Author Topic: Please read  (Read 4053 times)

Offline RJ

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Please read
« on: April 22, 2012, »
I keep reading about people that have an issue with there ETD and try to do work on the SMD chips thinking this must be the issue. There is a few things I want the users to think about.

1st, as hard as it is to believe the odds are the issue is an assemble issue or configuration issue. If your dongle came on the first coop there is a small chance you could have a solder issue with the SMD chips as we did have a few, But there is a much higher chance it is either assembly or as we are finding out configuration issue.

there is also something going on with one of the firmware versions also that seems to not work for some using DMX.

If your ETD came on the second coop it is likely the problem is not the SMD chips.

The problem is when someone has an issue they post. When they don't they don't. and if one person says they fixed it by doing something with the SMD chips then people coming behind figure this must be their issue. This is where things go very wrong fast.

If you can not see a problem for sure with them do not expect the problem is the smd chips. If you think you see a bridge be away there are traces under the chips and people keep trying to fix these and damaging pcbs. Once you do this it is a real problem that I am not able to do much about.

Soldering .5 mm chips is not something everyone has the skills to do and once you go wrong it is really a mess.

If you can see a bridge for sure or a chip that is not seating properly then let me know so I can fix it for you send me a pm and I will take care of it.

But if you work on fixing the SMD yourself I can not help you after that point. 

Be aware if you can not show me a problem but just think this is the issue I am not accepting projects to repair for users. I can not do so with 3000 members.

I have taken 3 ETD in so far to look at with users sure it was an SMD issue.
Not one has been, one did have a chip crooked but not enought to cause an issue and each one had soldering issues even throught they had went over it again. They did not work I resolder the through hole items and they started working.

a couple of users thought they had issues with the SMD and found that they had cut off leads laying in between the pins of the SMD chips. The little trimmings for the through hole parts need to be watched carefully from getting into the stuff. 

I am beginning to wonder if more advanced devices requiring SMD parts on DLA is just not a good idea.

RJ       
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Offline rmp2917

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Re: Please read
« Reply #1 on: April 23, 2012, »
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I am beginning to wonder if more advanced devices requiring SMD parts on DLA is just not a good idea.

I certainly hope this does not end up being the case. I think it will limit our capabilities especially with fewer and fewer through hole parts being available.

I agree that people seem to be too quick to blame the SMDs when they cannot find the problem. Once you start messing with them, you can make things much worse in a hurry if you aren't careful.
« Last Edit: April 23, 2012, by rmp2917 »

Offline jess_her

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Re: Please read
« Reply #2 on: April 23, 2012, »
RJ and all,
I  believe all Linux products are great designs. The problems I see is if one doesn't understand it then that must be the problem Don't make assumptions, if another forum problem is like yours it may not be the fix.  Go back to the basics.
1)  are all of the components installed in the right places and orientation?
2)  Are all of the solider joints good, not a cold joint or to much solider?
3) My weakness is software, is it working right?
4) Do you need remove that component or are you making a guess?   
One  guy install a chip without a socket, me I wouldn't have touched it if it was working.
The forum is great. BUT be careful with advise both giving it and using it.

SMD is the chip of choice, please don't change it RJ.
Jess

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Offline pk

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Re: Please read
« Reply #3 on: April 23, 2012, »
I have been in the electronics business for 35+ years and have seen many changes in technology and packaging.  Many devices are only made in SMD versions due to the high pin count.  This is unfortunate for the experimenter and DIY'er due to the difficulty in working with the .5mm lead pitch.  For engineers, prototyping a circuit is not as easy today as it was 20 years ago.  Working with SMD parts requires a different and more advanced soldering skill set as well as a steady hand.

One possibility for the DIYer would be to mount the SMD parts on a daughter board that has pin headers which get soldered to the main PCB.  (Like the USB module in the dongle).  This adds expense and time but does offer the ability to test the SMD component before shipping it in a kit.  Users would know that the soldering of the SMD device is good and the chip works.  However, this is a lot of extra work and RJ is busy enough as it is.





Offline keitha43

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Re: Please read
« Reply #4 on: April 23, 2012, »
I am one who messed up his etherdongle trying to fix what I thought was a short between pins on the Ethernet chip. All voltages read on the forum were ok. Both leds on the magjack glowed steadily as soon as power was supplied. The pic programmed normally. They did not flash when hooked through a crossover cable to my laptop of when connected to my switch. I just got impatient waiting to see if anyone could fix it at the academy. I decided to try what some people said fixed theirs. Not knowing anything about surface mount components (at least not until I attend the adv soldering class at the academy) it was my bad judgement to attempt to do what I thought would fix it. So I am not complaining I will just have to wait for another coop. I do wish there were test points in the boards so you could say if you have a certain voltage you know that part of the board is ok.

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Offline Steve Gase

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Re: Please read
« Reply #5 on: April 23, 2012, »
I am one of the problem children...  when I saw the suggestion that the SMD bridges could be a problem... that the first coop had issues... and when I coupled that with how simple the rest of the build was... well I jumped on that as the cause of my problems.

when you (apparently) exhaust other explanations, and the door to a SMD problem opens just a crack -- it becomes the most obvious explanation.

when the discussions gravitate towards using flux and solder braid as a remedy -- and it still doesn't solve the problem, then another idea to use a solder sucker is offered...  well at that point it is really too late for reason. :)

i will say that I became convinced that I was seeing a bridge UNDER a couple legs, which I didn't see with any other boards.

but I certainly agree that other options should be FULLY pursued before going anywhere near SMD fixes, and then only with someone who knows what they are doing.
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Offline RJ

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Re: Please read
« Reply #6 on: April 23, 2012, »
Guys it is more than you two and I am not pointing out any certain members I have pms with others that are not posted with the same problem of damaging the chips or pcbs. If the legs are damaged I can replace chips, pcbs are a little harder but I can fix most of them. It is a problem of time. I am struggling to get the Academy stuff ready and work on code for the beta testing on the conductor, Finish code for the DSC, work and family. I will have a few pcbs to post avaliable but no time to get them ready at the moment.

I agree and do try to stay away from SMD when ever possible but things like the ETD are not possible in through hole as no parts for the ethernet that have the proformance needed are avaliable in non SMD.

RJ
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Offline keitha43

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Re: Please read
« Reply #7 on: April 23, 2012, »
I knew you were extremely busy which is why I didn't want to bother you with a pm. I will try to get another board from you whenever you get to it but in the meantime I will wait for another coop and order 2 to be safe. If I eventually get all 3 working I may sell 1 off. For old eyes like mine what kind of magnifying glass works good? The device at Radioshack with the clamps gets poor ratings. Would something like this-

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work to see better? I think if I could have seen better I would have realized it was a trace.

Offline caretaker

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Re: Please read
« Reply #8 on: April 23, 2012, »
Another member with a non working ED.  I realize that RJ wants to keep this board as non technical as possible but I think there needs to be some information put in the wiki to allow users who do have some technical knowledge some trouble shooting information.  I well realize that in some cases members would not have certain tools (scope, logic probe come to mind) to do everything necessary to find a problem on a troubled board but with some basic information it would at least allow us to check things out before asking for more experienced help.  From a personal standpoint it does get frustrating when you put together dozens of electronic kits that have worked flawlessly and then you solder up one and it doesn't work and the main advice you get is touch up your solder joints when that is the first thing you did when it didn't work.
Jeff Squires
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Offline RJ

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Re: Please read
« Reply #9 on: April 23, 2012, »
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For old eyes like mine what kind of magnifying glass works good? The device at Radioshack with the clamps gets poor ratings. Would something like this-

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work to see better? I think if I could have seen better I would have realized it was a trace.

I use a big old cast iron desk/lamp mag unit dad and mom gave me. Weighs more than a truck I swear but works good for soldering.

for inspection of small smd I have and use one of these with the more powerful lens in it.
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 You have to have you nose almost touching stuff but you can almost see the atoms in the solder. not really but it does work well.

RJ
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Offline keitha43

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Re: Please read
« Reply #10 on: April 23, 2012, »
Looks like 2.6x is the most powerful lens for it. I don't know if that would be strong enough for me. I think I will try the cheap one first with up to 10x and if I don't like it I will order yours. I guess when I had monovision laser surgery last year to read without glasses I should have specified 2.6x or higher magnification in that eye. ;) That is me squinting looking at SMD components!
« Last Edit: April 23, 2012, by keitha43 »

Offline Rogelio

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Re: Please read
« Reply #11 on: April 23, 2012, »
I use the Donegan DA5, 2.5x  with 8" focal length.  I also have a cheap Harbor Freight one but the optical quality is not as good.  The higher magnification puts me too close to the solder fumes.  yuk.

Offline deanathpc

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Re: Please read
« Reply #12 on: April 24, 2012, »
SMD's are a pain when it comes to troubleshooting..  20+ years myself between military and civilian sector.  It gets even worse when dealing with communications and frequencies in the microwave range with 300 or so pins from one device.

Save yourself the frustration and just get in contact with RJ.  Even those of us who have done this for some time know better at times. lol  But usually don't follow our gut. :)

The nice thing about SMT is that you can fit so much more into so much less space.  But when it comes to assembly and troubleshooting well not so much...  Can really be a pain..

We used to use a magnifying glass with light on it for all levels of troubleshooting / repairs.  The problem is that those are expensive.  I have yet to find something in my price range for home.  I'll have to look on ebay or craigs list to see if i can find one that will work.

Dean
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Offline Mimir

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Re: Please read
« Reply #13 on: April 24, 2012, »
I found a video that has some good information about surface mount soldering.

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It has some really good information and some pretty cool techniques for soldering several different kinds of SMD's.

He also shows a couple of ways to unsolder them.  One of the ways uses a special solder that is designed to stay melted for a much longer time than normal.

John