I think you're right. I read through the posts, but I didn't realize that there was a year gap. You might get better results if you started a new thread, or at least edit the first post with a line at the top stating that there's a new line of questioning. At least, that's what I have done in the past on other forums.

Thanks for taking my post in a non-hostile way. Again, I didn't mean to criticize, just offer alternatives. That said, I have definitely removed components in a destructive way. But since learning of ChipQuik, it has been my go-to method for SMD removal when great care is needed. I'm not a spokesperson for ChipQuik, I have no stake in the company or anything like that. I just think it's a really great product that is not so well known, so I like to share info about it whenever it's relevant.

Good idea, I´ll think about a new (better) title for this topic and edit it.

In the meantime I found that "DMA channel 2" is indeed used for floppy-drives in AT systems, so a dead "DRQ2" input at the 82C362 would explain the failing floppy drive.

Maybe someone shorted pin6 (DRQ2) and pin7 (-12V) when pulling out an ISA card... 🙁

Yesterday I removed the defective chip and I even found a donor board with a working SL82C362, but then I noticed (right before I started to solder it) that the SL82C362 is QFP 160 while the original SL82C362SX is QFP 128!

Finding one of those could be a tough job, I couldn´t find any other mainboard model based on this chip in my collection so far.
Maybe someone here has any information?

ziggy587 wrote on 2023-05-29, 12:41:

I think you're right. I read through the posts, but I didn't realize that there was a year gap. You might get better results if you started a new thread, or at least edit the first post with a line at the top stating that there's a new line of questioning. At least, that's what I have done in the past on other forums.

Thanks for taking my post in a non-hostile way. Again, I didn't mean to criticize, just offer alternatives. That said, I have definitely removed components in a destructive way. But since learning of ChipQuik, it has been my go-to method for SMD removal when great care is needed. I'm not a spokesperson for ChipQuik, I have no stake in the company or anything like that. I just think it's a really great product that is not so well known, so I like to share info about it whenever it's relevant.

Chip quik is great for removing ICs I agree, but how do you clean it off all the legs of a fine pitch QFP before reusing the chip? I've only used it to removed defective parts that I no longer care to use

maxtherabbit wrote on 2023-06-04, 15:19:

Chip quik is great for removing ICs I agree, but how do you clean it off all the legs of a fine pitch QFP before reusing the chip? I've only used it to removed defective parts that I no longer care to use

What I usually do is hold the chip between my thumb and index finger, then use a drag technique with the soldering iron along with gravity to pull all of the alloy down. So if it's a QFP, I'll do two sides then rotate it around and do the other two sides. I can usually get most of it to ball up and fall off from it's own weight. Or a gentle shake gets it off while it's still molting. And I'll even gather up the ChipQuik alloy that falls off, melt it back together, and reuse it! I've definitely reused a blob of the ChipQuik alloy a few times, although if it's a delicate or tight area I'll use fresh alloy since it's easier to apply from the spool as oppose to a blob.

Alternatively, and probably a more professional approach, would be to use desoldering wick / braid. The kind that has flux in it works best for this situation. Come to think of it, even if I use the iron tip and gravity to clean most of the alloy off, I'll still follow up with braid just to be sure I have removed as much as the alloy as possible. I guess I'm just cheap and I like to save materials 🤣. I still haven't finished the first package of ChipQuik that I've ever purchased. And I like to use as little braid as possible. No sense using only braid when you can get the bulk of the solder off by other means.

I'm not terribly interested in trying to freehand hold the QFP and shake it, the risk of dropping it or bumping into something and bending legs is too great. I was considering cutting 4 lengths of braid to sit under the legs, applying paste flux and then hitting it with hot air. I don't care about trying to reclaim the chip quick

For me, I guess it depends on the size of the chip and also the rarity of it. For a smaller QFP, it might be too hard to hold with two fingers. A large one though, no problem. I'm usually not so concerned with breaking legs if it's a brand new chip or if I'm the first one removing it from the factory. Used chips though, I've learned not to press my luck with. That said, the harder the chip is to replace the more care I tend to take with it. If I'm going to take a more careful approach to cleaning the legs with braid, I'll lay the chip down on a 4 or 6" ceramic tile. The smooth glossy kind. It's a nice flat surface that can take the heat from the iron without breaking (or sinking the heat). Then I'll come in with the braid on the iron tip and hit the legs up a few at a time (depends on the spacing). But I wont run the braid perpendicular to the pins because that's a good way to bend pins. Using a ceramic tile might not be an approved method, but it's something I came up with when I was younger and it's worked so well that I'll still use it.

Using the braid with hot air seems like it could work fine, and might be especially good if you're concerned about the strength of the pins. You would just want to remove the chip from the braids before removing the heat, otherwise you might have some of the braids stuck to the legs.