Tough Problem To Locate Need Help - Page 1
Forum section: electronics / beginners

author: tony3d
author_rank: Frequent Contributor
timestamp: April 22, 2016, 01:24:55 pm
content: Hi all, I have been into electronics now for about a year, and have learned a lot from this site. Don't replay have the expertise to repair things yet, but I am learning. I have an issue with one of my HIFI Components, a Harman Kardon CDR26 Cd recorder. It has a playback cd drive on the left, and a record unit on the right. The unit on the right works fine, the one on the left fails to read a disc, and comes up with disc error after several attempts to read it. At first it had every sign of a failing Laser, because it gradually became worse. So, I found the play drive on Ebay, bought it, replaced it, and had the exact same problem. I had noticed that The unit would sometime read when it heated up a bit, so while I had it opened I got a hair dryer out and just heated the board in different areas, and found it would read instantly, and play fine so long as the board was warm. So I narrowed it down to this area of the board, but really can't see anything very obvious. I mean it's so sensitive I can hold the dryer 3 feet away for 5 seconds, and it will work! Going to be very hard to locate. I only have a solder station with no special attachments. Closest thing I have is a very small ball tip. There are a lot of surface mount components here I would rather not ouch LOL! Any suggestions would be great! By the way H/K no longer repairs this machine. I took apart all the ribbon cables, and checked the continuity of them with my Fluke, and all were fine.

author: Whales
author_rank: Super Contributor
timestamp: April 22, 2016, 01:30:43 pm
content: See if you can narrow down the problem further using your hot air. Try heating only a small part of your board and slowly heat more sections until the problems disappears.

author: Codemonkey
author_rank: Regular Contributor
timestamp: April 22, 2016, 01:33:35 pm
content: If you can't heat a small section of the board, you could heat it all up until it works and then use some freeze spray to cool bits selectively until it doesn't work.

author: Whales
author_rank: Super Contributor
timestamp: April 22, 2016, 01:39:26 pm
content: Can you 'constantly' test the board or do you have to perform an action (eg pressing a button and waiting) after heating it to check if it works?If you can constantly test the board then try pressing the SMD components against the board, one by one, with a wooden skewer.

author: CJay
author_rank: Super Contributor
timestamp: April 22, 2016, 02:05:07 pm
content: Always always check the basics first.Visual:Are there any components showing signs of stress, I.E. are they or the board around them discoloured, have any capacitors tilted over or swollen up?Electrical:Does it have the correct/sensible voltages coming onto the board? You can check when it's cold and faulty and again when it's working.Do the voltages make it to the relevant chips? (you can usually find datasheets or at least pin outs for most chips)Are there any crystals on the board, are they oscillating? A missing clock signal will cause all sorts of problems.Does the disk spin?Do not look at it directly but does the laser light up? (an infra red laser as used in a CD player will, when viewed at an offset angle)

author: tony3d
author_rank: Frequent Contributor
timestamp: April 22, 2016, 03:11:09 pm
content: Quote from: Whales on April 22, 2016, 01:39:26 pmI can constantly test the board because the sound will begin to Crackle as the board cools. I'll give this a try. I see no physical defect that looks suspicious. This section of the board I'm showing is definitely the area the problem exists in. the heat does not effect the right side of the board which I believe is the record decks side, which works fine. This is so frustrating, but at least I'm on the right track.

author: mij59
author_rank: Frequent Contributor
timestamp: April 22, 2016, 03:22:49 pm
content: Seems to me the solder joint of the bottom left cap is broken.Check the SMD cap's with an ESR meter.Check for dust etc. on the lens of the laser.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 22, 2016, 03:23:20 pm
content: Quote from: Codemonkey on April 22, 2016, 01:33:35 pmNow that Radio Shack is gone where can I get a can of this spray?

author: dacman
author_rank: Frequent Contributor
timestamp: April 22, 2016, 03:43:32 pm
content: You could use canned air upside down.

author: cvanc
author_rank: Frequent Contributor
timestamp: April 22, 2016, 06:58:58 pm
content: Solder joint in question (and sharp eyes for finding it!):

author: tony3d
author_rank: Frequent Contributor
timestamp: April 22, 2016, 10:42:04 pm
content: Quote from: cvanc on April 22, 2016, 06:58:58 pmYes, I'm going to hit that tomorrow! Looks like that may be it!

author: DimitriP
author_rank: Super Contributor
timestamp: April 22, 2016, 11:11:45 pm
content: The pins on the left side of IC 403 don't look quite right.Also the ribbon cable is plugged in at an angle. The left side looks like it's almost out.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 25, 2016, 04:39:06 pm
content: Have tried everything. Pressed down on almost every component with a pencil eraser, Touched the cap in question with a soldering tip, straightened the ribbon cable, and pressed down on a variety of traces with the pencil eraser. Yet, if I hit just even the top right corner of the board with a hairdryer on low heat for only 5-10 seconds, it works! OMG!!

author: DimitriP
author_rank: Super Contributor
timestamp: April 25, 2016, 05:05:53 pm
content: Sounds lke it's time for some signal probin'. Do you have a schematic, or more importantly a 'scope?

author: mij59
author_rank: Frequent Contributor
timestamp: April 25, 2016, 05:10:33 pm
content: Maybe there's intermittent contact in L442, could be part of a power rail for IC403.

author: miguelvp
author_rank: Super Contributor
timestamp: April 25, 2016, 05:12:53 pm
content: Quote from: tony3d on April 25, 2016, 04:39:06 pmSeems he fixed it.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 25, 2016, 05:37:56 pm
content: No, I meant after holding the heat for that length of time, it works. I think I have narrowed down to two components. The electrolytic cap in this image or the one above, soon as I hit these two with cold air it stops working! Touched both sides of the cap with my solder station, and no dice. not sure how to tackle the one above. pressing on either does nothing. Wonder if the cap is bad?

author: tony3d
author_rank: Frequent Contributor
timestamp: April 25, 2016, 05:55:28 pm
content: Quote from: mij59 on April 25, 2016, 05:10:33 pmI do have a cheap OWon Scope! Like I say I'm still a beginner. I'm really not sure what that L442 component is? Is it a resistor or a cap?

author: DimitriP
author_rank: Super Contributor
timestamp: April 25, 2016, 06:37:06 pm
content: Quote from: tony3d on April 25, 2016, 05:55:28 pmNeitherTake a look and herehttps://en.wikipedia.org/wiki/Reference_designatorand there will be a quiz later

author: tony3d
author_rank: Frequent Contributor
timestamp: April 25, 2016, 06:51:28 pm
content: Quote from: DimitriP on April 25, 2016, 06:37:06 pmSo it's an Inductor?

author: tony3d
author_rank: Frequent Contributor
timestamp: April 25, 2016, 06:55:01 pm
content: I'm just hoping it's not this Sony Cxd3023r DAC. It's discontinued! Probably why H/K won't repair it anymore?

author: stmdude
author_rank: Frequent Contributor
timestamp: April 25, 2016, 06:57:28 pm
content: Quote from: tony3d on April 25, 2016, 06:51:28 pmCorrect. The most basic test of an inductor would be to check continuity and/or resistance. It should be close to 0 ohms.Try checking on the component, and away from it (as in, the component it's connected to, a via, etc), to check the solder.The component has wide legs that are wrapped underneath it. You should be able to re-flow it by simply holding your iron against the metal side until the solder underneath melts. Repeat for the other side.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 25, 2016, 07:18:21 pm
content: I'm getting between .2-.4 Ohms, and it does have continuity. I'm really beginning to think it's that Sony Dac Which is discontinued! Did touch both sides with the solder tip, made no difference. Can hold the hear 2 feet away for just seconds, and it plays fine. Really weird!

author: tony3d
author_rank: Frequent Contributor
timestamp: April 25, 2016, 07:28:57 pm
content: I think I'm going to have to give up on this player, and just use the right deck. Really close, but no prize! I don't see anything else on the board that looks off in this area. I have touched multiple point with my iron. I think it could be that chip itself! Maybe there's a disconnect inside?

author: tony3d
author_rank: Frequent Contributor
timestamp: April 25, 2016, 07:30:47 pm
content: Almost considering mounting a small heater to the bottom of the lid. it just needs to be heated slightly. It's a bandaid, but hey if it works......LOL!

author: rrinker
author_rank: Super Contributor
timestamp: April 25, 2016, 07:41:57 pm
content: 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.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 25, 2016, 07:43:16 pm
content: The heat could be spilling over onto that chip. Really hard to do with a hair dryer LOL!

author: DimitriP
author_rank: Super Contributor
timestamp: April 25, 2016, 07:46:25 pm
content: Quote from: tony3d on April 25, 2016, 07:43:16 pmThat's why scope probes are pointy.

author: stmdude
author_rank: Frequent Contributor
timestamp: April 25, 2016, 08:13:24 pm
content: 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

author: mij59
author_rank: Frequent Contributor
timestamp: April 26, 2016, 03:09:05 am
content: Quote from: tony3d on April 25, 2016, 06:55:01 pmAre there beads of solder between the legs of the IC ?

author: tony3d
author_rank: Frequent Contributor
timestamp: April 26, 2016, 05:52:41 am
content: Non I can see with an eye loop!

author: Gyro
author_rank: Super Contributor
timestamp: April 26, 2016, 08:31:44 am
content: 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....

author: tony3d
author_rank: Frequent Contributor
timestamp: April 26, 2016, 03:26:38 pm
content: Quote from: Gyro on April 26, 2016, 08:31:44 amI think I'm pretty much over it at this point. Just tired of messing with it.

author: Shock
author_rank: Super Contributor
timestamp: April 26, 2016, 03:41:06 pm
content: 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.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 26, 2016, 04:44:41 pm
content: Quote from: Shock on April 26, 2016, 03:41:06 pmI 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?

author: mij59
author_rank: Frequent Contributor
timestamp: April 26, 2016, 05:08:07 pm
content: Quote from: tony3d on April 26, 2016, 04:44:41 pmSomewhat brute force methodhttps://www.youtube.com/watch?v=p1zhfYHUIIY] https://www.youtube.com/watch?v=p1zhfYHUIIY

author: DimitriP
author_rank: Super Contributor
timestamp: April 26, 2016, 06:08:39 pm
content: Quote from: tony3d on April 26, 2016, 04:44:41 pmOf 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"

author: Shock
author_rank: Super Contributor
timestamp: April 26, 2016, 11:23:29 pm
content: 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 asshown 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.

author: DimitriP
author_rank: Super Contributor
timestamp: April 27, 2016, 04:44:08 am
content: QuoteThat's not really a braid problem, it's a technique problem.

author: Shock
author_rank: Super Contributor
timestamp: April 27, 2016, 07:57:20 am
content: The other technique I forgot to mention is using two irons.Quote from: DimitriP on April 27, 2016, 04:44:08 amCan 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?

author: Gyro
author_rank: Super Contributor
timestamp: April 27, 2016, 08:40:42 am
content: 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.

author: KE5FX
author_rank: Super Contributor
timestamp: April 27, 2016, 09:31:43 am
content: Pro tip: get a (cheap) second soldering iron.

author: CJay
author_rank: Super Contributor
timestamp: April 27, 2016, 12:20:08 pm
content: Quote from: tony3d on April 26, 2016, 04:44:41 pmApply 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.

author: jitter
author_rank: Frequent Contributor
timestamp: April 27, 2016, 01:43:25 pm
content: Quote from: rrinker on April 25, 2016, 07:41:57 pmThis was my first idea as well: a cracked via that reconnects because the heat makes the copper expand...

author: tony3d
author_rank: Frequent Contributor
timestamp: April 28, 2016, 01:32:30 pm
content: Quote from: Gyro on April 27, 2016, 08:40:42 amYour 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?

author: tony3d
author_rank: Frequent Contributor
timestamp: April 28, 2016, 01:50:41 pm
content: OK, I found the Service Manual. Looks like Cap 457 is a 10uF 16 volt cap! Positive end is the angled side correct?

author: Brumby
author_rank: Unknown
timestamp: April 28, 2016, 02:10:32 pm
content: Does this help?

author: tony3d
author_rank: Frequent Contributor
timestamp: April 28, 2016, 02:19:50 pm
content: Quote from: Brumby on April 28, 2016, 02:10:32 pmYup! 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!

author: tony3d
author_rank: Frequent Contributor
timestamp: April 28, 2016, 02:22:32 pm
content: 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?

author: Shock
author_rank: Super Contributor
timestamp: April 28, 2016, 06:19:45 pm
content: 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.

author: KE5FX
author_rank: Super Contributor
timestamp: April 28, 2016, 07:19:55 pm
content: Quote from: tony3d on April 28, 2016, 02:22:32 pmThat's a myth. It'll be fine.

author: Gyro
author_rank: Super Contributor
timestamp: April 28, 2016, 07:38:46 pm
content: It's got to be worth a try, even if only to confirm (or not) the diagnosis. If you bend the leads right you shouldn't need to tape anything.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 28, 2016, 07:44:39 pm
content: I'm going to give it a try tomorrow. Thanks for all the help. Just never messed with SMD components before, and really don't have the proper tools to do so. If this bandaid works, I'll be happy. I checked the entire deck out for the right record drive, and everything else is still working fine!

author: jitter
author_rank: Frequent Contributor
timestamp: April 28, 2016, 07:59:37 pm
content: Quote from: tony3d on April 28, 2016, 02:19:50 pmIn that case, maybe you should get the service manual and find out what it does.A copy can be foundhere(wait for the word "...processing..." to change to "Get Manual").C457 and L441 are on page 75, upper left of IC402. They're on the output of IC410, a 2.7 V voltage regulator.Thou shalt measure voltages... so, before you go and solder anything parallel, first measure if there's 2.7 V present across the cap, cold and warm.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 28, 2016, 08:04:22 pm
content: Quote from: jitter on April 28, 2016, 07:59:37 pmGood Idea. Thanks! I already put it all back together, because I kinda gave up on it, but I'll give it one more try. I know that the other side of the board has no reaction to the heat, and all I can do is isolate other components with a cardboard tube. soon as I heat up the cap it plays fine. Blast some compressed air on it for just a few seconds, and it immediately drops out. Hope this is it!

author: jitter
author_rank: Frequent Contributor
timestamp: April 28, 2016, 08:20:23 pm
content: Well, after looking a bit more at the schematic, C457 seems to be in the right spot for your symptoms.The signal from the pickup is first processed by IC403 and its outputs go straight to IC402. The 2.7 V is used all around IC402 (along with 3.3 V).Yeah, definitely worth checking.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 28, 2016, 08:55:10 pm
content: Quote from: jitter on April 28, 2016, 08:20:23 pmYup! Well this will be my first diagnosis LOL! The deck is beautiful other than that, sound fine and works for about 4 minutes when heated. I will definitely try this tomorrow.Never thought of just paralleling a regular electrolytic.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 29, 2016, 12:18:17 pm
content: Well, It's not the cap. I'm getting 2.640 volts cold! I'm afraid this repair will probably be beyond my expertise. Damn so close! I'll leave it opened incase anyone has more ideas.

author: CJay
author_rank: Super Contributor
timestamp: April 29, 2016, 01:29:54 pm
content: Quote from: tony3d on April 29, 2016, 12:18:17 pmTry it and see if it works.That 2.64V may have significant ripple, noise or be dipping as the DAC and other circuitry is initialising.It will only cost you a few pennies to replace the cap.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 29, 2016, 01:37:52 pm
content: Quote from: CJay on April 29, 2016, 01:29:54 pmCan I just solder onto this cap? Really don't want to try to remove that SMD with just my soldering station. Trouble is it would be twice the capacitance right? Was going to use a through hole cap.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 29, 2016, 02:12:53 pm
content: Ok, I soldered the negative lead of the through hole to the neg side of the SMD, then while loading a disc touched the pos to the pos of the SMD, and it mounted! first time with no heat! Wish I could get that cap off! really afraid to mess with it. But this does seem to work!

author: tony3d
author_rank: Frequent Contributor
timestamp: April 29, 2016, 02:23:01 pm
content: Well I soldered the pos on, and it works Perfectly! My first lagiamite repair thanks to all your help! You don't know much this means to me, because this deck was the last Christmas present from my brother who passed away 7 years ago. Lot of sentimental value is attached more than anything! Thanks again for all the great help! Learned a lot to! This also helped dissipate my fear of working on a board! Thanks again to all. I'll post pics shortly. Just letting play a while LOL!

author: tony3d
author_rank: Frequent Contributor
timestamp: April 29, 2016, 02:42:51 pm
content: Here it is. Been play for nearly 30 minutes Plugged into my Emotive RSP2 Preamp driving my Crown XTI2000 Power amp! Sounds perfect! no skipping, no audible distortion, Just perfect! Thanks again for all the help!

author: tony3d
author_rank: Frequent Contributor
timestamp: April 29, 2016, 03:08:29 pm
content: Now it dubs from deck to deck with no errors! Use to be when that cap was going bad I couldn't get through one recording without it loosing it's way half way through! Works perfect now!

author: Gyro
author_rank: Super Contributor
timestamp: April 29, 2016, 03:38:14 pm
content: Congratulations on the localization and the fix!

author: tony3d
author_rank: Frequent Contributor
timestamp: April 29, 2016, 03:56:18 pm
content: Quote from: Gyro on April 29, 2016, 03:38:14 pmThanks! Could have never done it without all the help! Been playing fine for over an hour!

author: cvanc
author_rank: Frequent Contributor
timestamp: April 29, 2016, 04:23:38 pm
content: Here ya go Tony! Nice job.

author: Brumby
author_rank: Unknown
timestamp: April 29, 2016, 04:25:40 pm
content: I'll add my congratulations as well.You do realise that by tracking the fault zone down with a hair dryer, you had done 75% of the head scratching? Without that, it would have had a much more challenging exercise.It's great to see a piece of equipment repaired, especially when it's something special.

author: Shock
author_rank: Super Contributor
timestamp: April 29, 2016, 04:46:41 pm
content: Grats and good work for having a go.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 29, 2016, 04:52:52 pm
content: Quote from: Brumby on April 29, 2016, 04:25:40 pmI guess, but without the guidance from this forum, and reassurance, I probably would still have a failed component! I've built a bunch of kits, breadboard circuits, and experiment, but never actually fixed something like a hifi component! It feels great, and makes me want to play with other broken stuff LOL! I know electrolytics are always something you should check first, now I believe it! It was tough to do with a hair dryer. I used a toilet paper tube to isolate components around the ones I was heating up. Started at the left side of the board heating, and cooling, and moving to the right. The cap is rather close to a DAC, and was worried it may have been the little wires in the chip. After repeating the process several times I narrowed it down to one little section of the board. I soldered the negative side first, then carefully held the pos side in place while loading a disc. When I saw it worked I finished! Been playing, and recording perfectly! Throughout all this, I also had removed all the ribbon cables, checked their continuity, trimmed them, and re-sat them. Still can't believe it worked. Now that I think of it I wonder if my scope would have shown a lot of ripple? Was the voltage regulator shutting things down?

author: jitter
author_rank: Frequent Contributor
timestamp: April 29, 2016, 04:53:25 pm
content: Good to know you fixed it!

author: tony3d
author_rank: Frequent Contributor
timestamp: April 29, 2016, 04:59:22 pm
content: Makes me want to buy tweezers!

author: tony3d
author_rank: Frequent Contributor
timestamp: April 29, 2016, 05:02:09 pm
content: Quote from: cvanc on April 29, 2016, 04:23:38 pmThanks LOL! That's just about how I feel!

author: jitter
author_rank: Frequent Contributor
timestamp: April 29, 2016, 05:16:26 pm
content: Quote from: tony3d on April 29, 2016, 04:52:52 pmI don't think it was a ripple that was the problem as the 2.7 V is derived from a regulated 5 V.I think it was more like a stability issue caused by too high ESR on a worn out cap, as suggested earlier in this thread.The voltage regulator wasn't shutting down, but there may have been instability causing IC402 to malfunction.Edit: I just noticed that the main power supply unit is not a linear job but an SMPS.The presence of an inductor in the 2.7 V may be there to help block any remaining switching noise (linear regs, i.e. IC410, do not do a good job at filtering out higher frequencies).Or maybe the noise from IC402 is kept from going back into the 5 V supply by that little inductor.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 29, 2016, 05:22:27 pm
content: Thanks for the explanation! I downloaded the service manual, and will follow the circuit. Does that cap filter the step down voltage from the 5 volt supply?

author: jitter
author_rank: Frequent Contributor
timestamp: April 29, 2016, 05:34:29 pm
content: I edited my previous post.Quote from: tony3d on April 29, 2016, 05:22:27 pmI take it you mean C457. I would consider its function more to be like a buffer of the 2.7 V and to keep the output of IC410 stable.Most voltage regulators require some capacitance with a certain amount of ESR to stay stable. Ageing caps will slowly drift outside those specs.IC402 likely draws current from the 2.7 V in a pulse like fashion which could have caused instability in the 2.7 V once the cap wore beyond a certain limit.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 29, 2016, 05:42:04 pm
content: Quote from: jitter on April 29, 2016, 05:34:29 pmYes, the 457 is the one I replaced. I see what you mean. Makes sense!

author: tony3d
author_rank: Frequent Contributor
timestamp: April 29, 2016, 05:44:34 pm
content: It's been playing for hours now with no problems! Someday, I may muster up enough nerve to actually replace the cap with a proper surface mount cap, but first I need to buy a few things LOL! If I were to do that, I would probably just replace all the caps. A year ago I replaced both drawer belts.

author: jitter
author_rank: Frequent Contributor
timestamp: April 29, 2016, 05:52:24 pm
content: Quote from: tony3d on April 29, 2016, 04:59:22 pmThe quick and dirty (very dirty) thing I often do at work if I'm lazy is heat one pad and pin of the cap, wait till all solder under that pin has melted and then tilt the cap up as far as it will go without applying much force. Then repeat the other pin the same way. Often it works first go, sometimes I need to go back to the first pin if a solder bridge was drawn.Now this is not a recommended method, but in a pinch, it should work. Just make sure you don't tilt the cap before the solder on the pad has completely melted (it extends under the cap), you don't want to lift the pad too.I don't think I would recommend keeping the original cap in place as it may leak electrolyte and corrode the traces on the pcb.Quote from: tony3d on April 29, 2016, 05:44:34 pmYes, it seems likely that eventually other caps will go too, but for now: enjoy the music!

author: tony3d
author_rank: Frequent Contributor
timestamp: April 29, 2016, 06:58:14 pm
content: Quote from: jitter on April 29, 2016, 05:52:24 pmYes, Eventually I will replace it with the proper surface mount cap! I am going to buy tweezers first though. Should have them anyway. I looked for any signs of leaking around the caps, and didn't notice anything.

author: Brumby
author_rank: Unknown
timestamp: April 30, 2016, 03:45:55 am
content: Whether you fit an SMD capacitor of just keep the one you have used won't really matter - but removing the faulty one is a good idea.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 30, 2016, 10:45:59 am
content: I can buy tweezers for my AOYUE Solder Station for $31.00! I may order those next week. Then it should be a pretty simple desolder event LOL! So once I remove the old one just use braid to soak up all the old solder off the pads, then coat them with new solder, and solder in my new cap correct?

author: jitter
author_rank: Frequent Contributor
timestamp: April 30, 2016, 10:55:17 am
content: No, you need to hold the cap in place and apply the ironwhileadding solder.What you describe is done all too often, but since (most of the) flux has already gone, you don't get as good a join.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 30, 2016, 11:13:03 am
content: Quote from: jitter on April 30, 2016, 10:55:17 amI'm referring to replacing it with a new SMD CAP. If you don't coat the pads first how does the solder get underneath the cap? I figure if I remove the old one, may as well have it look right.

author: jitter
author_rank: Frequent Contributor
timestamp: April 30, 2016, 11:37:47 am
content: It would be the same as with the through hole cap, but you get to see less of the action. The solder will be drawn under the pin by capillary force.With SMD components, you want them to sit flush against the pcb before you start soldering. This goes especially for muli-legged components such as ICs but it's nice to have a cap sit straight on the board as well. That means removing old solder first.To make things easier, you start with adding fresh solder to one pad only and then fix the cap on that pin first. Make sure it's aligned properly before you solder the other side.This vid does it that way (but try to align the cap with fewer attempts), what I always do in addition is inspect the first pin and redo it with a bit of fresh solder if it doesn't look nice and shiny.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 30, 2016, 12:12:41 pm
content: Quote from: jitter on April 30, 2016, 11:37:47 amOk. Thanks for the video! I always apply the heat to 8)the leg, pad first then add solder to through components, but never worked with SMD STUFF BEFORE. With tweezers to remove old components, and these techniques, I'm getting a much better understanding. I may just look for some old circuit board with these type of cylinder SMD caps on it to experiment with first. Would not want to do anything to damage the boards pads at this point.!

author: tony3d
author_rank: Frequent Contributor
timestamp: April 30, 2016, 12:17:20 pm
content: Wonder if it would be OK to first coat the board pads, then use a flux pen to coat the caps pads, then solder it in place? Just be less to fiddle with.

author: jitter
author_rank: Frequent Contributor
timestamp: April 30, 2016, 12:46:07 pm
content: It'll work too.

author: tony3d
author_rank: Frequent Contributor
timestamp: April 30, 2016, 12:51:37 pm
content: Quote from: jitter on April 30, 2016, 12:46:07 pmOk great!

author: tony3d
author_rank: Frequent Contributor
timestamp: April 30, 2016, 03:13:09 pm
content: I know that the cap I replaced was 10uf only because I downloaded the service manual, and looked it up. So the middle number is the capacitance, the bottom the voltage limit, what's the top number for, and how go you know if the capacitance is "uf", or "nf" just by looking at the cap. This cap just says 10.

author: jitter
author_rank: Frequent Contributor
timestamp: April 30, 2016, 06:48:24 pm
content: Good question.Usually the appearance of a cap betrays its technology. An electrolytic capacitor, ceramic capacitor, metalized film capacitor, tantalum capacitor (among others) are all looking quite recognizable (google them).Once you know the type, you know the typical range of values and the unit used. An electrolytic capacitor uses uF (or more correctly µF) as unit, i.e. micro Farads. On a cap with enough room to print on, you will see e.g. 10 µF/16 V. On this SMD cap space is limited and only 10/16V was printed.Sometimes you can't even find the values without looking up a code in a datasheet. The one in the image below is a 4.7 µF cap, and I believe "J" should be in a table in the datasheet for the max. voltage.SMD ceramic capacitors have no value printed on them. Through hole ceramic capacitors use the unit pF, pico Farads. Often only a value is printed on it, say "104". It's the same system (as e.g. for resistors) with value and multiplication (power of 10), so 104 means 10 · 104= 100,000 pF = 100 nF = 0.1 µF. Often a code needs to be looked up to know more, e.g. the max. voltage.

author: tony3d
author_rank: Frequent Contributor
timestamp: May 01, 2016, 01:00:14 am
content: Quote from: jitter on April 30, 2016, 06:48:24 pmThanks again for the explanation!