Mopick - Posted - 03/08/2013:  11:45:54

So I'm working on telecomm boards from a customer.  This board is an OC12 transceiver which probably won't mean a lot to most of you but it's fast. 622 mbs, a lot of bandwidth for DSL, video on demand, etc.

The customer complaint says the board was causing BER Maint alarm  (Bit Error Rate) when the temperature went to -10 degrees F.  Excuse me!  I live in Florida.  How am I supposed to test for that.  Then it dawned on me that by the time they got that board out of service and got it to me and I get it back to them the -10 degree weather will be over until next year.  Problem solved.....can kicked down the road.

Edited by - Mopick on 03/08/2013 11:51:25

Lumpy - Posted - 03/08/2013:  11:54:06

Brogan maintenance. That's what we used in the Air Force. One swift kick with the boot and viola. LOL.

Mopick - Posted - 03/08/2013:  12:14:23

quote:

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Originally posted by Lumpy

Brogan maintenance. That's what we used in the Air Force. One swift kick with the boot and viola. LOL.

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Oh yeah!  That's the first round of troubleshooting here.

Dieselten - Posted - 03/08/2013:  13:05:05

Freezing Spray. Apply to the board and use percussive maintenance (i.e. tape the board)  until the fault manifests itself. This is a good way to isolate the most difficult of all intermittent faults, the dry-joint. In a previous career I spent hours hunting down and terminating these elusive faults.

Brian T - Posted - 03/08/2013:  13:06:53

Got a fridge with a freezer in your shop?

Bill Rogers - Posted - 03/08/2013:  13:15:08

I've done just the reverse when troubleshooting an intermittent part--the recorder went down after maybe 10 minutes of use, but when pulled, the chassis was fine.  It was heating up in the case, but out of the case the open air kept it cool; a hair dryer soon found the culprit--a condenser that was quickly changed out, solving the problem.

Mopick - Posted - 03/08/2013:  14:22:34

Yep.  You guys know your stuff.  I've been an engineering tech for over 25 years and freeze spray / hot air cannon are in my bag of dirty tricks.  Bill Rogers is dating himself (me too).  I haven't heard a capacitor called a condenser in long, long time.  Definitely old school.  

Brian, I do have a freezer here.  I've done that before.  Here in FL, we have so much humidity that as soon as you pull the frozen board out, the humidity condenses and moisture gets all over the board, in the coils, etc.  

We called our customer in Alaska (I was wondering where they found -10 F temperatures).  They said to just send the board back, it's right at the edge of the manufacturers specs and they would put it in a warmer RST.

Mopick - Posted - 03/08/2013:  14:27:59

quote:

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Originally posted by Bill Rogers

I've done just the reverse when troubleshooting an intermittent part--the recorder went down after maybe 10 minutes of use, but when pulled, the chassis was fine.  It was heating up in the case, but out of the case the open air kept it cool; a hair dryer soon found the culprit--a condenser that was quickly changed out, solving the problem.

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I see this all the time.  The equipment in the cabinet / shelf gets hot and fails.  I put the board on an extender out in the open air and it won't fail.  I put it back in the shelf with higher temps and it fails within a few minutes.   That's when I put it back on the extender and start blowing hot air on isolated components until it fails again.  A quick shot of freeze spray brings it back up to verify. 

It's usually the microprocessor IC, which is a BGA with 256 balls.

Mopick - Posted - 03/08/2013:  14:31:30

quote:

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Originally posted by Bill Rogers

I've done just the reverse when troubleshooting an intermittent part--the recorder went down after maybe 10 minutes of use, but when pulled, the chassis was fine.  It was heating up in the case, but out of the case the open air kept it cool; a hair dryer soon found the culprit--a condenser that was quickly changed out, solving the problem.

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You probably know what a mulitvibrator is don't you?   

dat - Posted - 03/08/2013:  14:43:16

I used to do a lot of electrical on cars, sometimes it's hard to pinpoint something that only happens at certain times driving at 60 mph and hits a bump.  you know what to look for, but it could be most anywhere there is a connector or component.   much easier if it breaks and stays broke instead of the "at times"

donc - Posted - 03/08/2013:  15:29:33

We had one line of modems that customers would stack in one big pile with other modems and routers etc. These would actually warp. This would be a typical heat problem. At -10 F degrees I would wonder if the shelf or cabinet contacts are contracting and basically unplugging themselves. Anywhere where outside humid air is getting in is where all sorts of problems are possible. I would be asking what kind of environment [i.e. humidity and temperature] that these cards are subjected to.

Jeff 1965 - Posted - 03/08/2013:  16:27:38

I don't know about you but I would complain too if I had to work in that weather. My FMAO bit would toggle to true in no time.

Interesting. A circuit board complains that it's too cold and then it gets sent to Florida.

Edited by - Jeff 1965 on 03/08/2013 16:32:09

mike gregory - Posted - 03/08/2013:  19:04:23

quote:

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Originally posted by Jeff 1965

I don't know about you but I would complain too if I had to work in that weather. My FMAO bit would toggle to true in no time.

Interesting. A circuit board complains that it's too cold and then it gets sent to Florida.

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 This is why the machines rose in revolt: Didn't like that only some of them got to spend winter in Florida.

Bart Veerman - Posted - 03/08/2013:  20:36:36

Yay, major trouble shooting experts here!

Sorry, can't answer your question but if I could weasel in one of my own:

JVC stereo receiver, 5.1 surround sound, the center channel keeps cutting out. When I blip the volume control and/or jiggle the speakers wires at the receiver the sound comes back - no audio distortion when speakers on  or cut-out. So far I've squirted contact cleaner in the volume control, the only moving part, to no avail. Plugged & unplugged all IC & edge board connectors - audio still keeps cutting out. Volume control shot? Cold solder joint at the speaker terminals? Gremlins?

fivebranch - Posted - 03/08/2013:  20:41:39

My solution is a BFH.!!:-)

Mopick - Posted - 03/08/2013:  20:43:10

quote:

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Originally posted by Bart Veerman

Yay, major trouble shooting experts here!

Sorry, can't answer your question but if I could weasel in one of my own:

JVC stereo receiver, 5.1 surround sound, the center channel keeps cutting out. When I blip the volume control and/or jiggle the speakers wires at the receiver the sound comes back - no audio distortion when speakers on  or cut-out. So far I've squirted contact cleaner in the volume control, the only moving part, to no avail. Plugged & unplugged all IC & edge board connectors - audio still keeps cutting out. Volume control shot? Cold solder joint at the speaker terminals? Gremlins?

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 I would suspect a solder joint at the terminal.  You may have to look close to see it, but a lot of times a cold solder joint actually gets a crack in the solder and you can see the lead move.  Sometimes it just looks like a ring around lead.

Mopick - Posted - 03/08/2013:  20:48:38

I want to know who signed me up for this?  Hidden lead BGA's (Ball Grid Array IC).  Teeny tiny surface mount components.  Micro mini.  When I went to school we had resistors with leads that stuck through a single or double sided PCB.  Chips with leads.   I've had to adapt with the times.  I never dreamed in 1983 when I graduated from college that technology would advance this far.  We were playing Tron at the arcade.  I learned PLC, COBOL, FORTRAN on an IBM 360 Main Frame.  Nobody had PC's.  Well I did have a TI99-4A and Commodore 64. 

trapdoor2 - Posted - 03/09/2013:  12:33:13

quote:

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Originally posted by Mopick

 

I want to know who signed me up for this?  Hidden lead BGA's (Ball Grid Array IC).  Teeny tiny surface mount components.  Micro mini.  When I went to school we had resistors with leads that stuck through a single or double sided PCB.  Chips with leads.   I've had to adapt with the times.  I never dreamed in 1983 when I graduated from college that technology would advance this far.  We were playing Tron at the arcade.  I learned PLC, COBOL, FORTRAN on an IBM 360 Main Frame.  Nobody had PC's.  Well I did have a TI99-4A and Commodore 64. 

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 BGA...aaaarrrrrgggghhh. I was a QE for a decent sized contract Electronics Mfg from '92 - '99. We started placing BGAs in '98 as I recall. No big deal to pick and place (all high-speed machine stuff) but the gals out on the repair line would spend hours and hours trying to troubleshoot and/or repair a BGA board. They had a hard time removing them w/o toasting the board and asked for a specialized removal process. I developed a neat little reciprocating saw that would slide underneath the BGA component and actually saw thru all the balls without damaging the component or the board. By the time I demoed it, the bigwigs decided it was cheaper to toss the whole board rather than fix it.

Mopick - Posted - 03/09/2013:  16:53:58

quote:

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Originally posted by trapdoor2

quote:

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Originally posted by Mopick

 

I want to know who signed me up for this?  Hidden lead BGA's (Ball Grid Array IC).  Teeny tiny surface mount components.  Micro mini.  When I went to school we had resistors with leads that stuck through a single or double sided PCB.  Chips with leads.   I've had to adapt with the times.  I never dreamed in 1983 when I graduated from college that technology would advance this far.  We were playing Tron at the arcade.  I learned PLC, COBOL, FORTRAN on an IBM 360 Main Frame.  Nobody had PC's.  Well I did have a TI99-4A and Commodore 64. 

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 BGA...aaaarrrrrgggghhh. I was a QE for a decent sized contract Electronics Mfg from '92 - '99. We started placing BGAs in '98 as I recall. No big deal to pick and place (all high-speed machine stuff) but the gals out on the repair line would spend hours and hours trying to troubleshoot and/or repair a BGA board. They had a hard time removing them w/o toasting the board and asked for a specialized removal process. I developed a neat little reciprocating saw that would slide underneath the BGA component and actually saw thru all the balls without damaging the component or the board. By the time I demoed it, the bigwigs decided it was cheaper to toss the whole board rather than fix it.

 

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 We're a small repair shop and until recently BGA failure was a non-repair for me because I didn't have the equipment.  My company gets GOOD money to repair these OC12 XCVR's and it kills me to non-repair a board.  I looked into a BGA re-work machine but were in the area of 30K.  So I started looking into it and found a way that I can replace the BGA manually.

I get pre-balled BGA's and that is a big plus.  In the old days you would have to re-ball an IC, then place it on the board.   You had to have a temperature controlled oven, etc.

I found a low tech company called Stencil Quick that makes an self adhesive, high temp, stencil.  Once you remove the old IC and clean the pads, you stick the stencil over the pads.  Fill the holes with solder paste, place the IC in the stencil and heat with hot air to melt the solder paste.  This BGA is a Motorola processor and I can replace them with a high degree of success.

Take the old IC off,  blowing hot air from underneath and from above.  I get the chip off as fast as I can and cut the hot air.

Clean up the pads with solder wick and an alcohol wipe.

Trim and place the Stencil Quick with each aperture directly over a pad.

Fill the apertures with solder paste.

Place the BGA onto the apertures, while observing proper alignment and orientation.

Heat with hot air from above and below to melt the solder paste.  I have a temperature profile stored in my machine that just melts the solder paste but not the balls on the BGA.

Success!

wizofos - Posted - 03/10/2013:  16:07:32

Reading this thread brought back some memories of working night shift in a computer room. We had a check reader/sorter connected to our 360/40 mainframe. It kept getting intermittent failures. Called in IBM and the customer engineer ran every diagnostic he had but could not figure it out. So he had all of  us in the computer room do the bunny hop around the machine to see if that would cause the failure.  No go. So he goes down to his car and comes back with a 2 pound rubber fine adjusting tool and starts hitting the frame. His logic, it was a lose connection and whacking it would either fix it or cause it to fail permanently so he could find it.

Funny to see a bunch of computer operators and keypunch operators doing the bunny hop around that machine.

We decided not to tell the boss about that, management thought the night shift  people were all crazy anyway.

Kenneth Logsdon - Posted - 03/10/2013:  17:35:20

Well thats gratifying, I was gonna say "when in doubt use a bigger hammer"...