Kempachi343
New Member
Hi,
I've just built up a 5-15vdc power supply, which I want to be capable of about 8amps. This is my first attempt at an electronics project, I researched everything for this project off this forum.
I followed the design on the attached diagram, Even tho he is using a 26v input. I used the same components, I used a 0ohm - 20kohm tripot as the voltage adjustment. My input is 17vdc after a bridge rectifier and 4700uF capacitor. I couldn't find 0.1ohm 10w resistors, so I used 5w instead.
When I first tested it out, I had 8.5v no matter what I set the tripot too, I added in a test lead between - and the other leg of my tripot, I didn't solder it in at first because in the spec sheet for LM723 I saw a resistance through there was only for higher voltage circuits, and I wasn't completely sure I was reading the diagram right.
After I'd added this lead in, I had 8.5v - 14v adjustments, I was very happy, and proceeded to try a load on it. I hooked up a pair of motors that I expected would draw around 6A, they ran, although only drawing about 3A, and I could tell the motors had no grunt in them, after about 5 seconds the motors stopped, and my voltage dropped down to about 2v.
The tripot only adjusts around 0.1 of a volt now, yet when I remove my test lead between - and the other leg, I get the 8.5v again. I'm still getting 17v after my rectifier and capacitor, the tripot is still functioning, the resistors are still 0.10hms, the wiring still looks good, the heatsink which I used to mount 2N3055 on wasn't hot at all.
That leaves me with LM723, the 3 transistors, and the 100Pf capacitor. Is there anyway to test these components to find out which has failed? And also can anyone give me some insight as to why this happened?
Cheers,
Daniel.
I've just built up a 5-15vdc power supply, which I want to be capable of about 8amps. This is my first attempt at an electronics project, I researched everything for this project off this forum.
I followed the design on the attached diagram, Even tho he is using a 26v input. I used the same components, I used a 0ohm - 20kohm tripot as the voltage adjustment. My input is 17vdc after a bridge rectifier and 4700uF capacitor. I couldn't find 0.1ohm 10w resistors, so I used 5w instead.
When I first tested it out, I had 8.5v no matter what I set the tripot too, I added in a test lead between - and the other leg of my tripot, I didn't solder it in at first because in the spec sheet for LM723 I saw a resistance through there was only for higher voltage circuits, and I wasn't completely sure I was reading the diagram right.
After I'd added this lead in, I had 8.5v - 14v adjustments, I was very happy, and proceeded to try a load on it. I hooked up a pair of motors that I expected would draw around 6A, they ran, although only drawing about 3A, and I could tell the motors had no grunt in them, after about 5 seconds the motors stopped, and my voltage dropped down to about 2v.
The tripot only adjusts around 0.1 of a volt now, yet when I remove my test lead between - and the other leg, I get the 8.5v again. I'm still getting 17v after my rectifier and capacitor, the tripot is still functioning, the resistors are still 0.10hms, the wiring still looks good, the heatsink which I used to mount 2N3055 on wasn't hot at all.
That leaves me with LM723, the 3 transistors, and the 100Pf capacitor. Is there anyway to test these components to find out which has failed? And also can anyone give me some insight as to why this happened?
Cheers,
Daniel.
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