Hi E,hi C,
Look at this marked up image.
What is the load current on the Vreg output.?
E
The load has to be a guess, but I'd say a little over >1A
C
Hi E,hi C,
Look at this marked up image.
What is the load current on the Vreg output.?
E
Hi D,it looks like the voltage regulator is not working
If that is true, the 5V reg needs a heatsink with less than 10C/W thermal resistance.Hi E,
The load has to be a guess, but I'd say a little over >1A
C
Hi S,The PCB could be alright maybe.
Working with the decoupling caps would begin to show certain wave shaping.
the blue might be acceptable possibly more capacitance would be going beyond what was needed
in this example for the given load.
View attachment 233160
Hi E,If that is true, the 5V reg needs a heatsink with less than 10C/W thermal resistance.
The copper pad on the PCB is not enough.
The power supply that I was looking at starts with 9V ...Hi S,
Can you clairify please?
Are you talking about PCB6 that the initial question is about? So If I added the suggested decoupling capacitors, then it whould work.
NOTE: I made two PCB6s. The one with the fault, and one I abandoned for some reason? previously, which worked ok, and didn't have any Capacitors on yet (But it's not going to be used) as I'm adding the suggested Caps, on PCB7.
C
Hi S,The power supply that I was looking at starts with 9V ...
https://ww1.microchip.com/downloads/en/DeviceDoc/Explorer_16_32_Schematics_R6_3.pdf
I looked briefly at the two commercial development boards for the old 18F4 series 40 pins very complex.
I was hoping the picture could be compared to what you had PCB6 but I see you are moving a fast pace.
it is not easy to talk about either of those boards without a detailed study and history, a lot of work.
The 4431 secondary internal osc 125kHz might be problem I am really not sure.
Hi S,The pdf ( one of microchip's) later power supply designs reflects design changes for later chips.
You still have to work backwards correcting for all the old chips so having feelings of disgust and frustration
at times using a coping strategy of starting fresh. The other comments on thermal and load are good
possibly improvement on the latest power supply design will be a decision of cost and PCB improvement.
The numbers of layers and parts density would be a different department.
Hello C,Hi D,
Why do you say that?
C
Hi D,Hello C,
I just looked at the initial scope screen and the thought came to mind, I admit I did not read all the other replies nor is my comment one arrived at thru careful analysis. It was off the cuff.
Sorry for not offering a better analysis,
D
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