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Old 10 August 2014, 22:04   #1
britain4
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A question about capacitors...

I do apologise if this is a daft question... Just something that crossed my mind and I can't find anything from a Google search.

Would it be acceptable to replace the SMD capacitors in an A1200 with through-hole components instead of SMD?

I know the immediate thoughts are going to be a big NO - but I thought since this is the usual way to replace the SMD caps on a Sega Game Gear (google it), it might be easier than soldering SMD components?

I like to think I did quite a good job on my Game Gears (they all work perfectly anyway) so I'd feel more comfortable doing it on my A1200 (which I have no plans on selling) too.
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Old 10 August 2014, 22:14   #2
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It is possible but it won't be as durable since the leaded components will stress the footprints more, so vibrations or shocks could cause them to rip off the footprints.

That being said, I have done it before using the plastic bottom of the old SMD capacitors if I did not have the correct ones. That way, they will be mounted almost as close to the PCB as the originals, if you can find leaded with the same pin spacing as the old SMD ones.
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Old 11 August 2014, 02:49   #3
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It's not uncommon for people to do this, but I don't consider it an acceptable repair.

If you took your Amiga to be professionally repaired and someone did this, would you be happy with it? Of course not. So why would you be happy with it if you did it yourself?

A job worth doing is a job worth doing properly.
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Old 11 August 2014, 04:19   #4
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I've done this but I don't recommend it. The electrical compatiblity is fine but the mechanical fit isn't and it is very easy to tear off the SMD pads with the through hole capacitors due to the mechanical stress that is placed on them.

I don't know how good your soldering technique is but there is a youtube video of someone recapping an A4000 with a soldering iron. I think it is in German. The guy has a really good soldering technique of heating alternate sides of the SMD capaicitors and lifting them in a rocking pattern till it comes off and then he cleans up the pads and solders the new ones on with a fine tipped soldering iron. There all also really inexpensive hot air stations. I'm thinking about getting one but I'm not going to try and recap my Amigas until I've practiced on a few scrap circuit boards.
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Old 11 August 2014, 06:00   #5
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the surface mount ceramic MLC types are a better option..

Last edited by Paul_s; 10 October 2019 at 18:57.
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Old 11 August 2014, 08:26   #6
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No, the ceramic SMD capaciators is not an alternative of SMD Electrolytes for several reasons. First, capacitance. Ceramic SMDs is usualy in the ranges of pF-nF capacitance, where electrolytes are in the µF range. If there's a electrolytic capaciator in the design, replace it with a electrolytic one! And is there a ceramic one, replace it with a ceramic one! (But I must say I've never come across a broken ceramic cap .

And as people wrote before, you can fit a radial electrolytic cap most time to replace a surface mounted, but the pads on the PCB are designed for surface mounted caps.

Another hint is that all C= computers are using non-RoHS solder (Tin-Lead solder), so some precautions can be in place when using RoHS compliant solder (Tin-Silver-Copper). After desoldering, try to clean up as much of the (when desoldering) remaining mix of Tin-Lead / Tin-Silver-Copper from the pads with (recommended) Chemtronics "No Clean" 60BGA5 copper braid. This braid is designed for cleaning SMD pads after desoldering. And when refitting, use RoHS compliant solder.
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Old 11 August 2014, 09:10   #7
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I've used through-hole caps to replace SMD when I didn't have any SMD caps on hand, and it works but it's not ideal. SMD caps are easy to solder, so there's no reason to avoid them.
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Old 11 August 2014, 11:48   #8
britain4
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Well the concensus seems to be much as I thought, that it works but is not a proper repair.

I think I will leave it and go for the proper surface mounts and practice on an old board maybe as the last thing I want to be dealing with is a lifted pad (I've already read about the ceramics and I'm not using those haha)

Thanks xtal for the advice there and I'll try and dig that youtube video up as it sounds like a good reference.

Quote:
Originally Posted by Hewitson View Post
If you took your Amiga to be professionally repaired and someone did this, would you be happy with it? Of course not. So why would you be happy with it if you did it yourself?
Funny you should mention that as on my first Game Gear I did send it off to be done, to the most well known Game Gear repair guy and that came back with radials! Funny how standards differ, perhaps it's because they're not worth tuppence compared to a mint Amiga. I do get your point though, it's hardly the most professional way I will admit.
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Old 11 August 2014, 13:51   #9
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Quote:
Originally Posted by Xtal View Post
No, the ceramic SMD capaciators is not an alternative of SMD Electrolytes for several reasons. First, capacitance. Ceramic SMDs is usualy in the ranges of pF-nF capacitance, where electrolytes are in the µF range. If there's a electrolytic capaciator in the design, replace it with a electrolytic one! And is there a ceramic one, replace it with a ceramic one! (But I must say I've never come across a broken ceramic cap .

And as people wrote before, you can fit a radial electrolytic cap most time to replace a surface mounted, but the pads on the PCB are designed for surface mounted caps.

Another hint is that all C= computers are using non-RoHS solder (Tin-Lead solder), so some precautions can be in place when using RoHS compliant solder (Tin-Silver-Copper). After desoldering, try to clean up as much of the (when desoldering) remaining mix of Tin-Lead / Tin-Silver-Copper from the pads with (recommended) Chemtronics "No Clean" 60BGA5 copper braid. This braid is designed for cleaning SMD pads after desoldering. And when refitting, use RoHS compliant solder.
Ah, it's a good job I've not replaced any caps for a while.

The only reason I suggested is I've seen folk replacing the audio circuit caps in A4000's for ceramic types? I guess it comes down to the range the ceramic ones can cover (and the audio circuit in an A4000 for example will be very low in rated capacity I'd imagine).
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Old 11 August 2014, 14:38   #10
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The only capacitors that should replace electrolytics are are tantalum capacitors. They have similar capacitance ranges vs size and are a bit better quality. Electrolytic capacitors are far from ideal for audio but the Amiga's 8 bit audio doesn't need really good caps. Most of the Amiga's electrolyitic caps are for power supply filtering. The reason that they are used is that you can get a lot of capacitance in a small package with electrolytics.
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Old 11 August 2014, 22:37   #11
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You can replace any SMD capacitor of an Amiga with a ceramic replacement (the exact values are available) and won't feel or hear any difference.

Removing the electrolytic SMDs by slowly rotating them with pliers (do not pull!) is also a good technique.
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Old 12 August 2014, 03:26   #12
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You won't get the same size capacitance in the same size with ceramics. The power supply filtering won't be as good, only faster transients will be suppressed. There are SMD tantalum capacitors too. I've found a 3640 will work fine with the power bus capacitors completely removed but that is really not that good an idea. The power supply capacitors help maintain a steady voltage to the chips and suppress transient voltage spikes and noise.

I would replace the motherboard capacitors with either the exact replacement electrolytics or equivalent SMD tantalum capacitors.
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Old 12 August 2014, 06:03   #13
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Quote:
Originally Posted by bubbob42 View Post
Removing the electrolytic SMDs by slowly rotating them with pliers (do not pull!) is also a good technique.
I wouldn't recommend doing this as you may pull a pad off the board.
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Old 12 August 2014, 15:36   #14
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Quote:
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I wouldn't recommend doing this as you may pull a pad off the board.
I reworked half a dozen boards (even with badly leaking caps) like this and never pulled off a pad. If you kill a pad with this method it may come off with the other techniques anyway.

In my experience, most pads get killed by heat.
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Old 12 August 2014, 15:42   #15
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Quote:
Originally Posted by Ami_GFX View Post
You won't get the same size capacitance in the same size with ceramics.
Yes, you do. Most modern SMD ceramics even have higher voltage ratings (which can not hurt, along with the correct capacity of course) and will fit exactly.


Quote:
The power supply filtering won't be as good, only faster transients will be suppressed.
All my boards work fine and rock stable with ceramics.
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Old 12 August 2014, 23:29   #16
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Quote:
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All my boards work fine and rock stable with ceramics.
They are not ment for the task of which your using them. The two audio output one's, yes, but main motherboard one's no.
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Old 13 August 2014, 02:37   #17
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Quote:
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Yes, you do. Most modern SMD ceramics even have higher voltage ratings (which can not hurt, along with the correct capacity of course) and will fit exactly.




All my boards work fine and rock stable with ceramics.
Can you give me a specific example? Like a 47mf 16V surface mount ceramic capacitor. The capacitance of ceramic capacitors is a function of the surface area of the plates separated by a ceramic insulator. There is no chemical component like in electrolytics.
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Old 13 August 2014, 08:34   #18
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47µF 16V ceramics from Digikey. Physical sizes look approximately suitable too.

(I assume you didn't actually mean millifarad, I don't think any Amiga uses huge caps like that )
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Old 13 August 2014, 13:22   #19
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Quote:
Originally Posted by Ami_GFX View Post
Can you give me a specific example? Like a 47mf 16V surface mount ceramic capacitor. The capacitance of ceramic capacitors is a function of the surface area of the plates separated by a ceramic insulator. There is no chemical component like in electrolytics.
Your forgeting they are not polorized. If you were ment to use ceramics, then they would never have used electrolytics.
Try using a ceramic caps in a smoothing circuit of a PSU, .
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Old 13 August 2014, 13:42   #20
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There is no advantage to using a polarised capacitor. The fact that electrolytic capacitors are polarised is a "disadvantage" (actually trade-off for higher capacitance) which arises from the physical construction of the electrolytic capacitor. An ideal capacitor is not polarised.

I don't see any obvious problem in using all ceramics on an Amiga mobo, but it would be nice to do some ripple measurements before and after with a scope.

Of course one may prefer to replace like-for-like just to retain the original looks of the board.
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