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  1. #1
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    Testing electrical components

    As a new tech the biggest problem for me is my lack of knowledge using a multimeter and testing electrical components. Aside of testing continuity I am clueless when it comes to testing motors, circuits, solenoids, photo interrupters, thermistors, and thermostats. I feel comfortable reading the wiring diagrams but don't know how to put any of that information to use, as I lack any official training if anyone could point me in the direction of useful resources for testing of the components listed above that would be great.

  2. #2
    Service Manager 2,500+ Posts
    Testing electrical components


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    Re: Testing electrical components

    Relax. I haven't used a meter but maybe once or twice this year. And that was to check a wall outlet or a fuse. The days of testing components on a circuit board are long gone. I haven't needed to look at a schematic or wiring diagram for years! Nowadays "technicians" are IT / Networking people trained to be copier techs. Machines are self diagnostic and error codes help a lot. What separates the men from the boys is experience and confidence that comes years after working on the machines.

    When I first started in this Biz (back when machines were driven with chains and paper submersed in tank of fluid) I was using a meter, wiring diag's, etc few times a week. Over the years as machines became more electronic and eventually digital I seemed to use meter less and less, to almost never now. Think I even started a thread on this forum about meter and what's not being used anymore.

    Best of luck

  3. #3
    Service Manager 10,000+ Posts
    Testing electrical components

    Phil B.'s Avatar
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    Re: Testing electrical components

    Quote Originally Posted by copyman View Post
    Relax. I haven't used a meter but maybe once or twice this year. And that was to check a wall outlet or a fuse. The days of testing components on a circuit board are long gone. I haven't needed to look at a schematic or wiring diagram for years! Nowadays "technicians" are IT / Networking people trained to be copier techs. Machines are self diagnostic and error codes help a lot. What separates the men from the boys is experience and confidence that comes years after working on the machines.

    When I first started in this Biz (back when machines were driven with chains and paper submersed in tank of fluid) I was using a meter, wiring diag's, etc few times a week. Over the years as machines became more electronic and eventually digital I seemed to use meter less and less, to almost never now. Think I even started a thread on this forum about meter and what's not being used anymore.

    Best of luck
    totally agree ... I use my meter more for around the house ( outlets ) or to test voltage and continuity on my son's 50cc scooter. The main thing is to be able to read the manual and relate to listed diagnostic codes.

  4. #4
    Senior Tech 250+ Posts driving lots of miles's Avatar
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    Re: Testing electrical components

    I have been repairing copiers for 3 1/2 years and have used a meter maybe twice, and both times they were in the shop for repair.

  5. #5
    Service Manager 1,000+ Posts
    Testing electrical components


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    Re: Testing electrical components

    BlackCat is going to shame us, but it's true. You don't need it beyond testing outlets.

    If your employer ever sends you to a class, pick the brain of the instructor. They love talking about it and know a lot.

  6. #6
    Master Of The Obvious 10,000+ Posts
    Testing electrical components

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    Re: Testing electrical components

    Quote Originally Posted by JR2ALTA View Post
    BlackCat is going to shame us, but it's true...
    Sorry, yes, I use the meter every day.

    I'll do this by categories:

    Motors:
    There are very few motor failures, and they're usually fairly obvious (like the motor doesn't turn). Motors with 4 or more wires and not a circuit board built onto it are pulse motors which have multiple sectors. Each sector is a continuous loop that advances the armature a certain number of degrees. For example a (6) wire pulse motor has (3) sectors, each advancing the armature 120 degrees of a rotation. Each sector is a low resistance loop, close to (0) ohms and infinite to the motor housing.

    Motors with a circuit board mounted to them are controlled by a driver circuit, and an not so easily tested with a meter.

    Motors with two wires (often red and black) are typically 24vdc. You can read resistance across the wires. As you rotate the armature the resistance will alternate open, closed, open, closed. You can check for a supply voltage. Keep in mind that most copier circuits are ground switching. That means that the +24vdc is always present at the motor, and the main board starts the motor by connecting the ground (same as frame ground).
    The good news is that most copiers have a test mode to run individual motors on demand.

    Solenoids:
    Most solenoids operate on 24vdc. It's a continuous coil with a ~80 ohm resistor in series. You can test it for resistance across the two wires (~80 ohms, but don't get hung up on looking for a specific value, just not infinite), and resistance from the coil to the solenoid mount (should be infinite). You can also test the DC voltage same as the 24vdc motor.
    On a side note there are a few exceptions. Occasionally you'll come across a solenoid with multiple coils, sometimes a diode in circuit (which means it will only show resistance in one direction), and sometime a rare earth magnet built in.
    Solenoids can fail in four ways:
    1) the sound damping foam pad gets sticky, releasing slowly after a while energized.
    2) the plunger magnetizes, releasing slowly or not-at-all after a while energized.
    3) the coil opens to infinite ohms
    4) somebody oils the plunger (never oil a solenoid, clean with alcohol only)
    The good news is that most copiers have a test mode to run individual solenoids on demand.

    Clutches:
    Most clutches operate on 24vdc. It's a continuous coil. You can test it for resistance across the two wires (~80 ohms, but don't get hung up on looking for a specific value, just not infinite), and resistance from the coil to the solenoid mount (should be infinite). You can also test the DC voltage same as the 24vdc motor.
    The good news is that most copiers have a test mode to run individual solenoids on demand.

    Photointerrupters:
    Most have (3) wires:
    1) +5.0vdc
    2) frame ground
    3) sensor output
    First: on low DC volts range connect black to frame, then check each of the sensor leads with the sensor blocked then unblocked. The pin that stays at 5.0vdc blocked and unblocked is the hot. The pin that stays at 0vdc blocked and unblocked is the frame ground. The pin that changes when you block/unblock the sensor is the output. Here's where there's some variation:
    Some photointerrupter's output are close to 0 vdc blocked and close to 5.0vdc unblocked
    Some photointerrupter's output are close to 5.0vdc blocked (triggers around 3.5vdc) and close to 0 vdc unblocked
    Mainly you're looking for the change.
    Now the best part: most copiers have a service mode that will allow you to test photointerrupters. What that service mode does not tell you is the actual output (your sensor peaking at 3.6vdc won't always properly trigger the board).

    Thermistors:
    Thermistors are measured in resistance at a high range. This is another case where the actual resistance value is not as important as seeing ~400K ohms at room temperature, and about 250K ohms at finger temperature. At actual fixing temperature the thermistor will be down in the hundreds of ohms. Just watch for a dead short or open circuit.

    Thermostats:
    Thermostats should be 0 ohms at all times. It's rare, but I have seen thermostats the start to increase in resistance as the load of the heat lamps is applied. The way to test for this is heat up the fuser and re-check the thermostat when full hot.

    Notice that you can test most of these components in service mode. That's great for a catastrophic failure, but for an intermittent issue it won't always help you. =^..^=
    If you'd like a serious answer to your request:
    1) demonstrate that you've read the manual
    2) demonstrate that you made some attempt to fix it.
    3) if you're going to ask about jams include the jam code.
    4) if you're going to ask about an error code include the error code.
    5) You are the person onsite. Only you can make observations.

    blackcat: Master Of The Obvious =^..^=

  7. #7
    Service Manager 2,500+ Posts
    Testing electrical components

    Hansoon's Avatar
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    Re: Testing electrical components

    At least 20 minutes of Cat's life went into this. OK he has 9 life's anyway.

    Good to fresh up knowledge again, thanks Cat.

    Hans
    " Sent from my Intel 80286 using MS-DOS 2.0 "

  8. #8
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    Re: Testing electrical components

    Quote Originally Posted by blackcat4866 View Post
    Sorry, yes, I use the meter every day.

    I'll do this by categories:

    Motors:
    There are very few motor failures, and they're usually fairly obvious (like the motor doesn't turn). Motors with 4 or more wires and not a circuit board built onto it are pulse motors which have multiple sectors. Each sector is a continuous loop that advances the armature a certain number of degrees. For example a (6) wire pulse motor has (3) sectors, each advancing the armature 120 degrees of a rotation. Each sector is a low resistance loop, close to (0) ohms and infinite to the motor housing.

    Motors with a circuit board mounted to them are controlled by a driver circuit, and an not so easily tested with a meter.

    Motors with two wires (often red and black) are typically 24vdc. You can read resistance across the wires. As you rotate the armature the resistance will alternate open, closed, open, closed. You can check for a supply voltage. Keep in mind that most copier circuits are ground switching. That means that the +24vdc is always present at the motor, and the main board starts the motor by connecting the ground (same as frame ground).
    The good news is that most copiers have a test mode to run individual motors on demand.

    Solenoids:
    Most solenoids operate on 24vdc. It's a continuous coil with a ~80 ohm resistor in series. You can test it for resistance across the two wires (~80 ohms, but don't get hung up on looking for a specific value, just not infinite), and resistance from the coil to the solenoid mount (should be infinite). You can also test the DC voltage same as the 24vdc motor.
    On a side note there are a few exceptions. Occasionally you'll come across a solenoid with multiple coils, sometimes a diode in circuit (which means it will only show resistance in one direction), and sometime a rare earth magnet built in.
    Solenoids can fail in four ways:
    1) the sound damping foam pad gets sticky, releasing slowly after a while energized.
    2) the plunger magnetizes, releasing slowly or not-at-all after a while energized.
    3) the coil opens to infinite ohms
    4) somebody oils the plunger (never oil a solenoid, clean with alcohol only)
    The good news is that most copiers have a test mode to run individual solenoids on demand.

    Clutches:
    Most clutches operate on 24vdc. It's a continuous coil. You can test it for resistance across the two wires (~80 ohms, but don't get hung up on looking for a specific value, just not infinite), and resistance from the coil to the solenoid mount (should be infinite). You can also test the DC voltage same as the 24vdc motor.
    The good news is that most copiers have a test mode to run individual solenoids on demand.

    Photointerrupters:
    Most have (3) wires:
    1) +5.0vdc
    2) frame ground
    3) sensor output
    First: on low DC volts range connect black to frame, then check each of the sensor leads with the sensor blocked then unblocked. The pin that stays at 5.0vdc blocked and unblocked is the hot. The pin that stays at 0vdc blocked and unblocked is the frame ground. The pin that changes when you block/unblock the sensor is the output. Here's where there's some variation:
    Some photointerrupter's output are close to 0 vdc blocked and close to 5.0vdc unblocked
    Some photointerrupter's output are close to 5.0vdc blocked (triggers around 3.5vdc) and close to 0 vdc unblocked
    Mainly you're looking for the change.
    Now the best part: most copiers have a service mode that will allow you to test photointerrupters. What that service mode does not tell you is the actual output (your sensor peaking at 3.6vdc won't always properly trigger the board).

    Thermistors:
    Thermistors are measured in resistance at a high range. This is another case where the actual resistance value is not as important as seeing ~400K ohms at room temperature, and about 250K ohms at finger temperature. At actual fixing temperature the thermistor will be down in the hundreds of ohms. Just watch for a dead short or open circuit.

    Thermostats:
    Thermostats should be 0 ohms at all times. It's rare, but I have seen thermostats the start to increase in resistance as the load of the heat lamps is applied. The way to test for this is heat up the fuser and re-check the thermostat when full hot.

    Notice that you can test most of these components in service mode. That's great for a catastrophic failure, but for an intermittent issue it won't always help you. =^..^=



    Thanks for the response blackcat. I had asked two fellow employees (neither have any experience repairing copiers) specific questions about copier components and it was obvious I already knew more than them. The distributor that my company bought some of the machines from has an in house tech never gives any useful help other than read the manual which I always do before attempting to contact him anyways.

  9. #9
    RTFM!! 5,000+ Posts allan's Avatar
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    Re: Testing electrical components

    I use a tester every other day. Mostly to check mains voltage and to test ICP's and fuses.
    Lately Had a KM C654e give a C9401 CCD gain adj error intermittently that was caused by a bad surge protection plug.
    Found 15V RMS between neutral and ground. Removed the plug and the problem was gone!
    Would not have been so easy without the tester.
    Whatever

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