I've been doing some maintenance on @mrbombermillzy's MegaST. This is the board he has been doing dual-shifter research with and wanted it to be given some love. Here is the work I've been doing to it.
This is a Mega ST4 with C100167-001 Rev B motherboard
- a02 motherboard overview.jpg (649.65 KiB) Viewed 1721 times
The Mega ST (please correct me if I'm wrong) has this little PCB which I think is called the 'blitter patch'. I haven't worked on a Mega ST before so I might be wrong, but either way that little board will need to come off. @mrbombermillzy wants the CPU to be socketed. It would be silly to have this blitter patch board soldered to the CPU, because if he removes the CPU to add an accelerator etc, then the blitter board would come off with the old CPU. So I'll have to work out a creative way to keep it attached to the motherboard.
- a03 blitter patch.jpg (303.72 KiB) Viewed 1721 times
Removal of blitter patch, will use the heat gun for this.
- a04 blitter patch removal.jpg (398.15 KiB) Viewed 1721 times
Always a good idea to add new solder to anything that needs to be removed on these old boards, this helps when using the solder removal tool and allows the old solder to be removed much more easily, protecting the pads and vias.
- a05 add new solder to cpu before removal.jpg (429.41 KiB) Viewed 1721 times
CPU socket is now removed
- a06 cpu removed.jpg (529.22 KiB) Viewed 1721 times
New CPU socket fitted
- a07 new socket fitted.jpg (488.28 KiB) Viewed 1721 times
I'm going to attempt to fit the blitter patch board INSIDE the CPU socket, here I am chipping away at the plastic between pins 12-18.
- a08 chip away to pin legs.jpg (436.71 KiB) Viewed 1721 times
Blitter patch before fitting
- a09 blitter patch before fitting.jpg (478.19 KiB) Viewed 1721 times
Blitter patch fitting nicely in the area
- a10 blitter patch fitting.jpg (468.49 KiB) Viewed 1721 times
Now I carefully add wires to the pins
- a11 wiring up blitter patch.jpg (457.91 KiB) Viewed 1721 times
Now the blitter patch is fully installed within the CPU socket
- a12 blitter patch installed.jpg (440.95 KiB) Viewed 1721 times
Here is another photo angle of it installed
- a13 blitter patch installed 2.jpg (558.63 KiB) Viewed 1721 times
I was kind of hoping that there would be enough clearance for the CPU to fit in with the blitter patch board underneath it. This didn't turn out to be the case, so I added another layer of turn pin socket headers to give the CPU enough clearance.
- a14 add height to cpu socket.jpg (499.78 KiB) Viewed 1721 times
CPU re-installed
- a15 cpu installed again.jpg (516.8 KiB) Viewed 1721 times
The dual-shifter board does not seem to sit level!
- a16 shifter board is not level.jpg (318.78 KiB) Viewed 1721 times
The shifter board seems to be hitting the DMA chip. The DMA chip is so high because it is socketed. I will remove the socket for the DMA and solder it directly into the motherboard to give the shifter board enough clearance.
- a17 shiter board hitting DMA.jpg (332.45 KiB) Viewed 1721 times
Here is the underside of the shifter board, it is using turn-pin PCB pins, so I will change the motherboard socket to turn-pin in order to give the shifter board a much more stable connection.
- a18 underside of shifter board.jpg (440.83 KiB) Viewed 1721 times
DMA removed
- a19 dma removed, overview.jpg (579.89 KiB) Viewed 1721 times
Argh!!! My solder sucker keeps getting clogged up on the REAR side, how frustrating!!
- a20 argh why does my solder sucker do this.jpg (200.99 KiB) Viewed 1721 times
