Why do you think the output of a NE555 will survive being shorted with an 8 ohm speaker?Remove the 100 ohm resistor between pin3 and the speaker. You can either replace it with a 1000uF capacitor or wire pin 3 directly to the speaker if you have a good old fashion NE555.
Why did you add a capacitor between the 555 and the 2N3055?
You told me to put a 470uf cap there look at post #32.
Remove the 100 ohm resistor between pin3 and the speaker. You can either replace it with a 1000uF capacitor or wire pin 3 directly to the speaker if you have a good old fashion NE555.
Why did you add a capacitor between the 555 and the 2N3055? Then the 555 #2 and the 2N3055 will not work properly. A capacitor is used if the output of the amplifier is push-pull and there is a single polarity supply (the 2N3055 is not push-pull). Also the capacitor you added might have destroyed the output of 555 #2. Maybe you did this before and that is why 555 #2 does not work properly?
Since your 555 #2 was marked "AC NE555" and it could not drive the 100 ohms resistor in series with an 8 ohms speaker then I suspect it is not a good or normal 555. Swap 555 #1 and 555 #2. If the 555 #2 cannot activate the relay then it is bad.
An NE555 can easily produce 10.5V into the 100 ohms in series with the base of the 2N3055 to produce a base current of 103mA. Then the 2N3055 can produce a collector current of 1A to 1.6A in the speaker. The AC power in the speaker will be 4W to 10.3W which will blow up your little speaker.
10W from the 2N3055?
When a 2N3055 is turned on hard, its collector to emitter voltage produces a max saturation voltage loss of about 0.4V when its collector current is about 1A and its base current is 100mA. Then with a 13.2V supply, an 8 ohm speaker gets (13.2V - 0.4V)/8 ohms= 1.6A and its power for half the time is (1.6A squared x 8 ohms)/ 2= 10.2W. If 555 #2 is good then it can produce about 103mA into the 100 ohms resistor in series with the base of a 2N3055 and the output of the 2N3055 into the speaker might be only 1A instead of 1.6A so the power in the speaker will be only 4W.
Guess what? The 1kHz and 1.5kHz is a squarewave that produces only 2W to 5W. The high frequency harmonics produce the other 2W to 5W that maybe the speaker or your hearing cannot produce.
The output of the 2N3055 is not push-pull so DO NOT USE A SERIES CAPACITOR FROM THE 2N3055 TO THE SPEAKER!
If you used a push-pull audio amplifier and it produces sinewaves, not badly distorted squarewaves like a 555 does, then a coupling capacitor blocks DC and low frequencies and is needed when there is a single polarity supply. The speaker voltage swings positive and negative because the coupling capacitor stays charged at half the supply voltage.
But the capacitor feeding the speaker is a highpass filter that cuts off low frequencies. There is a simple formula to calculate the cutoff frequency of a coupling capacitor feeding a certain load impedance.
A 470uF capacitor feeding an 8 ohm speaker cuts 43Hz to half the power (-3dB) of much higher frequencies and the 0.1uF capacitor you guessed about cuts radio frequencies higher than the AM broadcast band and less. The middle of the AM band would be at 1/5th the max power, ultrasonic squeaks from bats would be at a fairly low level and audio sounds would have levels lower than you can hear.
Gary, you seem to be making random circuits that are usually wrong. Instead, you should learn the basics of the electronics parts you are using.
1) Your 39 ohms is overloading the output of the 555.
2) Your capacitor polarity is (are) backwards which causes it to act like a piece of wire. If the polarity is corrected then it charges then discharges negatively into the base of the transistor damaging the transistor (that is why others added a diode).
You showed a push-pull amplifier that must be 59 years old. Transistor amplifiers have not used audio transformers for at least 50 years.
I think you are using an expensive monster old 2N3055 because you have some. Its massive heatsinked 15A of current and 115W is not needed in your 1.6A/10W circuit. A smaller TIP31 transistor would work fine at 1/10th the cost.
Of course, the backwards polarity is a piece of wire that works but the correct polarity capacitor charges quickly on the first positive half-cycle of the audio then has nothing to discharge it from then on.With 47uf cap connected from pin 3 of 555 to B of 2N3055 + on B circuit works. Turn cap around with - on B circuit works but volume is 99% lower. I have to listen close to hear it osc.
Add the 100 ohm resistor with cap still connected - to B no change circuit works volume is so low it is hard to hear.
Because the backwards capacitor is a piece of wire.With 100 ohm resistor and 47uf cap in series + on B circuit works good.
Because that is how the circuit should be without a capacitor.Remove 47uf cap leave the 100 ohm resistor between pin 3 and B volume has gone up very noticeable louder.
No. Twice the power sounds only a little louder. 10 times the power sounds twice as loud. The power went from 0.5W to 5W.volume has gone up very noticeable louder, 1w is now 1.1w of sound.
Because the output of the 555 is severely overloaded.Remove 100 ohm resistor pin 3 connected directly to B, 555 is stuck on 1KHz it will not osc.
No. When the supply is only 13.2V and the speaker is 8 ohms then a perfect output transistor fed with enough base current will produce an output of (13.2V squared)/8 ohms= 21.8W for half the time which is 10.9W. Like all transistors, the 2N3055 has a small saturation voltage loss so when the 555 provides it with a base current of 160mA through a 62 ohms resistor then the power in the 8 ohm speaker is 20.5W for half the time= 10.2W.Looks like output of 555 needs to be stronger to get more power from 2N3055.
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