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Old Nov 18, 2014, 02:33 AM
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davidmc36's Avatar
Canada, ON, Ottawa
Joined Oct 2010
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The SMD Codebook seems to indicate "CJ" is a zener diode.

http://www.marsport.org.uk/smd/mainframe.htm

But I don't seem to see a MMBZ4683 with five pins.
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Old Nov 18, 2014, 04:58 PM
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Australia, NSW, Sydney
Joined Sep 2011
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I found a circuit diagram that could be of use.
Please see attached pdf
I you are able to source the component please let me know.
Possible part No. LP3985IM5X-3.3
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Old Nov 18, 2014, 08:31 PM
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United States, CA, Redondo Beach
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Quote:
Originally Posted by davidmc36 View Post
The SMD Codebook seems to indicate "CJ" is a zener diode.

http://www.marsport.org.uk/smd/mainframe.htm

But I don't seem to see a MMBZ4683 with five pins.
Thanks Dave for providing the SMD Codebook. I perused the content and searched for two terms, CJ for the base and SOT23-5 for the packaging and a number of components fell out. They were all voltage regulators and primarily the Low-Dropout (LDO) variety. Now I need to figure out the voltage since the components range from 1.5V to 5V.

Quote:
Originally Posted by szakacs View Post
I found a circuit diagram that could be of use.
Please see attached pdf
I you are able to source the component please let me know.
Possible part No. LP3985IM5X-3.3
The schematic nailed it. Thanks Szakacs! The operational voltage of 3.3V will help me narrow down which LDO regulator I need to buy. The SMD Codebook will give some cross-references. Hopefully, this component will bring these two GPS modules back to life.
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Old Nov 25, 2014, 04:12 PM
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Just an update ....
I searched and found a local supplier for part No. LP3985IM5X-3.3. a low-noise ultra LDO CMOS. AUD$5.00 for five items
Received the item yesterday and replaced the faulty regulator and all is GOOD. What was just a piece of junk due to the magic smoke syndrome is now a functioning GPS unit again....I do enjoy the occassional win ...
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Old Nov 26, 2014, 11:53 AM
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Originally Posted by szakacs View Post
Just an update ....
I searched and found a local supplier for part No. LP3985IM5X-3.3. a low-noise ultra LDO CMOS. AUD$5.00 for five items
Received the item yesterday and replaced the faulty regulator and all is GOOD. What was just a piece of junk due to the magic smoke syndrome is now a functioning GPS unit again....I do enjoy the occassional win ...
That's great! I' m encouraged.

I ordered 5 similar LDO regulators from Mouser yesterday for under $8 US. I'll post an update on the two modules I'll be fixing.
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Old Dec 01, 2014, 02:29 AM
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Hello everyone, I've run into a bit of a problem trying to change the baud rate for my gps serial connection in the config.h. Thing is I changed it to 57600 and now the gps connection is intermittent, it flashes the blue led on and off in my mw board, and also in the GUI it does the same, red to green, intermittently. Anyone else encountered something like this? If so how did you solve it? I was trying to change the baud rate of the gps itself, later on, but found out that the usb to serial cable I have is not FTDI but PL-2303. One final question does removing the gps battery reset it's settings to default? I will try tonight to unplug the gps battery and if that doesn't work I will buy an FTDI adapter. I just don't wanna buy it if the gps itself is done for.
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Old Dec 02, 2014, 01:04 AM
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United States, CA, Redondo Beach
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I received the LDO regulators from Mouser today. I discovered the biggest challenge is de-soldering the old components from the two GPS modules. I failed at both removing some of the trace from the board and ended up with a crappy job of soldering the new components in their place.

I was able to see an intermittent light from the module's LED when I powered up but this was after I fidget with the new component putting pressure here and there.

The repair might have worked if I was more careful removing the old components. I even tried snipping a leg but the kinetic energy from imparted tore off the trace. Maybe the only way to get these things off is a heat gun with a small outlet and some foil to protect the surrounding components. Either way fixing this stuff is not worth it. Time to order the newer MT3339.
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Old Dec 02, 2014, 09:34 AM
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Quote:
Originally Posted by Whirligig View Post
I received the LDO regulators from Mouser today. I discovered the biggest challenge is de-soldering the old components from the two GPS modules. I failed at both removing some of the trace from the board and ended up with a crappy job of soldering the new components in their place.

I was able to see an intermittent light from the module's LED when I powered up but this was after I fidget with the new component putting pressure here and there.

The repair might have worked if I was more careful removing the old components. I even tried snipping a leg but the kinetic energy from imparted tore off the trace. Maybe the only way to get these things off is a heat gun with a small outlet and some foil to protect the surrounding components. Either way fixing this stuff is not worth it. Time to order the newer MT3339.
Where can you get a good MT3339 ?
I'm not sure which is the best source for these GPS .. NEO-u-blox are very populare but MT GPS are not easy to find
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Old Dec 02, 2014, 10:17 AM
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Would rather get those new Ulbox m8n gps. Someone is report very good results in the witespy RTFHawk thread.
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Old Dec 02, 2014, 04:07 PM
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Whirligig .. I do understand your issue. I too found the problem of replacing the regulator an issue.
Because I do not have a smd hot air gun, What I did was instead of trying to desolder the part I used a very sharp blade to apply pressure on and cut through each of the five legs as close to the chip as possible. Then using a good magnifying glass, a bright light and a clean soldering iron, I then heated and removed the remaining leg bits off the pads.
Then with patience and a very small tipped soldering iron I managed to place and solder in the new part.
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Old Dec 03, 2014, 02:53 PM
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Originally Posted by e_lm_70 View Post
Where can you get a good MT3339 ?
I'm not sure which is the best source for these GPS .. NEO-u-blox are very populare but MT GPS are not easy to find
A reputable source but not cheap would be Adafruit, Pololu, and Sparkfun. You can try searching for MTK3339 or MT333o on Ebay.

I can dust off my my $16 Ublox neo 6m but I think the best update rate is 1hz.
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Old Dec 03, 2014, 03:09 PM
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Originally Posted by szakacs View Post
Whirligig .. I do understand your issue. I too found the problem of replacing the regulator an issue.
Because I do not have a smd hot air gun, What I did was instead of trying to desolder the part I used a very sharp blade to apply pressure on and cut through each of the five legs as close to the chip as possible. Then using a good magnifying glass, a bright light and a clean soldering iron, I then heated and removed the remaining leg bits off the pads.
Then with patience and a very small tipped soldering iron I managed to place and solder in the new part.
I may have another chance at salvaging these modules, point to point wiring.....
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