Microelectronics | Z80 Microcomputer Power Supply

Synopsis

You might be looking for the Romanian Version (Versiunea in Limba Romana).

The power supply of the Z80 microcomputer that I have built back in 2009 had some design and execution problems. Thus I have decided to revise it. With this occasion I have moved it to a separate project. Thus from the existing problems I can recall:

  • using of a non-standard delayed power relay -- which became defective, being over 30 years old
  • too thin tracks for +5 V and +12 V power rails
  • too thin pads for the leads of the rectifier bridges

I have corrected the respective errors and I have added an LED to signal the presence of the delayed main board power supply. I have also reconfigured the printed circuit tracks and increased their width where appropriate. As before, the power supply is capable of delivering the following voltages:

  • +12.0 V / 1.5 A (max) -- instantaneous power for the hard disk drive
  • +5.0 V / 1.5 A (max) -- instantaneous power for the hard disk drive
  • +5.0 V / 1.0 A (max) -- delayed power for the main board

As regulators for the voltages required by the hard disk drive, I have used linear integrated circuits as follows: MA7812 produced by Tesla for the +12 V rail and M323 produced by IPRS for the +5 V rail.

For the power supply to be able to deliver the voltages and amperages mentioned above, I need a power transformer with the following specifications.

  • Primary: 230 Vac
  • Secondary #1: 13 Vac / 3 A
  • Secondary #2: 7.5 Vac / 3 A

Regarding the construction of the power transformer, I have chosen a toroidal type. From the specifications above, one can observe that the transformer is overrated for this application. But what I am aiming is that the power supply will run as cold as it could.

I will use this power supply for the Zeta2 Microcomputer designed by Sergey Kiselev, that I assembled some time ago.

Schematics

Next up comes the revised electrical schematic of the Z80 microcomputer power supply (click on the schematic to enlarge the image).

Fig. 1: Electrical schematic of the Z80 microcomputer power supply

Fig. 2: Printed circuit tracks for the Z80 microcomputer power supply -- TOP layer.

Fig. 3: Printed circuit tracks for the Z80 microcomputer power supply -- BOTTOM layer.

Fig. 4: Simulation of the printed circuit board for the Z80 microcomputer power supply -- TOP layer.

Fig. 5: Simulation of the printed circuit board for the Z80 microcomputer power supply -- BOTTOM layer.

Printed Circuit Boards (PDF)

In case you want to build this power supply, here is the printed circuit scaled 1:1, in PDF format. All files contain mirror printed circuit tracks.

Click on the desired filename to download it.

Pictures

In this section you will find pictures of the project.

Printed circuit board for the power supply -- TOP layer.

Printed circuit board for the power supply -- BOTTOM layer.

VER. 1.2 REV. B versus VER. 1.3 REV. E. -- component layer.

VER. 1.2 REV. B versus VER. 1.3 REV. E. -- tracks layer.

Completed power supply.

Tracks and soldering layer.

Detail of the Vishay filter capacitors.

Detail of the relay delayed power and power voltage regulators connectors.

The completed power supply has hexagonal spacers fixed in M3 screws.

Detail.

Burn-in testing with a 40 Mb IDE hard disk.

I have finally installed the heatsink with the power voltage regulators.

M323 (LM323) and MA7805 (LM7805K).

Seen from another angle.

Together with the Zeta2 Z80 microcomputer.

The power transformer.

All sub-assemblies of the microcomputer.

Thank you for your interest in this site.


Copyright © 2004- Alexandru Groza
All rights reserved.
VER. 1.0 | REV. A