The DNS 80A and 80B tracks have varying main computers depending on the serial number and configuration of the track. This article discusses the power supply for a FC-9821Ka computer, which is not the same as the FC-9821Ke. Before following the diagnostic procedure below, ensure that the computer you are inspecting is the Ka.
Front view of DNS 80 FC9821Ka main computer
Rear view of DNS 80 FC9821Ka main computer
View of an FC-9821Ke installed in the DNS 80B (very similar appearance to FC-9821Ka)
View of an FC-9821Ke installed in the DNS 80B (very similar appearance to FC-9821Ka)
The power supply is mounted on the inside of the back wall of the computer box. Molex cables drop down to the motherboard and attach to five connectors to power the majority of the computer (a separate cable goes to the hard drive). Below is a photograph of these connections viewed from the side. An illustrated representation of these connections has also been provided (drawn from the perspective of facing forward from the rear of the computer and looking top-down onto the motherboard).
Image of power supply connections to DNS 80A/B FC2981Ka motherboard
Top-down view illustrated representation of power supply connections to DNS 80A/B FC9821Ka motherboard
The black wires are all connected to GND. Relative to GND the DC levels on the other wires are as follows (assume pin 1 is the leftmost for each connector in above illustration):
DC1:
1) EMPTY
2) RED — +5V Vcc 3) ORANGE — +12V 4) BLUE — -12V (note this is a negative supply) 5) 6) BLACK — GNDDC2:
1) 2) BLACK — GND
3) EMPTY
4) 5) 6) RED — +5V Vcc
DC3:
1) 2) 3) GREEN — +5V Vdd
4) 5) 6) BLACK — GND
DC9:
1) WHITE — +2.015V
2) 3) RED — +5V Vcc
DC10:
1) 2) 3) WHITE — these are actually unused. Note that these wires lead to an interconnect which does not involve these conductors (in other words, they are floating).
4) BLACK — GND
5) 6) RED — +5.082V *NOT Vcc – these are an isolated 5V supply*
7) WHITE — +5.049V
If your DNS 80 track is completely inoperable/dead, you may have a bad computer. And it may be as simple as a dead supply. Or the computer may need to be replaced (i.e. bad motherboard). Check the DC voltages out of the supply. If you don’t get these numbers, the supply is the culprit. If you do get these numbers, the motherboard is likely bad. In either case, contact www.GetSpares.com to seek repair or replacement.