VOGONS


First post, by vico

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The two ports on my USB 2.0 card aren't working properly; if I plug my speakers into either one, the LED on the right speaker barely reacts, so I suspect the voltage reaching those two ports is too low.

Looking at the images, can anyone give me a clue as to which components on the card might be failing?

Reply 1 of 7, by Lylat1an

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Component C57 beneath the "blank" port doesn't look right to me.

The traces in that area appear to go toward the non-working ports as well.

Reply 2 of 7, by The Solutor

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Start checking F1 ~ F4, likely they are old school micro fuses, which burns if a short or overload happens.

Newer cards come with PTC or "fuses" that restore continuity when they cool down

P.S. Note that apparently there are five ports but only four fuses, so two ports must be connected to the same line, which is consistent with your problem

Reply 3 of 7, by rasz_pl

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Lylat1an wrote on Yesterday, 22:07:

Component C57 beneath the "blank" port doesn't look right to me.

no unpopulated ports, its a crystal, cap is crooked but soldered ok

The Solutor wrote on Yesterday, 23:43:

Note that apparently there are five ports but only four fuses, so two ports must be connected to the same line, which is consistent with your problem

concurred, F4 is smoked
vico measure resistance of F4, or just solder a wire below it

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Reply 4 of 7, by vico

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Indeed, fuse F4 is open; thanks to everyone for your help

Reply 5 of 7, by HwAoRrDk

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Those aren't fuses. They're zero-ohm resistors, as shown by the marking "000". Manufacturer cheaped-out and didn't actually install fuses. So this board has no current limiting or circuit-breaking for attached USB devices.

F4 resistor might have failed open-circuit because it burned out due to excess current draw on the associated port. Likely to happen because the manufacturer didn't even use an appropriately-sized part - those things are probably only good for <500mA.

Reply 6 of 7, by The Solutor

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HwAoRrDk wrote on Today, 07:23:

open-circuit because it burned out due to excess current draw on the associated port.

Do you realize that this is, more or less the description of a fuse? In our case a fuse that proved itself on the field.

If they tested those bridges and realized that the break around the intended current, kudos to them to have used a bit of lateral thinking to spare some little money.

Let me tell a story, few years ago I used to buy a commercial liquid accelerant to light my stove. It used to cost 2€ /for a 1 liter bottle. Not a gift but acceptable.

Then they stopped to sell that brand and started to sell a different one that did cost almost 5 euros for a 3/4 of liter bottle.

I didn't mind to spend that for something which is kerosene, no matter what the label tells.

So I looked around and on the same shelf few meter apart ther were

1) A "lamp petroleum" can (which is kerosene) less than 2 euro for a liter.

2) "The barbecue / fireplace lighter" (which is kerosene), almost 5 euro for 3/4 l.

3) A bottle of "liquid destainer" (which is kerosene), 9 euro for 1/2 liter.

Aside the obvious laugh about how modern consumerism works and how definition matters, guess what I bought (and still buy this day) 😁

Here we are almost in the same situation

Reply 7 of 7, by NeoG_

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HwAoRrDk wrote on Today, 07:23:

F4 resistor might have failed open-circuit because it burned out due to excess current draw on the associated port. Likely to happen because the manufacturer didn't even use an appropriately-sized part - those things are probably only good for <500mA.

They basically relied on the current capacity of the 0 ohm resistor to be the fuse, it's a dodgy way to do it but it does approximate a fuse. Just not one that is predictable or safe.

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