HP W2408H No Power (Surge) Repair - Success

[jamalC]

Re: HP W2408H No Power (Surge) Repair - Success

Probably yes, supposed you power on che monitor only one time, the NTC is there to protect the diode bridge from Power surge due to high current requested to charge the big cap the first switching on.

the monitor didnt poweroff

so i soldered the sck 037 back.

something I noticed: i can hear the high pitched sound (like capacitor charges?). and high pitched, i mean there is a ramp of the pitch going up (slow attack of the envelope)

hey thanks for replies guys!!

[jamalC]

Re: HP W2408H No Power (Surge) Repair - Success

SCK037: 15mm Dia.
At room temp (25c) the resistance is 3 Ohms (Zero power, no current flow), full steady state current is 7A Max at 25C, at this current flowing the resistance will drop down to 0.091 Ohms. It is NTC so as the temp goes up when the current start flowing its resistance will go down.

thank for the explaining, very usefull.

[jamalC]

Re: HP W2408H No Power (Surge) Repair - Success

... Found out it should have been reading 5 OHMs when cool. Replaced thermistor with 5 OHM resistor and the monitor powered up.

im a bit puzzled why this guy says that this thermistor should be reading 5 ohm instead of 3??

[jamalC]

Re: HP W2408H No Power (Surge) Repair - Success

i also went through all diodes and resistors, all are reading nothing suspicous.
what is this guy i marked with a blue circle? it says some numbers on his back (0734 8178 y). what could his purpose be in this universe .) and how can i test him?

[vinceroger69]

Re: HP W2408H No Power (Surge) Repair - Success

i think its a optocoupler but not sure how to test it though.

[jamalC]

Re: HP W2408H No Power (Surge) Repair - Success

i think its a optocoupler but not sure how to test it though.

thx for the reply!

do optocouplers live long and strong?

[jamalC]

Re: HP W2408H No Power (Surge) Repair - Success

.... Replaced thermistor with 5 OHM resistor and the monitor powered up. .....

just replaced thermistor with 5 ohm (2 * 10ohms in parrallel was reading 5.6) and they both blew up.

[stj]

Re: HP W2408H No Power (Surge) Repair - Success

lol - because it probably pulled over 30w through them!

[jamalC]

Re: HP W2408H No Power (Surge) Repair - Success

lol - because it probably pulled over 30w through them!

aaahhh ...

[Davi.p]

Re: HP W2408H No Power (Surge) Repair - Success

Jamal maybe thermistor is not yor problem, it has a bit of resistance when you put the AC plug in but after it become as invisible, do some readings, for example in volt at the bigger capacitor, you must read about 320v. Use gloves for safety.

[budm]

Re: HP W2408H No Power (Surge) Repair - Success

24 inch monitor, lest say you are drawing 2A (if it is really drawing that high, more likely to be around 1A or so) through 5 Ohms = 20W of power, so about 10W per resistor. How big are the 10 Ohms resistors?
May be you still have bad circuits that is drawing too much current too.

[stj]

Re: HP W2408H No Power (Surge) Repair - Success

2a? with leds maybe, but not with rack of cfl's in it!
this monitor is rated at 130w

[jamalC]

Re: HP W2408H No Power (Surge) Repair - Success

Jamal maybe thermistor is not yor problem, it has a bit of resistance when you put the AC plug in but after it become as invisible, do some readings, for example in volt at the bigger capacitor, you must read about 320v. Use gloves for safety.

i'll defo do this. thx

[jamalC]

Re: HP W2408H No Power (Surge) Repair - Success

24 inch monitor, lest say you are drawing 2A (if it is really drawing that high, more likely to be around 1A or so) through 5 Ohms = 20W of power, so about 10W per resistor. How big are the 10 Ohms resistors?
May be you still have bad circuits that is drawing too much current too.

yea this is why im a newbee: i took the "usual" ones, you use with a breadboard.
but now i guess i will be ordering one(s) with +30W

[stj]

Re: HP W2408H No Power (Surge) Repair - Success

breadboard? you mean 1/3w resistors!! damn that must have been fireworks - on a small scale.

[jamalC]

Re: HP W2408H No Power (Surge) Repair - Success

breadboard? you mean 1/3w resistors!! damn that must have been fireworks - on a small scale.

hahahhahaha

[budm]

Re: HP W2408H No Power (Surge) Repair - Success

2a? with leds maybe, but not with rack of cfl's in it!
this monitor is rated at 130w

Really! Lets see now, his line Voltage is 230VAC, so 2A = 460W!, 130W will be less then 1A. The unit also has PFC.
Check your math, or how you say it, lacking?

[stj]

Re: HP W2408H No Power (Surge) Repair - Success

my math? i got the wattage from HP's specs page!

[budm]

Re: HP W2408H No Power (Surge) Repair - Success

my math? i got the wattage from HP's specs page!

Yeah, so 130W with 230V, how many Amp will that be?
jamalC, is in Denmark.
Do the math again.

Hint P= I *E
130W @230vac = 0.565A
130W @120Vac = 1.083A.

I would say that the original Thermistor was blown due to bad parts on the power supply board that he needs to carefully inspect.

[jamalC]

Re: HP W2408H No Power (Surge) Repair - Success

I would say that the original Thermistor was blown due to bad parts on the power supply board that he needs to carefully inspect.

hey. what do you mean original Thermistor? you mean mine or Ryans (who bought a new thermistor and it worked?