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FOG MACHINE PCB FAULTY

Discussion in 'Troubleshooting and Repair' started by partyanimallighting, Jul 12, 2013.

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  1. partyanimallighting

    partyanimallighting

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    Oct 22, 2012
    Hi, I'm having an issue with a fog machine not outputting 110V to the heating element. I'm not sure if it's a defective relay or another part. Any help will be appreciated.
     

    Attached Files:

  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Can you hear the relay clicking on and off as it is supposed to be switching the power to the element?
     
  3. partyanimallighting

    partyanimallighting

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    Oct 22, 2012
    Hi *steve*, when I power up the pcb I do hear the click from the relay but there are two relays on the pcb so I'm not sure if it's only one or both that are clicking on. I'm not sure (not too versed in tracing pcb's etc.) but I think one relay switches the voltage to send 110V to the heating element and the other relay switches on the voltage to the 110V fluid pump.
     
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    You should be able to trace the tracks from the two 110VAC output connectors back to the relays, to find out which relay switches the heater and which relay switches the pump. It seems likely that the heater is switched by the relay closest to the edge of the board.

    The two pins at the top end (in the picture you posted) of the relay will be the coil connections; the circuitry should apply a DC voltage (probably 12V or maybe 5V) across those pins to turn on the relay. You should be able to measure this voltage with a multimeter to see whether the fault lies in the relay or in the circuitry that drives it.

    If you find that the drive circuitry is not producing the expected voltage, follow the track from that relay coil to see which part of the circuitry it connects into, and post close-up photos of both sides of that part of the board. The pictures need to be in focus and well-lit. Outdoor illumination, but not direct sunlight, is best.
     
  5. partyanimallighting

    partyanimallighting

    322
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    Oct 22, 2012
    Hi guys, sorry for the late reply. I did some poking around and here are the results. KrisBlueNZ, I measured the voltage at both relays and I'm getting 12V at the inner relay (this one drives the pump) and 0V at the outer relay. There are two regulators, LM7805 and LM7812, on the upper right hand side of the pcb and, based on what you taught me on previous repairs, these are supposed to output 5V and 12V respectively, and I'm getting correct readings on these (4.99V and 16.78V). There are two diodes (??? not sure what they are) above the relays and I'm getting 12V on the one above the inner relay and 0V on the other (feeding the heater). I also traced back to two 3 pin triacs (??? again, not sure of the name) a little above and to the right of the inner relay and I'm getting 12V at the bottom one and 0V on the top. Hope these readings help.
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    If you're getting 12V on the relay, then the reading if 16.8V on the 12V reg is probably wrong. You may be reading the input voltage.

    It would be unusual to have both triacs and relays.
     
  7. partyanimallighting

    partyanimallighting

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    Oct 22, 2012
    Hi Steve, I'm not too sure of the exact names for the parts. I just included links to photos of both front and back.
     
  8. partyanimallighting

    partyanimallighting

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    Oct 22, 2012
    Hi Steve, sorry about the wrong reading. That was input voltage on the LM7812 I'm getting the correct reading, 12V at output.
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    OK, a BTA16 is a triac. And I'm glad you have 12V at the output of the 12V reg.

    Can you explain a little more about the fog machine? Does it just turn the fan on/off, or is there a speed control? (or perhaps does it modulate the temperature to the heater)?

    It might be useful for you to show us what plugs in where (i.e. heater, fan, etc) and which relay you hear clicking on and off. I assume this is consistent with the fan activation?
     
  10. partyanimallighting

    partyanimallighting

    322
    4
    Oct 22, 2012
    Hi Steve, the machine is fairly straightforward. 110V in to power the pcb and there are two 110V outputs controlled by the relays. The outer relay feeds the heater coil via the 110V outputs located next the the 110V inputs. The inner relay sends 110V to the pump via the 110V output located above the copper wound coil between the two yellow capacitors at the bottom of the pcb. Plug in, switch on, remote states "Warming up" and when the heater reaches the correct temperature, the remote states "Ready to fog". Press the FOG button on the remote, the pump sends fluid to the heater, and fog is output. The single multi-pin terminal at the top of the pcb is for the remote and the other two at the top is for DMX input and output. Other than that there's a terminal with two screws on the upper left for the temperature sensor for the heater. Hope this helps.
     
  11. partyanimallighting

    partyanimallighting

    322
    4
    Oct 22, 2012
  12. partyanimallighting

    partyanimallighting

    322
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    Oct 22, 2012
    Hi Steve, I believe the issue is between the voltage regulators and the relays. You're the experts.
     
    Last edited: Jul 16, 2013
  13. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Thanks for the explanation of how the unit operates.

    As best I can tell from those photos, the triac controls the pump and both the relays are involved in the circuit that supplies the heater.

    The outer relay clearly controls the heater, but the function of the inner one is not clear. It is also in the current path to the heater, but it may also be involved with the pump. It may be being used as a changeover relay, but I can't say for sure because I can't see what tracks (if any) are on the top side of the board, underneath the relay.

    It could be useful to see a photo of the top side of the board with both relays temporarily removed, if that wouldn't be too much trouble.

    Looking at the coil side of the relays (the north ends, on the top side picture), they are both supplied from the same voltage rail - you can see that the cathodes (stripe end) of the diodes next to the relays are connected together. This rail should have +12V on it, relative to the main circuitry ground; I assume it does, otherwise neither relay would be working.

    The relay coils and are switched by the two transistors north-east of the inner relay. They are controlled by the circuitry north-east of them; probably from outputs from the microcontroller(s) (the ICs with paper labels on them).

    Can you measure the voltages on both ends of those two diodes at the coil ends of the relays (relative to circuitry ground, which will be available on the heatsink tabs of the regulators). That could be helpful. Also could you post the markings on the relays.

    A photo of the top side with the relays removed might be the next step.
     
  14. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
  15. partyanimallighting

    partyanimallighting

    322
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    Oct 22, 2012
  16. partyanimallighting

    partyanimallighting

    322
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    Oct 22, 2012
    The non-valid like before was probably a picture I deleted because of poor quality. Just let me know what you want me to check next and I'll get the results back to you.
     
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