Final Assembly and Checkout

From Spare Time Gizmos' Wiki

Revision as of 18:31, 22 April 2011

Begin the final assembly and testing of your SBC6120-RC with these steps.

• If you are installing a VT6 module, remove the front panel, install the VT6 with its spacers on the circuit board, and replace the front panel.

• Insert the PROMs into their sockets.

□ - U6, 27C256 PROM “high”
□ - U7, 27C256 PROM “low”

• Insert the GALs in their sockets.

□ - U4, ATF22V10CQZ, “MEM1”
□ - U31, ATF22V10CQZ, “MEM2”
□ - U13, ATF22V10CQZ, “IOT1”
□ - U14, ATF22V10CQZ, “IOT2”

• Install the HD6120 CPU IC at U1. Be careful and make sure that all pins go into the socket properly.

• Take a jumper block and place it over the pair of pins in the BAUD box to select the desired baud rate. 9600 baud is a good place to start.

• Install the BR2325 Li coin-cell in the holder labeled 'B1'. The positive terminal should be UP.

• Measure the voltage across R3 using a high-impedance voltmeter. This is used to measure the stand-by current for the SRAM. It should be around 0.1VDC.

• Measure the resistance across D1 with the positive lead of the ohmmeter at the banded end. Resistance should be 1K or more.
• Attach the console jack to a dumb terminal or to a PC's serial port using a straight-through RS-232 cable. If you are using a PC use a terminal program such as hyperterminal. Set the terminal program to 9600 baud, 8 data bits, one stop bit, no parity. The baud rate setting of your terminal program should match the baud rate setting of the BAUD jumper block.

• Set the front panel register display rotary switch to the POST position. This causes the system to display the power-on self-test (POST) codes in the leftmost three LEDs of the register display. This will be useful should there be a problem discovered during start up.

• Apply power to the SBC6120-RC2 using a current-limited power supply set to provide no more than 500mA.

• Verify that current drain is in the range of 200 mA to 350 mA. (Current varies depending on how many LEDs are illuminated.)

• The terminal should display the monitor start-up message. If it does, congratulations! Your SBC6120-RC2 is now operational! Have fun using the PDP-8, the very first personal computer.

• If the terminal does not display the monitor start-up message, check the POST LEDs for the POST code. They will provide a general indication of where the problem might lie.

Congratulations! Your SBC6120-RC is now assembled and working. You'll probably want to read Using the Front Panel next.