F100 issues

Just got an F100 in what appears to be fairly good, but obviously old condition. When it first arrived, I tested it out, and it seemed to work beautifully. Took it to it's first gig (mostly just to try it out in practice, I didn't really need it), and hooked it up. It heated up fine, but the pump wouldn't run.
Now, back in the shop, I measured the voltage on the pump leads, and it seems to be 110VAC, whether or not the run button is pressed (timer is turned off on the timer remote). I also measured with a scope, the input voltage to the pump optocoupler. You can see a train of pulses when you press the Run button.

So, to me this says that the problem is either the SCR, the pump, or the optocoupler.

With the power off, the resistance across the pump windings is high, but not open (about 1 Meg).

What should the resistance of the pump windings be? Is this indicative of a bad pump?

If this is the case, does anybody here have a surplus pump they wouldn't mind selling?

I haven't really worked much with SCRs but I seem to remember they require a load to work properly, so is this why the voltage is 110VAC? Is the pump not giving enough load to the SCR for it to work? Or is this a bad SCR?


Thanks,

Jeff
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    ok, so now i'm even more baffled. I have 2 mainboards.. one from my unit, and one from a freind's (muvement on this board).

    On my board:

    I replaced the opto, the SCR, the diode (D4). The pump works if connected directly to 110V. When the fog button is not pressed, there is no signal on the input to the opto. When it is pressed, there is signal (120Hz with pulse width variable by the output pot), but also, when it is pressed, R17 burns up (pretty spectacuarly, with lots of smoke and a puff of flame). I can't seem to find any shorts or bad parts in that section of the circuit.
    Oh, and in steady state (when the button is not pressed, before R100 burns up), I measure ~120VAC across the pump leads (but the pump isn't running).

    On Neil's board:
    Replaced the opto, and the SCR. D4 measures fine. R16, R17, and R18 all seem fine. Using it in the same chassis as above, so the pump is the same. Have signal on the input to the opto when the button is pressed, just like on my board. Can't detect any changes on the output. Steady state voltage across the pump leads is a low AC voltage (8vac or so, whether the button is pressed or not). Haven't been able to find any open circuits or bad components. This seems more like an open than a short to me, where the other board feels like a short, but i can't find either of them...

    ideas?? things to check??
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  • 0
    ok, so now i'm even more baffled. I have 2 mainboards.. one from my unit, and one from a freind's (muvement on this board).

    On my board:

    I replaced the opto, the SCR, the diode (D4). The pump works if connected directly to 110V. When the fog button is not pressed, there is no signal on the input to the opto. When it is pressed, there is signal (120Hz with pulse width variable by the output pot), but also, when it is pressed, R17 burns up (pretty spectacuarly, with lots of smoke and a puff of flame). I can't seem to find any shorts or bad parts in that section of the circuit.
    Oh, and in steady state (when the button is not pressed, before R100 burns up), I measure ~120VAC across the pump leads (but the pump isn't running).

    On Neil's board:
    Replaced the opto, and the SCR. D4 measures fine. R16, R17, and R18 all seem fine. Using it in the same chassis as above, so the pump is the same. Have signal on the input to the opto when the button is pressed, just like on my board. Can't detect any changes on the output. Steady state voltage across the pump leads is a low AC voltage (8vac or so, whether the button is pressed or not). Haven't been able to find any open circuits or bad components. This seems more like an open than a short to me, where the other board feels like a short, but i can't find either of them...

    ideas?? things to check??
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