exxos's Atari, Amiga & retro forum

Afternoon all.

As documented elsewhere, I picked up an STFM motherboard for testing DSTB1 & likely other projects.

It's not in great nick -- more on that anon -- but for starters I needed a socketed 68k slot. After a bit of inspection, I decided the snips had to come out. Here's how I did it:-



BW

Very interesting to see how one can do it. I myself failed miserable in removing 68k cpu :P Without any bigger knowledge i tried to remove the solder with a soldergun and it went as expected :|

/zChris

It depends upon your desoldering gun and technique.

I removed mine with my Hakko quickly and without any difficulty. The CPU just dropped out.

Interesting! Did you do any special prework to make it suck ALL the solder?

Generally just add new solder (making sure that all the old solder has fully melted), flux,and leave the gun on the joint for a few seconds (and rotate the bit on the pin until it moves freely) before pulling the trigger to suck, and continue to such and rotate for a few seconds before removing the bit and finally taking the finger off the trigger (after removing it fro the surface).

Also, if a pin is being difficult, more flux and resolder before trying again, holding the tip on the job a bit longer and sucking for more time and wiggling the pin more. :-)

If this doesn't do it then you need a hot air station to heat the legs on the component side until the solder melts and lift *gently* with an electrical screwdriver until it starts to move, then lift.

Alright, how hot do you use? My soldering gun is on 400 degrees, maybe thats too hot.

Usually I use about 350C, but you need to keep the gun moving continuously so as not to overheat any one part of the board.

If I ever where to remove a 68k again I'd probably go that route too :)

When I socketed mine I didn't want to destroy the CPU so I bought myself a desoldering station believing it would make everything super easy..
In hindsight I probably should have practiced on something else first.. it ended up a success in the end but it was quite a hassle to get there, most likely due to my poor technique :)

@agranlund you mention a desolder station I found a desolder gun helped to removed the main pins solder but it was not so good at the GND and VCC pins. Thats where I used @stephen_usher's method of heat gun on those pins. Overall the CPU comes out nicely and unscathed.

zChris wrote: 27 May 2022 06:50 Very interesting to see how one can do it. I myself failed miserable in removing 68k cpu :P Without any bigger knowledge i tried to remove the solder with a soldergun and it went as expected :|

I know the dilemma. I really wanted to preserve the chip, but I caramelised my first revision of DSTB1 trying to desolder just one 32 pin header strip.

Know one's limitations, I figured! :lol:

BW