Power supply for USB to SATA adapter smoked on first use.

[David Farber]

I bought this item last year. www.ebay.com/itm/331250999094 I didn't have an
occasion to use the power adapter until last month when I had a SATA
notebook drive to check. (When I bought it, I was mainly interested in the
PATA adapter which does not require the separate power supply as the power
is derived through the USB port.)

I had everything wired to go when I plugged in the AC cord into the adapter.
Kaboom and poof. I saw a nice spark from the AC terminals as it first made
contact with the adapter. I remembered when I purchased it and did some
research into the feed back of the seller and found a few similar comments
like this:

"Plugged In..Smoked..Almost Caught
Fire..Garbage..BEWARE!!!!!!!!!!!!!!!!!!!!!!!!! Buyer:
USB 2.0 to IDE SATA S-ATA 2.5 3.5 Hard Drive HD HDD Converter Adapter Cable
New (#331250999094) US $8.75"

I think if someone else reported this happening, then this must be happening
often. Before I opened the case of the power box, I could hear what sounded
like a part rattling inside. I think it what was left of the fuse. Inside
there was a component labeled F1 on the pc board except all that was left
were the two pico(?) fuse terminals (maybe it was just a thin jumper wire?).
I also found that the pc traces had melted near the AC input. It didn't take
long to find three of the four bridge diodes were shorted (I removed them
from the board to check for other shorts as shown in the photo) as well as
the switching power transistor, and a 0.22 resistor in series with it. The
photo is here.
http://webpages.charter.net/mrfixiter/images/Electronics/Sata_adapter/PC-board-sata-adapter.jpg

I decided to contact the seller and let them know that their device was a
fire hazard. I'm fairly certain that the internal fuse is supposed to blow
before the pc traces melt. I got a response that offered me a free
replacement even though it was more than a year old. I took them up on their
offer and have received the replacement which I haven't plugged in yet.
(When I do, it's going to be in a series with 60 watt light bulb!) The issue
of it being a fire hazard wasn't address by the seller. I looked for some
kind of government approved sticker but did not find one. Would it make any
sense or would it be just a waste of time to make some kind of consumer
report about this device? How large a fuse would have to be in the circuit
to allow the traces to burn up?

Thanks for your reply.
--
David Farber
Los Osos, CA

 

[mike]

On 9/2/2015 7:14 PM, Jon Elson wrote:

David Farber wrote:

How large a fuse would have to be in
the circuit to allow the traces to burn up?
The problem is, except for very special energy-limiting fuses, the fust does
NOT limit the current before it blows. It allows whatever current the unit
will draw for some amount of time before blowing. So, it is possible for
even a 1A fuse to allow fairly thick circuit traces to burn through when the
device has a dead short. It would not be unusual for a 1 A fuse to allow
maybe 100 A in a dead short situation, for a few milliseconds.

Jon

I haven't done any UL certification in over two decades,
but I expect that the test REQUIRES that the traces don't
fuse before the real fuse.

It's widely suggested that chinese crap doesn't test for
anything. They just slap on a fake sticker and sell it cheap.
Cuz that's what we cheapskates want...cheap...

 

[Jon Elson]

David Farber wrote:

How large a fuse would have to be in
> the circuit to allow the traces to burn up?
The problem is, except for very special energy-limiting fuses, the fust does
NOT limit the current before it blows. It allows whatever current the unit
will draw for some amount of time before blowing. So, it is possible for
even a 1A fuse to allow fairly thick circuit traces to burn through when the
device has a dead short. It would not be unusual for a 1 A fuse to allow
maybe 100 A in a dead short situation, for a few milliseconds.

Jon

 

[Phil Allison]

Jon Elson wrote:

How large a fuse would have to be in
the circuit to allow the traces to burn up?


The problem is, except for very special energy-limiting fuses, the fust does
NOT limit the current before it blows. It allows whatever current the unit
will draw for some amount of time before blowing. So, it is possible for
even a 1A fuse to allow fairly thick circuit traces to burn through when the
device has a dead short.

** The thin wire of a 1A fast fuse would normally melt and open well before a PCB track a few mm wide can do so.

It would not be unusual for a 1 A fuse to allow
maybe 100 A in a dead short situation, for a few milliseconds.

** What happens with large overloads, like 100 times, is the fuse wire vaporises and initiates an arc from end to end of the fuse. Such arcs show negative resistance and so are very destructive - substantial copper tracks and
wires vanish instantly until another fuse link or breaker trips.

Of course, special fuses types exist that can handle fault currents of thousands of amps without arcing - microwave ovens and Fluke DMMs use them, but not small appliances.


.... Phil

 

[whit3rd]

On Wednesday, September 2, 2015 at 6:42:40 PM UTC-7, David Farber wrote:

I bought this item last year...when I plugged in the AC cord into the adapter.
Kaboom and poof.
...have received the replacement which I haven't plugged in yet.
(When I do, it's going to be in a series with 60 watt light bulb!)

The light bulb in series is a bad plan; the power supply will, in order to deliver
regulated output power, draw higher current due to the lower input voltage,
and fry the fuse, even if it isn't faulty.

Most common problem that makes the fuses fry: shorted diode in the AC
rectifier (usually full bridge).

 

[Jon Elson]

mike wrote:

It's widely suggested that chinese crap doesn't test for
anything. They just slap on a fake sticker

Yup, that's the REAL problem, FAKE UL and other certification stickers!
Very scary. My mother in law got some surge suppressor strips some time
ago. They had UL labels. If you turned them over, the plugs would fall
out, even the FIRST time they were used. No grip to the contacts in the
outlets. I sent the info on these to the UL comments address, and never
heard back from them. I expected they'd WANT to know about fake labels, but
apparently there are tons of these.

Jon

 

[Ralph Mowery]

"whit3rd" <whit3rd@gmail.com> wrote in message
news:8adcc2bf-ab1c-43c1-ac27-01184a05d1f1@googlegroups.com...

...have received the replacement which I haven't plugged in yet.
(When I do, it's going to be in a series with 60 watt light bulb!)

The light bulb in series is a bad plan; the power supply will, in order to
deliver
regulated output power, draw higher current due to the lower input
voltage,
and fry the fuse, even if it isn't faulty.

Most common problem that makes the fuses fry: shorted diode in the AC
rectifier (usually full bridge).

The light bulb will limit the current to around what the bulb is rated for.
That is a 100 watt bulb will limit at about 1 amp and a 60 watt bulb to
about 1/2 amp. At low current the bulb is like a very low resistance and
as more current is drawn and the bulb lights up it acts like a higher
resistance.

 

[David Farber]

Ralph Mowery wrote:

"whit3rd" <whit3rd@gmail.com> wrote in message
news:8adcc2bf-ab1c-43c1-ac27-01184a05d1f1@googlegroups.com...
...have received the replacement which I haven't plugged in yet.
(When I do, it's going to be in a series with 60 watt light bulb!)

The light bulb in series is a bad plan; the power supply will, in
order to deliver
regulated output power, draw higher current due to the lower input
voltage,
and fry the fuse, even if it isn't faulty.

Most common problem that makes the fuses fry: shorted diode in the AC
rectifier (usually full bridge).

The light bulb will limit the current to around what the bulb is
rated for. That is a 100 watt bulb will limit at about 1 amp and a 60
watt bulb to about 1/2 amp. At low current the bulb is like a very
low resistance and as more current is drawn and the bulb lights up it
acts like a higher resistance.

I was thinking of connecting the bulb without a load just to make sure there
were no direct shorts before I plugged it in the very first time, not to use
it like that in a real-world situation.

Thanks for your reply.
--
David Farber
Los Osos, CA

 

[David Farber]

Phil Allison wrote:

Jon Elson wrote:


How large a fuse would have to be in
the circuit to allow the traces to burn up?


The problem is, except for very special energy-limiting fuses, the
fust does NOT limit the current before it blows. It allows whatever
current the unit will draw for some amount of time before blowing.
So, it is possible for even a 1A fuse to allow fairly thick circuit
traces to burn through when the device has a dead short.

** The thin wire of a 1A fast fuse would normally melt and open well
before a PCB track a few mm wide can do so.

It would not be unusual for a 1 A fuse to allow
maybe 100 A in a dead short situation, for a few milliseconds.

** What happens with large overloads, like 100 times, is the fuse
wire vaporises and initiates an arc from end to end of the fuse. Such
arcs show negative resistance and so are very destructive -
substantial copper tracks and wires vanish instantly until another
fuse link or breaker trips.

Of course, special fuses types exist that can handle fault currents
of thousands of amps without arcing - microwave ovens and Fluke DMMs
use them, but not small appliances.


... Phil

Wouldn't all of the current have to go through the shorted diodes (1N4007)
and shouldn't they show some sign of physical destruction? Other than being
electrically shorted, they were physically unscathed.

Thanks for your reply.
--
David Farber
Los Osos, CA

 

[whit3rd]

On Friday, September 4, 2015 at 1:24:29 PM UTC-7, David Farber wrote:

Wouldn't all of the current have to go through the shorted diodes (1N4007)
and shouldn't they show some sign of physical destruction? Other than being
electrically shorted, they were physically unscathed.

If a diode fails short circuit, it can be lower resistance than associated wiring
or fuses (i.e. it cooks everything else in the circuit, but stays cool).

 

[junebug1701]

On Wednesday, September 2, 2015 at 8:42:40 PM UTC-5, David Farber wrote:

I bought this item last year. www.ebay.com/itm/331250999094 I didn't have an
occasion to use the power adapter until last month when I had a SATA
notebook drive to check. (When I bought it, I was mainly interested in the
PATA adapter which does not require the separate power supply as the power
is derived through the USB port.)

I had everything wired to go when I plugged in the AC cord into the adapter.
Kaboom and poof. I saw a nice spark from the AC terminals as it first made
contact with the adapter. I remembered when I purchased it and did some
research into the feed back of the seller and found a few similar comments

I have one exactly like that and of course I tested it when it arrived. It's been working fine for several years running external hard drives for backing up files. Before using the new one I would connect a 12V bulb to the output as a load and see what happens when you apply power. Chinese quality control is almost non-existant, but when you get a good one, it seems to last. What do you expect for less than 10 bucks?

 

[David Farber]

junebug1701 wrote:

On Wednesday, September 2, 2015 at 8:42:40 PM UTC-5, David Farber
wrote:
I bought this item last year. www.ebay.com/itm/331250999094 I didn't
have an occasion to use the power adapter until last month when I
had a SATA notebook drive to check. (When I bought it, I was mainly
interested in the PATA adapter which does not require the separate
power supply as the power is derived through the USB port.)

I had everything wired to go when I plugged in the AC cord into the
adapter. Kaboom and poof. I saw a nice spark from the AC terminals
as it first made contact with the adapter. I remembered when I
purchased it and did some research into the feed back of the seller
and found a few similar comments

I have one exactly like that and of course I tested it when it
arrived. It's been working fine for several years running external
hard drives for backing up files. Before using the new one I would
connect a 12V bulb to the output as a load and see what happens when
you apply power. Chinese quality control is almost non-existant, but
when you get a good one, it seems to last. What do you expect for
less than 10 bucks?

At any price, I would not expect it to blowup the first time I use it! If I
do use a light bulb, I will start at the other end in front of the AC power
input where the short was.
--
David Farber
Los Osos, CA