Electronics > Beginners
LM317AHVT and Heatsink
Zero999:
--- Quote from: mike_mike on December 02, 2018, 02:07:44 pm ---
--- Quote from: Hero999 on December 02, 2018, 01:26:39 pm ---Going from what you've said, I suspect it was the solder joint to the potentiometer. It will probably work if you put the original potentiometer back. As I said before, it's likely it was a connection problem.
--- End quote ---
Before I change the PCB, I tested with the wires of the potentiometer soldered on the PCB, and the result was that the voltage still dropped from about 19.87V to about 17.87V.
In this case, does it still was a connection problem ?
--- End quote ---
Then it's more likely there's lose connection inside the potentiometer. Intermittent connections can be difficult to spot.
My advice is don't use that suspect potentiometer in another project. Junk it. Using parts which could be faulty will just cause frustration and time wasting later on.
mike_mike:
It can be a lose connection inside the pot even if the pot is a multiturn pot ?
I forgot to mention that I used a multiturn pot...
How can I check for sure to see what component is making that problem ? I want to have a good power supply. I already made a few supplies in the last few years and they were oscillating... so I don't know what should I do... I am also very maniac in electronics and I want that those power supplies to be made by me.
Zero999:
It's not uncommon for any potentiometer to develop an intermittent failt, multi-turn or not. The fact it works now suggests it was a problem with the pot. It's possible it was something else of course.
mike_mike:
Could those voltage drop problems be a result of oscillations ?
If yes, then how can I find the oscillations ?
I already tested with the scope on the output (please have a look at the previous posts).
mike_mike:
Hello,
I am working at a new project. The schematic is attached in this post. The project uses an LM317T and a PNP pass transistor (TIP36C). I marked on the schematic the pins for LM317 and TIP36. LM317 and TIP36 will be connected to the board using wires.
I made the layout but I am not sure if it is correct.
I read a few documents about layout guidelines and I tried to respect some rules in this layout: I divided the schematic into low current and high current zones, I added copper planes for GND, I put the unpolarised capacitors near LM358, I put the bridge rectifier and 0.1R resistor in the lower part of the layout - because of the heat generated, I tried to make the traces as short as I could.
The DRC does not return any error, but I want to know if the layout guidelines are respected ?
If the layout guidelines are not ok, could you help me to correct the problems ?
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