Your output cap for the regulator (or more specifically, the decoupling cap for the 555 timer) is much too small. For TTL 555 timers, you need a HUGE decoupling capacitor (like 10uF) because they actually produce a ~150mA short-circuit due to shoot-through in the internal totem pole output transistors whenever they switch (or so I am told). CMOS versions don't have this problem but have lower drive current.
Your input source to the regulator does not have enough current I think. That is why you see big spikes on your 5v. 2v spikes on Vcc are not good. I think you need a stronger supply before your regulator. Like I asked before, what is your input voltage source, and give specs.
Can you power your circuit, including regulator from your bench power supply?
Try to use bigger resistors and a smaller capacitor - The current in the RC timing branch is too high for the power supply and for the 555's discharge transistor at pin 7.
Eg: with 820Ω, 2kΩ, and .001µF (= 1nF) you have the same frecuency with one tenth of the current.
Intersil makes a Cmos ICL7555. In its datasheet they say that the shoot-through current when an ordinary 555 switches is 400mA.
Two supply bypass capacitors should be used. One is a 0.1uF ceramic type to stop the very narrow high frequency spike that the 10uF electrolytic type cannot filter.
1) I built up this circuit and got nearly 240K frequency and 44% duty cycle.
2) But when use a normal LM340T5 to produce a 5V to the LM555 timer the frequency immediately drop to 190KHZ.
Your output cap for the regulator (or more specifically, the decoupling cap for the 555 timer) is much too small. For TTL 555 timers, you need a HUGE decoupling capacitor (like 10uF) because they actually produce a ~150mA short-circuit due to shoot-through in the internal totem pole output transistors whenever they switch (or so I am told). CMOS versions don't have this problem but have lower drive current.
I agree that the capacitors are too small but I would go with a 250 uf on the input of the reg and a 1000 uf on the output. That should smooth things out
Try to use bigger resistors and a smaller capacitor - The current in the RC timing branch is too high for the power supply and for the 555's discharge transistor at pin 7.
Eg: with 820Ω, 2kΩ, and .001µF (= 1nF) you have the same frecuency with one tenth of the current.
I agree that the capacitors are too small but I would go with a 250 uf on the input of the reg and a 1000 uf on the output. That should smooth things out
He did say: LM340T5. Which is why I was able to quote Vinmin from the datasheet in a previous post, and why I suggested his 6.8V input may not be enough to allow his part to regulate.
(You must have missed that part of the discussion )