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James Jaragosky
07-08-2010, 8:46 PM
If this post does not belong here I apologize in advance. It is a bit of a cross platform topic.
My inverter for my rabbit laser has been eating fuses lately. it has slowly consumed 5 fuses over the last 12 months. It usually happens on very warm days after 3 or 4 hours of continuous use. this last week it has gone through four fuses in three days. my shop is only partially heated and cooled.
This last week has been very busy for me, having the laser go down every few hours has been a real nuisance. Today I installed four 240 outlets to eliminate the inverter. This required the replacement of the male ends of all the rabbit supplied equipment cords. One each for the laser,chiller exaust fan,and blower motor. I spent nearly $100 on parts. I hope that this cures the problem permanently.
I used 220 air conditioner receptacles and plugs. For wire, I used 10 gauge 3 wire and left the neutral dead at both ends. while I was at it I added a second ground to the laser cabinet.
So far everything has been running well for the last 4 hours.
Jim J.

Dan Hintz
07-08-2010, 9:12 PM
The PS is probably pulling more current than usual or passing noisy spikes from the switcher back towards the input. Check for dry caps... the PS is Chinese made, and those companies loooove to substitute the cheapest part possible(even if it doesn't fit... AMHIK).

James Jaragosky
07-09-2010, 8:13 AM
The PS is probably pulling more current than usual or passing noisy spikes from the switcher back towards the input. Check for dry caps... the PS is Chinese made, and those companies loooove to substitute the cheapest part possible(even if it doesn't fit... AMHIK).
Dan, I have no Idea what a dry cap is, let alone how to check for one.
I should have just gotten a 240 volt power strip off ebay. however I am in a bind and did not have time to wait for it to ship.
I ran the machine hard until 2am trying to catch up on orders. Not a whimper out of it.:)
Jim J

John Noell
07-09-2010, 4:00 PM
A dry cap is an electrolytic capacitor that has had the (liquid) electrolyte leak out (thus ruining it). This usually shows as bulged tops and/or brownish stain at bottom or something similar. For a fascinating read of the history caused by bad caps, check out badcaps dot net. (Bad caps are at the heart of the big lawsuit pending against Dell and the cause for millions of $$ in losses.)

James Jaragosky
07-09-2010, 8:12 PM
A dry cap is an electrolytic capacitor that has had the (liquid) electrolyte leak out (thus ruining it). This usually shows as bulged tops and/or brownish stain at bottom or something similar. For a fascinating read of the history caused by bad caps, check out badcaps dot net. (Bad caps are at the heart of the big lawsuit pending against Dell and the cause for millions of $$ in losses.)

John, thanks for the education on dry capacitors.
So far today I have ran the laser twelve hours stopping only to change files and material. everything is running fine. I won't miss the inverter at all.
Jim J.

James L Barber
07-10-2010, 10:06 PM
Jim,

Not to niggle semantics here, but do you mean the 120V->240V step-up transformer supplied with the Rabbit lasers?

The reason I ask is because a John mentioned, it's a bit suspicious for something as simple as one of those transformers to start blowing fuses unless (1) one or more windings is shorted in the transformer or (2) something in the laser is drawing more current than it should.

If the transformer actually *does* have shorted turns, then your solution is the right one, and you'll actually use a smidgen less power running 240V direct. My concern would be that if the laser PS is drawing more current than it used to. If so, then running it until it quits isn't advisable.

I don't know which Rabbit you have or what wattage tube, but it wouldn't hurt to put an 'amp clamp' on the 240V main to the laser PS, then compare notes with someone like Ray Scott to determine if the current draw is within a reasonable range. A WAG on my part would be 2 to 3 amps @ 240VAC maximum for a 40-60W laser, not including loads from the chiller, air assist compressor, etc. Anything more than that and you might consider replacing the PS before it fries and takes your controller with it. It's not all that likely it would damage the tube, but since the controller is the most expensive single component it's worth protecting.

My .02 only. I'm a new Rabbit owner but an old engineer. ;-)

--jim
Rabbit RL-40-6040

AL Ursich
07-11-2010, 12:02 AM
A dry cap is an electrolytic capacitor that has had the (liquid) electrolyte leak out (thus ruining it). This usually shows as bulged tops and/or brownish stain at bottom or something similar. For a fascinating read of the history caused by bad caps, check out badcaps dot net. (Bad caps are at the heart of the big lawsuit pending against Dell and the cause for millions of $$ in losses.)

I spent a good 2 hours on the Bad Cap site..... Good Stuff for another OLD Tech... Many years ago I was a Sony Service Tech and made lots of overtime replacing the bad Caps in 17 and 19 inch CRT Monitors... My Sony after hours job.... Fixed Play Stations, DVDs, Home Phones and Cameras by day.... They had lots that needed the fix.... Great Overtime... fun Work...

As for the old Tech Wisdom about buying something OLD.... 1960's and early 70's... Expect that the old paper Caps are dried out..... The Audio from old Tube Amps made a HUM with bad caps....


I am with the guy that thinks the Inverter is really a Step Up Transformer... A Inverter usually takes in DC and makes Chopped AC... But some Battery Backup Inverters take in AC and store it in batteries and if needed turn the DC into AC Again.... Or Clean up the AC Power if designed that way....

As for the blown fuses.... I am in the court that over time the windings of the Step Up Transformer are starting to Short..... The wires are covered with a insulating coating like Lacquer or Varnish. So we start out with a Transformer with 100 turns in the primary and 200 turns on the secondary. In Theory 115 Volts AC into the Primary steps up to 230 volts AC when going through my paper transformer. There are many ways to measure AC... Peak to Peak, RMS and so on.... For simple numbers we will call it doubled... 230... Or 120 in and 240 out...

A real transformer has windings and metal cores designed to more efficiently do the job limiting stay flux... So back to the wire coating..... In my 20 years as a Navy Analog Computer Tech all the way from Vacuum Tubes to Microprocessors, I have seen a few Relay and Transformer Coil failures.... Even got permission to steal the high speed relay from a Cooking Galley Exhaust Fan controller to repair a much needed Radar in the Gulf when the coils shorted on the Radar relay.

When the wires of a transformer are wound together much care is taken to prevent the coating on the wires from being damaged.... As the wires are wound on each other. While in operation the Transformer and Relays Coils vibrate when AC Power is applied. This rubbing and rubbing sometimes causes the coating on the outside of the wires to wear off.... So if that 100 turn primary coil in my example earlier shorted 2 wires in turn 70 and turn 90.... This would effectively make the 100 turn Primary Coil turn into a 80 Turn Coil due to the path of least resistance..... Now the current goes UP in the Primary side and the Voltage goes DOWN in the Secondary Side....

The Point is.... The Current and Voltages are going to be OFF..... Off in what is expected.... That is why the fuses were blowing.... Shorted turns in the Transformer Wndings.....

Things that cause shorts in the windings....

Cheap coatings....

Poor handling of the coated wire.

Physical Shock of the Transformer..... On my 3 Navy Tin Cans, the 5 inch Gun Shooting caused much stress to Transformers.....

HEAT.... If the Transformer is getting hot due to a heavy load or winding damage over time.... Poof goes the protection devices... The Fuses.... HELP.... :eek:OVER CURRENT:eek:.... Something IS Wrong..... Look at me.....

So a lot of Useless Info..... But Old Guys and a keyboard.... Look out.... It's midnight and I just finished watching Boston Legal a second time... So Funny....

Check out this post for a picture of my first computer....

http://www.sawmillcreek.org/showthread.php?p=651013#poststop

Sounds like the Electrical Wiring Project nipped this problem in the Butt as Barney Five would say.... Nipped Nipped Nipped....

AL

James Jaragosky
07-11-2010, 10:57 AM
I spent a good 2 hours on the Bad Cap site..... Good Stuff for another OLD Tech... Many years ago I was a Sony Service Tech and made lots of overtime replacing the bad Caps in 17 and 19 inch CRT Monitors... My Sony after hours job.... Fixed Play Stations, DVDs, Home Phones and Cameras by day.... They had lots that needed the fix.... Great Overtime... fun Work...

As for the old Tech Wisdom about buying something OLD.... 1960's and early 70's... Expect that the old paper Caps are dried out..... The Audio from old Tube Amps made a HUM with bad caps....


I am with the guy that thinks the Inverter is really a Step Up Transformer... A Inverter usually takes in DC and makes Chopped AC... But some Battery Backup Inverters take in AC and store it in batteries and if needed turn the DC into AC Again.... Or Clean up the AC Power if designed that way....

As for the blown fuses.... I am in the court that over time the windings of the Step Up Transformer are starting to Short..... The wires are covered with a insulating coating like Lacquer or Varnish. So we start out with a Transformer with 100 turns in the primary and 200 turns on the secondary. In Theory 115 Volts AC into the Primary steps up to 230 volts AC when going through my paper transformer. There are many ways to measure AC... Peak to Peak, RMS and so on.... For simple numbers we will call it doubled... 230... Or 120 in and 240 out...

A real transformer has windings and metal cores designed to more efficiently do the job limiting stay flux... So back to the wire coating..... In my 20 years as a Navy Analog Computer Tech all the way from Vacuum Tubes to Microprocessors, I have seen a few Relay and Transformer Coil failures.... Even got permission to steal the high speed relay from a Cooking Galley Exhaust Fan controller to repair a much needed Radar in the Gulf when the coils shorted on the Radar relay.

When the wires of a transformer are wound together much care is taken to prevent the coating on the wires from being damaged.... As the wires are wound on each other. While in operation the Transformer and Relays Coils vibrate when AC Power is applied. This rubbing and rubbing sometimes causes the coating on the outside of the wires to wear off.... So if that 100 turn primary coil in my example earlier shorted 2 wires in turn 70 and turn 90.... This would effectively make the 100 turn Primary Coil turn into a 80 Turn Coil due to the path of least resistance..... Now the current goes UP in the Primary side and the Voltage goes DOWN in the Secondary Side....

The Point is.... The Current and Voltages are going to be OFF..... Off in what is expected.... That is why the fuses were blowing.... Shorted turns in the Transformer Wndings.....

Things that cause shorts in the windings....

Cheap coatings....

Poor handling of the coated wire.

Physical Shock of the Transformer..... On my 3 Navy Tin Cans, the 5 inch Gun Shooting caused much stress to Transformers.....

HEAT.... If the Transformer is getting hot due to a heavy load or winding damage over time.... Poof goes the protection devices... The Fuses.... HELP.... :eek:OVER CURRENT:eek:.... Something IS Wrong..... Look at me.....

So a lot of Useless Info..... But Old Guys and a keyboard.... Look out.... It's midnight and I just finished watching Boston Legal a second time... So Funny....

Check out this post for a picture of my first computer....

http://www.sawmillcreek.org/showthread.php?p=651013#poststop

Sounds like the Electrical Wiring Project nipped this problem in the Butt as Barney Five would say.... Nipped Nipped Nipped....

AL
Al, Thanks for the interesting and informative explanation.
I could have worn the windings down as the transformer was mounted on the same plate as the compressor and was vibrating all day long. The transformer has rubber feet, how much they migrated the vibration from the compressor is questionable.

That's one old computer.

AL Ursich
07-11-2010, 8:46 PM
You may have hit the nail on the head.... The Transformer picking up vibration from the air compressor and the windings getting shorted....

The High Speed Vibration caused so much trouble with the CarveWright little hobby CNC.... The Quick connect for the Router bits spinning at high speed.... So many broken electrical parts because of it... They have finally replaced the QC with a Carve Tite... My point being that sometimes vibration can play a more serious part in equipment failure than we think....

Good Job on the Direct Wiring setup.

Yes, that is a old computer.... Synchros and Servos and lots of gears....

AL

pete hagan
07-11-2010, 10:22 PM
I eliminated the step up transformer long ago and have ZERO issues with the power (ok except for the brown outs from construction). I think the design is at fault but it does have a honker of a transformer in the case.

I would suggest anyone who has a Chinese laser to install a 220 service box for their setup. If you use single receptacles you will need at least (3), Laser, Air compressor, chiller.

MOST IMPORTANT - change the plug ends on your equipment! Don't use a 120vt 20amp receptacle for your setup. You will fry something even if it is just you in the shop. I have been working with electricity for 30 years and still see people trying to use the wrong plug/receptacle combo.

Use a NEMA plug (Google nema plug) / Receptacle combination and I would suggest that you use a common one like L6-20R / L6-20P. This is a twist lock (can't easily kick out of the wall) plug that carries 20amp at 250vt. You can buy at Home Depot or Lowes but look on eBay and your local electrical shops. STAY SAFE!

Ken Adams
07-11-2010, 11:19 PM
James- I have the same unit as you, after 3 months I've replaced due to failure the e-stop on the machine and the power switch on the transformer. I have been replacing them with Allen Bradley industrial controls as they fail. I hope the touch control panel doesn't die or I will be having words with the supplier. I have replaced them due to needing the machine up and running. Usually these failures have occurred when deadlines loom... putting me in a rock and a hard place with warrantee issues.

James Jaragosky
07-13-2010, 1:08 AM
Jim,

Not to niggle semantics here, but do you mean the 120V->240V step-up transformer supplied with the Rabbit lasers?

The reason I ask is because a John mentioned, it's a bit suspicious for something as simple as one of those transformers to start blowing fuses unless (1) one or more windings is shorted in the transformer or (2) something in the laser is drawing more current than it should.

If the transformer actually *does* have shorted turns, then your solution is the right one, and you'll actually use a smidgen less power running 240V direct. My concern would be that if the laser PS is drawing more current than it used to. If so, then running it until it quits isn't advisable.

I don't know which Rabbit you have or what wattage tube, but it wouldn't hurt to put an 'amp clamp' on the 240V main to the laser PS, then compare notes with someone like Ray Scott to determine if the current draw is within a reasonable range. A WAG on my part would be 2 to 3 amps @ 240VAC maximum for a 40-60W laser, not including loads from the chiller, air assist compressor, etc. Anything more than that and you might consider replacing the PS before it fries and takes your controller with it. It's not all that likely it would damage the tube, but since the controller is the most expensive single component it's worth protecting.

My .02 only. I'm a new Rabbit owner but an old engineer. ;-)

--jim
Rabbit RL-40-6040

I am drawing 1.3 amps on the laser so all looks good there.
everything is working fine now that I have eliminated the step up transformer.
Been running the laser 12-18 hours a day the last few days and no problems as of yet.
Jim J.