Toshiba Adapter

[mockingbird]

I have a busted Toshiba laptop adapter here. Symptop is that nothing happens when I connect it to my laptop. Tried a different adapter (Asus) with the same spec and the light did come on. I had been having some blue screens sometimes and I suspected the adapter was failing and now it finally did. (I hope the fuse didn't blow).

My question is, there are two Rubycon ZLH in the adapter that are 25v 820uf and I suspect that they are the problem. In my posession I have:

Sanyo OSCON SP 4v 820uf
Sanyo OSCON 16v 150uf

Are either of these suitable for my application? If not, do you think Panasonic FC or FM would suit the job?

[Scenic]

Re: Toshiba Adapter

25V caps?
sounds like a standard 19V 3.x A ac adapter.

if you want fireworks, you could try the OSCONs..

[kaniki]

Re: Toshiba Adapter

those caps are soo under rated that it is not even funny.. if you said go from a 25 v to maybe a 21 v then i would say you could give it a try, but 4v???

[mockingbird]

Re: Toshiba Adapter

I dunno, people are always substituting electrolytic caps with much lower value polymer caps. The sanyos are polymer, so...

In any case, I replaced the 25V 820uF Rubycon ZLH caps with identical Rubycon "ZL" caps. No change.

Am I looking at replacing the primary or should I look for a fuse and check continuity?

[retiredcaps]

Re: Toshiba Adapter

Post a pic so we can see.

Am I looking at replacing the primary or should I look for a fuse and check continuity?

[momaka]

Re: Toshiba Adapter

I have a busted Toshiba laptop adapter here. Symptop is that nothing happens when I connect it to my laptop.

Use a voltmeter to check if the output voltage is present first. If not present, it could be a shorted wire on the output or a bad start-up cap (if PSU design uses one). If voltage is normal, find something to use as a load on the adapter, then check the output voltage again.
Either way, pictures would be useful. Post a few if possible.
Also, never use polymer caps in a power supply unless it had polymer caps originally.

[mockingbird]

Re: Toshiba Adapter

Ok, here's a pic:

[momaka]

Re: Toshiba Adapter

Wow, quick replay!
So, did you check if the output voltage is present? If not, use your multimeter to check if there's a short between ground and positive output. If there is none, check fuse and bridge rectifier on primary side. If those are fine, go ahead and replace the start-up cap (from what I can see on the picture, this should be the small electrolytic cap between transformer and high voltage cap). Strictly stay with the same uF rating.
Let me know if that yields any results.

[mockingbird]

Re: Toshiba Adapter

If it's the bridge rectifier, I'll end up buying a new adapter. It's too much of a pain desoldering all the components so I can unscrew it from the heatsink.

So I'll check the fuse and the startup cap.

Why don't you suspect the primary?

Thanks

[momaka]

Re: Toshiba Adapter

So I'll check the fuse and the startup cap.

That's fine. Normally when the bridge rectifier fails, the fuse will also fail so you don't really need to check it. But if fuse is failed, definitely check the bridge rectifier.

Why don't you suspect the primary?

It's usually rare to see it go bad. Even high voltage caps from crappy brands do fairly well, and that's because they filter line voltage, which doesn't put much stress on the caps due to the low frequency (50/60Hz).
If you have a capacitance meter, just check if it has proper capacitance. If you don't, replace it only if you find that everything else is fine but power adapter is still not working.

By the way, what brand is this adapter? (should be printed on the label - otherwise check UL number) Looks like a Delta or Lite-On.

[mockingbird]

Re: Toshiba Adapter

It's a Delta 75 watt. It seems they're all either made by Delta or Lite-On these days. Their naming seems uniform. ADP-75xx xx. The watts are interchangeable and the suffix depends on the connector diameter and the polarity.

[PCBONEZ]

Re: Toshiba Adapter

I dunno, people are always substituting electrolytic caps with much lower value polymer caps.

NEVER!
NEVER!
NEVER do this if you don't KNOW what voltage they are on!
NEVER!

.

[mockingbird]

Re: Toshiba Adapter

So let me ask you this... Is it safe to put an equivalent value polymer cap to replace an electrolytic cap, or should you always look for one at half the uF value?

[c_hegge]

Re: Toshiba Adapter

As momaka was saying, don't poly-mod a PSU at all. You will make the ripple much worse than it is meant to be as the other components won't be tuned to them. For a this PSU, I think panny FM would be a good option. The ESR would be closer to what the other parts are tuned for and they have a fairly high endurance lifetime. Nichicon HE would probably be a good option as well.

For motherboards, use half the capacitance on the VRM, but keep it the same or close elsewhere.

[PCBONEZ]

Re: Toshiba Adapter

Reducing the uF only applies to VRMs.
The practice is based on a document that KC8 either uploaded or linked to [oh???] couple years ago that discussed VRM design.

Anything outside of that is an experiment. Might work. Might not.

.

[mockingbird]

Re: Toshiba Adapter

As momaka was saying, don't poly-mod a PSU at all. You will make the ripple much worse than it is meant to be as the other components won't be tuned to them.

Yes, I know this, I'm also aware that a motherboard with electrolytic caps will overclock better than a polymer motherboard because of this.

To prove your point, I will quote you from an article I read a while back on HardwareSecrets:

Even though it uses solid capacitors, this unit presented somewhat high noise and ripple levels. Below you can see the results for test five with the unit delivering 700 W.

(The unit in question is a Gigabyte Odin Plus 700w)

So it CAN be done, the noise and ripple levels were within acceptable levels, albeit a bit high. Since were on this topic, do you know if tantalum caps have good ripple suppression? (MSI and Gigabyte are now using tantalum on their higher end motherboards)

[PCBONEZ]

Re: Toshiba Adapter

There are at least 3 kinds of Tantalum caps and their characteristics vary.
In general Tantalum caps will over-heat from ripple.

The one that is -almost- good enough for motherboards has liquid electrolyte that will eat the board if it leaks and so far is only available in very small uF values.

They do sometimes get used on Laptop mobos in POL regulators due to small uF needed there, not so much ripple in the app, and small size of the cap.

.