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Old 15 October 2018, 08:46   #1
Marchie
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Safest desoldering strategy.

The time has come to hack at my beloved A2000 again. This time I need to remove RAM chips.

The last time I tried to remove an on-board component I just used a solder wick and it was a nightmare (and that was only for a crystal). The chances of me getting eight 20-pin RAM chips off without doing damage is slim to none, so what's the safest strategy? (Not worried about the RAM, just the board!)

What is the safest way to do this? Desolder station? ChipQuik? Both? Neither?
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Old 15 October 2018, 08:56   #2
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A desoldering station with a vacuum pump is the nicest way to get this done. Hakko does a very nice gun shaped one that I can recommend.

If you are on a budget, there are chinese vacuum stations too at a lower price, these can also get the job done.

If you don't wish to spend a lot of money, use a pair of electronics wire snips, clip off all the legs near the chip package, then desolder each leg individually. Clean the holes on the PCB with a spring loaded desoldering pump.

Don't use braid, you'll only lift pads/tracks with that.
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Old 15 October 2018, 08:56   #3
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If desoldering a crystal was difficult then I can only imagine you have a crap soldering iron.

A desoldering station is generally the best way to desolder through hole components, however a good one is going to set you back several hundred dollars.

An alternative is to cut the chips off the board, then remove each pin individually. There is still a good chance of damaging the board if you are not experienced.

Why do you need to remove all 8 chips? It's very unlikely that they're all bad. I'd suggest that some more thorough diagnosis should be done.
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Old 15 October 2018, 09:20   #4
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if you cut the legs do it parallel to the pcb so you dont accidentally hit the board
and solder wick or braid isnt a good choice for through hole anyways always best to use a sucker of some kind whether like said above or manual types
anyways i hope when soldering you had correct temps tip and flux and kept the iron clean at all times

Last edited by nexus; 15 October 2018 at 10:16.
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Old 15 October 2018, 10:49   #5
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Solder wick is perfectly fine once you allow for the heat it absorbs. I use it all the time for cleaning up after desoldering parts (I use an electric desoldering pump for the main part of the work). If it's lifting pads or tracks, the solder isn't getting fully soaked up and is cooling down before you've finished absorbing it, so you're not using enough heat. The correct width braid is also a factor here, as if it's too thin it can't absorb all the solder from the joint in one go, resulting in a mess, and too thick will absorb more heat from your iron.

Don't bother with a spring-loaded desoldering pump unless you are getting a decent one with a silicone nozzle. The hard plastic nozzles won't give you a good seal and will only add to your frustration.
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Old 15 October 2018, 13:31   #6
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As usual thank you for the advice all.

Quote:
Originally Posted by Hewitson View Post
If desoldering a crystal was difficult then I can only imagine you have a crap soldering iron.
I'll admit my soldering iron isn't great, but it's mostly just the operator who's crap Though to be fair they guy who did eventually help me take if off had a bugger of a time with it too...

Quote:
Originally Posted by Hewitson View Post
Why do you need to remove all 8 chips? It's very unlikely that they're all bad. I'd suggest that some more thorough diagnosis should be done.
Upgrading from 1mb to 2mb.

Quote:
Originally Posted by Daedalus View Post
Don't bother with a spring-loaded desoldering pump unless you are getting a decent one with a silicone nozzle. The hard plastic nozzles won't give you a good seal and will only add to your frustration.
Yeah, been there failed at that too!

I should be able to get someone at the user group (who actually knows what they're doing) to help me desolder. Mostly was just wondering if ChipQuik offered any possibility of making it easier or minimising potential damage to the board, but I doesn't seem so, so I'll happily save my money.

It's unfortunate for me that I mostly want to use my Amiga rather than work on it Yet at the same time it's just so much fun upgrading it...I'm my own worst enemy.
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Old 15 October 2018, 13:37   #7
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I double the leg cutting strategy. I would only suggest being very cautious as certain cutters can bend legs which leads to unwanted impact on solder pads and tracks.

Perhaps a sharp knife could be used with all due care. This is what I ended up with when removing PLCC from a board with very thin and unreliable copper, after my cutters tore a few tracks off.

A good idea would be to use some old PC mobo for practice.
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Old 15 October 2018, 13:55   #8
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Chipquik! (or variant) wetted with flux, fast simple and safe. just re-tin the pads before you solder replacement. It reduces melting point and prevents accidental lifting of pads
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Old 15 October 2018, 16:52   #9
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I find the spring loaded vacuum device works OK in conjunction with a good iron works about 90% of the time, and the other 10% are taken care of with a solder braid. It is not a fast process by any means. A good desoldering pump would be much faster, but more expensive.
If you are doing just one job, a simple spring vacuum pump is fine. If you are making a career out of it, get the real tools.
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Old 15 October 2018, 17:05   #10
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I don't know if its already been said but make sure you're cutting the solder wick to the smallest necessary length, otherwise you're just heating a coiled copper heatsink.

Again, its probably been said but make sure you're using flux - the results are night and day.

IF they're through hole components then a good desoldering pump can work wonders (I have a blue Draper one from amazon if you're looking).

Lastly... for surface mount, nothing beats hot air in my opinion. Low enough temperature just to melt the solder, and just wait (with flux of course). As you get experienced you can just increase the temp and have one hand on the airflow knob and the other holding the nozzle. SMD parts come away in seconds - have an 'instrument' (a bloody toothpick will do) to poke at the SMD stuff. Gently. When it's ready it'll move away from the pads with the minimum pressure.

Again, i'm sure i'm repeating the above posts, not had time to read em yet lol

John

Last edited by project23; 15 October 2018 at 17:31.
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Old 15 October 2018, 17:14   #11
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On the subject of chinese cheap solder stations:

I have a Katsu (hahaha i know) model 312080 'double LED LED homothermal desoldering table' (again, hahaha).

It is safe, which is the first consideration - the solder tip is grounded at least, not checked what fuses it has, never had it apart.

Anyway - it is surprisingly good and at the time I got it, it got pretty good reviews considering its price, which was around £50 from amazon?

The soldering iron side is questionable (the rubberised part of the iron itself tends to ride up like a skirt, ), but the temperature control is consistent (if in need of calibration) and it'll accept the same soldering tips as the hakko, so you can replace (as i have) the tips with good quality ones.

The hot air side though, is great. If i ever upgraded to a genuine Hakko iron i'd still keep the Katsu for regular use of the air gun. Comes with several nozzles, consistent (and I believe accurate) temperature range, variable airflow and has never failed me.

Don't get me wrong, this is a budget station with a capital China, but it has served me so well that despite having the means to replace it with a much better one, I still haven't in over a year.

Here is a link to it on Amazon:

https://www.amazon.co.uk/KATSU-Tools.../dp/B00BKXVNYS

For 43 quid ya can't go wrong, seriously, but there may be better at that price range now so maybe check first. I know Katsu have a new model but I think they got it right with this one and I love the colour. You can always upgrade later, to your hearts content, all the way to thousands and thousands of dollars. But we all start somewhere, and though I thought this station would be step 1, it's actually turned out to be step 1 and 2... But its China so half of them probably come with the displays upside down and the screws missing. Maybe I got lucky. I'm actually quite serious about this - people have received them with loose connectors on the front - but once you've given it a check over and corrected any mistakes i'm sure its fine.

Anyway, to the experienced - stop laughing at my professional Katsu station.

John

EDIT: And if you're currently using a 'plug straight into the wall' soldering iron, make sure you immediately go cut the plug off it and throw the iron at the car of the neighbour you hate the most.

(Seriously though the difference between that and a temp controlled station, no matter how crap, is night and day)

Last edited by project23; 15 October 2018 at 17:35.
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Old 16 October 2018, 02:16   #12
Marchie
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All great advice, thanks.

The double-up of advice is actually helpful - once two or three people say the same thing you see a pattern emerging.

Quote:
Originally Posted by Dynamic_Computi View Post
I find the spring loaded vacuum device works OK in conjunction with a good iron works about 90% of the time, and the other 10% are taken care of with a solder braid. It is not a fast process by any means. A good desoldering pump would be much faster, but more expensive.
If you are doing just one job, a simple spring vacuum pump is fine. If you are making a career out of it, get the real tools.
I could never get the spring loaded device to the solder before it solidified again. Almost certainly operator error though...

Quote:
Originally Posted by project23 View Post
On the subject of chinese cheap solder stations:

I have a Katsu (hahaha i know) model 312080 'double LED LED homothermal desoldering table' (again, hahaha).

It is safe, which is the first consideration - the solder tip is grounded at least, not checked what fuses it has, never had it apart.

Anyway - it is surprisingly good and at the time I got it, it got pretty good reviews considering its price, which was around £50 from amazon
As someone who only solders/desolders once or twice a year, I'm going to look into this. Thanks John!

Quote:
Originally Posted by kipper2k View Post
Chipquik! (or variant) wetted with flux, fast simple and safe. just re-tin the pads before you solder replacement. It reduces melting point and prevents accidental lifting of pads
There's at least one recomendation for ChipQuik, thanks Kipper.

Last edited by Marchie; 16 October 2018 at 02:22.
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Old 16 October 2018, 02:28   #13
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there are cheap desoldering irons
https://www.ebay.com/itm/Solder-Suck...cAAOSw0bJZt3QB
never used but its the cheapest
then there are these types also cheap
https://www.ebay.com/itm/Hot-30W-220...wAAOSwzJ5XX9Hj
cant speak for them as i never used but they are cheap options
i use hakko FR-300 personally
but back in the day i used to use the old school squeeze suckers types
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Old 16 October 2018, 16:12   #14
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If you MUST use a desolder pump thingy get one of these and toss the rest in the bin! I have a large kit of soldering stuff, including desoldering vacuum, soldering iron stations etc and these little sucker pumps are brilliant and well built:

https://www.ebay.co.uk/itm/silicone-...JEea:rk:1:pf:0
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Old 16 October 2018, 16:36   #15
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Quote:
Originally Posted by ElectroBlaster View Post
If you MUST use a desolder pump thingy get one of these and toss the rest in the bin! I have a large kit of soldering stuff, including desoldering vacuum, soldering iron stations etc and these little sucker pumps are brilliant and well built:

https://www.ebay.co.uk/itm/silicone-...JEea:rk:1:pf:0
Just a quick question on this desolder pump (i'm thinking of getting one myself).

How does it stand up to the heat? The tip on mine (don't know the material) has held up pretty well to heat. I can hold it against the iron or under the air unless i'm using very high temperatures. (There's some minimal deformity around the tip)

I would absolutely f*%king LOVE a cheap desolder pump that like yours forms a good seal, and takes the heat well enough that i can actually melt the bloody solder

Last edited by project23; 16 October 2018 at 16:42.
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Old 16 October 2018, 16:52   #16
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Quote:
Originally Posted by project23 View Post
Just a quick question on this desolder pump (i'm thinking of getting one myself).

How does it stand up to the heat? The tip on mine (don't know the material) has held up pretty well to heat. I can hold it against the iron or under the air unless i'm using very high temperatures. (There's some minimal deformity around the tip)

I would absolutely f*%king LOVE a cheap desolder pump that like yours forms a good seal, and takes the heat well enough that i can actually melt the bloody solder
Biggest selling point is the tip is heat resistant and forms a good close seal, so it sucks the solder up with minimal fuss! Also it can be replaced! I bought a bunch of replacement tubes for mine. It is also VERY well built! I suspect that is down to the fact it is Japanese made. It just oozes quality. It is easy to clean aswell the list just goes on... I sound like a sales rep for these things lol.
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Old 16 October 2018, 17:47   #17
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I also recommend the chipquick method for desoldering single components.
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Old 16 October 2018, 19:50   #18
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chip quick is amazing. i removed an 030 and coprocessor with that stuff (using hot air and chip quick.
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Old 16 October 2018, 20:33   #19
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chip quick is amazing. i removed an 030 and coprocessor with that stuff (using hot air and chip quick.
Wish I'd have known about this stuff last week!

Here's a pic of my jerry rigged setup for removal of a direct-soldered 030 from a TF530 i'd messed up:
You can't really see in the pic, but the 530 was balanced in such a way as when the solder got to the right temp it would simply 'drop' out. I was obviously there to catch it (though it was bloody hot!).

Anyway I had to have the air at a very high temperature, plenty of flux, and the nozzle far away enough from the board so that the air flow just about covered the area of the chip. I don't have an IR thermometer at the moment - it's high on my list of things to get next! Anyway at the point the air hit the board the temp had obviously dropped a lot (which is why I had it set so high), so hopefully no damage came to the chip. You can't see (it's off pic), but a small fan is blowing across the bottom side of the board in an effort to keep it cool.

It worked! But the chip was so hot to the touch that I couldn't hold it until some seconds had passed - that being said, it wasn't hot enough to blister my skin and it cooled pretty fast, so I have my hopes that its still functional. There was certainly no (extra) damage to the board or the traces around the chip etc. It'd be a shame if the chip was dead though as it's a rare example of a genuine NOS 030RP33. Nothing special, just definitely genuine.

Next time I'll use bloody ChipQuik!!

Cheers guys,

John
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Old 16 October 2018, 21:20   #20
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Quote:
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Here's a pic of my jerry rigged setup for removal of a direct-soldered 030 from a TF530 i'd messed up
brownie points for creativity :^)

the major advantage of chip quick is that you dont need much heat at all. only takes a few seconds of hot air (i set mine at 300C) before it is molten, and it stays molten much longer than plain solder. for $15 you get maybe a foot of the stuff, but i think it's worth it.
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