Audio issues on A600, possibly recap needed at best?

[ajk]

Is it this stuff? Looks like zinc chloride based flux, for somewhat more crude applications. I'd say don't use it for electronics work.

[Turrican_3]

Originally Posted by ajk

Is it this stuff?

I would say the answer is a definite "yes" !

And yes, as I said before I think I'll just get rid of it, by proper disposal of course.

[project23]

That looks like your bog-standard 'water soluble flux' they sell at DIY stores over here for work on copper piping with a torch and brazing rods or whatever.

I have a tub here for just that. I've also used it very occasionally on things like metal sheilding on the A601 etc, but never on electronics (and nor would i!)

It might be worth keeping around to use as ajk said in crude applications such as metal sheilds or the like? It's usually pretty cheap though.

[Turrican_3]

Ok I think I'm finally ready to finalize the replacement caps order.
Needless to say, I see there is like a million purchase options, and possibly more.

Two quick (?) questions here:

1. I've read on a Panasonic capacitor line tech sheet that their OS-CON caps actually has no liquid electrolyte... is that true, and if so would that mean when the caps eventually fail, damage is likely to be far less devastating than a "regular" cap leaking acid?

2. does it make sense to invest extra money on very high-end caps, or is it safe enough to purchase a decent set from a well known brand? any suggestions, if the latter is true?

[Gordon]

Why not buy a kit with them all in one pack?
https://www.retrobench.com/shop

[Daedalus]

Polymer / organic polymer capacitors don't have a liquid electrolyte, so they won't leak in the future. A lot of people use them for that very reason. They are more expensive, but worth it for peace of mind.

However, I don't normally use them myself, instead just using high end parts with standard electrolytes and a good life expectancy. The capacitors used at the time by Commodore were pretty poor quality - leakage from high quality capacitors should be as rare as it is for the through hole types used in the A500 for example.

Currently I tend towards Würth capacitors - good quality, and they're red as a bonus

[nogginthenog]

Japanese caps are generally considered the best. Sanyo, Panasonic, Hitachi etc.
Buy them from a decent seller. It's not going to be expensive.

[Turrican_3]

Originally Posted by Daedalus

Polymer / organic polymer capacitors don't have a liquid electrolyte, so they won't leak in the future
[...]
Currently I tend towards Würth capacitors - good quality, and they're red as a bonus

So it's true, they don't leak... good to know, now I just have to decide between them and regular ones, I'll take note of this Wurth brand, thanks!

Since we're here... I think I'm getting a bit nervous about the hot air procedure on particularly crowded areas (especially the one near the power supply), so I wonder if you guys could suggest a B plan just to be on the safe side: I'm referring to the tweezer (?) soldering iron that can be seen on the video I posted before.

Is there any inexpensive solution available?

With a bit of luck (had to fiddle with keywords) I was able to find a couple of tools but they're like 200+ pounds each!?

Considering the relatively limited size range of the Amiga motherboard caps a couple of "U-shaped" tips (again, wording is likely wrong on my part) might do the trick as well, possibly?

Originally Posted by nogginthenog

Japanese caps are generally considered the best. Sanyo, Panasonic, Hitachi etc.

Thanks!

Originally Posted by Gordon

Why not buy a kit with them all in one pack?

That's an option obiuosly, but I'd like to be able to specifically choose the caps I purchase.

[ajk]

When using hot air in crowded areas, shielding the nearby components with regular kitchen foil helps in most cases. You'll want to have the foil folded over two or three times, so that a little bit of air is captured in between. This will help with the insulation. Kapton tape is also useful for keeping foil in place, and will not melt like regular tape.

A good alternative for "hot tweezers" is simply to use two soldering irons. When I bought my current soldering station, I kept the old iron too. Using an iron in each hand it is easy to pick off capacitors from the board. Of course, this won't work in very tight spots where getting even one iron in there is difficult.

Suitably shaped tips help. One of my most used tips has a slight curve, which often makes it possible to reach around components where a straight tip can't go.

[Turrican_3]

Hmm, kapton (I've already purchased this, in multiple sizes) + kitchen foil then, ok!

I should be able to find my old soldering iron somewhere, but I think I will need a smaller tip for the new soldering station (it's a "dual" unit, hot air + regular) to adopt this strategy.

Thanks! :-)

[jbenam]

Originally Posted by Turrican_3

Since we're here... I think I'm getting a bit nervous about the hot air procedure on particularly crowded areas (especially the one near the power supply), so I wonder if you guys could suggest a B plan just to be on the safe side: I'm referring to the tweezer (?) soldering iron that can be seen on the video I posted before.

Is there any inexpensive solution available?

Don't waste your money on those I have a very high-end soldering station and I decided to buy tweezers for it hoping they would help me with SMD caps (it's not like I have any issues with them using hot air - never lifted a pad - but you know) and it turned out it's utterly useless. I bought the smallest tip available and it's still not small enough. I later saw there's another revision of my tweezers which *might* be better at SMD electronics, but I don't want to waste any more money like that I'll just put the money in an high-end hot air station and call it a day.

Oh, and the cheaper ones? I bought one 10 years ago, it has been laying at the bottom of my toolbox since then

[Hewitson]

I've used the Hakko tweezers. They're not bad, but they're certainly not as good as a decent hot air setup (with foot pedal for paste dispensing).

[Turrican_3]

Thanks again guys for all of the advice.

Here I am with a little (?) progress report: you'll read aboud good, not-so-bad, and bad news.

Good news first: I've successfully completed the decapping procedure!
A bit surprisingly perhaps, it was the 4 non-SMD caps that turned out being the most difficult to remove. I used a regular solder iron fot those, while kapton tape + hot air gun proved a relatively easy and fast combo for the removal of all the SMD stuff.

Not-so-bad news: being a bit too worried about the ATA connector, I put too much force while applying the kapton tape on its edge, and broke pin 44 while doing so. Strangely (?) enough though, the hard disk seems to be working flawlessly, I guess that might be due to conflicting reports I'm reading regarding the actual functionality of this pin so I'm not going to worry that much (I believe it shouldn't be that difficult to replace the whole connector if needed)

Bad news last: upon further microscope inspection I noticed at least one broken track near the capacitors on the far right, those two nasty little boys apparently did everything they could to destroy my A600. Would it be possible to fix this track by connecting the cap to the bottom layer or the VIA itself using a short, thin wire?

Second, I'm quite sure I have to replace the op amp (bought a couple of TL084 chips, I understand they're a valid replacement for the original, and they're cheap) but I'm worried this isn't the only thing that might have suffered irreparable damage.

And not only that (please have a look at the short attached videos), I'm afraid I haven't cleaned well enough the PCB itself with the isopropyl alcohol. There's a gelatinous coat spread over many places, I'm still unsure whether that's residual flux (since it was originally in gel form) or acid, and if it's the latter I wonder if and most of all HOW am I supposed to finally remove it, considering I can see it in many VIAs as well.

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[jbenam]

Originally Posted by Turrican_3

Thanks again guys for all of the advice.

Here I am with a little (?) progress report: you'll read aboud good, not-so-bad, and bad news.

Good news first: I've successfully completed the decapping procedure!
A bit surprisingly perhaps, it was the 4 non-SMD caps that turned out being the most difficult to remove. I used a regular solder iron fot those, while kapton tape + hot air gun proved a relatively easy and fast combo for the removal of all the SMD stuff.

Not-so-bad news: being a bit too worried about the ATA connector, I put too much force while applying the kapton tape on its edge, and broke pin 44 while doing so. Strangely (?) enough though, the hard disk seems to be working flawlessly, I guess that might be due to conflicting reports I'm reading regarding the actual functionality of this pin so I'm not going to worry that much (I believe it shouldn't be that difficult to replace the whole connector if needed)

Bad news last: upon further microscope inspection I noticed at least one broken track near the capacitors on the far right, those two nasty little boys apparently did everything they could to destroy my A600. Would it be possible to fix this track by connecting the cap to the bottom layer or the VIA itself using a short, thin wire?

Second, I'm quite sure I have to replace the op amp (bought a couple of TL084 chips, I understand they're a valid replacement for the original, and they're cheap) but I'm worried this isn't the only thing that might have suffered irreparable damage.

And not only that (please have a look at the short attached videos), I'm afraid I haven't cleaned well enough the PCB itself with the isopropyl alcohol. There's a gelatinous coat spread over many places, I'm still unsure whether that's residual flux (since it was originally in gel form) or acid, and if it's the latter I wonder if and most of all HOW am I supposed to finally remove it, considering I can see it in many VIAs as well.

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I don't advice removing thru-hole components using hot air - while it works, it usually requires too much heat over a big area (which might damage the board) when compared to a soldering iron + suction pump.

The gunk in the videos looks like the solder paste you spoke of some posts ago. It's highly corrosive (not in a matter of days, but in a matter of months, if not properly cleaned, stuff will stop working). Isopropyl doesn't cut it for flux cleaning - there are specific products which will help. Also, a compressor (canned air probably isn't strong enough) might be a good way of getting rid of it. You can shoot air at high pressure and let the gunk fly away from inside the vias.

About the broken tracks, just scrape enough protective layer from the nearby track and put a bit of wire to fix it. This also works for broken vias (I've got one such issue in my A4000's audio circuit), just let the wire reach the other side, solder it and check with a multimeter if the bridge wire successfully restored the broken via.

[Daedalus]

Indeed, using a hot air gun alone to remove through hole parts should be avoided. However, using a hot air gun to preheat a larger area of the board will help when it comes to removing the part with an iron, since a cold ground plane will absorb a lot of the iron's heat before the solder melts.

IPA can be used for cleaning up "no-clean" flux, but it takes a lot of it. If it is no-clean flux, it won't be corrosive in itself, but it will hold dirt and other residues from the work that can be. If it's "water soluble", then you need to follow the proper process and use the proper chemicals to fully remove it, as the flux's instructions will tell you.

For that broken trace, I would put a thin piece of wire through the via and solder that along the trace to a little beyond the break. That will ensure that any damage within the via is taken care of too.

[Turrican_3]

Originally Posted by Daedalus

For that broken trace, I would put a thin piece of wire through the via and solder that along the trace to a little beyond the break. That will ensure that any damage within the via is taken care of too.

Great advice as usual, thanks!

Originally Posted by jbenam

The gunk in the videos looks like the solder paste you spoke of some posts ago.

You mean the white-ish one I was unsure of? If so no, I didn't use that on the Amiga. I used a no clean gel-like flux (first photo on the left here)

I guess I will try the compressor method and report back.

Thanks to you, too!

======================

I've already replaced the op-amp and put the brand new 22uF capacitors on the right side. In a few days (I'm too busy until the weekend unfortunately) I will try to better clean the PCB as suggested and proceed to the installation of the caps near the RCA audio jacks.

Plus, I'll try to check for broken tracks (hopefully there aren't any more!) and see if audio is back.

[jbenam]

Originally Posted by Turrican_3

You mean the white-ish one I was unsure of? If so no, I didn't use that on the Amiga. I used a no clean gel-like flux (first photo on the left here)

Right, well, yep, what you see is exactly that I used it for a bit and while I haven't really re-tested stuff I've soldered with it, it should technically be no-clean. While it's explicitly marked as such, please keep in mind that 99% of the AMTech fluxes sold around (especially here in Italy) are fakes produced for cheaps in the Far East. As such I cannot guarantee you that it's actually no-clean

If you can find the flux cleaner from Kontakt Chemie, that's what I advice - KC's stuff is top notch. Otherwise it should be pretty easy to find the one from Due-Ci almost anywhere in Italy. While not as good as KC's it does the job.

[Turrican_3]

Originally Posted by jbenam

please keep in mind that 99% of the AMTech fluxes sold around (especially here in Italy) are fakes produced for cheaps in the Far East.

Yep I found out about that after purchasing it because I googled for the product name, and the company website states something like original units are different than mine... so I guess it's really a clone. :-\

Unfortunately there's not a lot of electronics stores in my area and I was a bit in a hurry , I also have to say I don't think I like this gel-type flux so yesterday I purchased a liquid one on ebay.

Hope it proves good enough (and possibly no clean for real ), thanks again!

[jbenam]

Originally Posted by Turrican_3

I also have to say I don't think I like this gel-type flux so yesterday I purchased a liquid one on ebay.

Hope it proves good enough (and possibly no clean for real ), thanks again!

I do personally find liquid flux to be really hard to work with, at least on SMD. Maybe I should've purchased a known brand?

[Turrican_3]

Honestly I have no idea, what I said before was just personal preference (albeit formed on a slightly small sample size), definitely not technical opinion.

I guess I will find out soon.