Like the car doesn't have enough of it's own problems

[12string]

The dashboard in the GTI has been acting up.  Speedo and tach occasionally freeze.  Clock and odometer recently disappeared.

These things are notorious for cracked solder joints, so I took the thing out and reflowed all the pins.  Went to put it back in the car, I had left the key in, dead battery.  Charged it, reinstalled, Got the clock and odo back,   Tach came up, but I didn't drive anywhere because every warning light was lit up!

Apparently I need to be a bit more careful soldering: 

[maddmaxx ★]

The problem is also very often the fault of the connectors on the ends of the underdash ribbon cables.  I'm not up on the latest cars but a while back they used the cheap connectors that just pushed the bare ends of the ribbon cables against the ckt boards.  Varying temps and humidity take their toll and voila.  Those problems are often fixed by disconnecting and reconnecting the cables.

^^^The ckt board in the pic above needs to have the flux cleaned off.  Alcohol and a toothbrush will do it.  I have a secret mixture of 1/3 Isopropyl alcohol, 1/3 hexane and 1/3 acetone, but that's more difficult to make at home.

[donkpow]

Well, I can see your problem from here You are zoomed in too far.

[maddmaxx ★]

Just now, donkpow said:

Well, I can see your problem from here You are zoomed in too far.

No it's a VW.  Mazdas have other problems.

[Ralphie ★]

Can you blame someone else?

 

[Ralphie ★]

The Troubleshooting Flowchart.

 

[donkpow]

2 hours ago, maddmaxx said:

No it's a VW.  Mazdas have other problems.

Zoom, zoom.

[JerrySTL ★]

The bigger the blob, the better the job!

[12string]

I didn't add any solder, that flux bubbled out form the existing stuff.  It looks like no clean, but I hit it with flux off anyway to get rid of any loose bits.  Like capacitors, I think there's one missing, there's a pair of pads that look like they once had a part.  I can't find a schematic or even a good picture, but just guessing by the type of circuit, I'll drop in a .1 and hope.

[Page Turner]

...what's your best time for the Kessel run ?

[maddmaxx ★]

26 minutes ago, 12string said:

I didn't add any solder, that flux bubbled out form the existing stuff.  It looks like no clean, but I hit it with flux off anyway to get rid of any loose bits.  Like capacitors, I think there's one missing, there's a pair of pads that look like they once had a part.  I can't find a schematic or even a good picture, but just guessing by the type of circuit, I'll drop in a .1 and hope.

It looks like the rectangular cross section cap balanced up on it's corner near the center of the board belongs on the pads to it's left and the 0 ohm jumper belongs on the pads just to it's left and slightly down.   Without a schematic that's just a guess based on the size of the pads/components and the appearance they give of having been pushed to the right.

[12string]

Those were easy.  The one I found blown all the way under the stepper motor for the Speedometer appears to be the one I suspected was missing.  Who knows what else fell off, there are a lot of uninstalled parts, but I can't find any other pads with disturbed solder.  These parts are a pain to solder with a tip!  But I'm not putting air back on it and risk blowing more off!

[maddmaxx ★]

3 hours ago, 12string said:

Those were easy.  The one I found blown all the way under the stepper motor for the Speedometer appears to be the one I suspected was missing.  Who knows what else fell off, there are a lot of uninstalled parts, but I can't find any other pads with disturbed solder.  These parts are a pain to solder with a tip!  But I'm not putting air back on it and risk blowing more off!

  Those were big parts on my workbench.  Because of the cost of setting up robots to build only 1 or 2 prototype boards I became the micro electronics guy who built boards by hand under a microscope.  It would take me about a week to put about 1100 pieces on a board by hand and that was still significantly cheaper than a machine build.  More fun was mining down into the internal layers of multilayer boards and altering traces when the prototypes didn't work as expected (that's why they're prototypes.

At any rate, to work on parts like that you need just a normal tip say between .031 or .050.  Getting surface mount parts off the board however is best done with two soldering irons or perhaps (too expensive for home) a set of thermal tweezers.  To make life easier, a hot plate can be used to preheat the board to about 150C so that it takes less time with the iron (s) to get the parts off.  Good tweezers to handle the parts and some level of magnification like a ring light with lens makes it easier.

Washing boards in water can be dangerous because not all IC's are hermetically sealed.  We had to vacuum bake all washed boards for our work.

 

[12string]

I have enough trouble with 0603's, Anything smaller and I'm out.  I'm not posting pictures of my repair. But my job is to tell people where to put them, not do it myself.  We do have plenty of tools, but no experienced techs to use them.

I would have been OK had I not rushed the original job and didn't pay enough attention to the air velocity.  I put them back on with a tip, but it probably would have been easier to wipe the pads and use paste and air.

[Prophet Zacharia]

I just bought Audi Maintenance. For a price, I'm covered for all routine services through 45,000 miles. I'm not about to solder anything in my car, especially not an electronic piece OF my car.

[maddmaxx ★]

18 hours ago, 12string said:

I have enough trouble with 0603's, Anything smaller and I'm out.  I'm not posting pictures of my repair. But my job is to tell people where to put them, not do it myself.  We do have plenty of tools, but no experienced techs to use them.

I would have been OK had I not rushed the original job and didn't pay enough attention to the air velocity.  I put them back on with a tip, but it probably would have been easier to wipe the pads and use paste and air.

I disliked using air extractors for that very reason.  Because I specialized in prototypes that were hard to replace I tended to use the hot plate preheat with a pair of Weller thermal tweezers for individual parts.  For large scale chips the decision had to be made as to which was more valuable, the board or the part.  If it was the board I'd cut the part off and clean up the pads.  If the part was too valuable (think $10,000 individual IC, space qualified) then I'd suck it up and use a hot air chip extractor.

I designed many of the boards we used but because of my experience with the hands part I believe that the company valued my tech side more than the engineering side.  Many of the techniques used had to be invented along the way.  My stock in trade was hand mounting things like 1" 256 pin programmables with .07 pin centerlines.  At that size I'd use hand placed solder paste that looked like little silver marbles in olive oil under the microscope along with a sort of capilary action that pulled them toward the hot pin I was working on.  When I taught people how to do it I'd start them on every 4th pin to keep enough cold pins between the one's being soldered.  Everyone would laugh and say "it looks so easy when you do it".  It's really just a matter of lots of practice though.

I hated no clean solder however.  It's a scam as it's only weaker flux than normal not really non corrosive.  You get a poorer joint and a false sense of security.

It's a dying art as machines are used for more and more work.  Still for very low volume prototypes it's faster and cheaper in most cases.  

[Indy]

Yeah, looks like you slipped with the soldering iron a little.

 

Would like to say, I've never done that, but I've done a lot of fine pitch soldering and anyone who has, has done this.  If they say they haven't, they either are lying or haven't really done a lot of rework.

[12string]

6 minutes ago, Indy said:

Yeah, looks like you slipped with the soldering iron a little.

 

Would like to say, I've never done that, but I've done a lot of fine pitch soldering and anyone who has, has done this.  If they say they haven't, they either are lying or haven't really done a lot of rework.

wasn't an iron, I was using air and blew the other parts right off without realizing it until I plugged it back in and it got wAcky

[Indy]

15 hours ago, 12string said:

wasn't an iron, I was using air and blew the other parts right off without realizing it until I plugged it back in and it got wAcky

Oh yeah, air is really bad about that.  It's a cool tool, but I prefer an iron for this kind of stuff.  Only thing I've used air for is removing chips.

[Ralphie ★]

Bump for the Troubleshooting Flowchart, one of the great classics of Engineering Arts and Literature.