BE QUIET! BQT P5-420-S1.3 troubleshooting

[yokoono]

I have BTQ P5-420W-S1.3.
PWM controller (8 pins) for +5vSB it"s exploded. What IC work?
What is the value of CX (exploded)?.
ps. Sorry for my bad english.

[POM_MJ]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

I thought the circuit wasn't 5VSB part, that could be main switching part.
the PWM chip might be UC3842/UC3843.
see the reference circuit attached.

[yokoono]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

With uc3842 or uc3843 or uc3844 +5vsb is not standing.
Variable between 4v and 4,5v (pulsate).

[POM_MJ]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

With uc3842 or uc3843 or uc3844 +5vsb is not standing.
Variable between 4v and 4,5v (pulsate).

I mean, the PWM chip (might be UC384x) and the transistor in your circuit drawing in #1 post are parts of main switching, not 5VSB circuit.

the 5VSB circuit wasn't use the PWM chip UC384x, it could be 2 transistors circuit.
and your 5VSB problem seem to be badcaps symptom.

[yokoono]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

No. 5VSB is witch ic pwm and n-mosfet.
Power circuit is witch TL494 and 2 transistors.
The caps it"s good.

[POM_MJ]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

may be your PSU is using Fuhjiyuu caps, like this one (images from google).
Fuhjiyuu are known crap caps, check your PSU caps.

[POM_MJ]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

Ok, I was wrong.
the PWM is UC3842 with 2SK2645.

Firstly, please try to change both 5VSB caps. I guess they're bad.

[POM_MJ]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

and this one.

[yokoono]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

URAAA! That"s it!
I change the caps. And the value for cx?

[POM_MJ]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

CX is used in soft-clamp circuit, I guess it value is 0.01uF/1KV.

[yokoono]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

Thank you very much POM-MJ.
You are a gentelman.

[POM_MJ]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

You are welcome.

[yokoono]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

Don"t work.
POM-MJ, please, what is wrong?

[POM_MJ]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

I would check all components in the circuit, include TL431 on secondary side.
may be some resistors were burnt.

Did you have change 5VSB capacitors?
I thought the PWM exploded due to heavy work because of leakage capacitors on secondary side.

if you post details of your PSU pictures, would help much.

[yokoono]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

I change all capacitors, tl431, 1N4148, DZ18V, MOSFET,optocuplor and resistors (all,all).
Maybe the value(s) of component(s) isn"t correct(s). Were blacks.

[POM_MJ]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

your PSU is now "+5vsb is not standing ,variable between 4v and 4,5v (pulsate)", right?
Which component(s) were burnt into black?

[yokoono]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

In this moment with the values of electrical diagram:
U(v) pin 7 - 11-12v valiable
U(v) +5vsb - 2v but the electric current through mosfet is too big.
The frequency of uc3844 is 190khz.

[POM_MJ]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

The 5vsb transformer could be burnt (wires short).
try to replace with a known good one for test.

[yokoono]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

The 5vsb transformer could be burnt (wires short).
try to replace with a known good one for test.

Big problem.

[POM_MJ]

Re: BE QUIET! BQT P5-420-S1.3 troubleshooting

Are you replace PWM chip with UC3844 ?

I thought it's caused the problem.
UC3844 has 50% duty cycle max., UC3842 has 100% duty cycle max.