Burnt resistor

[newtothis]

Ok I am working on an ATX PSU, namely a corsair TX650.

This PSU came to me after it went bang on its owner... The underside on the secondary side of the board was black... after cleaning with IPA i found a vaporized MOSFET and using my DMM found a few blown SMD resistors... Having replaced these I have one last issue :

There is a through hole resistor that has fried... the bands are unreadable and I have no idea what OHM this resistor was... Is there any way at all of working this out?

Thanks

[shovenose]

Re: Burnt resistor

corsair stuff is impressing me less every day.

[c_hegge]

Re: Burnt resistor

Post a picture of it. Maybe someone here might have a similar unit for reference.

[kaboom]

Re: Burnt resistor

i found a vaporized MOSFET and using my DMM found a few blown SMD resistors...

It's bad enough when thru-hole parts blow, resistor color bands, etc. SMT does not belong in "consumer" type power supplies. Completely non-serviceable.

corsair stuff is impressing me less every day.

I almost-almost recommended one of the OP's power supplies to someone, based on what someone else told me. So glad I didn't.

It seems that one should stay away from these "unified brand" companies, regardless of what made them well known in years past.

For good RAM, get it from a reputable RAM maker.
For a good power supply, get it from a reputable PS maker.
For a good case, get it from a reputable case maker.
And so on...

[newtothis]

Re: Burnt resistor

I have successfully repaired surface mount components on PSU's a few times

[newtothis]

Re: Burnt resistor

This is the resistor that has blown on this PSU,

After looking at many inside pics of these PSU's Im pretty certain its the same as a few others in the supply, Though im not familiar with the banding...

BROWN - GREEN - SILVER - RED - BLACK

Can someone tell me the rating please?

Thanks

[PeteS in CA]

Re: Burnt resistor

SMT does not belong in "consumer" type power supplies. Completely non-serviceable.

Have a love-hate thing with SMT parts. Many/most have no value markings. Finding a wrong value? Good luck! And as for 0805 and smaller parts that are marked, get out a magnifier and maybe a flashlight (torch), too. OTOH, SMT is what it takes to achieve modern power densities; 40 years ago a 500W or 600W P/S required two-person carry or a pallet jack.

[Elysarian]

Re: Burnt resistor

You seem to be forgetting that a 500-600w power supply 40 years ago would have been a linear unit, not a switch-mode (high wattage linears have huge transformers and usually require hefty heatsinks on the regulators)...

As far as I'm aware SMPS's weren't used in computers until 1977 when the Apple II was launched.

I do agree though that surface-mount components are necessary in modern computer PSU's but it's more to do with cramming more components into what is essentially a fixed size enclosure to allow a higher power output (I've seen 500 watt units where the only smt components have been on the 5vsb daughterboard).

Re-reading that last paragraph I do appear to be essentially agreeing with you though

[newtothis]

Re: Burnt resistor

Seems to be drifting off topic here....

Anyone recognise the rating?

[Pentium4]

Re: Burnt resistor

That would be a 0.15Ω resistor, but that seems too low, can you get some closer pictures of it?

[newtothis]

Re: Burnt resistor

Unfortunately no, The one in this PSU is fried beyond recognition.

I have had to use pics from google

[budm]

Re: Burnt resistor

That resistor can be the Source resistor for the MOSFET, or the fusible resistor for the B+ Feeding the B+ o the MOSFET. That low value is about right, but you should trace out the connection to see how it is being used in the circuit since you may have other damaged components that took out this resistor.

[Elysarian]

Re: Burnt resistor

if the resistor was feeding the "vaporized" FET then it (the FET) likely failed short just before it popped, taking the resistor and other components with it...

"fusible" resistors are usually low values like this but are (at least in properly designed circuits) meant to fail open in order to protect other components.

I'm still not that great at reading 5-band resistors (they confuse my old-skool brain) but 0R15 is a "preferred" value so is plausible (depending on where in the circuit it is of course).