JRR
Member
If you have the Orange Atari video game test fixture one thing you MUST watch out for are broken wires to the 22-pin card edge connector. Broken wires on the ground circuits can lead to problems with stray voltages introduced to switches, etc. where normally they would be grounded via the UUT PCB edge connector.
This is a BAD design - they did not interconnect the commons in the A/B/C plugs, rather the Atari engineers trusted the edge connector to do the job.
I found this out the hard way, blew some gates on an old board where the Test switch common was tied to pin 22 along with the center-tap of the 25VAC (Variac voltage setting) and should have been tied to the game board common. However the switch wire to pin 22 was broken inside the heat-shrink sleeve and left the test switch connected to the center tap of the transformer.
Turning on the test switch then blew the 74LS244 TTL gate...
I am considering two solutions:
1) make a simple test card and plug so each pin of the 22-pin connector goes to an LED and test the fixture regularly! Good plan in any case, may make it more sophisticated so it tests all the switches, voltages, etc. - with 44 pins one can self-test lots of things in the CTS-1 fixture...
2) jumper the pins that go to joined lines at the 22-pin connector via the PCB so even if a wire breaks then bad voltages will not be introduced to the board...however I have forty some test harnesses and I don't want to repair all of them. I will probably go with option one for now and gradually rewire the plugs when I have work-experience students who can do the job.
John :-#)#
flippers.com
This is a BAD design - they did not interconnect the commons in the A/B/C plugs, rather the Atari engineers trusted the edge connector to do the job.
I found this out the hard way, blew some gates on an old board where the Test switch common was tied to pin 22 along with the center-tap of the 25VAC (Variac voltage setting) and should have been tied to the game board common. However the switch wire to pin 22 was broken inside the heat-shrink sleeve and left the test switch connected to the center tap of the transformer.
Turning on the test switch then blew the 74LS244 TTL gate...
I am considering two solutions:
1) make a simple test card and plug so each pin of the 22-pin connector goes to an LED and test the fixture regularly! Good plan in any case, may make it more sophisticated so it tests all the switches, voltages, etc. - with 44 pins one can self-test lots of things in the CTS-1 fixture...
2) jumper the pins that go to joined lines at the 22-pin connector via the PCB so even if a wire breaks then bad voltages will not be introduced to the board...however I have forty some test harnesses and I don't want to repair all of them. I will probably go with option one for now and gradually rewire the plugs when I have work-experience students who can do the job.
John :-#)#
flippers.com
