Author Topic: Tough Problem To Locate Need Help  (Read 15171 times)

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Offline rrinker

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Re: Tough Problem To Locate Need Help
« Reply #25 on: April 25, 2016, 07:41:57 pm »
 Those traces look fairly solid through that area, but if it is definitely heating those two components and not the DAC chip that does it - perhaps there are some bad vias.

 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #26 on: April 25, 2016, 07:43:16 pm »
The heat could be spilling over onto that chip. Really hard to do with a hair dryer LOL!
 

Offline DimitriP

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Re: Tough Problem To Locate Need Help
« Reply #27 on: April 25, 2016, 07:46:25 pm »
The heat could be spilling over onto that chip. Really hard to do with a hair dryer LOL!

That's why scope probes are pointy.
   If three 100  Ohm resistors are connected in parallel, and in series with a 200 Ohm resistor, how many resistors do you have? 
 

Offline stmdude

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Re: Tough Problem To Locate Need Help
« Reply #28 on: April 25, 2016, 08:13:24 pm »
Put something above the DAC to shield it and try again. A few seconds at 2 feet away shouldn't allow the PCB to heat up enough for it to creep to the DAC.

Also, while the DAC has been discontinued, there are dealers that still have stock: https://octopart.com/cxd3023r-sony-13010981

 

Offline mij59

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Re: Tough Problem To Locate Need Help
« Reply #29 on: April 26, 2016, 03:09:05 am »
I'm just hoping it's not this Sony Cxd3023r DAC. It's discontinued! Probably why H/K won't repair it anymore?

Are there beads of solder between the legs of the IC ?
« Last Edit: April 26, 2016, 03:20:50 am by mij59 »
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #30 on: April 26, 2016, 05:52:41 am »
Non I can see with an eye loop!
 

Online Gyro

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Re: Tough Problem To Locate Need Help
« Reply #31 on: April 26, 2016, 08:31:44 am »
Heat can slightly revive a dried out electrolytic capacitor. There was a common failure mode on some old Infocus projectors where they would only start up if you blew a hairdryer through the air inlet. It turned out to be a dried out startup capacitor (a little 10uF one) in the power supply.

You could try applying a little direct heat to C457 or just swap it. It's a long shot but....
Chris

"Victor Meldrew, the Crimson Avenger!"
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #32 on: April 26, 2016, 03:26:38 pm »
Heat can slightly revive a dried out electrolytic capacitor. There was a common failure mode on some old Infocus projectors where they would only start up if you blew a hairdryer through the air inlet. It turned out to be a dried out startup capacitor (a little 10uF one) in the power supply.

You could try applying a little direct heat to C457 or just swap it. It's a long shot but....

I think I'm pretty much over it at this point. Just tired of messing with it.
 

Offline Shock

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Re: Tough Problem To Locate Need Help
« Reply #33 on: April 26, 2016, 03:41:06 pm »
Capacitor ESR lowers with heat and the SMD caps of that era also leak. I think you have found the problem and the capacitor needs replacing.
Soldering/Rework: Pace ADS200, Pace MBT350
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Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #34 on: April 26, 2016, 04:44:41 pm »
Capacitor ESR lowers with heat and the SMD caps of that era also leak. I think you have found the problem and the capacitor needs replacing.

I really don't think I have the proper tools to change out an SMD. I just have a plain old solder station. Don't you need tweezers, or a reflow gun?
 

Offline mij59

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Re: Tough Problem To Locate Need Help
« Reply #35 on: April 26, 2016, 05:08:07 pm »
Capacitor ESR lowers with heat and the SMD caps of that era also leak. I think you have found the problem and the capacitor needs replacing.

I really don't think I have the proper tools to change out an SMD. I just have a plain old solder station. Don't you need tweezers, or a reflow gun?

Somewhat brute force method https://www.youtube.com/watch?v=p1zhfYHUIIY] [url]https://www.youtube.com/watch?v=p1zhfYHUIIY [/url]
 

Offline DimitriP

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Re: Tough Problem To Locate Need Help
« Reply #36 on: April 26, 2016, 06:08:39 pm »
Capacitor ESR lowers with heat and the SMD caps of that era also leak. I think you have found the problem and the capacitor needs replacing.

I really don't think I have the proper tools to change out an SMD. I just have a plain old solder station. Don't you need tweezers, or a reflow gun?

Of course not.

Use solder braid.It's cheap, silent and you don't have to start a thread of 5 pages on "which rework station to buy" :)
   If three 100  Ohm resistors are connected in parallel, and in series with a 200 Ohm resistor, how many resistors do you have? 
 

Offline Shock

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Re: Tough Problem To Locate Need Help
« Reply #37 on: April 26, 2016, 11:23:29 pm »
The problem with desoldering braid is solder left under the component leg which can take the pad with it if it solidifies again, I prefer melting both pads at once.

If no form of hot air, you can make some improvised desoldering tweezers as shown in this thread. No need to remove the end of the tip, a temporary setup will do, use a decent thickness copper wire.

You could also make a short loop of copper wire to reach from one pad to the other, form it then tin the tips of the wire and solder it in place with a blob of solder. By heating the middle with an iron with some solder to aid in thermal transfer you can achieve melt at both pads and remove with pliers or tweezers.

Another riskier method is put a blob on each pad and alternately heat the pads without being to aggressive on dwell time. Go several times back and forwards and the board will take some heat then give one side a little extra attention then immediately hit the other side and go for removal.

Use flux if you can it helps, as well as practicing scrap boards.

 
Soldering/Rework: Pace ADS200, Pace MBT350
Multimeters: Fluke 87V, 117, 27/FM     >>> Fluke 51/52 Thermometer Parts Required <<<
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Offline DimitriP

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Re: Tough Problem To Locate Need Help
« Reply #38 on: April 27, 2016, 04:44:08 am »
Quote
The problem with desoldering braid is solder left under the component leg which can take the pad with it if it solidifies again

That's not really a braid problem, it's a technique problem.

   If three 100  Ohm resistors are connected in parallel, and in series with a 200 Ohm resistor, how many resistors do you have? 
 

Offline Shock

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Re: Tough Problem To Locate Need Help
« Reply #39 on: April 27, 2016, 07:57:20 am »
The other technique I forgot to mention is using two irons.

Quote
The problem with desoldering braid is solder left under the component leg which can take the pad with it if it solidifies again

That's not really a braid problem, it's a technique problem.

Can you elaborate on your technique and how you overcome surface tension leading to a sweat joint under the legs of the surface mounted aluminum electrolytics then? Do you use this same technique on surface mount ICs?
Soldering/Rework: Pace ADS200, Pace MBT350
Multimeters: Fluke 87V, 117, 27/FM     >>> Fluke 51/52 Thermometer Parts Required <<<
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Online Gyro

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Re: Tough Problem To Locate Need Help
« Reply #40 on: April 27, 2016, 08:40:42 am »
Alternatively, if you're really worried about removing the SMT cap, then solder a same value through-hole capacitor across the solder pads of existing one, without removing it.

If it is reviving sufficiently with heat then it is unlikely that there is any serious PCB corrosion underneath it. Paralleling a new one would at least confirm the diagnosis, and probably provide a 'permanent' fix.
Chris

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Offline KE5FX

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Re: Tough Problem To Locate Need Help
« Reply #41 on: April 27, 2016, 09:31:43 am »
Pro tip: get a (cheap) second soldering iron.
 

Online CJay

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Re: Tough Problem To Locate Need Help
« Reply #42 on: April 27, 2016, 12:20:08 pm »
Capacitor ESR lowers with heat and the SMD caps of that era also leak. I think you have found the problem and the capacitor needs replacing.

I really don't think I have the proper tools to change out an SMD. I just have a plain old solder station. Don't you need tweezers, or a reflow gun?

Apply solder to the connections (more solder is easier to melt than a tiny amount, it's about thermal contact), grab part with tweezers or fine pliers and very gently pull, melt the solder on one leg, the part should lift a tiny bit. melt the solder on the other leg, it should lift a little more.

Try to imagine the force you'd need to use to pick the part up with the tweezers to give you an idea of how much you need to pull on the part.

Too much and you might pull the pads from the board.

Repeat until you can lift the part away with the tweezers/fine pliers.

Clean up the pads with solder wick.

Replace part.

Those little SMD caps are dreadful for failing like that.
M0UAW
 

Offline jitter

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Re: Tough Problem To Locate Need Help
« Reply #43 on: April 27, 2016, 01:43:25 pm »
Those traces look fairly solid through that area, but if it is definitely heating those two components and not the DAC chip that does it - perhaps there are some bad vias.

This was my first idea as well: a cracked via that reconnects because the heat makes the copper expand...
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #44 on: April 28, 2016, 01:32:30 pm »
Alternatively, if you're really worried about removing the SMT cap, then solder a same value through-hole capacitor across the solder pads of existing one, without removing it.

If it is reviving sufficiently with heat then it is unlikely that there is any serious PCB corrosion underneath it. Paralleling a new one would at least confirm the diagnosis, and probably provide a 'permanent' fix.

Your saying don't remove the SMD cap, and just solder a through hole electrolytic cap onto the edges of the SMD component? Maybe put electrical tape around the SMD cap to prevent shorting? Will this actually work? Just make sure it's at least 16volt. How do you read the value on this cap? Never dealt with SMD caps before?
« Last Edit: April 28, 2016, 01:42:41 pm by tony3d »
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #45 on: April 28, 2016, 01:50:41 pm »
OK, I found the Service Manual. Looks like Cap 457 is a 10uF 16 volt cap! Positive end is the angled side correct?
« Last Edit: April 28, 2016, 01:55:48 pm by tony3d »
 

Offline Brumby

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Re: Tough Problem To Locate Need Help
« Reply #46 on: April 28, 2016, 02:10:32 pm »
Does this help?

 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #47 on: April 28, 2016, 02:19:50 pm »
Does this help?



Yup! Looks like the angled edge is positive, and the black marked edge Negative. Thats what I thought. So the cap must be smoothing the voltage, and the Inductor behind it is smoothing the current? Is it a power supply thing maybe. I don't know I'm just guessing LOL!
 

Offline tony3d

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Re: Tough Problem To Locate Need Help
« Reply #48 on: April 28, 2016, 02:22:32 pm »
The through hole cap I have is a 50volt 10 uF cap. someone told me that it won't last because of the higher voltage rating. I would have thought it puts less strain on the cap no?
 

Offline Shock

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Re: Tough Problem To Locate Need Help
« Reply #49 on: April 28, 2016, 06:19:45 pm »
Unless I'm mistaken that additional capacitor in parallel trick only works when the capacitor has a reasonably high leakage current or is open, to add capacitance back. If the capacitor is acting more as a short this may not correct the problem and removing the original cap still is required.

As surface mount capacitors of this age also can physically leak electrolyte onto the PCB this is another reason to remove it and others if they check bad. Left unchecked electrolyte will start to eat into the copper traces and making an otherwise simple capacitor replacement repair, turn into a time consuming PCB repair.
Soldering/Rework: Pace ADS200, Pace MBT350
Multimeters: Fluke 87V, 117, 27/FM     >>> Fluke 51/52 Thermometer Parts Required <<<
Oscilloscopes: Rigol DS1054Z, Phillips PM3065
 


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