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Maximum Memory Supported by 80386 Motherboard

For large ground planes, you gotta preheat the board. In a pinch you can use a hot air gun, but a temperature controlled hot air station is much preferred to not turn it into a charcoal briquette.

Double ironing is another trick to get extra heat into stubborn pins, along with some low melt solder to dilute the old stuff.

If you're done asking nicely, you can use a Hakko 551 lol. That thing gets so hot it glows red in the dark.
 
Sure, but it will get just about anything dismounted. :)

If you're desperate, try working with a fusible alloy (e.g. Cerrobend) to lower the melting point of the solder. Lower heat won't damage components. Also sold as Chip-Quik.

I find that clearing solder vias works really well with hollow stainless needles. Doesn't damage the via.
 
wrljet said:
@GiGaBiTe I'm not recommending it either. But there was no way *I* was going to manage to unsolder those things without wrecking the board.
Each socket is a dual, 60 pins, 8 of which go to a power or ground plane.

I was never able to fully clear the solder properly from some of those ground holes, and wound up using a *tiny* drill just large enough for the pin to fit.
No amount of flux, Hakko vacuum, solder wick, etc. worked for me.

Vibration wasn't bad, and didn't hurt anything. For me, it was either this way or the board was simply going in the trash.
Click to expand...
I have a logic board that I am going to practice removing 30 pin SIMM sockets as I think this would be a useful skill to have. I plan to use a Hakko to remove the bulk of the solder and then use hot air to remove the socket. This has worked well for removing 40 pin DIP chips so I don't see why it wouldn't work well for 30 (60) pin SIMM sockets.
 
Yeah, I don't think removing 30-pin SIMM sockets (60 pins since they are sistered) is something I'll be doing again any time soon. If ever.

I managed to accomplish what I wanted, w/o wrecking the motherboard.

So I'm happy.

In general, despite (or perhaps because of) having been doing this stuff for more than 50 years, I'm nervous about cooking stuff on PCBs.

I've seen many cheap boards (8080/Z80 era) with lifted traces. And I remember when we were scolded to use little aluminum heatsink clamps on the leads when soldering transistors.
 
Chuck(G) said:
If you're desperate, try working with a fusible alloy (e.g. Cerrobend) to lower the melting point of the solder. Lower heat won't damage components. Also sold as Chip-Quik.
Click to expand...

Cerrobend and Chip-Quik aren't the same. Cerrobend has cadmium in it, while CQ doesn't, it uses bismuth and some other things.
 
I didn't say that they were the same. The point is that a fusible alloy will do the job--and Chip Quik is one of those. I just happen to have a pile of the 158 alloy, since I often work with thinwall brass tubing. Apparently, it's not called Cerrobend anymore. I suspect that Chip Quik is one of the CS Alloy wire stock, with a hefty price jump attached.

 
I have used the technique of using a heavy copper wire (like solid 14 ga) and plenty of flux and solder, and a heavy iron tip, to successfully remove parts like DB-25 connectors from boards like the Xerox 820.

I didn't think to use that on the 60 pins worth of dual SIMM sockets on the 386 motherboard,
 
I just received another board, a 386SX, with some Varta damage, and it's got cheesy SIMM sockets, too, with some physical damage.
 
My Olivetti M380XP9 can support up to 56 MB of RAM. That is a 80486DX-33 machine. But it's not actually completely onboard... The mainboard only supports up to 8 MB, and the rest is added by up to four special 32 bit wide ISA memory cards. Unfortunatelly I don't have such cards so my machine has only 8 MB on 8x 1MB SIMM modules. (4MB modules not supported)
 
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