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Thread: Power supply questions?

  1. #1
    Join Date
    May 2009
    Location
    Portland, OR
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    87

    Default Power supply questions?

    Good evening,
    I must have a secret unconscious yearning to learn more about the inner workings of my tools. I have managed to blow the meanwell power supply on my 04 3G PRT standard this time, and was looking for some guidance. I can replace what I believe to be the issue(a blown transistor in the power supply), but was wondering if there may be a better way. Reading that the meanwell reduces voltage when high temps are reached, is there another power supply that may be more appropriate for the hot/dusty conditions that these tools run in? Can I run any 48v power supply that matches the 6.3 amp/48v configuration?Thanks, Marc

  2. #2
    Join Date
    Mar 2008
    Location
    Tulsa Oklahoma
    Posts
    1,236

    Default

    Look up the power supply on the web, see if you can download a schematic for it. Then troubleshoot just like you would any other electronic device. Be sure its input is correct before going further, if the input is wrong, the output will be wrong. Does it have an internal fuse? Did the transistor become the fuse?

    One question: Why did the PS burn out? Whatever caused the last one to burn out may cause the next one to burn out also. Is something shorted? Check your wiring harnesses for rubbing areas.
    Changing part of a power supply is likely to be frustrating unless you really understand how the power supply works internally. Usually when things fail more than one component is involved.

    If the transistor became the fuse, there is a reason. Transistors only fail for three possible reasons:
    1) Mechanical destruction. (Did it get hit? probably not.)
    2) It got too hot. (Most likely. are you providing adequate air flow?)
    3) Excessive voltage (did lightning strike? Not likely you would not know.)

    As to "can you substitute power supplies".. absolutely! Just be sure the capacity is at least as good as what you are replacing. Not all power supplies are created equal.. the key parameters are output voltage and current as you have noted. Dont overlook the quality of regulation and the efficiency ratings. If heat dissipation was the problem, be sure NOT to get a less efficient power supply or it wont last long. Most modern power supplies are about 95% efficient so you are pretty safe there. The old one may not have been that efficient, power supplies have improved a lot since switching regulator technology became common.

    If in doubt, just call ShopBot and have them send you a new Power Supply.

    Hope that helps-

    D
    "The best thing about building something new is either you succeed or learn something. Its a win-win situation."

    --Greg Westbrook

  3. #3
    Join Date
    Jan 2004
    Location
    iBILD Solutions - Southern NJ
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    7,427

    Default

    Try to replace the original MeanWell SP-300-48 with the same thing if you can. When you get it, use a volt meter to adjust the voltage to 44v. There is a little plastic screw on the unit for this purpose. If you are running a 3G box (without 4G upgrade) it is important to keep the voltage down to 44v in order to compensate for voltage generated when decelerating the gantry. The drivers in the 3G boxes are not tolerant of overvoltage, which is why SB detuned the power supplies.

    I have no idea how many motors you are running simultaneously, but if you have a dual Y motor config, with a 5' wide tool with 2 Z axes, you should really have an SP-500-48 Meanwell in there. (500w vs 300w). If looking for a replacement, the SP-500-48 is physically larger, but will give you some reserve power. 3G boards 'rollin heavy' with more than 4 motors, had a double stacked board and an SP-500-48 PS.

    The cooling fan could have been dust bound and/or burned out. That's where I'd look first. Here's the spec sheet.

    -B
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - IBILD.com

  4. #4
    Join Date
    May 2009
    Location
    Portland, OR
    Posts
    87

    Default

    Dana,
    At this point, I am a bit unsure as to what caused the spike, blowing the transistor. That morning, I turned on both the control PC and the windows PC at the same time, which I hadn't done in the past. This is what triggered the spike. With that said, I had previously been getting missed comm errors and blowing the wall breaker on several occasions. I had been sorting through this issue. I removed all other accessories from that circuit and doubled up on my grounds. My kill a watt meter read 1.5 amps to the plug, so I coud'nt figure out why it was tripping. Since the beggining, when turning on the control box it has always had a somewhat of a hard start, but bein as this is a new bot for me, I wasn't sure what to expect. When the power supply blew, I heard a distinct pop. Upon inspection of the PS, I found that the fuse had blown(replaced it), but that it had popped the transistor as well. Conditions were quite dusty, I am hoping that this was the problem. Not sure what else to do at this point.

  5. #5
    Join Date
    May 2009
    Location
    Portland, OR
    Posts
    87

    Default

    Brady,
    I did see the plastic adjustment knob on the PS. I will adjust accordingly. nothing fancy on the gantry, single y motor, 3hp spindle. Does that mean I can safely use a larger power supply? Then just dial down to to 44v? I am hoping this all came about because of the dust over the years and I did make it a habit of blowing everything out on a reg basis, but one cannot expect to reach into all areas to remove the dust, and it was pretty bad when I pulled it.

  6. #6
    Join Date
    Jan 2004
    Location
    iBILD Solutions - Southern NJ
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    7,427

    Default

    Marc,
    Yes. You can use a higher wattage PS, but keep that voltage down in the 44-46v range or you WILL cook your motor drivers.

    I'd recommend looking on Ebay for either an SP-300-48 or SP-500-48. Market price seems to be somewhere around $175-200 for either. The 500w one is not as long, but taller than the 300w one. EITHER will work and both were offered from the ShopBot factory.

    If you can't find one, I have at least one of each here - as in, I don't necessarily want to let them go if you can get one online...but will sell one if it helps a brother in need.

    -B
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - IBILD.com

  7. #7
    Join Date
    May 2009
    Location
    Portland, OR
    Posts
    87

    Default

    Brady,
    Thanks for the hospitality. I believe I can find one. I am also going to replace the transistor in this one, and use as a back up. Hope to have things back up and running next week-Marc

  8. #8
    Join Date
    Dec 2011
    Posts
    16

    Default

    04 Prt Standard 4g board
    Thinking We are needing a new power supply
    Just verifying that the Meanwell SP-500-48 will run my older standard PRT. Don't do electronics much but am pretty comfortable doing basic installs and hookups. Dialing SP-500-48 down to 44v ect. Is it that straight forward or should I be on the lookout for some gotchas.
    Thanks in advance

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