Constructing the new 1130 MRAM board, part 2

SOLDERING THE INTEGRATED CIRCUITS ONTO THE BOARD

The four remaining chips, two tristate buffers, the MRAM memory device and a quad NAND gate, were soldered down first.  These were also installed using solder paste, a metal stencil and my hot air gun. 

Based on a suggestion by one of my regular blog readers, I have ordered a hot plate to work atop while using the hot air gun and solder paste (for future soldering work). I tend to put on paste one chip at a time, then flow the solder paste, which I thought would be slowed by having the entire board heated. I will need to adjust my workflow for soldering to add in the hot plate. However, for chip removal it will always be better than starting with a cold board and directing the hot air gun to loosen each part. 

OTHER PARTS ADDED TO THE BOARD

Next up were 18 surface mount transistors plus 18 pullup resistors. These were all hand soldered with a traditional soldering tool. Once all the active parts were in place, I moved over all the gold pins that form the three connectors for the IBM Solid Logic Technology (SLT) cables. Each connector has 24 pins in two rows of 12. 

I had to extract all 72 pins from the prior board and clean them up, before I could install them in the new PCB. I used a connector I stripped out of an independent vendor's add-on product that would connect to 1130 or 360 systems. This served as a guide for all the pins, to keep them aligned until I soldered them in place, so that the IBM cable connector will slide smoothly onto the pins. 

The last item to add will be the FPGA board which plugs in with the USB connector at the outside left edge of the finished assembly. I had previously programmed the Digilent CMOD S7 board with the control logic to drive my design. 

I called it a day before finishing, not having added the third connector, but everything else is assembled on the board and ready for inspection and then testing. 

All chips, transistors, resistors and capacitors are installed

24 pins to be removed - one SLT connector - from old board

Pins from three connectors removed and ready for new board

Similar connector to the SLT 2 x 12 cables

The spare connector positioned in place as guide

Pins will be inserted through board into guide connector

Completed installation of 24 pins into one connector

FPGA board sitting in place on board