"Nothing" isn't a reading an oscilloscope makes. What does it show?
A flat line. I get the same reading when probing across C2 which suggests Q1 isnt being switched on and off by the signal generator?
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"Nothing" isn't a reading an oscilloscope makes. What does it show?
A flat line.
Yes, I figured that much. There is something else it is telling you - care to share it with the guy who's trying to help you?
Is it getting hot?
Press the CH2 menu button, select "DC input", and try reading it again.
It will be higher than 0V. If you still see 0V, get a voltmeter (using the DC setting) and double-check it. We need to see where the collector of Q2 is sitting to figure this out.
BTW - you aren't trying to operate those 2 transducers in parallel, are you?
Does your power supply have an overload trip? If Q2 stops oscillating (perhaps because of damping by the epoxy/glass) while Q1 is 'on' then the standing Q2 current will be excessive and drop the supply volts.
Have you tried the holed piezo in circuit without the sig gen and with J3/J4 shorted?
If you've only got 45mm water pressure the glass plug is a bit OTT. If you could remove it and instead use a thin clear plastic or glass cover (microscope cover glass?) over the hole, on one face of the piezo, there would be much less mechanical damping. Assuming the piezo is being driven in thickness mode (rather than in a flexure mode), the plug is presently acting like a clamp to prevent vibration of the piezo. With the plug gone it might then be able to oscillate freely.
^ Yes! Try a 220Ω resistor in place of C2 and see if that gets it going at the high frequencies.