HEC-250LR-T ATX Computer psu

[joshnz]

Hello my power supply for my old pc went pop during a power dip when ups kicked in.

Found the 5vstb controller a TOP222Y has failed 42ohms drain to source,
and a resistor that I can't identify it's color code is "yellow violet gold gold" that is what made the pop sound.

[Pentium4]

Re: HEC-250LR-T ATX Computer psu

Guessing no MOV's in there? Pictures?

[joshnz]

Re: HEC-250LR-T ATX Computer psu

Not much too see does have mov's

[Escort Eagle]

Re: HEC-250LR-T ATX Computer psu

I think the resistor value should be 47K, but I am not sure . Can you draw a schematic for 5VSB Primary Section only . And have you any datasheet of TOP222Y Mosfet ?

[TELVM]

Re: HEC-250LR-T ATX Computer psu

There are two MOVs between the primary caps:

[joshnz]

Re: HEC-250LR-T ATX Computer psu

Here is circuit same as in data sheet.

[joshnz]

Re: HEC-250LR-T ATX Computer psu

All i need to know is resistor value to replace and replace TOP222Y.
And hope no high voltage pulse went out the secondary.

[Escort Eagle]

Re: HEC-250LR-T ATX Computer psu

Then It should be a fusing Resistor of 4.7Ω/1W . Use a 100W series bulb tester at test condition for avoiding damage .

[joshnz]

Re: HEC-250LR-T ATX Computer psu

It is a 1/4watt or less I know that much by its size.
It will be a over a month for replacement top222y to arrive.

[Pentium4]

Re: HEC-250LR-T ATX Computer psu

Since this thing is pushing 14 years old and you've already got it torn apart, you should replace the lytics. Looks really well built for its age and wattage.

[joshnz]

Re: HEC-250LR-T ATX Computer psu

Since this thing is pushing 14 years old and you've already got it torn apart, you should replace the lytics. Looks really well built for its age and wattage.

Will do.
It's full of CapXon.

[Pentium4]

Re: HEC-250LR-T ATX Computer psu

Wow those are all CapXon? They held up pretty well! I wonder if they're still in spec.

[joshnz]

Re: HEC-250LR-T ATX Computer psu

I don't have a esr meter or a captance meter that goes over 200uf so won't know

[everell]

Re: HEC-250LR-T ATX Computer psu

Then It should be a fusing Resistor of 4.7Ω/1W . Use a 100W series bulb tester at test condition for avoiding damage .

I would argue that the resistor value should be 0.47 ohm.

[joshnz]

Re: HEC-250LR-T ATX Computer psu

I would argue that the resistor value should be 0.47 ohm.

That is what I was thinking due to it been smaller than a 1/4 resister.

[kc8adu]

Re: HEC-250LR-T ATX Computer psu

that 3rd band could be silver...
it looks different than the 4th.
which is gold.

I would argue that the resistor value should be 0.47 ohm.

[Agent24]

Re: HEC-250LR-T ATX Computer psu

I have one of these HEC-250LR-T v1.1 sitting here, also dead. As long as the same resistor isn't blown I can tell you what yours is supposed to be, tomorrow.

What's the refdes of your dead resistor?

[Agent24]

Re: HEC-250LR-T ATX Computer psu

Well, that's interesting. R011 is OC on mine too. But I can confirm it's Yellow-Violet-Gold-Gold, so assuming they used a normal code then it's 4.7 Ohms, 5%.

My TOP222Y though measures 30 Megohm G-S (both directions)

Also there is a missing component near the comparator, looks like R41. Is that same component missing on yours? (see approximate center of photo)

A first I thought it might have vaporised since there are leads but no body, but there are no burn marks or carbon so maybe that's not the case. Very strange.

[joshnz]

Re: HEC-250LR-T ATX Computer psu

Ok agent I seen your thread on this psu I'll have a look at mine when I get home.

They top222y is not a mosfet it is a ic with a mosfet built in.

It has pins
Drain negative of transformer
Source DC -
Control VCC and Feedback

What is the reading between Drain and Source.

[Agent24]

Re: HEC-250LR-T ATX Computer psu

Sorry, where I said "gate to source" should have been "drain to source"

Or in other words, the two right-most legs on the package when viewed from the front.