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I can only come up with two causes to this mysterious capacitor and that is wrong polarity, which it is not as unit_339 stated, or a bad capacitor and since you fed the regulator from a battery, or DC supply, we can leave out all the thoughts about excessive ripple. The zener diode (7V5 1W) itself does not affect the capacitor in any way unless it is located very close to it and run very hot. This zener should run cool with only (Iz ~49 mA) 370 mW pd. Also, as soon as there is even a light load on the 7,5 volts the power dissipation decreases and then it runs cooler.

Since you used the scope and found no anomalies we can be assured that the VR is feed by pure DC. If you put a resistor with higher resistance it will decrease the voltage regulators ability to meet up with an increased load, but here we are dealing with a very light load so I guess it does not matter. You bet I would like to have that Cobra on my bench, but I am in Sweden!

Think I will continue with the Spirfire MarkII!

<blockquote data-quote="Tech5" data-source="post: 844655" data-attributes="member: 65569">I can only come up with two causes to this mysterious capacitor and that is wrong polarity, which it is not as unit_339 stated, or a bad capacitor and since you fed the regulator from a battery, or DC supply, we can leave out all the thoughts about excessive ripple. The zener diode (7V5 1W) itself does not affect the capacitor in any way unless it is located very close to it and run very hot. This zener should run cool with only (Iz ~49 mA) 370 mW pd. Also, as soon as there is even a light load on the 7,5 volts the power dissipation decreases and then it runs cooler.Since you used the scope and found no anomalies we can be assured that the VR is feed by pure DC. If you put a resistor with higher resistance it will decrease the voltage regulators ability to meet up with an increased load, but here we are dealing with a very light load so I guess it does not matter. You bet I would like to have that Cobra on my bench, but I am in Sweden! <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f606.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=":LOL:" title="Laugh&nbsp; &nbsp; :LOL:"&nbsp; data-smilie="19"data-shortname=":LOL:" />Think I will continue with the Spirfire MarkII! <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f60a.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=":giggle:" title="Giggle&nbsp; &nbsp; :giggle:"&nbsp; data-smilie="18"data-shortname=":giggle:" /></blockquote>

[QUOTE="Tech5, post: 844655, member: 65569"] I can only come up with two causes to this mysterious capacitor and that is wrong polarity, which it is not as unit_339 stated, or a bad capacitor and since you fed the regulator from a battery, or DC supply, we can leave out all the thoughts about excessive ripple. The zener diode (7V5 1W) itself does not affect the capacitor in any way unless it is located very close to it and run very hot. This zener should run cool with only (Iz ~49 mA) 370 mW pd. Also, as soon as there is even a light load on the 7,5 volts the power dissipation decreases and then it runs cooler. Since you used the scope and found no anomalies we can be assured that the VR is feed by pure DC. If you put a resistor with higher resistance it will decrease the voltage regulators ability to meet up with an increased load, but here we are dealing with a very light load so I guess it does not matter. You bet I would like to have that Cobra on my bench, but I am in Sweden! :LOL: Think I will continue with the Spirfire MarkII! :giggle: [/QUOTE]

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