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Old 09 July 2019, 11:53   #1
solarmon
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A1200 rev 2B - recap - C407 10uF tantalum capacitor?

Hi,

I'm planning on doing a recap of my Amiga 1200 revision 2B myself.

I bought the premium recap kit from Retro Bench:

https://www.ebay.co.uk/itm/AMIGA-120...t/163527164624

This includes an 10uF tantalum SMD capacitor for the C407 labelled capacitor.

My question: is this C407 10uF tantalum really required to be replaced?

The reason I ask is because I'm a bit concerned on how to remove the tantalum SMD capactor. With the other types (can and through hole) I know what to do (the can type ones I will use the snip method).

Without a hot air rework station I think I will have trouble getting this tantalum capacitor off the board?

I'm also concerned about the two caps next to the keyboard connector. There is not much space to work with there - so I will have to be extra careful. I might remove the audio jacks to give a bit more space, but the tightest area is next to the keyboard connector. I think I will use kapton tape and aluminium foil on the connector to help reflect/absorb the heat.

Any advice/suggestions?
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Old 09 July 2019, 12:22   #2
Hewitson
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Hi, removing and soldering SMD caps (or resistors) without a hot air station ain't rocket science.

Some people recommend just twisting them off with tweezers, I'm personally not a fan of this method. I use a soldering iron, and tweezers, and alternate between sides until the component is removed.

The reason you need to keep alternating is to minimise the mechanical stress on the pads. And of course it goes without saying, practice on something you don't care about first.
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Old 09 July 2019, 13:38   #3
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The tantalum probably doesn't need to be replaced as urgently as the electrolytics, since they don't leak. Older revisions use an electrolytic in that position so that would be more urgent. But if you have it there, no harm in replacing it. The method should be pretty similar to replacing all the SMT electrolytics on your board - what are you doing for them?

Edit: I'm not a fan of snipping them, or any other physically stressful method. Especially if the capacitors have leaked, it's all to easy to rip a pad off the board. I've seen and repaired boards damaged by people using such methods, despite them "doing it right" by following guides they found on the internet.

Last edited by Daedalus; 09 July 2019 at 17:23. Reason: Never finished what I was writing...
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Old 09 July 2019, 16:50   #4
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I've seen tweezer soldering iron but only as accessory for rework stations. These are ideal since you can literally heat both sides and lift off in one go. The same is true for putting new components back on board.
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Old 10 July 2019, 07:55   #5
Krashan
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I have such hot tweezers and they work very good, recapped a few A1200s with them. Problem with snipping is, the plastic base of the capacitor always works as a lever, multiplying force applied to pads. Then "operator" does not feel this multiplied force and thinks he does it gently.
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Old 10 July 2019, 12:16   #6
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Thanks for all the feedback!

I can't justify (yet) getting a new soldering station just for the tweezers.

I've tried to look for replacement tweezer heads for my soldering station, but it is just a cheap one (Precision Gold A55KJ) I got from Maplins before they went under, which has 5-pins. The replacement heads I have found on eBay all seem to be 6-pin ones - so they won't be compatible.

Maybe something like this might just work instead...

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Old 10 July 2019, 22:43   #7
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I've been practiing a bit recapping on some old PC parts, I've become fairly good at TH but I've found SMD removal a whole lot harder. In my experience I would not use the twist method if you don't want to risk damaging the PCB, I gave it a go and some of the pads got pulled up sometimes.

I think the best method I've heard for desoldering SMD caps and the one I'm likely to try in the future is to buy another £30 iron and dual wield, heat up both sides and try to move the part off the pads.
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Old 10 July 2019, 22:53   #8
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Some have used hot air blowers but this risks causing them to blow/pop which can be dangerous.
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Old 10 July 2019, 23:03   #9
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If a capacitor is particularly bad it can burst, yep, but that's pretty rare. There's a much higher chance of causing a capacitor to burst if your air temperature is too high, but then you're probably also melting nearby parts and blowing other nearby parts off the board... Ultimately, hot air is one of the best ways of removing them, but like any situation, you need to know your tools and get lots of practice.
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Old 16 July 2019, 09:33   #10
solarmon
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Anybody had experience, and would recommend, such a 48W standalone tweezer soldering iron?

https://www.ebay.co.uk/itm/Desolderi...G/113567163466

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Old 16 July 2019, 10:15   #11
lesta_smsc
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Quote:
Originally Posted by solarmon View Post
Anybody had experience, and would recommend, such a 48W standalone tweezer soldering iron?



https://www.ebay.co.uk/itm/Desolderi...G/113567163466



That's handy! I didn't realise it came as a standalone product. I'd anticipate use to be same as other rework station if you could adjust temperature.
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Old 17 July 2019, 11:48   #12
solarmon
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Well, for £8 on Amazon Prime, I just couldn't resist - so I've ordered one and will see what it is like:

https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1

I also found some reviews of it - first one (in French), being most relevant for SMT cap removal, although I notice that it was being tested on an Amiga (1200?) motherboard...:

[ Show youtube player ]
[ Show youtube player ]
[ Show youtube player ]

Last edited by solarmon; 17 July 2019 at 12:00.
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Old 17 July 2019, 12:11   #13
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I just realised that the French Youtuber Steel-alive (https://www.youtube.com/user/FritZ8139/) , from the first video, has three videos that compares SMT cap removal on an Amiga 1200:

Snip (not twist):
[ Show youtube player ]

Hot air:
[ Show youtube player ]

Tweezers:
[ Show youtube player ]

Last edited by solarmon; 17 July 2019 at 12:18.
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Old 19 July 2019, 12:20   #14
solarmon
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So, got the tweezers, and my quick impression of it is that it does the job...mostly.

The power lead is quite short, so you need to make sure you have an AC socket quite close. The tips take a while to heat up, but does get hot enough for SMT cap removal.

However, due to the design and bulk of the tips, there are some SMT caps that I could not easily reach in the correct orientation (because it being obstructed by other components or parts):

* C236 and C239 - the two by the RF modulator
* C324 and C334 - the two by the keyboard connector

But, for £8 I think it is good value for money!
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