ISA Backplane

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MicroATX ISA Backplane - Version 1.1

This backplane supports bus width up to 16 bits. It has onboard POST code indicators as well as a -5V regulator allowing you to use it with modern power supplies.

Isa-backplane.jpg

Available For Sale

[For sale at my eBay store]

  • Bare PCB
  • Individual Components
  • Full Component Kit

Features

Required Tools

  • Soldering Iron,
  • Rosin core solder
  • Wire cutters
  • Pliers
  • Multimeter (optional: if you want to check for shorts)

Assembly Steps

Start with the shorter components first. This way you can lay the board down flat on the table and be able to solder them in. The taller components go next. The recommended order is as follows.

1. IC Sockets

component type reference Name Qty
socket U5, U6, U7 14 pin 300 mil DIP socket 3
socket U1, U2 16 pin 300 mil DIP socket 2
socket U3, U4 20 pin 300 mil DIP socket 2

2. Capacitors

component type reference Name Qty
PCB PCB 1
Capacitor C1 - C51 10 uF ceramic, 5.08 mm lead spacing 51
Capacitor C52 1 uF ceramic, 5.08 mm lead spacing 1
Capacitor C53 - C59 0.1 uF ceramic, 5.08 mm lead spacing 7

Polarity doesn't matter unless you are using electrolytic ones.

3. ISA Slots

component type reference Name Qty
Connector BUS1 - BUS8 Edge Connector 98 Pin 8

4 LED Lights

component type reference Name Qty
Diode D1 - D5 5 mm LED 5

5 ATX Power connector

Board connector as it would appear looking down on the board. The plastic tab will be on the left side towards the inside of the board.

This is the layout of atx power connector pins looking down on the board.

Note also the power connector pins will need to be bent slightly with pliers as the pin spacing on the PCB is a little wider than the power connector spacing.

component type reference Name Qty
Connector P3 ATX Connector 1

LED Display Configuration

The ISA Backplane board supports a variety of 7-segment decoders and common anode / common cathode type LED displays. Please use the following table to determine the proper jumper pin configuration for J2 J3 and J4

7-Segment Decoders and Matching Displays

7-Segment Decoder Type Hexadecimal Support Matching Display Type J2 J3 J4 Built in current limiters 1
74LS47, 74LS247 Limited - Displays distinct figures for codes A-F Common anode 2-3 2-3 2-3 No
74LS48, 74LS248 Limited - Displays distinct figures for codes A-F Common cathode 1-2 2-3 2-3 No
CD4511, MC14511, 74HCT4511 No - Displays nothing (blank) for codes A-F Common cathode 1-2 2-3 1-2 No
Mitel MD4311BE Yes Common cathode 1-2 2-3 1-2 No
DM9368 Yes Common cathode 1-2 1-2 2-3 Yes
DM9370 Yes Common anode 2-3 1-2 2-3 No
DM9374 Limited - Displays distinct figures for codes A-F Common anode 2-3 1-2 2-3 Yes
D345D Yes Common anode 2-3 1-2 2-3 No
D346D Yes Common anode 2-3 Trim2 2-3 Yes
D347D Limited - Displays distinct figures for codes A-F Common anode 2-3 1-2 2-3 No
D348D Limited - Displays distinct figures for codes A-F Common anode 2-3 Trim2 2-3 Yes
  1. No need for current limiting resistor arrays (RR1, RR2), two 470 Ohm resistors should be used to limit current for the decimal point segment.These resistors should be installed between pins 8 and 9 of RR1 and RR2.
  2. For decoders D346D and D348D the RV1 trimmer should be installed instead of the J3. This trimmer is used to adjust the intensity of the LED display.

POST Codes and what they mean

[Reference information available here]

Power On and Test

The goal is to identify any short circuits that would cause problems. Before powering on the device check to see if there are shorts across any of the rails of the PCB.

  1. Turn on the backplane and use a volt meter to check voltage across the PCB including the expansion slots.
  2. Plug in the ATX power connector and the PCB and the standby light should go on.
  3. Then click the power button and the power lights should go on.
  4. The -5V regulator is option and if your power supply does not provide -5V then you can solder that in as well. Once the regulator is installed the -5V light should go on as well.