mercury pc power supply only 5vsb supply.

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Re: mercury pc power supply only 5vsb supply.

hi ,i connected the traces like in the pic,i get the same results .. 16v at one end and 0.76v at other end of resistor.. but now the 4148 diodes give reading when touched together both at one side,did i miss anything?

[R_J]

Re: mercury pc power supply only 5vsb supply.

I dont understand? "but now the 4148 diodes give reading when touched together both at one side"
What is the resistance measured to ground on the end of the resistor that has the low voltage?

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Re: mercury pc power supply only 5vsb supply.

when i kept opposite from the junction ,i.e the negative of D9 and positive of D 10 ,i am getting value in diode mode ,before i dint get that.
how to measure the resistance to ground?

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Re: mercury pc power supply only 5vsb supply.

hmm.. i kept the black probe in ground ,but with no power, i kept the positive probe on end of low voltage point-- its 590 in diode mode and 645 ohms in ohms mode

[playit]

Re: mercury pc power supply only 5vsb supply.

in 2000k ohms mode, black probe in black wire , red probe at low voltage gives 775 ohms, at 16v point -777 ohms

[playit]

Re: mercury pc power supply only 5vsb supply.

here i guess i attached the links correct..

[R_J]

Re: mercury pc power supply only 5vsb supply.

Yes that looks corect, the resistor supplies the 16 volts to the two transistors that drive the small transformer. It also supplies the voltage through one of the small diodes (D10?) then through R32 that connects to another part of the circuit, likely the wt7520 ic .

[playit]

Re: mercury pc power supply only 5vsb supply.

so whats the problem.. what should be changed? am not getting 12 v at other side of the resistor..what point to be checked now?

[playit]

Re: mercury pc power supply only 5vsb supply.

should i check voltages in D9/D10 again to be sure?? hmm by keeping positive probe on positive points of this 2 diodes ?

[R_J]

Re: mercury pc power supply only 5vsb supply.

Remove this jumper wire to isolate the circuit. This way the only components that are connected to the end of the resistor are within the yellow box. If the voltage is still less than 1 volt, there must be a bad transistor or diode in this area

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Re: mercury pc power supply only 5vsb supply.

i removed the jumper wire and checked the voltage ,it was still 0.76v . also checked the (c15)yellow color capacitor g104m (cant find what it is in internet) - value in diode mode- 576 stable , reversed - 1868(in some thousands) then disappears.
the diode (D11) 4148 is good.
i am using this multimeter- DT380D( just incase may be of somehelp)
the 2 transistors - Q5 is attached to jumper, Q6 attached to +ve of D13(ph4148) ,and there is a D12 at back of Q6.
these diodes are all short,giving continuity(long beep).
transistors giving beep too ,before it dint give beep.. saw some vids according to my multimeter.. it said its a sign of continuity and its short.
the transistors are H945P 8B3,if its not available what should i get instead? i was waiting for you reply,thanks a lot for showing up

[playit]

Re: mercury pc power supply only 5vsb supply.

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?

[R_J]

Re: mercury pc power supply only 5vsb supply.

What is the voltage drop of a BEEP? What is the resitance of a long BEEP vs a short BEEP?
If the diodes and transistors are checking shorted, replace them.
How long is a PIECE of string?
Check the internet for susbstitute diodes, I am not going to look for a replacements, Why are you replacing them? Are they shorted?

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Re: mercury pc power supply only 5vsb supply.

if i touch both of the multimeter leads i get long beep as its called shorting (source - youtube videos),so when i touch the legs of transistor ,i get the same beep as shorting..

the transistor-- the horizontal - black at base- 676- 699
reversed gave- red at base -1749 - 1852
the vertical at base- continuous beep - black at base- continuous beep-value decreases- o-1812
reversed gave - red at base- continuous beep value 0 - 362

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Re: mercury pc power supply only 5vsb supply.

i just saw a video in which the schotty diodes at output side gave continuity long beeps (meaning short) even when power supply is working good, they say it happens sometimes but have to remove it to test it to see if it really is good or bad,so i am thinking of just changing the transistors and 4148 diodes

[playit]

Re: mercury pc power supply only 5vsb supply.

What is the voltage drop of a BEEP? What is the resitance of a long BEEP vs a short BEEP?
If the diodes and transistors are checking shorted, replace them.
How long is a PIECE of string?
Check the internet for susbstitute diodes, I am not going to look for a replacements, Why are you replacing them? Are they shorted?

whats piece of string?

[R_J]

Re: mercury pc power supply only 5vsb supply.

whats piece of string?

It is like a beep from a meter

[playit]

Re: mercury pc power supply only 5vsb supply.

hmm the beep is just long continuous never ending..
also can i use high ampere transisitor ,h945-p is
Type - NPN
Collector-Emitter Voltage: 50 V
Collector-Base Voltage: 60 V
Emitter-Base Voltage: 5 V
Collector Current: 0.15 A

i might get 50v but different amperes like 2A
is it ok to replace wtih it?

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Re: mercury pc power supply only 5vsb supply.

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 ?

[R_J]

Re: mercury pc power supply only 5vsb supply.

It is likely the diodes are ok, you are being fooled by the meter beeping. I keep telling you you can NOT go by that. YOU NEED TO READ THE FARWARD VOLTAGE DROP when using the meter in diode test. Schottky diodes have a lower voltage drop (0.2xx) not (0.6xx)