Author Topic: External SoundCard Repair - **FIXED!**  (Read 14911 times)

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Offline MrJoeyJoeJoe

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #25 on: May 24, 2016, 06:00:19 pm »
Hey guys!
I've desoldered a few of the caps and they all seemed okay, but on double-checking C5 (10uf) it suddenly read 9792nf! 2 out of 3 times it reads like this, so I'm going to replace and see if it works!

A strange thing to note which I've never had happen before - is that on each cap, after heating and suctioning the solder off the second leg, the cap just fell out! I've never had it so easy!!
Thanks again for all your help, I'll let y'all know how I get on.
« Last Edit: May 24, 2016, 06:03:45 pm by MrJoeyJoeJoe »
 

Offline Anks

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #26 on: May 24, 2016, 06:57:59 pm »
9792nf Is pretty much 10uf
 

Offline PedroDaGr8

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #27 on: May 24, 2016, 08:53:39 pm »
Hey guys!
I've desoldered a few of the caps and they all seemed okay, but on double-checking C5 (10uf) it suddenly read 9792nf! 2 out of 3 times it reads like this, so I'm going to replace and see if it works!

A strange thing to note which I've never had happen before - is that on each cap, after heating and suctioning the solder off the second leg, the cap just fell out! I've never had it so easy!!
Thanks again for all your help, I'll let y'all know how I get on.

9792nf is 9.792uF. That is actually really close for a cap. Honestly, if I were you I would replace ALL of the caps. They are cheap, otherwise you will repair, then a new cap goes bad in a year or two. Diagnose and repair again, then a year or two later. Repeat continuously. Caps are limited life devices, they just don't last forever. The electrolyte dries out and they just don't perform as well as they should.
The very existence of flamethrowers proves that some time, somewhere, someone said to themselves, "You know, I want to set those people over there on fire, but I'm just not close enough to get the job done." -George Carlin
 

Offline janoc

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #28 on: May 24, 2016, 09:00:07 pm »
Keep in mind that electrolytic caps can have tolerances from -20 to +80% of the nominal value, so for a cap of 10uF anything between 8uF to 18uF is well in spec. That cap you have measured is likely just fine as far as capacitance is concerned. Also the accuracy of your cheap meter/tester likely sucks for these large capacitance values and there will be significant errors.

Worse, measuring the capacitance won't give you an indication whether the capacitor is good or bad - you must measure ESR. A bad bulging capacitor will happily measure its nominal capacitance despite having sky-high series resistance due to dried out/boiled off electrolyte. Such capacitor is essentially completely non-functional in the power supply but if you only measure capacitance, you will never know. That is why capacitance meters are pretty much useless for repairing switch-mode power supplies unless they measure ESR as well.

BTW, am I seeing right that the caps are CapXon brand? If yes, don't even bother to measure them - just replace all of them, even the large mains rated input cap. CapXon has the nickname "crapxon" for a very good reason - those capacitors have only one thing reliable about them - they reliably die, usually right after the warranty of the item is out.

« Last Edit: May 25, 2016, 06:55:05 pm by janoc »
 

Offline MrJoeyJoeJoe

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #29 on: May 24, 2016, 09:35:38 pm »
Hehe... 9000nf is 9.000uf?  :palm: Have I said before I'm somewhat of a noobie?
Well I guess I'm going to have to just replace all the caps then. Seeing as they're all 'Crapxon'  ;D
A proper ESR would be really handy, but $80 is about $30 more than I'd be willing to spend!
I know it would save money in the long-run though...

I'll check that D6 diode, replace all caps and check back!
 

Offline janoc

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #30 on: May 25, 2016, 06:57:30 pm »
You don't need to spend $80 for the Anatek one. I have something like this and it works well enough for the occasional repair job:
http://www.ebay.fr/itm/Digital-Capacitor-ESR-Tester-Internal-Resistance-Meter-Test-In-Circuit-/182066050731

 

Offline MrJoeyJoeJoe

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #31 on: May 25, 2016, 09:57:00 pm »
You don't need to spend $80 for the Anatek one. I have something like this and it works well enough for the occasional repair job:
http://www.ebay.fr/itm/Digital-Capacitor-ESR-Tester-Internal-Resistance-Meter-Test-In-Circuit-/182066050731


Awesome, that's much more within my price range!
Thanks a lot!
 

Offline MrJoeyJoeJoe

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #32 on: May 26, 2016, 02:17:32 pm »
Hey chaps!
I've taken out all of the caps, and also took out the D5, D6, D8 and D9 diodes which people suggested. On testing the two big diodes with the diode tester on my DMM the D8 one appears to be shorted! It reads 0.00 in both directions!
I'm starting to get that tingling feeling... Could this be it?

 

Offline Mephitus

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #33 on: May 26, 2016, 04:12:58 pm »
Your last photo of the back of the board, maybe its nothing, but check R31. It looks like it may be damaged. But I admit it could just be nothing.  :-//
A true gentleman must be prepared for anything. - Pepe le' Pew
 

Offline janoc

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #34 on: May 26, 2016, 10:39:31 pm »
Well, if the diode on the secondary went poof, that certainly wouldn't help things. It is possible that that voltage regulator on the heatsink may need replacing too now.
 

Offline EPTech

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #35 on: May 27, 2016, 12:58:23 pm »
Hi there,

Did you check that diode while the board was disconnected? If so, it is definitely broken and needs to be replaced. I have had schottky diodes die on me before without any apparent reason. Hey, sometimes they do. I hope for you none of the other circuits died from getting semi-rectified switch mode AC.  :o

The component on the heat sink may also be a double schottky rectifier. So check the part number before assuming it is a voltage regulator and measuring it as such.

Happy hunting, almost there.
Kind greetings,

Pascal.
 

Offline MrJoeyJoeJoe

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #36 on: May 27, 2016, 03:23:58 pm »
Your last photo of the back of the board, maybe its nothing, but check R31. It looks like it may be damaged. But I admit it could just be nothing.  :-//
Just checked R31 with a better light. Looks ok, thanks!  ;D
 

Offline MrJoeyJoeJoe

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #37 on: May 27, 2016, 03:31:05 pm »
Hi there,

Did you check that diode while the board was disconnected? If so, it is definitely broken and needs to be replaced. I have had schottky diodes die on me before without any apparent reason. Hey, sometimes they do. I hope for you none of the other circuits died from getting semi-rectified switch mode AC.  :o

The component on the heat sink may also be a double schottky rectifier. So check the part number before assuming it is a voltage regulator and measuring it as such.

Happy hunting, almost there.

Hi Pascal,
Yes the diode testing I did out of circuit. D5,6,8+9.

According to the part number on the heatsink next to the shorted D8 is a Dual Common Cathode High Voltage Schottky Rectifier.
How would one go about testing this? I presume out of circuit?
I have a DMM and a very cheap component tester/ESR.

 

Offline janoc

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #38 on: May 27, 2016, 07:51:56 pm »
According to the part number on the heatsink next to the shorted D8 is a Dual Common Cathode High Voltage Schottky Rectifier.
How would one go about testing this? I presume out of circuit?
I have a DMM and a very cheap component tester/ESR.

It is nothing special - those are just two diodes connected together by their cathodes and put in a single package. So you test it the same way as you would test a PNP transistor (treat the the common cathode as "base" and the the two anodes as "collector" and "emitter") using the diode test mode on a multimeter. You will just have to desolder it. Even your component tester should be able to test it - it should indicate it is a dual diode.
 

Offline MrJoeyJoeJoe

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #39 on: May 27, 2016, 10:18:10 pm »
It is nothing special - those are just two diodes connected together by their cathodes and put in a single package. So you test it the same way as you would test a PNP transistor (treat the the common cathode as "base" and the the two anodes as "collector" and "emitter") using the diode test mode on a multimeter. You will just have to desolder it. Even your component tester should be able to test it - it should indicate it is a dual diode.

Awesome, thanks for that. I'll check it out tomorrow.
Cheers.
 

Offline MrJoeyJoeJoe

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #40 on: May 28, 2016, 11:58:17 am »
Okay the double-diode appears to be good. It's reading O.L in the NPN position and then each diode reads about 0.300 in PNP.
Also my cheap-o tester recognized it as a 2xdiode with 340uf on each  :D

So I guess that's ok.
As you can see the board is looking pretty bare!

 

Offline janoc

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #41 on: May 28, 2016, 01:45:46 pm »
Okay the double-diode appears to be good. It's reading O.L in the NPN position and then each diode reads about 0.300 in PNP.
Also my cheap-o tester recognized it as a 2xdiode with 340uf on each  :D

I assume that was 0.3V (or 300mV) - that would be about correct forward voltage for a schottky diode (that's what the meter indicates in diode test mode). Or did you literally stick it into the transistor test socket that some cheap multimeters have?

So I guess that's ok.
As you can see the board is looking pretty bare!



Heh. I do hope you are taking notes where goes what and in what orientation/polarity, though. The board seems to be well labeled, but still. There is nothing dumber than to buy a bunch of new parts and have them release the magic smoke only because I was an idiot and have put something backwards or in a wrong place. A capacitor installed backwards exploding in your face is not fun.

When I am doing repair like this, I usually snap a few pictures using my phone for documentation and then label the caps and such over it on my PC. Or print it out and write it in by hand using a pen. That makes it easy to make sure that I am not messing something up during re-assembly.

I think the only thing that remains now is to replace the components with known good parts and see whether that has fixed it.
 

Offline MrJoeyJoeJoe

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #42 on: May 28, 2016, 03:42:03 pm »
I did plug it straight into the cheap-o tester  ;D and it gave me 369mv on each side and my DMM gave me 0.308 (volts?) so they're pretty similar results no?
Heh I'm not a stranger to that 'magic smoke' you talked about!  :-DD But I've learnt a lot from many of my mistakes and am more methodical now - I've also taken lots of photos with my phone  ;)

Just waiting for the replacement parts!
Thanks for all your help!
 

Offline janoc

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #43 on: May 28, 2016, 09:25:28 pm »
I did plug it straight into the cheap-o tester  ;D and it gave me 369mv on each side and my DMM gave me 0.308 (volts?) so they're pretty similar results no?

Yep, that's pretty much the same thing - the tester is not very accurate, so a bit of difference is to be expected.


Heh I'm not a stranger to that 'magic smoke' you talked about!  :-DD But I've learnt a lot from many of my mistakes and am more methodical now - I've also taken lots of photos with my phone  ;)

Well, the best way to learn :)

Just waiting for the replacement parts!
Thanks for all your help!

Hopefully it will work now!

 

Offline MrJoeyJoeJoe

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Re: External SoundCard Repair - Anyone know how to reset a TOPSwitch!?
« Reply #44 on: June 16, 2016, 02:05:16 pm »
 :o :o :o :o :o IT'S ALLIIIVVVVEEE!!!  :o :o :o :o :o :o 8)



I replaced all the caps and the faulty diode:




BEFORE:



AFTER:



My brother has already plugged it back into his studio and it all works fine again!




Thanks to all of you who have helped! Together we stuck it to the Man! (in this case the man being Consumerism)
Excellent result, and I've learned so much! ;D

Many thanks for the help!
Until next time!
Joe!
 

Offline janoc

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Re: External SoundCard Repair - **FIXED!**
« Reply #45 on: June 16, 2016, 07:39:18 pm »
Congrats!

I am sure you have learned quite a bit more than you have expected too :) And saved a nice piece of gear from the bin in the progress.
Btw, any particular reason why did you leave the diodes so high above the board? Having components flush is usually better for mechanical reason and there is less chance for something to short on the exposed leads too.

Just one tip - you want to get a better multimeter, especially if poking around mains powered gear. Those cheapies are OKayish to use in a car, but not safe to use  with mains voltages.
 

Offline macboy

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Re: External SoundCard Repair - **FIXED!**
« Reply #46 on: June 17, 2016, 01:55:00 pm »
Just one tip - you want to get a better multimeter, especially if poking around mains powered gear. Those cheapies are OKayish to use in a car, but not safe to use  with mains voltages.
I agree. When repairing any SMPS like this, you might be measuring voltages on the primary side. It is not uncommon for these to have a voltage-doubler circuit for 120 V use. So whether on 120 or 240 V mains, you can have 340 V or more on the capacitors. That much voltage on a cap is an explosion waiting to happen if something goes wrong. I would not trust any cheap meter to measure that. Cheap meters are best used when there is a risk of damage to the meter, such as measuring high-ish current on a low voltage circuit. For that you just don't use your Fluke(etc.) and risk blowing that $30 HRC fuse. You use the cheapy that has a $0.50 glass fuse (if any at all). Your best expensive meter is used when there is risk of damage to you, such as measuring lethal voltages on a capacitor.
 

Offline MrJoeyJoeJoe

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Re: External SoundCard Repair - **FIXED!**
« Reply #47 on: July 04, 2016, 03:23:57 pm »
Thanks guys, yes I guess it's time to look for a new DMM!
Janoc: I put the diodes back how I found them! :D I think they were that high off the board to better dissipate the heat?
Thanks again for all your help!

 

Offline David_AVD

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Re: External SoundCard Repair - **FIXED!**
« Reply #48 on: July 04, 2016, 09:25:00 pm »
Good to hear you got it fixed.  :)

Mounting of diodes and resistors up off the board is commonplace and can aid heat dissipation.
 

Offline janoc

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Re: External SoundCard Repair - **FIXED!**
« Reply #49 on: July 04, 2016, 09:44:33 pm »
Thanks guys, yes I guess it's time to look for a new DMM!
Janoc: I put the diodes back how I found them! :D I think they were that high off the board to better dissipate the heat?
Thanks again for all your help!

Heat dissipation, sure, but I doubt those diodes get significantly hot. If they did, they would have been on a heatsink. When I see parts mounted like this I am immediately thinking vibration and the forces the long leads transfer to the pads and solder joints. The former could peel off the board and the later crack.
 


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