Timer?

Discussion in 'General Electronics Chat' started by Johnny340, Jan 30, 2014.

  1. Johnny340

    Thread Starter New Member

    Jan 30, 2014
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    This double Trouser Press used to activate for 15 minutes with a push of the button and now it just stays on. Is there a timer component that could be at fault?
    Thanks for your input!
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Most likely a fault with the solid state components fastened to the side of the case.
    T1 T2?
    Max.
     
  3. Johnny340

    Thread Starter New Member

    Jan 30, 2014
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    Those are the momentary contact switches. Do you think that they both failed? Or is there a timer component that is shared by both?
     
  4. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    The IC's labeled 7242 are the timers, one for each press. It seems unlikely that both would go out at the same time, but possible. They don't seem to be in sockets, and so would be hard to replace.

    The other two ICs are optoisolators that control the two ICs attached to the case. These are most likely triacs that actually switch the heating elements on and off.

    What are the markings on IC1 near the transformer?

    What is the behavior of the lighted indicators above the pushbuttons? Do they go on and stay on?
     
  5. inwo

    Well-Known Member

    Nov 7, 2013
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    No, the parts labeled T1 and T2. Generally faults are in the power components.
    That's where parts are stressed the most.
    And they often fail shorted. Meaning "turned on".

    See if you can read the number on them. Like a C*** or D***.

    With power off, check across the different combinations of the three pins with a low reading ohmmeter.
    From the shadows, I'd suspect the top two pins shorted.

    Compare T1 and T2.
     
  6. Johnny340

    Thread Starter New Member

    Jan 30, 2014
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    Here are a couple better pics. The IC1 markings are in the mirror V-36087L
    The red lights illuminate when the buttons are pressed and stay on.

    Oh I see. Those are marked Q4010L5. With the ohm meter 42 on the outer two pins of T1 and 32 ohms on T2. No other combo registers resistance.
     
  7. MaxHeadRoom

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    Jul 18, 2013
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    Those a are 400v 10a Triac's (Q401L5's), test between the centre and left hand leads for short circuit.
    Max.
     
  8. inwo

    Well-Known Member

    Nov 7, 2013
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    They are triacs for switching the load.
    The top two pins are M1 and M2. As they check open with ohmmeter, probably ok.

    The two parts to the left are the isolated triac drivers then. (MOC)
    If you have a couple volts from pin 1 to pin 2 before pressing switch then the timer circuit is to blame.

    If you have no voltage then the driver is holding the triac "on" without a reason.

    Don't do this until someone else backs me up.:)
    Shorting the input led from 1-2 should turn off your load if MOC and triac are ok.
    (should be current limited)

    We will then know what part of the circuit is faulty.

    There is line voltage on the pin 456 side and on triac. Be careful if testing live circuit. Or get qualified help.
     
  9. inwo

    Well-Known Member

    Nov 7, 2013
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    I may be jumping the gun!:eek:

    What is down stream from timer?

    Stuck relay?
    How about a picture of the heater and circuit?
     
  10. #12

    Expert

    Nov 30, 2010
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    True. It's the 1-2 connection that can be shorted without blowing anything up.
    Use an alligator jumper so you don't have your hands in there when you turn the power on.
    This short should disable everything after the timer. If it does, the timer is bad. If it doesn't, the optoisolator or the triac is bad.

    Edit: You're doing OK inwo. Divide and conquer is the name of the game.
     
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  11. inwo

    Well-Known Member

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    Thanks, I've done it myself. But that's a little different than having someone else do it.

    I sure would have bet on Max/post #2.:confused:
     
  12. #12

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    Nov 30, 2010
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    We're still barking up the same tree as Max.
     
  13. inwo

    Well-Known Member

    Nov 7, 2013
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    Good call. They look like series led's to the MOC drivers.

    Cut the red wire.................NO NO the blue.............................:)
     
    #12 likes this.
  14. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    IC1 is a 7806 voltage regulator. Measure between pins 2 and 3 and be sure that you are getting 6.0 VDC +/- .2V.
     
  15. Johnny340

    Thread Starter New Member

    Jan 30, 2014
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    Ohms between center and left show no reading.

    Pins 1 & 2 show about 5 volts on IC4 and 3V on IC5 when plugged in and not activated with the push buttons. I didn't try shorting any pins yet...
     
  16. #12

    Expert

    Nov 30, 2010
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    5 volts looks like an open LED inside the opto or a bad ground for the opto, but that wouldn't make it stick, "on". Watching as you explore.
     
  17. Johnny340

    Thread Starter New Member

    Jan 30, 2014
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    Thanks for the quick replies and good ideas! I'm sure 'we' will figure this out. I'm just back from surgery today and need to hit the sack so I'll post my latest readings tomorrow.
     
  18. inwo

    Well-Known Member

    Nov 7, 2013
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    1 to 2 shouldn't be over 2 volts.
    A better check is the voltage across R5 and R6 along with the color bands will give a mA value.

    Don't forget to answer all the previous questions. Every question posted is important.

    The 6V regulator output value?
    The indicator status. On off?
     
  19. Johnny340

    Thread Starter New Member

    Jan 30, 2014
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    I have 1.17v between 1&2 only when the button is pushed. Shorting 1&2 turns it off + light off.

    So it sounds like a bad timer. I assume one timer is shared by both which also explains why both heaters behave the same.

    I get 5.9 volts there.

    I see 1.6v across R5 & R6 when On. The red LED lights behave properly.
     
  20. inwo

    Well-Known Member

    Nov 7, 2013
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    Yes it seems to be the timer circuit.

    Strange as it looks like two timers.
    What is the number on IC2 and IC3?

    The timing capacitors C3 and C4 set the time.
     
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