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Thread: Mobolazer SC-100 Scanner Controller

  1. #1
    Join Date
    Oct 2012
    Location
    Carver, MA.
    Posts
    185

    Default Mobolazer SC-100 Scanner Controller

    Hello,

    I have a Mobolazer SC-100 that is not working correctly.

    Click image for larger version. 

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Size:	2.40 MB 
ID:	43193

    The output looks like this:

    Click image for larger version. 

Name:	SC-100_output.JPG 
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Size:	1.79 MB 
ID:	43194

    All of the controls have a slight effect on the output, but not much. Only Gain(1), Gain(2) and Master seem to work correctly.

    Before I start poking around inside it, does anyone have the schematic for it?

    Any thoughts on what to look for?.

    All suggestions welcome.

    ED

  2. #2
    Join Date
    Apr 2007
    Location
    Costa Rica
    Posts
    517

    Default

    Did it ever work correctly? 45 degree spaghetti on open loop GM20 scanners can sometimes indicate a missing ground or ground loop. Start by verifying correct power supply voltages. Then check continuity through all the wires and connectors paying special attention to those connectors where the wires are pressed in. Sometimes a close visual inspection can solve the problem even without a schematic. Good luck!

  3. #3
    Join Date
    Apr 2008
    Location
    New Orleans
    Posts
    230

    Default

    Ed,

    Did you get this figured out yet? If not I have a few working sc-100 controllers and I can scope the output of different chips/sections and send you screenshots of the scope to give you an idea of where the signal is getting out of whack if you have an o'scope.

    I've been wanting to trace out the schematic but never have because my sc100s haven't given me any trouble. I might bring one to work and start tracing the schematic tomorrow or Thursday.
    Last edited by djeric68; 05-20-2014 at 20:31.

  4. #4
    Join Date
    Oct 2012
    Location
    Carver, MA.
    Posts
    185

    Default

    Hello,

    @Photonbeam
    You had suggested "Start by verifying correct power supply voltages.", I did just that and found the -12V line was at a steady 8.2 volts. I didn't think much of this because the -12V line feeds a 1N5273 8.2V Zener diode. I also burnished all the connector pins and reseated all the connectors. Still not working.

    @djeric68
    Thank you for your offer to scope signals for me. If you do trace the circuit, I would love a copy of it.

    I did get it working. The problem was stupid, a broken capacitor. While checking the voltages like Photonbeam suggested, I noticed quite a bit of ripple on the -12V line. I traced back from the input side of the regulator and happened to bump one of the filter capacitors, and it moved. One of the leads was broken off/burned flush with the body of the cap.

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ID:	43386

    I don't have a 2200UF@25V on hand but I do have a 470uf@35V. I replaced the broken cap and the power cleaned up.

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Size:	2.19 MB 
ID:	43387

    I re-tested and everything works fine. I have the correct capacitor in my cart at Digikey.

    Thank you for the help and suggestions with this.

    ED

  5. #5
    Join Date
    Apr 2007
    Location
    Costa Rica
    Posts
    517

    Default

    Congratulations! Use a little hot glue or RTV around the large caps to take the strain off the leads and protect from vibrating loose.

  6. #6
    Join Date
    Oct 2012
    Location
    Carver, MA.
    Posts
    185

    Default

    Hello,

    I installed the replacement capacitors.

    Click image for larger version. 

Name:	sc100-repaired1.JPG 
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Size:	2.19 MB 
ID:	43456

    Everything is working correctly now.

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Size:	1.87 MB 
ID:	43457

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Size:	1.90 MB 
ID:	43458

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Size:	1.89 MB 
ID:	43459

    @Photonbeam
    Warming up the hot glue gun right now.

    Thanks everyone.

    ED

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