PSU Testing W/O MB?

[ArmoredFist1994]

I just sent my board in to get recapped. The caps have burst and there is no doubt they're bad. The computer has always smelled like chemicals until I turn it on for a while then it goes away.

Well, the motherboard has been removed and the empty case still smells like the college chemistry lab. I'm wondering if the stench isn't coming from the power supply. If it is, I wonder if it's adversely affected the motherboard. Maybe it just still stinks from the burst MB caps?

Quick question....can I plug the Power supply in to the wall without the motherboard present and check all the voltages with a voltmeter? Would that damage anything? Would it identify anything?

I could, of course, just wait until the recapped board comes in then test the voltages (like it says in my old A+ book) with the board and PSU installed.

BTW: This is a proprietary PSU that looks like it's welded shut. There's a sticker that says "DO NO OPEN. NO USER SERVICIBLE PARTS INSIDE".

Pry it open and visually inspect the caps? Then test them for continuity with a meter perhaps?

Just wondering if my PSU is bad....don't want it to ruin my board when it comes back. I know just enough electronics to massively screw something up so any input is welcome

Opinions?

[Krankshaft]

Re: PSU Testing W/O MB?

If the PSU has a standard pinout jumper the green wire in the ATX connector to ground (one of the black wires).

Some supplies will run without a load if the fan spins when you jump the wires you're fine. Others will need a load an old hdd or case fan is fine for that purpose.

Check the 12V, 5V, and 3.3V rails.

[ArmoredFist1994]

Re: PSU Testing W/O MB?

If the PSU has a standard pinout jumper the green wire in the ATX connector to ground (one of the black wires).

Some supplies will run without a load if the fan spins when you jump the wires you're fine. Others will need a load an old hdd or case fan is fine for that purpose.

Check the 12V, 5V, and 3.3V rails.

Plugging in a hard drive, and/or fan didn't occur to me. I can certainly do that.

I do not have anything for that motherboard plug (I do believe it's a standard ATX connector). If a drive and/or a fan is all that's needed, I might give it a try.

I'm looking for significant variances in voltages, right? As an example, the 5V lead could read 4.5 or 5.5 or something and be within reasonable limits, but 6V or 4V would indicate a problem correct?

[momaka]

Re: PSU Testing W/O MB?

Regardless of how you're testing the PSU, the voltages may be fine, but what's more important is the ripple and noise the PSU is producing. The thing is, there isn't a way to measure ripple and noise with a DMM, so in that case a visual insepction of the internals of the PSU would be a better idea (just look for bulging caps or caps from bad brands). I'm sure there has to be a way to open that PSU somehow - without prying I mean . If you do get it open, be carefull around the two big electrolytic capacitors on the primary side where you have the high votage stuff. They usually get discharged automatically, but that's not always guaranteed (just avoid touching stuff alltogether in that high voltage area). If you had the PSU plugged in right before you decide to open it, unplugg it and give it a few minutes before opening.

Also, while you're at it, you might as well clean any dust in the PSU. Compressed air works great, but you can also use a soft brush with long bristles.

If you don't want to open the PSU and you still want to test it, do what Krankshaft said and add an old hard drive/cd-rom or a fan or two (preferably on the 12v and 5v lines - don't worry about loading the 3.3v line, as it's usually self-regulated).

[Krankshaft]

Re: PSU Testing W/O MB?

Not to mention you will be testing the PSU with a very light load in ideal conditions you would want to monitor the voltages with a MB at idle.

But in your case for a quick go no go check the HDD test is fine.

[ArmoredFist1994]

Re: PSU Testing W/O MB?

I did open the PSU tonight. It was not welded shut after all. There are caps in there that are identical in appearance to the ones on the board that popped but they look OK. There are a couple of caps that I thought had burst but on closer inspection they look like they're intentionally glued to another part I'm guessing to keep them in place better.

Then again all that may be melted together...what do I know !

I cracked open my old computer tech book and do recall that tests with a voltmeter are pretty useless because "voltages can spike and sag faster than the volmeter can measure."

I'm hoping it's OK....if this photo is too big, I can reduce it...just let me know. (it's big so you can see what the heck that stuff is!)

[shadow]

Re: PSU Testing W/O MB?

That all looks normal.

Yes it is glue holding the capacitors and the inductor. It is important for the inductor because they can vibrate which produces a high pitched noise when AC voltage or excessive ripple goes through them. I have also heard that capacitors can also vibrate and make a high pitch noise with excessive ripple. Don't know if that is true or not. The capacitor that you think may be melted, I am not sure. To me it looks normal. It could be just me thou.

[Krankshaft]

Re: PSU Testing W/O MB?

I cracked open my old computer tech book and do recall that tests with a voltmeter are pretty useless because "voltages can spike and sag faster than the volmeter can measure."

They should have also said testing a PSU without loading it down can lead you astray too. It may be in regulation when you test it with a light load but when it has to deliver a sufficient amount of current it falls out of regulation.

This is rare but it can happen.

But those books aim to put out glorified part swappers .

Good for me though I have got a slew of laptop power jacks since the Nerd Herd can't be trusted around a soldering iron .

That looks like that tan crap that conducts as it gets aged by heat for your sake I hope its not bridging any component leads.

That Teapo (by the looks of the vent) next to the inductor circled it looks a little domed from the pic is it? It may just be the flash playing tricks though.

[ArmoredFist1994]

Re: PSU Testing W/O MB?

That Teapo (by the looks of the vent) next to the inductor circled it looks a little domed from the pic is it? It may just be the flash playing tricks though.

The Teapo...is that the purple component? You are correct, it is just the flash. It's flat on the top.

So if I've got this straight, the brown stuff might actually become conductive with age???

If that's the case, they really don't build this stuff to last, do they?

I need this particular PC to work and work for quite a while. It has an important use in my job. Any suggestions?

[Wizard]

Re: PSU Testing W/O MB?

You have not mentioned what this machine is for so we can understand the situation better and this is not wise to invest in oddball machine that requires oddball PSU where regular PSU can be sourced quickly.

Is the mainboard odd as well?

Cheers, Wizard

[ArmoredFist1994]

Re: PSU Testing W/O MB?

It's oddball, old, proprietary, and not even mine...it belongs to my employer. It's used for law enforcement purposes in seizing digital evidence at search sites during search warrants.

The mainboard, LCD screen and PSU fit in a luggable pelican case.

I haven't personally invested anything in it but it's a useful tool. I can get by without it but it has it's uses and was quite expensive a few years ago.

[PCBONEZ]

Re: PSU Testing W/O MB?

Yes that's glue but vibration isn't why they are glued.
They use glue to hold some parts in place until they are soldered in during assembly.

.

[ArmoredFist1994]

Re: PSU Testing W/O MB?

Thanks! The computer does kind of take a bit of a physical beating while traveling in spite of efforts to pad everything.