Author Topic: Need suggestion for removing soldered groundplane  (Read 772 times)

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Offline Humanoid

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Need suggestion for removing soldered groundplane
« on: April 19, 2021, 09:49:04 am »
I'm refurbishing an old NES console and my digital TS100 iron is not doing well where there is large amounts of solder connecting the motherboard to the RF modulator and power supply. It melts it, but not evenly and not fast enough. Even if I boost the temp, getting all the solder to liquify is not working out well and may cause damage.

Is there a cheap iron anyone can recommend, or perhaps some other tool specifically for heating areas like this fast? I have solder wick and a solder sucker. I just need to heat these large pools of solder fast so I can remove them without damaging the pcb.

Image attached of what this area looks like (not mine, but same area).

Thanks
 

Offline SeanB

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Re: Need suggestion for removing soldered groundplane
« Reply #1 on: April 19, 2021, 10:11:45 am »
Add fresh solder, and use solder wick. For large things like this I tend to use a soldering gun with a tip, as that will put a large amount of heat in the small area fast.
 

Offline mvs

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Re: Need suggestion for removing soldered groundplane
« Reply #2 on: April 19, 2021, 10:17:32 am »
With a large tip, like C4, TS100 should have quite decent thermal performance. In hard situations you can assist with a second iron or you can preheat the board with a hot air station.
 

Offline Gyro

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Re: Need suggestion for removing soldered groundplane
« Reply #3 on: April 19, 2021, 12:57:55 pm »
Agreed, with a C4 tip it is a powerful beast - You didn't say what supply voltage you are running it at though.  :-\
Chris

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Offline Humanoid

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Re: Need suggestion for removing soldered groundplane
« Reply #4 on: April 19, 2021, 03:18:16 pm »
With a large tip, like C4, TS100 should have quite decent thermal performance. In hard situations you can assist with a second iron or you can preheat the board with a hot air station.

Agreed, with a C4 tip it is a powerful beast - You didn't say what supply voltage you are running it at though.  :-\

Thanks guys.

I do have a good power supply that supplies it with max it can handle. It heats up really fast and I boost it into the 400s when I need extra heat.

I actually have the C4 tip and thought I was using it. Apparently I'm braindead and was using the same shape tip but smaller size!  :palm: At 350C with a few bursts higher, it easily melted the solder fast.

So, the good news is, the C4 worked great!

Bad news is that the solder wick couldn't get the final bits of solder I need to free the tabs for RF modulator, so I have to buy a new solder sucker. Mine seems to have vanished (maybe the mrs threw it out thinking it was a blackhead gun). I wanted a better one anyway, so it's a good excuse for a new piece of gear :)
 
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Offline tszaboo

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Re: Need suggestion for removing soldered groundplane
« Reply #5 on: April 19, 2021, 03:31:44 pm »
For such jobs, don't do the wick first. Its going to transfer even more heat away, and not going to work as expected. Keep the board upside down, heat up the solder, and then whack the board on the table, so the molten solder can fly away from your ground plane. Do this a few times to remove solder, then you can finish off with the wick, since the thermal conduction and mass will be much lower.
And stay safe by doing this. Flying molten metal is a nasty thing.
Former username: NANDBlog
 

Online BrokenYugo

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Re: Need suggestion for removing soldered groundplane
« Reply #6 on: April 19, 2021, 03:57:12 pm »
I've done this twice, you need wide high quality wick, flux, and the biggest tip you have (I used a Hakko K profile), run at the highest temperature you can set the station. Soak the wick in RA flux, lay it over the joint and push the iron in against the wick. Repeat until cleared and have a fan going for the smoke. The K tip was especially good to get into the corners.

Even once you have all the solder gone it's a tight fit coming out. On some models the power/data pins are actually knurled and pressed into the modulator board, so you may need to desolder from the motherboard side, rather than the recommended modulator side, those big pins in big plated through holes are harder to desolder than the case tabs.

Replace the little electrolytic on the 7805's output with the best long life/high temp you can find and fit in there (I can dig up a part number if you want), when that one goes high esr the 7805 will oscillate and cause weird video problems.
« Last Edit: April 19, 2021, 04:49:39 pm by BrokenYugo »
 
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Offline harerod

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Re: Need suggestion for removing soldered groundplane
« Reply #7 on: April 19, 2021, 04:31:56 pm »
Most of the time I would recommend getting a secondary heat source for pre-heating. Even a ceran cooking plate would do nicely.

However, looking at this particular PCB I would recommend a cheap second soldering iron.

Before switching to JBC, I quite often had to pair my Weller Magnastat with a 5€ directly 230V powered soldering iron.
Everything has already been said, just not yet by everyone. - Karl Valentin
 
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Offline Humanoid

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Re: Need suggestion for removing soldered groundplane
« Reply #8 on: April 20, 2021, 05:01:34 pm »
I've done this twice, you need wide high quality wick, flux, and the biggest tip you have (I used a Hakko K profile), run at the highest temperature you can set the station. Soak the wick in RA flux, lay it over the joint and push the iron in against the wick. Repeat until cleared and have a fan going for the smoke. The K tip was especially good to get into the corners.

Even once you have all the solder gone it's a tight fit coming out. On some models the power/data pins are actually knurled and pressed into the modulator board, so you may need to desolder from the motherboard side, rather than the recommended modulator side, those big pins in big plated through holes are harder to desolder than the case tabs.

Replace the little electrolytic on the 7805's output with the best long life/high temp you can find and fit in there (I can dig up a part number if you want), when that one goes high esr the 7805 will oscillate and cause weird video problems.

I use chem-wik, but it's not very wide. I agree, wide would have helped a lot, I had to use a lot of it. I used amtech flux to try and keep the area flooded. I need to try some liquid flux for stuff like this to see if it's cleaner. The amtech left a lot of thick sticky residue. IPA and some swabs cleaned most of it though was a bit of a pain.

I don't have a K tip. C4 is biggest I have. K would definitely fit better in the corners because of the edge it has. I had to choose between the K and C4, C4 fit best at the time as I wasn't planning on doing anything like this.

Yeah, if you have a part number for the cap, will save me some time digging around. Thanks  :-+

 

Online BrokenYugo

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Re: Need suggestion for removing soldered groundplane
« Reply #9 on: April 20, 2021, 06:43:09 pm »
Looks like I used this one, of course they're out of them, double check the dimensions and see if digikey has any. What's important is that it's 10,000 hours@105C (so about forever in circuit, even cooking next to the 7805 heatsink) AND fits in there. Get two as there's another 100uf bulk decoupling cap on the main board.

https://www.mouser.com/ProductDetail/nichicon/uld1e101med1td/?qs=po041r8J5I7Kda6vFRnDrg%3D%3D&countrycode=US&currencycode=USD

I'd give my whole order but it's mixed up with another recap project and I don't remember what's what. The other electrolytics aren't too critical, the big one in the modulator lives a fairly easy life and the other little ones are just signal coupling caps, match the case size and value and it'll be fine. I was careful changing the two little signal ones in the modulator to have the lead bends and positioning just like the old ones, as they're near tuned circuits, but IDK if that's really so critical.
 
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Offline bobbydazzler

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Re: Need suggestion for removing soldered groundplane
« Reply #10 on: April 21, 2021, 10:41:11 am »
You can use wick for this just cut off a small piece at a time(so the heat can't escape into the rest of the wick).  Add lots of flux too and if you're having trouble add fresh solder.
 
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Offline Robert Smith Eco Warrior

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Re: Need suggestion for removing soldered groundplane
« Reply #11 on: April 21, 2021, 11:21:02 am »
I have a monster soldering iron I only use for soldering big cables, like car battery cables etc.
I think it is meant for doing the lead work on stained glass windows.
It gets too hot for electrical solder so I plug it in and then solder quickly as the temperature reaches about where it needs to be.
It is pretty crude but has a shed load of power to get big stuff heated.
 
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Offline JustMeHere

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Re: Need suggestion for removing soldered groundplane
« Reply #12 on: April 24, 2021, 04:34:44 am »
Chip Quick may help.  Dave did a video on it.

 
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Offline ogden

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Re: Need suggestion for removing soldered groundplane
« Reply #13 on: April 24, 2021, 06:00:34 am »
Preheat part of the board using hair dryer on highest heat lowest fan speed or electronically regulated air gun at let's 100oC. Make sure to ground board and yourself, don't touch PCB with blower. Preheated PCB's are much more easier to solder. You may need more than one heating/soldering cycle.
 

Offline Humanoid

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Re: Need suggestion for removing soldered groundplane
« Reply #14 on: April 24, 2021, 05:32:48 pm »
Preheat part of the board using hair dryer on highest heat lowest fan speed or electronically regulated air gun at let's 100oC. Make sure to ground board and yourself, don't touch PCB with blower. Preheated PCB's are much more easier to solder. You may need more than one heating/soldering cycle.

Thanks. I actually have a hot air gun. It gets up to about 300F/100C. It didn't occur to me to warm the board first. :palm: Newb gonna newb.

My new solder sucker arrives tomorrow so I will definitely try that out. I already removed most of the solder cleanly so hopefully it will be a quick procedure.
 

Offline Humanoid

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Re: Need suggestion for removing soldered groundplane
« Reply #15 on: April 26, 2021, 10:46:26 pm »
Looks like I used this one, of course they're out of them, double check the dimensions and see if digikey has any. What's important is that it's 10,000 hours@105C (so about forever in circuit, even cooking next to the 7805 heatsink) AND fits in there. Get two as there's another 100uf bulk decoupling cap on the main board.

https://www.mouser.com/ProductDetail/nichicon/uld1e101med1td/?qs=po041r8J5I7Kda6vFRnDrg%3D%3D&countrycode=US&currencycode=USD

I'd give my whole order but it's mixed up with another recap project and I don't remember what's what. The other electrolytics aren't too critical, the big one in the modulator lives a fairly easy life and the other little ones are just signal coupling caps, match the case size and value and it'll be fine. I was careful changing the two little signal ones in the modulator to have the lead bends and positioning just like the old ones, as they're near tuned circuits, but IDK if that's really so critical.

Thanks, man. Mouser seems to be out of that specific model, but I'll find another comparable and check Digikey. No worries on the order, I can just check the caps and see what they say.

My new tools came in today and this solder sucker kicks ass (Engineer SS-02). Best $25 I ever spent. I warmed the board with my heat gun and the sucker made quick work of what was left and a little wiggling separated the RF module from the motherboard. No damage was done to the pins or anything else. I also managed to disassemble the module. The large 25V 2200uF cap is definitely shot, couldn't get a reading off it—meter just gave me an OL.

I think I'm going to just replace all of the electrolytics in here and on the motherboard and get a new voltage regulator transistor while I'm at it. Are there any other caps that should be replaced besides electros? Also, should I stick to the values of the originals or should any have higher values?

The DC input looks a little sketchy too. Not sure if they make replacements exactly like the original. If not, I guess I'll just look for one that fits.

Thanks again for the help.
 

Offline Humanoid

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Re: Need suggestion for removing soldered groundplane
« Reply #16 on: April 27, 2021, 02:43:06 am »
While looking for an NES replacement DC input jack, I found this on Digikey.

Anyone know if this would suffice? rated at 48V and NES is I think 9v <1A

https://www.digikey.com/en/products/detail/tensility-international-corp/54-00129/9685438

If not, there's this from Mouser.
https://www.mouser.com/ProductDetail/Gravitech/CON-SOCJ-2155?qs=fkzBJ5HM%252BdCcpvFQyQZHtA%3D%3D
« Last Edit: April 27, 2021, 02:47:07 am by Humanoid »
 

Online BrokenYugo

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Re: Need suggestion for removing soldered groundplane
« Reply #17 on: April 27, 2021, 03:34:17 am »
Just change the electrolytics, no need to up the capacity, may go up in voltage to get the case size right. Impressive the big one failed, those usually hold up.

As long as the power jack dimensions are right it'll be fine.
 
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Offline brabus

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Re: Need suggestion for removing soldered groundplane
« Reply #18 on: April 27, 2021, 05:28:34 am »
Instead of wacking the board, I use compressed air.

Heat up the joint and stay there for a while, to ensure it's nicely melted and warm. Then a quick, precise blast of compressed air and all the solder will just fly away. Obviously you want to control the direction of the blast, so it goes towards a box or something that prevents the solder to fly all over the place.
 

Offline Humanoid

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Re: Need suggestion for removing soldered groundplane
« Reply #19 on: Yesterday at 08:14:08 pm »
Well, I got my components, recapped the NES, added a new input power jack, got a new power brick properly rated for it, cleaned it off thoroughly, powered it up and... dead. Totally $%&*!@ dead. No light even.  >:(

I'm wondering if maybe I bridged something in the power supply (lots of little resistors and such near the caps) or maybe I didn't bridge something that was previously. I did make sure to solder the RF housing plates where they connect to the PCB, and the A/V and RF connectors, and those few spots on the edges as well. The power jack fit properly (I bought 3 just to make sure one would fit) and it's not touching anything else. Not sure wtf the problem is.  |O

I did buy a K tip for my TS100 which works amazing on those ground planes and for reflowing, and damn near anything else you need to heat up fast or that's a heat sink. Made quick work for reassembly.

Well, I guess at this point it's time to disassemble the whole thing again and start probing to see where the power is actually reaching (or not reaching). Maybe it's the voltage regulator. Maybe there's a damaged or corroded trace or faulty SMD component that isn't visibly damaged. Hopefully I can figure this out. Either way, it has been a fun learning experience to date.
 


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