12V 60A car battery , maybe dead?

[Groundloop]

Thanks Groundloop.
Two things have happened. The 5W pot on the original circuit was damaged (burnt?) at the position where the circuit draws 0.6 Amps. I am assuming this because trying to set it to a current draw of 0.6 it either jumps to 0.4 or 0.8. I have not yet tried a 0.47uF Capacitor but will try it on the original circuit this weekend.

The second is that I have managed to get a used analogue oscilloscope. So the learning curve has suddenly steepened somewhat for me.

It is a Pintek PS-605 60MHz dual trace oscilloscope. I am sure that it will be more than adequate for my purposes. It has a really cool function where you can test different components such as resistors, capacitors, diodes and transistors. I am busy studying the manual and have managed to take some measurements on the second circuit that I built last night. If my calculations are correct the circuit oscillates at 11.9 KHz. (the wave length is 4.2 divisions at a time/div setting of 0.2uS) It was interesting to see that the waveform on the "positive" side of L1 and one of the outputs of L3 looks very similar except that L3 is more "noisy". 

The peak to peak voltage on the positive of L1 (again assuming that my maths/understanding has not failed me) is 40V. (4 Divisions at a setting of volt/div setting of 1V and the probe at 10x gives me 40V)

The Voltage on L3 (L1 and L3 are connected the same way and L2 is reversed) Taken at the same side as L1 looks the same and the frequency appears to be exactly the same. The voltage there is also about 40V.

Does this seem correct?

Here are pics of the two waveforms I am talking about. The second one is L3.

Thanks
Marnus

Marnus,

You have way to much DC bias current going to the base of your transistor. Solution is to increase the series resistor value
to approx. 150 to 200 Ohm.

Congratulations with your new o-scope. A two channel 60MHz o-scope is OK to have in a hobby electronic environment.

Use the minus rail as o-scope ground (where the transistor emitter is) and measure at the base of the transistor and
also at the collector of the transistor. Use the DC setting on your o-scope to see the DC offset. Probe to X10 and scope
voltage input at highest setting at start-up.

Alex.

[Mars67]

Hi Alex

Thank you very much for your patience and persistence. I will post the measurementss here when I get home this afternoon.

[Mars67]

OK so I played around with some different capacitors to see what impact they have on the circuit. I did not also get time to see what different resistors would do and I will see if I get time to check this evening. I took the DC measurements on the base and collector of the Transistor. With the original circuit I built using the 220nF Capacitor I measured a voltage average of 5.3V (the spikes differ in amplitude so I took the highest and lowest and averaged it) and the frequency of the circuit there is 4.26 KHz. On the collector the voltage is 35V and the frequency 4.3 KHz. I am attaching the two wave forms for the 220nF Capacitor only. The current I measured on the base is 0.485 A (with the circuit set to draw 0.6A from the ps)

Using a 330nF capacitor the values are Collector 5.5V, 1.01 KHz - Base  35V, 1.01KHz - Base current 0.425A (0.6A)
470nF Capacitor - Collector 5.7V, 2.04KHz - Base 36V, 2.04KHz - Base Current 0.425A (0.6A)

[Groundloop]

OK so I played around with some different capacitors to see what impact they have on the circuit. I did not also get time to see what different resistors would do and I will see if I get time to check this evening. I took the DC measurements on the base and collector of the Transistor. With the original circuit I built using the 220nF Capacitor I measured a voltage average of 5.3V (the spikes differ in amplitude so I took the highest and lowest and averaged it) and the frequency of the circuit there is 4.26 KHz. On the collector the voltage is 35V and the frequency 4.3 KHz. I am attaching the two wave forms for the 220nF Capacitor only. The current I measured on the base is 0.485 A (with the circuit set to draw 0.6A from the ps)

Using a 330nF capacitor the values are Collector 5.5V, 1.01 KHz - Base  35V, 1.01KHz - Base current 0.425A (0.6A)
470nF Capacitor - Collector 5.7V, 2.04KHz - Base 36V, 2.04KHz - Base Current 0.425A (0.6A)

Marnus,

If you run the circuit with a input of 9 Volt and the pot-meter is turned down to approx. zero Ohm, then the
maximum DC base current to the transistor should be 9/50 = 0,18 Ampere. When the pot-meter is turned
to maximum (500 Ohm) then the maximum DC base current should be 0,016 Ampere. So your measurement
of 0.425A base current can not be real or something is wrong. The pulses you measured from base to emitter
also looks wrong. Is the zero line on the o-scope at 0% or at the middle of the screen? For me it looks like you
are running the circuit with the base and emitter of the transistor swapped the wrong way? Have you
checked that? There should not be any large negative voltage spike on the base of the transistor because
the 1N4007 diode should remove any negative pulse voltage here. You should also disconnect the coils
and use a Ohm meter to check that it is NO short circuit between the three insulated coils.

Alex.

[Mars67]

Hi GL

I double checked and the transistor is definitely connected correctly. Looking at the bottom of the transistor with the pins above the mid line then pin 1 is on the left and that is the Base and pin 2, the emitter is on the right. The case of the Transistor is the collector. The emitter is the one connected to the common ground. I have quite an expensive clamp ammeter so I do not really have a reason to doubt its accuracy. Perhaps I am getting over reads due to the close proximity of the other wires although I made sure to get the correct wire in the clamp.

The previous wave forms posted I adjusted the vertical axis to be able to see the waveform properly. I am attaching the waveforms with the line on 0%. The waveform over the base/emitter is the first pic and the collector/emitter is the second pic. I am going to replace the 1N4007 diode this evening to see if there is anything wrong.

I checked the coils for a short again last night and did not find any. Both using a continuity tester on my multi meter as well as using the component testing mode of the oscope. It has a facility to indicate a short and I found nothing. I did get an AC current measurement on the base of 0.07 Amps with the pot open about two thirds (i.e. lower resistance)