Help in Power Supply

Hello again,


Merv, i found a problem with the diodes but did not find a problem with the LM317.

Here's another drawing to help illustrate this...note again that this is a view from the FOIL side...

Hi MrAl,

Good to talk to you again…hope all is well.

Now I'll put on my technical hat for a moment.

From your attachment directly above I see the following:

1. The input, pin #3, is correctly connected to the bridge and filter cap;
2. The output, pin #2, is incorrectly connected to the voltage adj circuit, the junction of R2 & VR1, vice the correct termination to the junction of R2, R3, C3 & CN2 (out);
3. The adj, pin #1, is incorrectly connected to the junction of R2, R3, C3 & CN2 (out), vice the correct termination to the junction of R2 & VR1;
4. The regulator, LM317T, can be mounted on the board in four different positions, all of which would be incorrect based on the existing board layout;
5. From the OP's post #7, the silkscreen is on the component side as shown in the second graphic of that post;
6. The initial placement of D2, cathode to the bridge and anode to the output, was correct, but now the anode is not connected to the output of the board.
7. D3 is correctly placed in the OP's post #12 IF the pinout of the regulator were correct, however, the placement and polarity shown above appears incorrect given any configuration of the 317.

My conclusion is the OP may have chosen the wrong component from the library during layout. The 78xx family of regulators would match the input, "common" and output pinout in the layout. I'm thinking maybe the OP may have assumed an identical pinout between the 78xx family and the LM317. Just guessing at this point, but it may be the root cause. What are your thoughts?

Cheers,
Merv

MRCecil said:

My conclusion is the OP may have chosen the wrong component from the library during layout. The 78xx family of regulators would match the input, "common" and output pinout in the layout. I'm thinking maybe the OP may have assumed an identical pinout between the 78xx family and the LM317. Just guessing at this point, but it may be the root cause. What are your thoughts?

Click to expand...

yes that is what happen the program i use contain only a general symbol for regulators(which was for 78xx) so pin#1 and pin#2 are incorrectly connected.this what cause the problem ,i'l fix it tomorrow and back with the result to here .

ahmelsayed said:

yes that is what happen the program i use contain only a general symbol for regulators(which was for 78xx) so pin#1 and pin#2 are incorrectly connected.this what cause the problem ,i'l fix it tomorrow and back with the result to here .

Click to expand...

Hello ahmelsayed,

Thank you for validating my hypothesis. Hey, we all have done something like that in the course of our careers, and more than once...let me count the ways!

Don't get down on yourself, but rather count it as a learning experience, from which you can grow and learn further.

Cheers,
Merv

Hi again,


Merv:
Thanks for being so persistent. I thought you were talking about the pinout of the LM317 as matching the board pinout the way it was labeled.
Anyway, here is a new board drawing which can be used to correct the problems. Feel free to check it over and find any remaining errors. Note that the color 'gray' is also used for the meter, both sides, light gray for the positive terminal.

Hi There,

May I just call you Al? MrAl seems so bloody formal.

Yes, that reconfiguration would work fine methinks. But would it not be simpler to just carefully twist the legs of the TO-220 to fit in the proper locations and reverse the polarity of D3? That is what I would do to get it corrected the same way (got practice with that ) without cutting traces and placing a long jumper. But maybe that is the hard way to use the existing board. Ya just really don't know until an issue like that winds up on your own bench.

MRCecil said:

Hi There,

May I just call you Al? MrAl seems so bloody formal.

Yes, that reconfiguration would work fine methinks. But would it not be simpler to just carefully twist the legs of the TO-220 to fit in the proper locations and reverse the polarity of D3? That is what I would do to get it corrected the same way (got practice with that ) without cutting traces and placing a long jumper. But maybe that is the hard way to use the existing board. Ya just really don't know until an issue like that winds up on your own bench.

Click to expand...

Hi again,


People here call me MrAl or Al, either one.

If you can find a simpler way to do it that's fine. You'll have to convince the OP to see if he wants to do it that way. But, what about the meter leads? The pot for that meter isnt wired right either so i included that board fix too. Check that part out see what you think.

hi MrAl , hi MRCecil
now it works as it should do. i spin the two legs (out,adj) and cover them with isolator to prevent short between them and didin't change any thing in the PCB just the IC.
the output is between 1.5 to 28 volts .
so thanks for u ,thanks very much.
but there something when i poweroff the output don't down to zero immediately but it take sometime nearly 10 secs , is that normal???

ahmelsayed said:

but there something when i poweroff the output don't down to zero immediately but it take sometime nearly 10 secs , is that normal???

Click to expand...

If it is shutdown unloaded, the supply will take some time to bleed down the 2200uf filter capacitor.