help with reflow unit

Discussion in 'General Electronics Chat' started by lokeycmos, Mar 31, 2013.

  1. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    the other day my yihua 8508D heat gun stopped working. the display comes on,but no heat or air flow. I have verified that the air pump works outside of the unit. there is some info on the unit here:

    it says that the heating element is supposed to be 90 ohms, but im measuring 20 ohms. I removed the connecter where the heating element connects to the circuit board. I measure 120v across the two connectors,but when I reconnect the heating element I only measure a few volts AC.

    im thinking that there may be more than one issue. does anyone have any advice or pointers for me? also, anyone know where I can get a schematic for it? thanks!
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    Last time I used my hot air pencil I forgot about the magnetic holder it needs to be in to start, does yours have one?

    If it's not something simple then it's a lot of grunt work if you don't have a schematic to follow.
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
    Follow the heater wires back to the pcb, i bet they go to the Triac {on the heatsink top right pcb} and {opto coupler white 6 pin chip Moc3041}

    There is an LM358 dual op amp that will be the thermostat, prob using a thermocouple in the heating element also.
    Last edited: Apr 1, 2013