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Weller soldering station Update

Discussion in 'Electronic Repair' started by radio10, Sep 16, 2012.

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  1. radio10

    radio10 Guest

    My thanks to all for helpful comments.

    Updates:

    1)Triac Gate disconnected as suggested by Jamie and No heat, so confirms Triac OK.

    2)No S/C between heating element and earth/common. Now looking upstream from Triac.

    3)I have checked the temp sensor in Iron (wand) and it's O/C ALL of the time. So, have substituted a low value Pot and can now create a variation in readout on Station display now, but still the element is ON all the time (red hot tip etc!)


    Richard
     
  2. N_Cook

    N_Cook Guest

    time. So, have substituted a low value Pot and can now create a variation in
    readout on Station display now, but still the element is ON all the time
    (red hot tip etc!)

    Have you tried forcing a change of the inputs to the op-amp?
    Any idea what the 8pinner is? presumably not an EEprom as nothing to store
     
  3. radio10

    radio10 Guest

    I think the MAX406 is an op-amp.

    I think the LT508 1298 might be a A-D converter but I can't find any info other than a vague reference. I was hoping this was an Opto.

    There is a 93LC46 which I believe is a PROM.

    Then there's the PIC16C57 28 pin device.

    All seems potentially OK, ie display works, voltages appear as expected.

    The fault seems to be the switching of the heating element which is locked ON all the time.

    However I notice there is nothing happening and no change to MT1 on the triac during any state including forcing the temperature sensing.

    I can see DC levels varying on the temp pot.
     
  4. N_Cook

    N_Cook Guest

  5. Jamie

    Jamie Guest

    Says here the LT508 is a Power Factor and PWM control voltage device.

    If you have a scope, probe the gate to common side and look for a
    pulse. If you see a pulse there like it's trying to turn off the gate,
    it is a good possibility the Triac could be bad.

    If you can look at the triac number and see if it is a sensitive
    type, these types are known to have issues and they could lock on..

    what I have seen happen in some cases is this, if the power supply on
    the control board bets a little noisy due to bad caps, a small ripple
    can be present at the gate and thus turning it on..

    If you are not sure about this, you can disconnect the gate and then
    do a meter ohm check between the gate and one of the terminals.. A
    non-sensitive gate type will have some resistance down in the 300 or
    less range. Most of them are in below 100 ohms..

    You many not have a opto isolator since the output voltage is most
    likely low to start with. One of my stations only uses 6 volts if I
    remember.. And a couple of others use 24 volts. Either way, the driving
    electronics more than likely is directly coupled to the gate. This is
    actually a bad idea btw. You happen to touch the tip some where in a hot
    spot of a piece of equipment, it can back track and take out the
    stations control electronics. The heater elements are suppose to be
    isolated, but HV tends to jump over boundaries.


    Jamie
     
  6. Phil Allison

    Phil Allison Guest

    "radio10"

    ** So tye iron is faulty - just as you were told.


    ** Such sensors are only a few ohms and typically drop in value as the tip
    heats.

    FFS buy a new iron.


    .... Phil
     
  7. N_Cook

    N_Cook Guest

    info other than a vague reference. I was hoping this was an Opto.

    What data could the Eeprom be used for storing , in a soldering iron
    operation?
     
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