Component C146 and heath of solderiron

The place to ask all those likely daft questions!
zChris
Posts: 194
Joined: Fri Nov 27, 2020 10:13 pm

Component C146 and heath of solderiron

Post by zChris »

Hello,

I was wondering what how warm most of you have when soldering / desoldering components on the atari? I had around 315 degrees using leadfree led. It seems a bit too hot but then again its old points on the motherboard so it might be a combination between these two that make some solderpads loose.

Also what capacity is the C146 ?

2021-09-20_23-00.png
2021-09-20_23-00.png (2.96 MiB) Viewed 2320 times
User avatar
stephen_usher
Posts: 5578
Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
Contact:

Re: Component C146 and heath of solderiron

Post by stephen_usher »

Ouch! That's one messed up set of pads, vias and traces! That board is wrecked!

I have my Hakko desoldering gun set at 350C as that's the lowest. My Ampex 15W soldering iron doesn't have a control on it but it never gets too warm. On the soldering station I have the iron set to 270C.

How precisely are you attempting to desolder these?
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
User avatar
exxos
Site Admin
Site Admin
Posts: 23495
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: Component C146 and heath of solderiron

Post by exxos »

stephen_usher wrote: Mon Sep 20, 2021 10:19 pm Ouch! That's one messed up set of pads, vias and traces! That board is wrecked!
I second that notion!
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
User avatar
rubber_jonnie
Site Admin
Site Admin
Posts: 10470
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: Component C146 and heath of solderiron

Post by rubber_jonnie »

stephen_usher wrote: Mon Sep 20, 2021 10:19 pm Ouch! That's one messed up set of pads, vias and traces! That board is wrecked!
I third that!! No going back on that one.

Personally I use 370C on my desolder gun, and 370C on my iron, however I use a relatively small tip on the iron so need to have it quite high to remain hot enough due to the lack of thermal mass.

Of course those are specific to my tools, and you may find your own to be different. I'd start off around 270C and slowly increase the temp until fresh solder melts easily on the soldering iron tip.

Of course it's not just about the temperature, but knowing when you've been on the joints too long, which is part of the problem here, along with good desoldering technique and knowing when a part is ready to come loose.

Also for these boards I only use lead solder, I find lead free to disagree with them, and it may not behave well with leaded. Also for desoldering you need plenty of flux.

I think C146 is the least of your worries, I'd approximate you've damaged 50% of the pads/vias along with the tracks that are ripped up, I'd suggest that board is only good for spares now. If you really want the value, I'd suggest downloading a schematic and look there.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
zChris
Posts: 194
Joined: Fri Nov 27, 2020 10:13 pm

Re: Component C146 and heath of solderiron

Post by zChris »

Hello everyone,

Yeah this was a donorboard to begin with. I think i will try to patch it up as a training session.

I use a desolder gun ZD-915 and then i have a little force on the other end to remove it.

/zChris
User avatar
DoG
Posts: 1125
Joined: Sat Apr 07, 2018 12:26 pm

Re: Component C146 and heath of solderiron

Post by DoG »

zChris wrote: Mon Sep 20, 2021 10:01 pm...
Also what capacity is the C146 ?
...
This and C124 should be a decoupling capacitor for the VCC to that chip. They are used to smoothen out the high frequency ripple on the power and provide a steady, in this case, 5V. They are normally around 100nF (0,1uF) and ceramic. But that also depends on distance from the VCC pin of the chip. They are non polarized. There is almost always one of these close besides a chip between VCC and GND.
User avatar
rubber_jonnie
Site Admin
Site Admin
Posts: 10470
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: Component C146 and heath of solderiron

Post by rubber_jonnie »

zChris wrote: Tue Sep 21, 2021 6:22 am Hello everyone,

Yeah this was a donorboard to begin with. I think i will try to patch it up as a training session.

I use a desolder gun ZD-915 and then i have a little force on the other end to remove it.

/zChris
If I'm honest, I don't think patching it up will help much, the damage is a bit severe, but at least it is only a donor board. However it would be worth using it to practise de-soldering.

What I think happened is that you didn't clear all of the solder, leading to the vias pulling and the tracks ripping as the chip was lifted out. It doesn't take much force to do this. With something large like the CPU, and especially areas like the GND pins, it can take a lot to clear the holes fully, and you may also need to use some solder wick from the top to clear some of the last bits of solder. For something large like a CPU I would probably use hot air to loosen those last tiny bits of solder, but you do need to be careful with that as the ST boards can burn quite easily.

Also, once you've cleared the holes from below, you need to check the pins are clear of the vias using a magnifying glass. More often than not, the pins will still be stuck to the outside edge of the via with a tiny bit of solder. You should heat with an iron and push the pin to the middle to ensure the pin is clear, at least at the bottom of the via.

Also, the rules for de-soldering are similar to those for soldering. Don't linger on a spot for too long or you'll lift the traces. Typically you're looking at about 3 seconds to form a solder joint, to de-solder is about the same, maybe a little longer, but the vacuum pump will cool the joint as the solder is sucked out and air comes through the via. Don't be tempted to hold it longer unless it's something like a heavy ground plane that is drawing the heat away. Holding too long will result in vias lifting. If something doesn't de-solder, move along and come back to it later.

I'm curious as to why there are large blobs of solder around some of the holes? Was this done afterwards? I'd expect all the holes to be clear at this point.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
zChris
Posts: 194
Joined: Fri Nov 27, 2020 10:13 pm

Re: Component C146 and heath of solderiron

Post by zChris »

Thanks for your input rubber_jonnie.

Yes the blobs was add later on holes that werent free. What i was removing was two rows of these. Was thinking to remove them and add a cpu since the socket was broken in the first place. But why is the dmg unrepairable? I cant add a CPU and patch it with small cables?

41002359-600x398.jpg
41002359-600x398.jpg (13.42 KiB) Viewed 2241 times
User avatar
rubber_jonnie
Site Admin
Site Admin
Posts: 10470
Joined: Thu Aug 17, 2017 7:40 pm
Location: Essex
Contact:

Re: Component C146 and heath of solderiron

Post by rubber_jonnie »

zChris wrote: Tue Sep 21, 2021 10:57 am Thanks for your input rubber_jonnie.

Yes the blobs was add later on holes that werent free. What i was removing was two rows of these. Was thinking to remove them and add a cpu since the socket was broken in the first place. But why is the dmg unrepairable? I cant add a CPU and patch it with small cables?

41002359-600x398.jpg
The damage is potentially repairable, but I would suggest if it is a donor board, it wouldn't be worth the time to do so.

From what I can see, nearly half the vias are damaged or missing on the top, and the condition is unknown underneath. There would be a great deal of additional wiring you'd need to do to repair this and if you are going to use it as a donor board, it just isn't worth the effort.

Just for reference, my approach to de-soldering something like that would be to snip all the plastic away from the pins, then heating each pin with a soldering iron and pulling the pin out with tweezers once the solder is liquid.

If I have a known dead chip, then this is an approach I would also take, snipping the legs where they enter the chip, removing the chip body and then removing each leg individually as above.

You can clean up the holes with wick or the de-solder gun afterwards. For possible good chips, it's de-solder gun all the way.

I think, having looked it up, we have the same model de-solder gun, so 350C-370C is a good place to be, if you have the temp too cool, then you can end up spending too long on the joints and causing damage that way.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
User avatar
stephen_usher
Posts: 5578
Joined: Mon Nov 13, 2017 7:19 pm
Location: Oxford, UK.
Contact:

Re: Component C146 and heath of solderiron

Post by stephen_usher »

zChris wrote: Tue Sep 21, 2021 10:57 am Thanks for your input rubber_jonnie.

Yes the blobs was add later on holes that werent free. What i was removing was two rows of these. Was thinking to remove them and add a cpu since the socket was broken in the first place. But why is the dmg unrepairable? I cant add a CPU and patch it with small cables?

41002359-600x398.jpg
Oh! Those pins are almost totally un-desolderable. The top of the pin forms a tight bond with the via and that won't allow all the solder to be removed. Once those are soldered in leave them!
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
Post Reply

Return to “NOOB QUESTIONS”