555 timer will not oscillate

[Michaelangelo]

I'm building a microphone mixer/pre-amp. To deliver +48V of phantom power to the microphones, I'm constructing a Cockroft-Walton Multiplier to turn the 18V across the two 9V batteries into 48V. To do this, I've set up a 555 timer. But the timer isn't working properly.

Here are my troubleshooting steps:

1. I originally had the rated 555 timer hooked up to the regulated +6V rail and the virtual ground between the two batteries. When the timer was connected, it would drop the regulator's voltage down to ~+700mV and then slowly raise to ~+2.8V before causing a simulation error.

2. I connected the timer to both my regulated +6V rail and my -6V rail. Running the simulation caused my +6V rail to drop to +6.4V and my -6V rail to rise to +1.4V.  The output of the circuit was a constant 6.4V rather than a square wave.

3. I switched the rated 555 timer for an ideal timer. Voltages on my rails were then +5.97V and -4.89V with an output of 10.9V constant.

4. I changed the resistance of the load from 200 to 1k. Then my voltages were +6.00V, -5.98V and my output was at 12V constant.

5. I changed the layout of my 555 timer to a more efficient design. Same problem.

6. I copied the circuit into a blank project and added +6V and -6V sources. It works there. Copying it back into my project and it doesn't work there.

I imagine that it must be one of the simulation settings. Which setting could be causing this to happen?

[WenR]

Hi Michaelangelo

It is a little bit hard to guess on what could be causing this issue without having the circuit to test it. Could you share your circuit with us?

I guess you have already checked that the simulation settings are the same for both cases (time step and simulation time) and that you are performing the same simulaiton. Is the 555 connected to any load in both cases? Have you tried moving the rest of your circuit to the board were the 555 works?

WenR