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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    Turns out it's not the pump. Supplying power temporarily directly to the pump causes it to work (found this out accidentally by shorting the SCR with a meter probe while trying to measure the output of the SCR).

    I actually think the problem might be the optocoupler at this point, but I think I'm going to just replace that entire portion of the circuit (because I'm pretty sure I burned up the SCR with my shaky hands) from the opto to the scr. I see what appears to be good signal going into the opto, but nothing on the output. won't cost much, and that will catch any other wierd things like partially burned resistors or bad diodes that may have either been originally contributing to the problem, or may have gotten burned when I shorted the SCR. Luckily, the traces all seem ok.
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  • 0
    Turns out it's not the pump. Supplying power temporarily directly to the pump causes it to work (found this out accidentally by shorting the SCR with a meter probe while trying to measure the output of the SCR).

    I actually think the problem might be the optocoupler at this point, but I think I'm going to just replace that entire portion of the circuit (because I'm pretty sure I burned up the SCR with my shaky hands) from the opto to the scr. I see what appears to be good signal going into the opto, but nothing on the output. won't cost much, and that will catch any other wierd things like partially burned resistors or bad diodes that may have either been originally contributing to the problem, or may have gotten burned when I shorted the SCR. Luckily, the traces all seem ok.
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