Replacing RAM sockets

[mazdaboi]

Anyone ever replaced one of the RAM SIMM sockets on an A4000 motherboard? On my A4000 there are two of them that have broken locking tabs. One of them has one side intact, so the RAM stays in pretty well. The other one (the outermost SIMM socket) has both tabs broke off and has been that way since I got it.

Right now I have a kludge in place involving a long screw and a piece of a CD jewel case wedged under my Video Toaster 4000 card. lol. It works, but isnt pretty.

I am familiar with soldering and desoldering, but was wondering if the traces and pads involved with the SIMM sockets are at all more delicate than average pads/traces... Are the pads through-plated?

[Castellen]

Before you begin the job, get hold of BRAND NEW replacement sockets.  Not just check they're available, but physically get them first!
Preferably get the decent ones with metal retaining clips.
Measure them to check they'll fit, and the pin placement and footprint is the same as the old ones.

All the pads are through hole plated.  There are lots of internal tracks connected to the pads, so it's essential not to damage any.

2 ways to remove a SIMM socket:

1. Get a decent vacuum assisted desoldering gun, like a Hakko 808 with a NEW 1mm tip to remove the solder from each joint.
Make sure each pin is totally free before removing the whole socket.
Unless you know how to use the desoldering tool correctly, you risk causing pad damage, so be very careful.

2. Apply a little fresh solder to each of the socket pins.  Using a conventional soldering iron, heat each pin one at a time, and as you do so, use needlenose pliers to gently pull the corresponding socket contact vertically upwards.
It's time consuming, but doesn't require special tools, and there's less risk of pad damage.

[Schoenfeld]

There's no need to replace the outermost socket. Just use an 8MB Simm in the third socket, this will give you the same memory as two 4MB Simms in third and fourth socket. Same wth first and second socket: Either two 4MB Simms there, or one 8MB Simm in the first socket, leaving the second empty.

Another clean way of de-soldering the socket (if you really want to do that) is a wave solder machine. Try to find a company that has one, spray a little flux on the bottom of the motherboard, and remove the socket over the wave solder. After that, empty the holes with a vacuum pump or solder wick (regulated iron needed, 4-layer boards can sink a lot of heat!), and put the new socket in.

Personally, I'd go for an 8MB Simm. If you can't get hold of one locally, try memoryworld.com - they have all kinds of legacy memory modules in stock, and they even have an Amiga specialist on the phone (at least an Amiga memory specialist).

Jens Schoenfeld

[Castellen]

Hi Jens, an honour to talk to you.
You've done some really impressive hardware and software over the years, keep up the excellent work!!


Regarding the SIMM sockets, I was going to suggest something similar, but apparently there are two broken sockets....
The wave soldering idea is neat, haven't tried that before.  I have access to a machine at work, but I doubt they'd appreciate me sticking computer motherboards through it. :-)
Might have to stick to my traditional methods.

Plus I don't think that many people would have a wave soldering machine handy. :-P

Of course another option would be to get somthing like a Cyberstorm mkII so you no longer need to use motherboard memory.

[redrumloa]

Hey Jens that's some great advise!! I was planning on replacing all 5 simm sockets on my A4K, now I only need to do 3:-)