Explorer II 100W Power supply problem

[Constant Laubscher]

I was engraving at 100% power and 38% speed when all of a sudden it was loosing laser power from 100% to about 30%. I could also hear that all the fans was running at half speed.
I measured the power to the tube and find that when I run the laser it only measures 31V and not the 46-49 Volt.
I disconnected the tube completely from any power and found that actually only one of the five power supplies was working.
Four had blown fuses and even if I replaced the fuses it still popped them!
Is there anyone out there that might have had the same problem in the past?

The machine is just out of warranty and I am looking for some ideas on what might have caused it to happened.

[Richard Rumancik]

Five power supplies? That is an unusual configuration. I am assuming that they are interconnected connected in some kind of series/parallel arrangement. Hard to visualize this with 5 supplies. If you can get some kind of wiring diagram from GCC that would help. If you post it maybe one of our resident electrical types can help. Usually GCC will supply a general wiring diagram. (You probably won't be able to get any schematics for the supplies themselves though. Good chance GCC buys them.)

I'd guess that there is a fault somewhere that is overloading the supplies but it's pretty hard to speculate. I doubt if 4 supplies would go bad at the same time, but maybe a single short is causing 4 of them to blow fuses.

If they are parallel connected then perhaps one supply went bad taking down the rest. Maybe you can isolate a bad one by trial and error. I'd try to put on a dummy load however like a resistance heater when troubleshooting.

One thing you could do is trace all the harnessing from the power supplies to the laser load and see if you can detect any wiring defects (pinched wires, melted insulation, etc.)

When the fuses blew the second time, did you have the laser tube load on them?

[Constant Laubscher]

No I removed all power connections.
I spoke to GCC but they don't fix them they just replace the power supplies.( so much for a technician) a plug and play exercise that would cost me $612 per power supply.
A tube repair if that would be the problem would cost between $6000 - $7000.
I shall do more investigating today and see if I can find the problem.
When your machine is out of warranty, you pretty much on your own or you can pay big money for there lack of skills to repair components.

[Constant Laubscher]

I have now ordered the components on the power supplies that popped.
I am still looking for any suggestions on what may have caused the problem in the first place? I hope that will be all that needs to be replaced.
Any advice?

[Kim Vellore]

Constant,
Could you post some specs., model number or pictures of the power supply. I am assuming it is a bank of switch mode power supply modules connected in parallel. You could disconnect the parallel connection replace the fuse, turn it ON and check the fuse to see how many fails and replace the failed module. You could try to identify and replace components in the module but usually there will be more than a few components that will fail.
The SMPS fails for many reasons and will not be related to specific laser manufacturer.

Kim

[Dan Hintz]

I agree with everything Kim just said...

[AL Ursich]

The Full Wave Rectifier is my first item to check. They go bad by opening or shorting. When I was repairing Power Supplies for Sony 1 in 10 shorted. That could account for the 4 blown fuses if they are hooked in parallel. One shorted to ground will blow the 4 at the same time.

Then look for bulged Electrolytic Capacitors.

Photographs of the inside of the Power Supply would be good... Depending on the amperage of the power supply there could be 4 large semiconductors screwed into a heat sink with braided leads that could be bad.

I really miss fixing stuff....

AL

[Constant Laubscher]

The same component is blown on all four ( thermistor).
I was waiting for the components to arrive, replace them and then see what else has failed. I do not have any access to a oscilloscope but will go with what is visible.
I shall post photo's later today.
Thanks for the advice from everyone .

[Richard Rumancik]

The thermistors on the front end of the supply are usually for limiting inrush current. They start off at high resistance allowing the caps to charge slowly and then go to almost zero resistance after a short time.

So why did 4 of them blow? Seems like all the power supplies saw something they didn't like. Maybe a shorted output causing excessive load? Did you have any power line disturbances on the input end (eg. lightning storms?) Do you have any power conditioning on the front end (surge suppressor)? If so check that the surge suppressor is still healthy. (per indicator light or else discolored surge suppressors) If you don't have one, you really should get one . . . and don't skimp. You want 2500 joules or more rating.

[Bruce Volden]

The Full Wave Rectifier is my first item to check. They go bad by opening or shorting. When I was repairing Power Supplies for Sony 1 in 10 shorted. That could account for the 4 blown fuses if they are hooked in parallel. One shorted to ground will blow the 4 at the same time.

Then look for bulged Electrolytic Capacitors.

Photographs of the inside of the Power Supply would be good... Depending on the amperage of the power supply there could be 4 large semiconductors screwed into a heat sink with braided leads that could be bad.

I really miss fixing stuff....

AL

C'mon Al...you have 3 CW's

Bruce

[Constant Laubscher]

I am sorry was busy with some projects. Here are some pictures of the power supplies & component that popped.

Kind Regards
Constant

[Richard Rumancik]

Interesting . . .You said the fuses popped when you initially replaced them. So either there was an overload or transient that blew the fuses AND the thermistors. I assume the thermistors are in series with the fuse. But I would have thought the thermistors would fail open-circuit. In which case the fuses would not blow a second time as there would be no input.

If they failed shorted (which is less likely) then they are out of the circuit and not doing their job as inrush-current protection. In this case, the fuse could blow a second time. Maybe it's too late to see if they are shorted (approx. zero ohms). Compare to a good one if you have any new ones left.

Maybe one of our resident technicians can shed some light on this.

[Constant Laubscher]

The parts have just arrived
Same result, I replaced the visible blown components but when I switch the power on they all blow again.( Thermistor & fuse)
I also see on one of the four power supplies that 2 semiconductors are blown.
All the tests I have done so far I have tested them individually and did not use the machines power source.

[Constant Laubscher]

Same result, I replaced the thermistor and fuse but they still blow as soon as you switch the power on. There must be something major wrong.

[Constant Laubscher]

Same result, I replaced the visible blown components but when I switch the power on they all blow again.( Thermistor & fuse)
I also see on one of the four power supplies that 2 semiconductors are blown.
All the tests I have done so far I have tested them individually and did not use the machines power source.