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Old 18 October 2018, 07:34   #21
nexus
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Originally Posted by project23 View Post
Does this mean zero experience in Amiga repair/maintainence or zero experience with an iron?

If you have the proper tools, do it yourself - it's really easy. By proper tools I recommend an air gun (soldering station, air blower, you know what i mean - and I know i'll get people disagreeing with this) - but you absolutely have to do it properly. Set the temp to the lowest you can to melt the solder, and use a nozzle the same size (roughly) as the cap. Aim the nozzle at the capacitor itself, not the pads individually. It'll take a longish time (because of the relatively low air temp), but eventually it'll slide off with minimum effort (a slight nudge with a needle, say). Obviously cover the thing in flux etc AND WEAR SAFETY GOGGLES.

Then use wick to remove the rest of the solder from the pads. Give it a clean in IPA and put the new ones in place however you find most comfortable to you. I did not use a gun for this. I added a small amount of solder to each pad, placed the cap, and soldered each side gently (read: low temp slow or high temp quick) until it flowed properly.

No problems since, and no problems with the pads or damage to the board (Except when removing the modulator but thats another bloody story )

Do not under any circumstances use the 'tried and tested' method of twisting the old caps off with pliers. Go watch some youtube videos of this failing miserably. Some people swear by it, and you might get lucky, but probabilistically speaking you WILL TEAR OFF A PAD.

Okay back to work now, peace!

John

EDIT: If you're worried they may have leaked a little, then a cotton-swab wash with lemon juice will neutralise the battery 'acid' before the IPA wash. If using a gun to remove the caps, then as they heat up if you smell a fishy sort of smell then they've leaked. I can't stress how easy this process was for me any more than by saying the through-hole caps (which you'd imagine would be easier) were the hardest for me to remove.
never use HOT air on capacitors

and the HOT tweezers he was talking about are 2 soldering irons connected like tweezers it heats both sides and that is proper HOT AIR is NOT and is very dangerous to even try that as the capacitor will explode
you dont heat up batteries or capacitors ever
only time you can do that is with ceramic smd caps never wet or tantalum
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Old 18 October 2018, 11:44   #22
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Originally Posted by nexus View Post
never use HOT air on capacitors

and the HOT tweezers he was talking about are 2 soldering irons connected like tweezers it heats both sides and that is proper HOT AIR is NOT and is very dangerous to even try that as the capacitor will explode
you dont heat up batteries or capacitors ever
only time you can do that is with ceramic smd caps never wet or tantalum
Sounds like your hot air is set too hot.
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Old 18 October 2018, 11:48   #23
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well the max cap temp is 105c so yeah and even more so with non leaded solder
you dont need hot air ever
you risk it exploding and damaging the board other components or yourself
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Old 18 October 2018, 11:51   #24
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105 degrees is the maximum *working* temperature at which they can function normally, though I suspect most of the old capacitors in Amigas are only rated for 85 degrees. There's also a maximum soldering temperature and a reflow heat profile which they are designed to withstand. How do you think they got on the board in the first place?
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Old 18 October 2018, 11:52   #25
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no thats the max temp period same reason why you dont hold the iron on it forever too
seen many people pop caps that way
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Old 18 October 2018, 11:54   #26
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I'll ask again: how do you think the parts ended up soldered to the board?
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Old 18 October 2018, 11:54   #27
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not with hot air
laser do that all day
through hole was wave solder
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Old 18 October 2018, 11:56   #28
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Laser soldering? Hahaha... How much do you think that would have cost in 1991? Reflow ovens were, and still are, the most common method of soldering SMT parts. Have you never read the data sheet of any of these capacitors? I suggest you do.
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Old 18 October 2018, 12:03   #29
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i never put caps in a reflow oven lol its dumb
and FYI wet caps can be reflowed once maybe 2 times but it does hurt that cap
and is not recommended
and that is under controlled conditions

not someone waving hot air over
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Old 18 October 2018, 12:13   #30
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i never put caps in a reflow oven lol its dumb
Wow, what a great argument. That's me and the rest of the electronics world convinced!

Quote:
and FYI wet caps can be reflowed once maybe 2 times but it does hurt that cap
and is not recommended
and that is under controlled conditions
Often boards are subjected to a couple of soldering passes during manufacture, so any parts designed to be reflowed (like SMT caps) can withstand a few passes. Of course, doing it a lot or for longer than the specified times will hurt the capacitor. But what are you going to reuse those dead, 25-year-old capacitors for anyway?

Quote:
not someone waving hot air over
I suggest you exercise more control when using your hot air gun. Lower temperature, steady, consistent movement, and use a thermocouple if you're unsure of the actual component temperature, just to make sure you keep to the required reflow profile. It's not actually that difficult, but if your technique involves waving hot air all over the place that's so hot it can burst capacitors, I can see why you'd have problems.
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Old 18 October 2018, 12:22   #31
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you arent getting it i would rather not hurt the cap as even the first time it hurts it
and i been doing this over 30 years i know i can take it off just fine with hot air but IM EXPERIENCED this is my profession

this is bad practice to teach some hobbyist repairing a old computer
you arent just heating that part either this is why i use IR when doing BGA
you arent gonna tape off and protect everything for each cap you do thats retarded
you are also needlessly stressing the pcb etc
again absolutely not needed and better not to do for a unskilled person

and FYI you can do it faster without

Last edited by nexus; 18 October 2018 at 12:28.
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Old 18 October 2018, 12:29   #32
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And what makes you think it's not my profession, and that my experience is any less relevant than yours? What do you mean by the "first time"? We've been talking about removing capacitors with hot air, in which case the state of the capacitor afterwards doesn't matter. Besides, it doesn't take that long to develop a reliable technique. A few hours practicing on a few old PC motherboards or routers will have any competent hobbyist up to a level where they can reliably remove SMT capacitors without any complications.

Also, what's the relevance of using IR for BGA parts? There are no BGA parts on any classic Amiga motherboard. Taping and protecting sensitive nearby parts is pretty normal for rework. Nothing "retarded" about it, but it's quite telling that you think there is.
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Old 18 October 2018, 12:34   #33
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well lol if you use hot air to remove caps then you must have a lot of time
and we been talking about many things now that have no concern to this guy and this topic as he wont be doing any of that
and i disagree with you making a new guy do hot air
and i never said there was BGA on a classic amiga motherboard
and yeah you protect everything when doing them
it retarded protecting and wasting time just to use hot air to remove a wet smd cap
anyways i stand by what i said this guy isnt gonna be buying a rework station etc and he doesnt need too
all he needs are tweezers simple effective and quick and easy
doesnt risk damaging anything
i dont even understand why this needs to be debated for someone new to soldering
better he learns that before ever using hotair as he will need the practice making good joints when adding new

many many pros who CANT solder
bad enough we have these horrible youtube videos teaching people

Last edited by nexus; 18 October 2018 at 12:52.
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Old 18 October 2018, 13:40   #34
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Originally Posted by nexus View Post
well lol if you use hot air to remove caps then you must have a lot of time
In my experience it's not that much slower than using a set of desoldering tweezers, and is more convenient for difficult-to-access capacitors. Far longer is spent on the rest of the process than actually desoldering in either fashion.

Quote:
and we been talking about many things now that have no concern to this guy and this topic as he wont be doing any of that
The topic had moved to suitable techniques for desoldering capacitors when you joined in with your questionable opinions, so now we're discussing those in the context of desoldering capacitors.

Quote:
and i disagree with you making a new guy do hot air
First off, nobody's making anyone do anything. Besides, you'd already decided that the OP wasn't going to do any of these things. Second, everyone has to start somewhere, and many people with through-hole competence have been easily able to take up hot-air soldering. Maybe this guy can expand his skill set by taking it up at some point in the future, and get more enjoyment from his hobby as a result. Also, being a public forum that's frequently used for technical discussions, it's a good idea to bear in mind the possibility of someone else reading the thread in the future - perhaps someone

Quote:
and i never said there was BGA on a classic amiga motherboard
True, you said you use IR for working with BGAs. I was just wondering why you brought that up, when it's totally irrelevant to the topic. Trying to impress people with your mad skillz?

Quote:
and yeah you protect everything when doing them
it retarded protecting and wasting time just to use hot air to remove a wet smd cap
I think attention to detail isn't your strong point. I particularly mentioned *sensitive* parts. Not every part needs to be protected.

Quote:
anyways i stand by what i said this guy isnt gonna be buying a rework station etc and he doesnt need too
all he needs are tweezers simple effective and quick and easy
doesnt risk damaging anything
And so he should go out and buy a pair, at probably a similar cost to a hot-air rework station? It's highly doubtful that he has some lying around the house. There are some capacitors that are awkwardly positioned for access with tweezers on the A1200. The risk of damage is probably higher than you're assuming. Both techniques have their risks and benefits - it's silly to write one off based on incorrect assumptions.

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i dont even understand why this needs to be debated for someone new to soldering
Again, not paying attention. He has said he already has experience soldering with an iron, just not with Amigas.

Quote:
better he learns that before ever using hotair as he will need the practice making good joints when adding new
Not getting the connection between experience with desoldering tweezers (or hot air for that matter) and making good joints. The two are very different activities with their own separate tools and techniques.

Quote:
many many pros who CANT solder
Probably true, but not sure what point you're attempting to make. The same goes for any profession - there are professional taxi drivers who are terrible at driving. There are also many more pros who can solder, and many pros who know how to rework boards and use hot air and set up reflow cycles and read data sheets.

Quote:
bad enough we have these horrible youtube videos teaching people
And there are also many very good videos showing good technique for using desoldering tweezers and hot air. That's the nature of the internet - being able to tell the good information from the bad information is a skill in its own right. ChuckyGang has some videos showing good technique though, should you be interested, and there are enough experienced people throughout the Amiga community that can be asked about the suitability of any particular video.
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Old 18 October 2018, 13:59   #35
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Jesus, I didn't expect all of this - i'll come back to it properly soon...

But I did say to use the lowest temperature possible to melt the solder... and to always wear safety goggles. I got this advice from a prominent youtube electronics 'tutor'.

You're going to blow up capacitors if you throw 400 degrees at them and heat them the wrong way.

If you use the lowest you can (solder depending) and aim it at the metal can of the cap, then its going to warm up just enough to slide off the pads (i mean the things are skin-touchable mere seconds later).

I'll read through this all now, but I just wanted to chime in with that.

John

Last edited by project23; 18 October 2018 at 14:55.
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Old 18 October 2018, 14:06   #36
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Btw: From this random datasheet:

https://www.mouser.co.uk/datasheet/2...cq-1320835.pdf

Quote:
Resistance to soldering heat

The capacitors are kept on a hot plate for 30 seconds,
which is maintained at 250°C. The capacitors shall meet
the characteristic requirements listed at right when they
are removed from the plate and restored to 20°C.
And...

Quote:
Category Temperature Range

–55 to +105°C
(From the same datasheet)

Quote:
Originally Posted by nexus View Post
no thats the max temp period
I guess you were wrong?

Don't forget we're talking AIR here at a distance of an inch or so from the cap. Not a hotplate and certainly (in my experience) not at 250C (at the cap)

John

Last edited by project23; 18 October 2018 at 15:18.
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Old 18 October 2018, 14:54   #37
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Originally Posted by Daedalus View Post
And what makes you think it's not my profession, and that my experience is any less relevant than yours? What do you mean by the "first time"? We've been talking about removing capacitors with hot air, in which case the state of the capacitor afterwards doesn't matter. Besides, it doesn't take that long to develop a reliable technique. A few hours practicing on a few old PC motherboards or routers will have any competent hobbyist up to a level where they can reliably remove SMT capacitors without any complications.

Also, what's the relevance of using IR for BGA parts? There are no BGA parts on any classic Amiga motherboard. Taping and protecting sensitive nearby parts is pretty normal for rework. Nothing "retarded" about it, but it's quite telling that you think there is.
First of all, I think you've said everything I would have wanted to say in response to nexus, and you're clearly more experienced so I appreciate that, thanks.



Second of all, that's exactly what I did. I spent (at most) an hour or so on an old router I think it was? No! A bit of really expensive (but severely broken) cisco equipment from work if i recall. The point is I had the technique down very quickly. Flux, reasonable airflow - and the temp I started at 180c about an inch and a half away and ramped it up until I got a quick technique down. For me I think it was around 220C? Took less than a minute to remove each cap.

I didn't advise the air temp to the OP because every station is different and mine could be poorly calibrated. If he's experienced with an iron then he should be experienced enough to know to try a new technique on waste components first before taking it to his beloved A1200.

Btw if anybody thinks 220C AIR for even a minute or two is going to damage a PCB, then even me with my hobbyist experience can sleep easy advising they see a specialist.

Caps explode because people take air rework stations, and try to get the caps off by aiming the airflow at individual pads. Every time the gun is switched from one pad to the other, the first cools down, and try as they may again and again the the process seems like a failure. So what to do? Increase the temperature of course! They think 'it isn't hot enough!', so they keep ramping up the temp until the cap goes BOOM and their face narrowly escapes a nasty burn or blindness (if they're stupid enough to not wear glasses).


The above words aren't mine (though i've paraphrased them). I can't take credit for them.

You heat the cap directly, low temperature and aiming straight at the cap - on the A600 i worked on, I had each cap off in less than a minute, and the boards were spotless. I then used wick to remove the excess solder, and cleaned up any leakage etc etc. I have pics somewhere i think if you want to see my 'burned up idiot board' sometime?

Oh, and i recommended adding the new caps with an IRON, so any talk of replacing good caps with air is null and void.

John

EDIT: OH! And this is important - I am not in any way advocating or recommending this method for through hole electrolytics. Use a desoldering pimp or solder wick or if the cap is small enough heat both leads simultaneously and pull. The problem with these through hole caps is they're often attached to a big ground plane though, so I found these to be a bit of a pain in the a$$. But yeah - no air on through holes - we're talking metal cased SMD electrolytics here, incase that wasn't clear.

Hahaha! Desoldering pimp!! I left that typo in because it made me laugh so much

Last edited by project23; 18 October 2018 at 15:45.
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Old 18 October 2018, 15:05   #38
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i'm not a professional, but i use the most efficient tools & hardware to make it right :

for SMD, i use an optional hot tweezers i bought in complement for my Yihwa soldering station.

It takes 10-15 seconds to remove one SMD capacitor. no lifted pad or whatsoever.

Clean job, removal of the remains of solder, IPA cleaning, and that's it.

I tried "hot air" on a non working PCB, and it's imprecise at best and uncomfortable.
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Old 18 October 2018, 15:10   #39
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Quote:
Originally Posted by dlfrsilver View Post
i'm not a professional, but i use the most efficient tools & hardware to make it right :
That's fine, its another way of doing it - as for the most efficient, i'm not sure what metric you're using to define this?

But seriously this isn't 'tweezers vs air', this is 'air should NEVER BE USED' DANGER DANGER AAAAAAH!

Ya know? You've got your way and it sounds like it works great, why not add some more information so that the OP can gain some useful knowledge of the technique and perhaps some good budget tools he can pick up?

Quote:
Originally Posted by dlfrsilver View Post
I tried "hot air" on a non working PCB, and it's imprecise at best and uncomfortable.
Then with respect, you're 'doing it wrong' - meaning I think perhaps you've given up too easily, or some other condition has made your mind up for you. It is certainly not uncomfortable (I even have a bracket set up to hold my air gun if necessary) - and its incredibly precise with the smallest nozzle (the size of the cap).

Kind regards as always,

John

EDIT: How the hell can an iron/tweezers be any more comfortable than an air gun?!
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Old 18 October 2018, 15:38   #40
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Can someone link me to a good budget example of these tweezers?

Because the only ones I can find so far are around the same price as a good budget soldering station like the one I listed.

I'm not flaming here, I'm genuinely curious because believe it or not I want some - they sound useful and as someone who has only been in this hobby for a couple of years they're new to me.

John

That's the difference here though isn't it - what actual information has been provided to the OP about tweezers and the technique to use them? Or at least what they are and how they relate to a soldering station, if at all? The point of my reply was to help him somehow. How have you (nexus) helped him? Other than to incorrectly warn him away from a technique that professionals and experienced hobbyists alike stand by (When. Done. Properly.).

EDIT: I removed some criticism from this part because I was confusing my first post in this thread with another thread.

Last edited by project23; 18 October 2018 at 16:41.
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