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Thread: ALC68 & A1000PS continental power supply help.

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    Laser Warning ALC68 & A1000PS continental power supply help.

    Hi all, im new to the forum and would appreciate some help with my new toy. I have had a few lasers in the past, mostly dpss units but I have just bought an ALC68 with a continental power supply. I paid 300 for it and it works fine and came with scanners attached, I have Beam sculpter 3D software to run the galvos, my question is that its a 220 volt power supply and came with a stepdown transformer 240-220, do I need to use the transformer or is it fine to plug the unit direct to our mains, Im an electrician and normally I would have no problem in doing this but im aware that lasers are very sensitive, does anyone have a similar set that runs fine without the transformer after all it is only 10% differance. Does any one know how I vary the current to the laser head, it currently runs at about 11 amps but I believe they can run up to about 26 amps for a short burst also I believe it to be fairly safe to run it at about 17 amp long term. There is no control on the power supply for adjustment, perhaps there is a septate control box that I dont have? Thanks for any help.
    Tony

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    What your stepdown is doing is reducing stress on the passbank transistors and setting the cathode voltage. The cathode voltage is critical. Increasing the input to the cathode transformer can drastically shorten the lifetime of your tube. So can decreasing it.
    Without a service manual for that unit, I cannot tell you what the limits are. Those PSUs are very rare, and I'm only aware of 1 other still in service and one on a shelf.

    Nominal American line voltage when that unit was designed was 220 +/- 5%

    Steve

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    You have a socket (nine pin D type I think) on the back of the supply which should let you control the laser in either "light mode" and "current mode", (which ever is greater rules the roost).

    Can't remember if it's opto coupled so carefull when mucking about with it !

    If you post a picture of this I am sure someone can help.

    I can't remember the pin-outs off the top of my head, and all my tec notes are in Barcelona but I am still in UK so I can't help much more than that.

    As Steve says be careful with the filament current which is critical, so get a reliable figure for that before using for long periods.

    Cheers
    Last edited by catalanjo; 10-26-2010 at 06:44. Reason: banana peel !

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    Red face

    Thanks for the advice guys, I will continue to use the stepdown transformer as its not worth the risk of damaging the tube, I will sort some photos of the unit and post them soon.
    Regarding the 9 pin plug on the back of the power supply, the laser will fire weather it has anything plugged in or no and im not sure that the controller supplied with it is the correct unit, it only has a simple switch on it that seem to do nothing, its something cobbled together by someone using a smoke machine switch and there is no option for varying the tube current, I will also take a photo of this.
    Would anyone have any idea what the controller should look like, or someone even have a schematics for it.
    Thanks Tony

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    Strangely just a quick update on the smoke machine controller that came with the laser, it has a 9V battery soldered on the back of the switch, what's that all about.

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    One wants to know what the tube current is, if the tube is free running, some supplies ramp to the max limit, when running open loop, which is bad.

    Steve

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    Thanks Steve, the current that is shown on the front of the power supply whilst the tube is running shows 11 amps, am I right in thinking this is the tube current?

    Tony

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    Yes, and if the meter is accurate, means it is idling and at low power, safely.

    Now this is the tricky part. There is a difference in most ION laser power supply systems between "FRAME GROUND" and control circuit ground, because they directly rectify the power line to DC.

    The trick will be to find the pin that is "Control Circuit Ground" on that 9 pin connector, so you can start applying a meter to the pins to find the ones that are outputs. The Pins that are not outputting signals that could be things like "Tube lit", "Cooling Flow OK"
    "Tube voltage" and "Tube Current" will be the constant light or constant current inputs.

    By default, at least one pin on the DB9 is control ground

    If Continental made a really, really good supply, case ground might be control ground, but now your at the point you need a technician skilled in the diagnosis of Operational Amplifiers and analog interfaces to make some educated guesses so that you can get the current under control.

    If I were standing there with a screwdriver, a 0-5 volt source and a DMM, it would take me perhaps 30 minutes maximum to figure this out. The problem is, I am not able to hop the pond in a single bound, so we need to find you a local, or a copy of the manual.

    I do not know who got the assets of Continental Laser, I suspect ILT, which was bought and sold a few more times. Thus, I suspect the data is not easy to get, if it exists at all.


    A simple way is to have a tech trace the cable back to the input card and locate the common ground traces on the circuit board. You then use a 0-5 volt source current limited by a 10K ohm resistor in series with the connector pin under test to start "probing".

    If you do not have a mate with the "geek gene" a few pounds/euros of parts from Maplins or RS Components wired to the following BMP drawing , plus careful use of a digital multimeter to probe the pins on the connector will result in some increase in current with careful use. One could also drag the whole means to a UK Laser Meet, where it will be tuned, peaked, reverse engineered, metered, and drooled on.

    Is the light sensor in the head wired and active or removed ?

    Maplin part numbers for my drawing:

    FW00A Potentiometer 1K linear
    M910R Resistor 910 six tenths watt
    M9K1 Resistor 9.1 K six tenths watt (OK to use 9K1 instead of 10K)
    NE19V PP3 battery clip.
    FH91Y Pushbutton, push to make.
    RK60Q 9 way male D-Sub Plug.

    Maplins use resistor values dating back to the era of tubes where the resistor values are based on square root of two progression, so a 910 and a 9K10 are close enough to my 1K and 10K modern values in my drawing.

    The idea is to turn the wiper to the ground side, make the test connections with the probes, and SLOWLY turn up the potentiometer watching for changes in the current, being ready to release the button if things go wrong or too fast.

    Steve
    Attached Thumbnails Attached Thumbnails SharkieProbe..bmp  


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    Guys, its all go horrible wrong, Before I stated that the tube was running at 11 amps.
    At the time of the reading I was supplying power to my garage using a standard extension lead, since realising that the power supply requires up to 40 amps* to run I have now hard wired the garage with a 60 amp supply. I think that the only reason I was getting a low reading was that the extension lead was acting as a restrictor for the power supply. With the new 60 amp supply to my garage, the laser was showing 29 amps and getting hot quickly so I didn't run it for long, the second time I tried it lased for a few seconds then stopped. I have done some basic tests on the head and I don't think the filament has gone as it gave continuity and I can see the igniter trying to start. There is also a faint orange glow coming from the back end of the tube. I have investigated the power supply and found that there is a bank of transistors about 10 or 12, each having a 5 amp fuse soldered to them. There is possible only 3 of them that are still intact, would it be that now the power supply is not providing enough power to start the tube. I'm hoping that this is the case and once I have replaced the fuses with some rusty nails that all will come back to life? then I can build the control thanks to Steve and get the amps down.
    Once this is sorted (hopefully) I intend to strip the unit and rebuild it as at the moment it quite a state as its been stood idle for many years before I bought it, I was hoping to use it at a friends firework party the weekend but I guess i will have to use my smaller dpss units, not the same thou.
    Thanks Tony

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    Turn the power down! Those tubes aren't designed for operation at 29A, nor are the power supplies. If the transistors aren't already blown, don't replace the fuse with a 'rusty nail', it'll just cause more damage to the system, replace them with the correct fuses and turn the power down to about 17A.

    I'd check that the filament isn't obstructing the bore, you've run it from an extension cord which has probably caused voltage sag then you've hammered it with 29A at god knows what filament voltage.

    Replace fuses with 5A fuse ( At correct voltage rating ), get controller plugged in - turn down current a little, fire it up and set it to around 17A.

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