Modification to SBC6120 sorted out, additional cable signals to 1130 Extender box wired up

MODIFIED HD6402 UART CHIP WITH SWITCHED CONNECTION

The Universal Asynchronous Receiver Transmitter (UART) chip has a number of pins that are used to configure the serial protocol as to the number of data bits, parity and stop bit length. The SBC6120 PCB ties these to VCC or ground as appropriate to select the default of 1-8-N with a single stop bit. 

The change was made by bending up two pins, to disconnect them from the PCB traces. They were wired to a DPDT switch which provides VCC and ground to the pins, alternately. That is, in one position, the first pin is hooked to VCC and the second connects to ground. The other position of the switch ties ground to the first pin and VCC to the second. 

PURPOSE OF THE TWO SWITCH POSITIONS

Based on the pins selected, this switch toggles between two configurations - 1-7-E-1 and 1-8-N-2. These were reasonable values for connection to the ASR-33 teletype I brought to VCF-W that year. As I no longer own a teletype, this is not needed and should be removed. 

REMOVAL OF THE MODIFICATION

I disconnected the wires that had been tacked to the lifted chip pins, then installed jumpers down to the PCB to restore the original functionality. The switch was then discarded.

REPAIR OF 160 PIN CONNECTOR MUST WAIT FOR EXTRACTOR TOOL

The two wires that came loose were at the top two positions, connector sockets A1 and A2, which are routed to FPGA connector pins D5 and D3. I made a try at soldering the wire to the end of the crimp connector as it sat in the connector housing, but it wasn't feasible to accomplish.

Left two openings are sockets A1 and A2

I therefore have to remove the two sockets that came loose, crimp the wires to new sockets, then re-insert. Because of the spring loaded tines that hold a socket in place, a special tool is needed that releases the tines and pushes the socket out of the holder. I purchased that tool plus some spare sockets but have to wait a few days to receive it before I can continue.

ADDITIONAL SIGNALS CABLE WIRED INTO THE 1130 EXTENDER BOX

I constructed an additional cable to sense and drive interrupt levels 0 and 1, for a fully generalized input-output control of the 1130 system. In addition, it carries a signal that triggers the three button press sequence for booting an 1130:

• IMM STOP
• RESET
• PROG LOAD

I brought the five wires from those signals to the screw terminals for the FPGA connector pin associated with each, as well as bonding the grounds together and hooking them to the PCB of the extender box. 

FINAL ASSEMBLY OF POWER SUPPLY INTO CASE

The power supply is installed and wired up, feeding the PCB and the Power Good lamp on the case. The extra wires out of the power supply were clipped off and covered with heat shrink tubing. At this point, once the two sockets are replaced on the 160 pin connector, I only need to drill some air vents for cool air intake and hot air exhaust before closing up the box.