power supply resistor voltage

hi , i dont know if its the right place to ask for help in fixing a power supply, may be someone who would like to help,please try ,thank you

i have a 400w power supply,i was getting only 5vsb . so from some friend in a online forum i got to know that R23(resistor) was open,so instead of an smd,i placed a hole thorough resistor,it worked. but i wanted to solder it well and spoiled the pads.

now that area is stripped but again i got help and completed the circuit i guess,still i am getting 16 volts at one of resistor and 0.76v at other end.is it normal or should i change any parts in it,please guide me, thank you, also please see the pics…

Hi,
Welcome to the forum.

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OR
http://forum.arduino.cc/index.php/topic,148850.0.html.

OPs picsw.

Personally it looks from the power supply has seen better days.
Where did you add the resistor?
What value did you fit?

TomGeorge:
Where did you add the resistor?
What value did you fit?

Do you suppose it is the thing sticking out in the last picture?

thank you so much for replying me,i am so stuck now .i was getting only 5vsb,no other voltages, it was a open R23 smd resistor ,it blew up i guess, so i got help from some forum, was told by a good person that it should be mostly a 1.5k 0.5w resistor, so i can put a hole thorough resistor for easy soldering,it worked ,all lights lit up ,fans started to run,but then i was trying to fix the resistor little better thats where i pulled off the whole pads.. and dint know what to do,got frustrated and threw the board..

now i got calm, so trying to fix and got help in finding out circuit trace around R23, now i am not sure if i am getting right voltages ,one person says its normal to get 16v at one side of resistor and 0.76v as it might be with transistor. but the person who was helping me with this was telling me see if it gets 16v or 12v at other end of resistor .. i so stuck.. i really want to see it work atleast once.. sorry for the long post.. please bear me thank you :slight_smile:

Paul__B:
Do you suppose it is the thing sticking out in the last picture?

yes thats the one.. in summary i am getting only 5vsb in psu tester,normally when i plug psu tester ,all lights lit up and the fan starts to run.
everyone says its a crappy psu.. but i just want to work for my case fans.. or atleast i wana see it work atleast once.. would give me great satisfaction..thank you for replying :slight_smile:


here in this pic i got help how to connect the ends.
"This is how the trace should be. and this is how to connect that 1.5k resistor. You need to connect the RED diode anode to the grey jumper wire (yellow trace)
One end of the resistor can connect to the jumper wire and the otherend to the blue diode cathode."

I am not sure exactly where the trace broke off, or how much broke off, but if there is still a trace there that you can connect to, you could try to scratch about an 1/8 of an inch off of the end of the trace with a thumbtack to get off the solder mask and expose copper. Do this on both traces. Then tin the pads you made with solder. Re-solder the through hole resistor onto those pads. If its legs arent long enough, solder a jumper wire onto one of the pads and solder that to a side of the resistor. Then, just solder the other end of the resistor to the other pad that you made and you should be good. Hope this helps.

i did that already ,thank you for replying,its in the last pic above.. just want to know if the readings are correct.. i am getting 16v at one of resistor and 0.76 at other end which goes to transistor and then to drive transformer.. is it a normal reading?

The voltage across resistors change based on the resistors resistance. If you changed the and resistor out with a through hole resistor of the same resistance, you should be good.

yes it did work after i changed ,but the problem now is the pads gone off and i am confused with the connections,but got help from a kind person and following his steps, i think i shorted some transistors ,and diodes(4148) ,so now i have to worry about getting those things in offline market or at a 2hour distance shops, by the way i am searching for all help i can get.. :slight_smile: please kindly see the circuits and give me some ideas/knowledge,i would be happy to work on it ,thanks for replying

the transistors are H945P 8B3,if its not available what should i get instead? and some diodes at output section on heatsink = stth1002ct gkdsnvu chn816, and stps2045ct 7sacdvw phl 806(2 in numbers)
could you tell me what alternatives i can use if i dont get these?

Most of us - and I say most - do really hate playing whack-a-mole with PC power supplies. :roll_eyes:

hope 1 day i get help to fix this or just get tired of it lol ,but not gona give up that easy.. kinda like riddle..interesting .going to use this to develop my patience ,manage my anger and else others :stuck_out_tongue:

Well I have to give you credit. You are persistent but my view is the same as in the other forum. Just let it go. :slight_smile:

Ron

havnt got tired of it yet..so will see :stuck_out_tongue:

Its common for multiple failures when a SMPS goes bang. Since you've one rail working apparently it might
be worth continuing, but its usually not worth the effort in my experience, as replacing one broken component
without replacing all the failed ones can simply blow it up again, if it was the victim of a cascade failure
rather than the cause of it.

Checking all the magnetics for continuity (assuming you have the schematic), then replacing all the semi-conductors, is the most likely strategy for success. If some magnetic component has failed and you just
mess around with the other components you won't get anywhere...

would need little clarity on choosing substitutes by the ratings on
stth1002ct -this is Fast Recovery Rectifiers 200v, 8x2 16A,fv -1.25 V
stps2045ct - this is Schottky Rectifier vrrm -45v, 10x2 20A ,vf- 0.84 V

how nearest i can get a component less or high.. ,which parameters to choose ?

MarkT:
Its common for multiple failures when a SMPS goes bang. Since you've one rail working apparently it might
be worth continuing, but its usually not worth the effort in my experience, as replacing one broken component
without replacing all the failed ones can simply blow it up again, if it was the victim of a cascade failure
rather than the cause of it.

Checking all the magnetics for continuity (assuming you have the schematic), then replacing all the semi-conductors, is the most likely strategy for success. If some magnetic component has failed and you just
mess around with the other components you won't get anywhere...

hi thank you for replying.. magnetic you mean transformer? i dont have schematic.. but a friend in another forum is helping me out ,dont wana trouble him a lot ..smiles..

MarkT:
its usually not worth the effort in my experience, as replacing one broken component
without replacing all the failed ones can simply blow it up again, if it was the victim of a cascade failure
rather than the cause of it.

Ergo - "Whack-a-mole"! :grinning:

"Since you've one rail working apparently it might
be worth continuing" :wink:

would need little clarity on choosing substitutes by the ratings on
stth1002ct -this is Fast Recovery Rectifiers 200v, 8x2 16A,fv -1.25 V
stps2045ct - this is Schottky Rectifier vrrm -45v, 10x2 20A ,vf- 0.84 V

how nearest i can get a component less or high.. ,which parameters to choose ?