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FT2232 free PCB - not working, help requested

Got a FT2232 breakout board from the Free PCB Drawer (thanks Ian!).  Soldering an SMD board is way above my skill level, but I figured it was worth a try.. and I think I did OK even if it's not all that pretty.  However, it doesn't work -- power LED doesn't come on and not recognized by the host computer.

I have very little electronics troubleshooting experience, so I'm humbly asking for assistance.  I verified that I'm getting +5v through the USB port by stabbing the backside of the connector with the voltmeter probes until I found two that read +5.  I'm seeing 1.37v across the power LED, by playing with a power supply and another LED I found that it didn't light until it got 1.5 or so.

The LDO power supply confuses me.  If I look at the datasheet (can't post url as a new user) it looks like pin 2 (center) is the ground and pin 1 should be the input voltage, but if I probe across those I get -1.17v; to see 5v I have to go pin 3 for + and pin 1 for -.  What I put on there was Digikey PN IFX25001ME; did I get the wrong regulator?

Otherwise - can you point me in the right direction for troubleshooting?  Other possibilities that come to mind is that I overheated something (the hot air seems to have discolored the two 4.7uF caps) or something's shorting, but I'd expect to see no voltage in that case.

Re: FT2232 free PCB - not working, help requested

Reply #1
Hi derekf,

Thanks for sharing your build.

My debug steps would be (I know you have covered some of these):
1. Measure between the outer pins of the USB connector, should be 5v. If not, short under USB jack (happens 50% of the time, if not to you, great job! you got the mojo)
2. Measure between bottom and middle (as seen here) pins of the VREG. It should be 3.3V. Or measure between sides of C2. If not 3v3 (I think you said 1.37, which is like 2 diodes, and almost certainly a short of some sort).

I'll continue in a second post so you can start reading this one...
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Re: FT2232 free PCB - not working, help requested

Reply #2
According to this schematic, measure on either side of C3, it should be 1.8V. If not, esp if it is 1.37, then there is a short in the 3.3volt supply somewhere.

http://dangerousprototypes.com/docs/ima ... bo-sch.png

I'm not sure about the regulator, I think they are bog standard. Here the Sot-223 regulators I ordered most recently:
http://dangerousprototypes.com/docs/Par ... Regulators

My rec is to get some flux, smear it all over the FT2232 pins. Then take some solder wick/copper braid, and wick up everything around the chip. I'd bet that if it is not under the USB jack, there is a short under or in the FT2232 pins.

Also: inspect the PCB. If it has a mark on the side (red line, black line) it passed E-test. If not, inspect it closely for bridges and problems. Esp. around the header holes. We made separation too close on a few designs and our PCBs weren't all good. See Arhi's Bus Blaster v2 board for example.

Be careful with the hot-air. I've not had much luck using it to mount SMD parts except QFN and LGA. For leaded stuff (CAPS, tqfp, etc) Iron is usually less stressful on you and the part.
Got a question? Please ask in the forum for the fastest answers.

Re: FT2232 free PCB - not working, help requested

Reply #3
Thanks Ian... 5.06v across the outer pins of the USB connector, yay me.  1.38 across the two pins of the VR.

Looks like (from the datasheet for the VR you posted), they're not all the same -- on the ones I got from Digikey, pin 1 is input, 2 is ground, and 3 is output; on the datasheet for yours, 1 is ground, 2 is output, and 3 is input.. so I think (hope) I've found my problem.  Will order some different VRs shortly and we'll see if that takes care of it.  No mark on the side.  Will flux/wick the chip as well.

Thanks again, for all you do.

Re: FT2232 free PCB - not working, help requested

Reply #4
Thanks for the update. I thought the SOT-223 VREGs were pretty standardized, like the little SOT-23-5s we use in everything. Good thing to know. Sorry I wasn't very helpful ;)
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Re: FT2232 free PCB - not working, help requested

Reply #5
Ok so yeah, two years later, I'd have hoped that my skills would be stronger now but it would appear that they are not.

I have removed the scorched 4.7uF caps, and off the board they read as ~4.7uF.  The power LED does not light even after being removed from the board, so I apparently overcooked it.

I started to work on troubleshooting the rest, but then I realized that the vreg was scorch-your-fingers level hot, and the FT2232 in the pin 1 corner wasn't too much cooler than that.

I'm guessing that this indicates a pretty severe short, and I'm guessing it's in that corner of the FT2232 (maybe pins 4 and 5?).  It looks like if I remove L1 and L2, then pins 4 and 9 will stop getting power and if that's the problem, the heat issue will go away.

Does it sound like I'm barking up the right tree?

Re: FT2232 free PCB - not working, help requested

Reply #6
Hi derekf,

Let me jump in on to your troubleshooting adventure. I'd read that the vreg(IFX25001) you've used before had different pinout and I did checked it and they surely are different. Good, you've done your first solution. Second, when you replaced it with the proper vreg (1-GND, 2-Out, 3-In) SOT-223 and it overheated, then I conclude that there is something shorting on the 3.3v after the the vreg. You could probe this by checking with a meter set on continuity test (across C2), if it beeps then there's something shorting on the 3.3v line (check for solder joints).

Yes, you could try to take both L1 and L2 as a guess then measure the voltage on the 3.3v (across C2) and powering it up again. should be reading  ~3.3v and vreg not overheating.

Isolate the main chip:
I would suggest removing the FT2232, clean its pad/footprint with solder wick. Then powering it up without the chip, check if the 3.3v is present. when the supply voltage (3.3v) are normal and vreg not overheating. try to solder the chip back.

Hope this helps :)

Re: FT2232 free PCB - not working, help requested

Reply #7
Yep, what Vimark said. You probably should go over the board with a strong magnifying glass or loupe and look for any shorts, especially around the chip and where there are components that are not aligned properly.

Ian was right about using an Iron. Air is good for removing the components, but it's very difficult to get good results putting them on with air. A good soldering station (or even a good iron) and a pair of tweezers will give you better results. Make sure you use plenty of good quality flux, it's messy, but you can clean it up with Isopropanol later.

LEDs, Diodes, etc. will often die or work poorly if overheated. Get *one* pad lightly tinned and tack down that end. Then, holding the part down, solder the other end. When cooled, properly solder the first end. With a little practise you'll be fine.

Ensure you have the chip oriented correctly also, as well as diodes, polarised caps, etc.

Re: FT2232 free PCB - not working, help requested

Reply #8
I have removed the chip (it won't be able to be reused, unfortunately) and I think I've ruined the board in the process.

There's a couple of the little fiddly traces at the top of the pic here that  have come free, and a couple on the right.



I know I've read that you can fix lifted traces, but I don't know about these tiny ones that the chip solders to.  Is there any point in ordering a new chip, or is the board shot?

Re: FT2232 free PCB - not working, help requested

Reply #9
That's not too bad, you should be able to repair that without too much bother I think. If you've written off the board, then consider this good practise and if you fix it, well that's a bonus. Its all a part of the learning process. I'm busy at the moment, but I'll write up some tips for you when I have time. In the meantime, if you haven't already, get yourself some good quality tacky paste flux (I recommend ChipQuik SMD291, but others will have their preferences), some good Solderwick (Soderwick size #2 is good) and some Isopropanol alcohol which is at least 99.5% pure (commonly available in spray cans). Don't power it up yet, wait till you've cleaned it up first.

Re: FT2232 free PCB - not working, help requested

Reply #10
Thanks for your vote of confidence.  I've ordered a new FT2232 chip and some of the SMD291 flux.  Guessing it'll be late next week when it arrives.

Re: FT2232 free PCB - not working, help requested

Reply #11
It will help if you have a decent soldering station like a Hakko (or one of the cheap Chinese clones), but it's not strictly necessary. First step would be to gently clean up the area with alcohol, but so we can see the damage a little better, but be very careful of the two bent tracks at the upper right, you don't want to break those, as they lead under the chip, so are harder to repair well.

Re: FT2232 free PCB - not working, help requested

Reply #12
[quote author="derekf"]Thanks for your vote of confidence.  I've ordered a new FT2232 chip and some of the SMD291 flux.  Guessing it'll be late next week when it arrives.[/quote]

How did you go Derek? Did you get the various stuff yet?

Re: FT2232 free PCB - not working, help requested

Reply #13
Hi,

I was fed up waiting for a coupon in the free PCB drawer where I took part several times in order to get a breakout board. I ordered the pcb on oshpark and build that ft2232h breakout myself since I had most of the parts at home.

attached is an image where I communicate with my phone through the board.

I've on pcb left, if yours is damaged I could provide you one.

Re: FT2232 free PCB - not working, help requested

Reply #14
Welcome to the forum. You shouldn't give up on the Free PCB drawer and / or competitions, I've won a number of PCB's from DP. Cool phone :)  I can just image the look on airport security guard's face when you shove that through the X-ray machine  ;)  "Um, yeah, it's the latest in uber-chic mobiles from Samsung, it's called 'le ply' and it exudes the natural earth feeling, whilst being at one with nature  ...when you're dialing for a pizza!"      I think that's much cooler than Sparkfun's dial-up bluetooth phone.
Very good of you to offer your board to Derek :)  I think he can repair his and learn from it, but if he just wants to get it going then your board would be the way to go.