Author Topic: Please help me repair a SMPS  (Read 2295 times)

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Offline zape

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Re: Please help me repair a SMPS
« Reply #25 on: November 10, 2017, 08:24:35 pm »
I have two bulbs 40W each so it is 80W
UPS shows 73W and it does not change if I connect the load

So the AC current is 0.6A
« Last Edit: November 10, 2017, 08:27:42 pm by zape »
 

Offline Armadillo

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Re: Please help me repair a SMPS
« Reply #26 on: November 10, 2017, 08:30:26 pm »
I have two bulbs 40W each so it is 80W
UPS shows 73W and it does not change if I connect the load

So the AC current is 0.6A

It is not short circuit. the bulb does light up in normal situation. You can take out the light bulb and plug it directly into the main to see what brightness is short circuit intensity.
Yes you learnt the bulb trick, but the teacher was not complete...... hahahahahahah LOL.

Edit: You are not using incandescent light bulb right...? hahahahaahahah LOL

Edit: And then maybe your backup power supply is charging the internal battery....... hahahahahaahha LOL....

Oops, sorry,..... just a lighter moment for all of us...

I have never used a UPS before, hence cannot recognise all the problems associated with it... example power limit etc...
« Last Edit: November 10, 2017, 08:38:08 pm by Armadillo »
 

Offline zape

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Re: Please help me repair a SMPS
« Reply #27 on: November 10, 2017, 08:43:48 pm »
It is an incandescent light bulb of course.
HMM let me check one thing
« Last Edit: November 10, 2017, 08:45:36 pm by zape »
 

Offline Armadillo

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Re: Please help me repair a SMPS
« Reply #28 on: November 10, 2017, 08:45:16 pm »
It is an incandescent light bulb of course.
I lights up exactly the same if I just plug it into mains

it depends before the UPS or after the UPS.
Do you think 0.6A is a short circuit?

Edit: 0.6A is not a short circuit. the series light bulb is only used for initial testing for short circuit. In this case, the light bulb as you used it with the UPS cannot discern or provide you with a useful cue between short and 0.6A.

So, you should plug back to the TV and turn it on.
 :D
« Last Edit: November 10, 2017, 08:51:41 pm by Armadillo »
 

Offline Armadillo

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Re: Please help me repair a SMPS
« Reply #29 on: November 10, 2017, 08:53:53 pm »

HMM let me check one thing

Don't say you wired it in parallel?
 

Offline zape

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Re: Please help me repair a SMPS
« Reply #30 on: November 10, 2017, 09:17:15 pm »
IT WORKS!  :-+ :-+ :-+ :-+ :-+

So how should I properly use this light bulb trick then?
 

Offline Armadillo

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Re: Please help me repair a SMPS
« Reply #31 on: November 10, 2017, 09:38:24 pm »
 :-+ :-+ :-+ :-+ :-+ Great news.

The light bulb trick is for initial testing in case of short circuit.
Purpose is to limit the voltage and current through the device under test.
So for me I would size the light bulb to be 20% of the full load power of the device under test.
So, if for example the DUT is 20 watts, so the light bulb should be 100W [around to your discerning ability of shorts].
The sizing is not for the light bulb to lights up or maybe abit.
the light bulb must be incandescent light bulb.
you must wired in after the isolating transformer [after any device that consume power] and in series to the DUT.

The isolating transformer must have the power sufficient for the DUT X 2.

I have 1500VA isolating transformer to meet the occasion.    ;D

 

Online xavier60

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Re: Please help me repair a SMPS
« Reply #32 on: November 11, 2017, 12:41:24 am »
The function of Q621 makes no sense. Its Collector would have to connect to the Gate of the MOSFET to reduce the MOSFET's on time, in case of excessive line voltage.
Hioki AS100D vom, HP 54645A dso, Fluke 87V dmm, AN8008 dmm, Agilent U8002A psu,  FY6600 function gen, New! Brymen BM857S-(With Battery)
 

Offline Armadillo

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Re: Please help me repair a SMPS
« Reply #33 on: November 11, 2017, 04:02:42 am »
The function of Q621 makes no sense. Its Collector would have to connect to the Gate of the MOSFET to reduce the MOSFET's on time, in case of excessive line voltage.

its "over voltage protect" not for "output over voltage" but for Q602 if the induced voltage at the Base continue to rise even after it had pulsed.    ;D
 

Online xavier60

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Re: Please help me repair a SMPS
« Reply #34 on: November 11, 2017, 07:31:55 am »
The function of Q621 makes no sense. Its Collector would have to connect to the Gate of the MOSFET to reduce the MOSFET's on time, in case of excessive line voltage.

its "over voltage protect" not for "output over voltage" but for Q602 if the induced voltage at the Base continue to rise even after it had pulsed.    ;D
Yes, that's the way it might seem from the way it's drawn. Not useful at all.
D621 rectifies the + half cycle or the forward half of the waveform rather than the fly-back half. The  voltage rectified by D621 will be proportional to the incoming line voltage.
Hioki AS100D vom, HP 54645A dso, Fluke 87V dmm, AN8008 dmm, Agilent U8002A psu,  FY6600 function gen, New! Brymen BM857S-(With Battery)
 


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