I was looking for a SCART connector in my bags full of parts and random stuff. I knew i had one. I didn't find it.
What i did find, was a card reader i'd gotten for free along with other stuff. It's a "Digital CR-70R 21-in-1 card reader". It's based on an Alcor Micro AU6375. The MiniUSB connector looked melted - i remembered that i tried taking it off sometime with the hot air gun, but ended up damaging it. It did test okay for continuity tho...
So i plugged it in to USB because i didn't recall what it did. It did nothing. Having more know-how now than i did 2 years back, i immediately noticed a 3.3v regulator. I tested its output, nothing. Input, nothing. Unplugged and tested for shorts, appeared to be good.
The input to the regulator came straight from the USB port, via a 0 ohm resistor (the SMD equivalent of a jumper wire). Tested good for continuity, but plug in to USB again and i was in for a surprise - i had 5v on the connector and on one end of the 0 ohm resistor, and nothing on the other end, to the input of the reg. I removed the resistor and replaced it with a blob of solder. Actually, why they added the 0 ohm resistor is beyond me, as it doesn't jump any traces, they could have simply connected the trace straight to the reg.
Plugged in and i got the LED to light up green, but no communication to the PC. The 3.3v reg had the right output, the crystal oscillator was working, the internally generated voltages of the AU6375 tested good too, but it just didn't work. All leads of the miniUSB connector tested good for continuity, and the two data lines went straight into the AU6375 (via some more 0 ohm resistors, but those were really okay), so i was convinced the IC was bust.
I found another card reader that i had, based on an AU6371, and with an absolutely laughable construction. It was so good it decided to melt itself a few years ago. Main IC was really shot on this one.
I thought i'd practice removing MiniUSB connectors, so i eventually transplanted the connector from the burnt card reader, to the one that did nothing. I thought i'd try it again, so i plugged it in and.... Installing device driver software. You gotta be kidding me.
GSM guys told me that they had connectors and fuses that tested good for continuity, but wouldn't let power thru, but i've never seen it myself until now. I now have a fully working card reader. My laptops have SD/MS/XD readers built in, and there's one of those floppy drive bay ones installed in my main computer, but if i ever need to use a CF card on my laptops, this one will come in handy.
Here's my way of replacing MiniUSB connectors:
1. Use soldering iron and braid to remove as much solder as possible from the shield to board connections.
2. Plug in USB cable.
3. Use hot air gun to heat the whole connector. Make sure you focus on the rear where the connections are, you don't want to strip those pads.
4. Twist on the USB cable you plugged in. The connector should come off cleanly.
5. Again with the iron and braid, clean the pads where the shield solders to, till there's no solder left. Leave the solder on the connector alone.
6. Apply flux to the connections.
7. Fit the new miniUSB and solder the connections. Use soldering iron only, using a heat gun would damage the plastic inside the connector. Just press with the tip of your iron on the connectors, the solder that was already there will be enough (that's why i told you not to remove it). The flux will prevent bridges from forming, so don't worry if the tip of your iron is too wide.
8. Solder the shield. Make sure the iron touches the shield firmly and heats it up, otherwise you'll get cold joints and it will break over time.
You're done.
What i did find, was a card reader i'd gotten for free along with other stuff. It's a "Digital CR-70R 21-in-1 card reader". It's based on an Alcor Micro AU6375. The MiniUSB connector looked melted - i remembered that i tried taking it off sometime with the hot air gun, but ended up damaging it. It did test okay for continuity tho...
So i plugged it in to USB because i didn't recall what it did. It did nothing. Having more know-how now than i did 2 years back, i immediately noticed a 3.3v regulator. I tested its output, nothing. Input, nothing. Unplugged and tested for shorts, appeared to be good.
The input to the regulator came straight from the USB port, via a 0 ohm resistor (the SMD equivalent of a jumper wire). Tested good for continuity, but plug in to USB again and i was in for a surprise - i had 5v on the connector and on one end of the 0 ohm resistor, and nothing on the other end, to the input of the reg. I removed the resistor and replaced it with a blob of solder. Actually, why they added the 0 ohm resistor is beyond me, as it doesn't jump any traces, they could have simply connected the trace straight to the reg.
Plugged in and i got the LED to light up green, but no communication to the PC. The 3.3v reg had the right output, the crystal oscillator was working, the internally generated voltages of the AU6375 tested good too, but it just didn't work. All leads of the miniUSB connector tested good for continuity, and the two data lines went straight into the AU6375 (via some more 0 ohm resistors, but those were really okay), so i was convinced the IC was bust.
I found another card reader that i had, based on an AU6371, and with an absolutely laughable construction. It was so good it decided to melt itself a few years ago. Main IC was really shot on this one.
I thought i'd practice removing MiniUSB connectors, so i eventually transplanted the connector from the burnt card reader, to the one that did nothing. I thought i'd try it again, so i plugged it in and.... Installing device driver software. You gotta be kidding me.
GSM guys told me that they had connectors and fuses that tested good for continuity, but wouldn't let power thru, but i've never seen it myself until now. I now have a fully working card reader. My laptops have SD/MS/XD readers built in, and there's one of those floppy drive bay ones installed in my main computer, but if i ever need to use a CF card on my laptops, this one will come in handy.Here's my way of replacing MiniUSB connectors:
1. Use soldering iron and braid to remove as much solder as possible from the shield to board connections.
2. Plug in USB cable.
3. Use hot air gun to heat the whole connector. Make sure you focus on the rear where the connections are, you don't want to strip those pads.
4. Twist on the USB cable you plugged in. The connector should come off cleanly.
5. Again with the iron and braid, clean the pads where the shield solders to, till there's no solder left. Leave the solder on the connector alone.
6. Apply flux to the connections.
7. Fit the new miniUSB and solder the connections. Use soldering iron only, using a heat gun would damage the plastic inside the connector. Just press with the tip of your iron on the connectors, the solder that was already there will be enough (that's why i told you not to remove it). The flux will prevent bridges from forming, so don't worry if the tip of your iron is too wide.
8. Solder the shield. Make sure the iron touches the shield firmly and heats it up, otherwise you'll get cold joints and it will break over time.
You're done.