the garage to be laser cut). Now I got nothing.