The drama continues: voltage drop from controller

[Jonathan Bowen]

So I was outa the woods and cooking along till yesterday. I replaced the blower with the harbor freight green one that everyone seems to recommend. It's convenient having a store down the street. In the process I had to disconnect my relay system that was powering the old one. I open the case and fiddled around a bit and then closed the door. It sparked for some reason. I fiddled around and didn't find anything wrong with it. However, now the controller is only outputting 3.6 Volts to the PSU and I'm not getting full power to the tube because of it. I tried switching to PWM mode but not sure I have it wired correctly yet. It got less power in that mode. The laser cut software is set to 100 max power and it was previously set to 72 to keep the current down to acceptable level. Not sure what to do with it at this point. I might swap the power supplies for the controller and see what happens. I need to pull my relays out and mount them externally anyway. The new power supply is a bit tight. I have the PSU wired with this configuration.

https://dl.dropboxusercontent.com/u/61862/psu%20wiring.jpg
I might need to work out something with an inline pot tied to the 5V line to get a higher voltage. Before I do that I'll test sending 5 volts directly into the PSU input and see what happens. So tired of working on this thing.

EDIT: Added info. Laser: Hurricane Lasers Agnes (Gweike) upgraded to 60 Watt tube with new power supply. Controller is MCP6515.

[Bill George]

Your clue is something sparked. I'd guess you had some wires shorted or touching and shorted out the 5 volt power supply.

[Jonathan Bowen]

I didn't short the PSU. It wasn't even on when the spark happened. I have no clue why it happened. If it was a power short then it would have happened over and over. It's not repeatable. Could have been static discharge but the only thing close to it are the PSU case and a 12VDC cable for the fan in the case.

[Dave Sheldrake]

Check the PAD Jon, make sure it is set to 100% for power on the screen.

H - TTL High = +5 volts will turn psu on , 0v = Off
L - TTL Low = Connecting this to ground will turn the laser on ,
WP - Water Protection = Interlock to ensure water pump is running
G = Ground
IN = Signal In ,
5V = 5 volts DC

A dead short is more likely to kill the card than the psu.

cheers

Dave

[Jonathan Bowen]

The PAD is set to 100%. The MCP6515 outputs a low to power the laser on. That is connected to TTL Low. With the analog output is connected to IN. I posted the wrong diagram but same thing just no TTL High input. The WP connector is connected to the water pressure sensor.

Nothing is dead but I'm just getting 3.6 VDC on the input. Might be a floating ground issue... Not sure if the case on the PSU is grounded or not.

[Bill George]

I was a bit hasty in my reply yesterday and for some reason I can not log in from my Android tablet to this Forum??? Maybe it was just a static voltage spark you saw?
Are your relays for the fan and pump 5 VDC coils maybe they are dragging down the 5 volt rail some way?

[Jonathan Bowen]

Well I double checked the controller and it's adjusting the voltage correctly. I can get 5VDC out of it. However the tube is stuttering a bit on startup and I'm only getting like 9 mA to the tube. As a side note. The spark seems to be some sort of static charge that is building in the laser. I did notice that the 60Watt tube has been shocking me when I was dealing with the connector after it has run a bit. The case shocked me today. I was reaching in to adjust the jumper to switch back to analog mode and got zapped. Bad enough that I thought I might have had been hit by 110VAC. I did notice that I had not connected a ground to the case of the high voltage PSU. I fixed that but it has not fixed the power issue. Lightobject said they had some come in that the voltage selector switch was bad and causing a power loss. I have yet to the their suggestion of pushing that switch in while it's running to see if I get a power increase. I have yet to do that but I did exercise the switch a few times and it feels fine. Not sure I'm comfortable fiddling with it while alone. I really need someone to stand at the controls

[Dave Sheldrake]

Humm check both ends of the trigger wire Jon, as to plying around near the HV unit while it's running....the voltage and amps are too low to kill you outright but cardiac arythmia is quite possible under some circumstances so I'd be rather loath (to say the least) to do it while the tube is firing. Check the entire length of the HT line for cracks as well.

The 9ma is the return from the tube (it's measured by the machine at the negative) so that doesn't always mean the PSU it could be the tube not "passing" enough current (bad tube etc)

I think at this point I'd be looking for a lose wire or leaking HT side

Cascading faults... I hate them with a passion, it feels like tail chasing ending up not knowing what part is at fault :(

best wishes

Dave

[Jonathan Bowen]

I'm used to working with high voltage stuff its more the issue of being forced to run around the machine so I can do a minor test. I have to run a cut file. I might redo the entire line as part of it isn't shielded with the silicon tube that came with the new PSU. I can say that this is probably the last chinese laser that I get.

[Dave Sheldrake]

Good one's are great Jon, bad ones are a nightmare, being honest there are likely only 3 retail companies on the planet I would buy a Chinese laser from (none of them are the actual manufacturers) HPC here in the UK, Rabbit and APLaser over in the US. Much of the problem seems to be a LOT of people and companies selling them don't actually understand their own products and are great when you want to give them money but useless for fixing stuff when it goes wrong.

I'm a big fan of Chinese machines but if you get problems you pretty much end up on your own in most cases. Diagnosing problems remotely on them makes the machines a real struggle sometimes.......heh and I often get asked why I won't sell lasers.....

cheers

Dave

[Jonathan Bowen]

So it was the voltage selector switch on the PSU. Pushing on it causing the power to jump. Lightobject caught the issues. I'm going to bypass the switch and get back to work.

I wouldn't be all that upset if it wasn't for the laser being vital to my company and failing during a very trying time. I'm transitioning with the company and this put a big speedbump in the road and I've been stretched thin lately. Hopefully everything will settle down after the move.

[Dave Sheldrake]

Strangely enough I've heard of a Redsail just yesterday with similar problems....

good to hear it's working now Jon :)

cheers

Dave