Losing power and a faint purple glow

[1n2]

Hi Guys.
My laser has been working lovely..cooling water nice and cool.
I have been cutting 3mm acrylic quite happily at 40% power and a speed of 6.50.
I noticed a suddenly weakening I now have to cut at MORE than 42% and at a slower speed of 3.5 or 4.
Ah dirt! I thought cleaned all mirrors and lens. I also very carefully checked the alignment all the beams hit bang in the centre right across the cutting bed.

I had another look at the alignment today it is still ok BUT I noticed that when the machine is first turned on there is no faint purple glow but after the test(laser) button is pressed the laser fires as expected but then there's a faint purple glow (towards the outlet end of the tube) its like the one you get down the centre of the tube when it fires but very very much fainter this glow stays until I turn the machine off . The glow does not return until the laser is fired again.


I also noticed a MUCH weaker burn the furthest corner from the y0-x0 position


hope someone can help


John

[waltfl]

Hi
change the tube power supply TL to TH and in the manufacturer settings too,
maybe your bed is not level or better the focal distance id different on the weak spots.
a fraction is more then enough to get a weak burn.
greetings
waltfl

Hi Guys.
My laser has been working lovely..cooling water nice and cool.
I have been cutting 3mm acrylic quite happily at 40% power and a speed of 6.50.
I noticed a suddenly weakening I now have to cut at MORE than 42% and at a slower speed of 3.5 or 4.
Ah dirt! I thought cleaned all mirrors and lens. I also very carefully checked the alignment all the beams hit bang in the centre right across the cutting bed.

I had another look at the alignment today it is still ok BUT I noticed that when the machine is first turned on there is no faint purple glow but after the test(laser) button is pressed the laser fires as expected but then there's a faint purple glow (towards the outlet end of the tube) its like the one you get down the centre of the tube when it fires but very very much fainter this glow stays until I turn the machine off . The glow does not return until the laser is fired again.


I also noticed a MUCH weaker burn the furthest corner from the y0-x0 position


hope someone can help


John

[1n2]

Thanks Walt for your time and help. I tried your suggestion but the tube still is glowing faintly until the machine is switched off then not glowing when switched back on until the laser has fired.

Now it seems the beam is extremely weak and is only just cutting close to the mirrors (ie near the home pos).....I have never had the power above 42...so I bumped it up to 50 & just it cut the same then 60 ..same again. It seems not to be able to fire higher than it is the only way I can get it to cut 3 mm acrylic now is have the speed to 1.5 .....I think this glowing and the short tube life are connected ???????? could the power supply be playing up ? its one of Marco's and only a few months old..

I will try and get a pic of the glowing

John

[1n2]

Could someone peek in the back of their machine to see if this glowing is correct ?...thanks

Sorry for poor pics but could not use flash

ok when machine is turned on (no glow)

off.jpg (34.62 KiB) Viewed 5242 times

Bright glow with laser firing

firing.jpg (28.01 KiB) Viewed 5242 times

dim glow after laser has fired ..this glow goes away the instant the machine is turned off.

glowing.jpg (27.92 KiB) Viewed 5242 times

As you can imagine I don't want to ruin a new tube if there's another issue here.

John

[waltfl]

hi john
I got a crazy idea check your connection between the DSP "Laser1" and the power supply, make sure you got a bridge between WP and G on the powersuply and the connection to ether TL or TH the setting in the manufacturer settings need to be the same ( ether high level for TH connection or low level for TL connection)keep in mind if you wana change something in the manufacturer settings you need first hit "read then change the numbers then hit " save"
it could be the power supply even if this is very seldom. check the tube wiring
the tube should not be glowing if the laser button or from the program is not on.
greetings
waltfl

Thanks Walt for your time and help. I tried your suggestion but the tube still is glowing faintly until the machine is switched off then not glowing when switched back on until the laser has fired.

Now it seems the beam is extremely weak and is only just cutting close to the mirrors (ie near the home pos).....I have never had the power above 42...so I bumped it up to 50 & just it cut the same then 60 ..same again. It seems not to be able to fire higher than it is the only way I can get it to cut 3 mm acrylic now is have the speed to 1.5 .....I think this glowing and the short tube life are connected ???????? could the power supply be playing up ? its one of Marco's and only a few months old..

I will try and get a pic of the glowing

John

[waltfl]

no this should not be at all.
it looks like the tube gets power from the power supply because this does not turn off.
now try to format the DSP with the display menue and then during download from the program
did you use the right OS update?
try also disconnect the DSP from the power supply the big green plug, then use the red test botton to fire the tube
and see if the glow is still there afterwards
greetings
waltfl

Could someone peek in the back of their machine to see if this glowing is correct ?...thanks

Sorry for poor pics but could not use flash

ok when machine is turned on (no glow)

off.jpg

Bright glow with laser firing

firing.jpg

dim glow after laser has fired ..this glow goes away the instant the machine is turned off.

glowing.jpg

As you can imagine I don't want to ruin a new tube if there's another issue here.

John

[1n2]

Hi Walt (again)

ok I just formatted (the memory yes? I could not see any other things to format)

still the same
However...
when unplugging the big plug and using the test ..the laser fires and no glow after!!!!!

So would seem the power supply is ok per se.

as for updates I am not sure I have done any ..would this have been when installing it all?
I have
Main board 7.12.12.26
LCD Board 5.12.02.29

for what its worth lasercad V6.46 (though the problems there without Lasercad open

John

[waltfl]

OK john
what connector on the dsp did you use for the laser???
make a picture from the connection on the DSP
check your ground connection especially the black or blue wire from the negative of the tube should not be connected to anythings else except the mA meter and the power supply not to the machine ground
make sure you got a good ground for all the parts with a extra ground rod on the outside.
greetings
waltfl

Hi Walt (again)

ok I just formatted (the memory yes? I could not see any other things to format)

still the same
However...
when unplugging the big plug and using the test ..the laser fires and no glow after!!!!!

So would seem the power supply is ok per se.

as for updates I am not sure I have done any ..would this have been when installing it all?
I have
Main board 7.12.12.26
LCD Board 5.12.02.29

for what its worth lasercad V6.46 (though the problems there without Lasercad open

John

[1n2]

HI Walt

We don't have actual ground rods here in the UK we have a ground built into our ring main plus earth bonding to all metal fittings (its the regulations)

I am sure I have good grounds all round...
I have been looking with my multi meter and heres some results
:-

With it set up for TH
The big plug unplugged from PSU I get.
On the PSU laser light is off and the TTL light is on
With laser button pressed I get TTL level high 4.7volts (5 volts being TL high so acceptable).
With the laser button released I get TTL level low 0.2 volts (anything below 1v is TTL "low").
------------------------------------------------------------------------------------------------
With the big plug plugged into the PSU I get
On the PSU the TTL light is off and the laser light on
With the laser button pressed I get 3.6v .... nicely above the 2v(ish) TTL threshold.
With the laser button released I get TTL level low 0.2 volts

So all seems ok there
after resetting

With or without the big plug connected I am getting no output at the PWM (can only read for a signal as my little frequency counter on my DMM does not go that high).
Briefly press laser and I get an output (signal) at the PWM this out put stays until I hit reset or turn machine off.I cannot see if the actual signal drops just there's a signal still present.

Ok so with a tiny bit of experimenting
I disconnected the TTL completely and reset machine..I then fired the laser but as expected no beam BUT the glow appeared so it seems that the DSP is wrongly putting out a PWM signal constantly after being fired.

John

Photo of wiring

connections.jpg (76.87 KiB) Viewed 5232 times

[Tech_Marco]

John:

It is very easy to tell if the DSP is sending wrong signal or not. Just draw two square box say 100mm * 100mm on two different layers
One set it to full power like 98% for cutting with 5mm/s speed. The second box, set the power to 50% and 5mm/s

Use you DVM to measure the output from "PWM vs Gnd" and you should read signal closed to 4.8V when the machine is doing the full power cutting. Then the voltage drop to about 2.6V when doing second cutting. The reading should be very stable and it drop only when the laser head run across from one box to another box. If you see that the output is stable, then the DSP is ok.

I guess the problem is the PWM circuit of the power supply. It can be test buy connect a 10K 3 leads potentiometer to "Gnd , In , +5V". Center tap is connect to the "In". Note, you need to unplug the connect to the DSP as what you're doing is testing fire power by analog control. By turning the VR (potentiometer), the laser output should change accordingly.

Hope this may help to find out the trouble


Marco

[1n2]

Hi Marco

Thanks for the answer
OK I did exactly as you said ..(although the power not being controlled is not the actual problem as you will see)

100 mm square at 98% I got 3.38 - 3.49 (as we would expect)
100 mm square at 50% I got 2.49, again, (as we would expect)

BUT when the cuts were finished the TTL level "cut off the laser" but the PWM still reads 2.49 volts which is making the laser glow...

I think the tube has definitely been ruined as the 98% 5mm cut only made a .5 mm groove in a sheet of 3mm laserable mdf

Now I continued an experiment along these lines and made the cuts the other way around
50% 1st 98% last this time after the cuts the PWM held the voltage to 3.59 which, again, is making the laser glow.

I used the pot and it did indeed alter the power output but it also made the tube glow as soon as it was turn up the slightest amount.

Now my conclusion of this is that it seems ok for the dsp to send the PWM signal while at rest but the power supply is not shutting down correctly /completely with the TTL to "off" If not then there's TWO problems.

One with the dsp sending a constant PWM voltage
Two the power supply not shutting off the output with the correct TTL level .

This constant low level firing is surely the reason my laser tube has not lasted more than, maybe, 150 hours.


John

[waltfl]

hi john
did you try to change the TTL to low in both connection on powersupply and in machine settings???
did you set the laser #2 to zero??? in the cutting file when you select the cutting perimeter?
I could not see which laser plug on the DSP you are using laser #1 or laser #2?
greetings
waltfl

HI Walt

We don't have actual ground rods here in the UK we have a ground built into our ring main plus earth bonding to all metal fittings (its the regulations)

I am sure I have good grounds all round...
I have been looking with my multi meter and heres some results
:-

With it set up for TH
The big plug unplugged from PSU I get.
On the PSU laser light is off and the TTL light is on
With laser button pressed I get TTL level high 4.7volts (5 volts being TL high so acceptable).
With the laser button released I get TTL level low 0.2 volts (anything below 1v is TTL "low").
------------------------------------------------------------------------------------------------
With the big plug plugged into the PSU I get
On the PSU the TTL light is off and the laser light on
With the laser button pressed I get 3.6v .... nicely above the 2v(ish) TTL threshold.
With the laser button released I get TTL level low 0.2 volts

So all seems ok there
after resetting

With or without the big plug connected I am getting no output at the PWM (can only read for a signal as my little frequency counter on my DMM does not go that high).
Briefly press laser and I get an output (signal) at the PWM this out put stays until I hit reset or turn machine off.I cannot see if the actual signal drops just there's a signal still present.

Ok so with a tiny bit of experimenting
I disconnected the TTL completely and reset machine..I then fired the laser but as expected no beam BUT the glow appeared so it seems that the DSP is wrongly putting out a PWM signal constantly after being fired.

John

Photo of wiring

connections.jpg

[1n2]

HI walt
sorry,
I am using laser1 (The one showing the dsp side of the connectors was badly out of focus))
Yes laser 2 settings set to 0.

Yes changed both the physical and software settings and remembered to read first.

I even tried with the wrong setting (for completeness) and indeed it was all back to front and still when the TTL was "off" the tube glows

Did you see my reply to Marco that with an analogue control (pot)? It glowed the instant the pot was moved (with and without any connection to the TTL )
would this not (normally) rule out the dsp?

Can you check the PWM voltage on your dsp when the cut (or test fire) is finished and see if the volts are still present. If so this will definitely mean my DSP is good.

John

[waltfl]

hi john
I will check the voltage on my machine and report it back.
greetings
waltfl

HI walt
sorry,
I am using laser1 (The one showing the dsp side of the connectors was badly out of focus))
Yes laser 2 settings set to 0.

Yes changed both the physical and software settings and remembered to read first.

I even tried with the wrong setting (for completeness) and indeed it was all back to front and still when the TTL was "off" the tube glows

Did you see my reply to Marco that with an analogue control (pot)? It glowed the instant the pot was moved (with and without any connection to the TTL )
would this not (normally) rule out the dsp?

Can you check the PWM voltage on your dsp when the cut (or test fire) is finished and see if the volts are still present. If so this will definitely mean my DSP is good.

John

[waltfl]

hi john
here are the data
laseroff = 0.22V
laser on = 3.65V
greetings waltfl

hi john
I will check the voltage on my machine and report it back.
greetings
waltfl

HI walt
sorry,
I am using laser1 (The one showing the dsp side of the connectors was badly out of focus))
Yes laser 2 settings set to 0.

Yes changed both the physical and software settings and remembered to read first.

I even tried with the wrong setting (for completeness) and indeed it was all back to front and still when the TTL was "off" the tube glows

Did you see my reply to Marco that with an analogue control (pot)? It glowed the instant the pot was moved (with and without any connection to the TTL )
would this not (normally) rule out the dsp?

Can you check the PWM voltage on your dsp when the cut (or test fire) is finished and see if the volts are still present. If so this will definitely mean my DSP is good.

John