<Sigh> :(
I have a Flatline on breadboard, which I painstakingly laid out to get everything right. Apparently, I wasn't painstaking enough. I get output, but it's REAL quiet, I can't hear any apparent sustain/compression action, and I'm not seeing the LED light up (I have the LED/LDR exposed until I see proof it's working).
By way of due diligence, I do know the following:
The battery is good -- it's putting out at least 8.8V.
The TL072 is good -- I had it set up as a preamp to test it a couple of days ago.
The LDR is good.
The LED lights when I connect it to a 9V battery and a 1K resistor.
I'm getting about +4.5V out of the bias network.
I suspect the problem might lie in the diode bridge. Setting that up on a breadboard is a lot harder than soldering it into a circuit.
Does anyone have any ideas about how to defibrillate this thing?
Help!
Well first of all, if the LED worked and you had it exposed, it wouldn't make much difference because the LDR would be reacting to ambient light as well. Anyway. Check your connections and then check them again. I still screw up sometimes on a breadboard, it just happens ;)
IIRC there's a resistir 220k? across the LDR.
Playing with the value of that R will Cause the LDR's variable resistance sweep to have more or less difference over the gain.
Hopefully soemone else will chime on this one, but you could try a 500k pot there, tagged' in' just to see if that helps and then measure it's resistance without changeing it [pull the pot from the circuit] then replace that fixed resistor with the measured pots value.
Pete:
Yes, I do have the 220K resistor in series with the LDR. While I can see how changing this resistor might have an effect on the overall performance of the circuit, why would it influence whether the LED lights up? Are you thinking that with the LDR I have, that the amplifier half of the op-amp might not be amplifying enough to send enough current to the rectifier?
Any hints about breadboarding that diode bridge? What a horror show THAT'S been!