Amiga power supply guide V1.12
Added information on the power ratings of stock power supplies
Added more information on ATX power supplies, relating to minimum loads and +12V balance
What to look for when purchasing a picoPSU and spotting fakes.
This document details how to diagnose and replace a faulty power supply on the Amiga range of computers.
Options for replacement using either an ATX PSU or smaller, compatible switchmode supplies are presented for the reader.
Original Amiga power supply ratings
Measured power consumption figures
ATX power supplies
Spotting fake picoPSUs
'Brick' power supply alternates
Amiga ATX PSU adaptors
ATX colour code
Re-wiring the original power lead
CD32 power supply mod
CDTV power adaptor
Wiring diagram for A1500/A2000
Wiring diagram for A3000/A3000D
Wiring diagram for A4000/A4000T
Original Amiga power supply ratings
This information has been collated from original power supply labels, schematics
or emails from fellow users. The information is presented here to help you
evaluate alternative supplies.
Amiga A500, A600 & A1200
+5V @ 20.50A
+12V @ 8.00A
-5V @ 0.30A
-12V @ 0.30A
Note: This system requires a 'tick' circuit which provides a 50/60Hz +/-10% reference signal to the video chipset or motherboard jumper J300.
Would require a simple linear regulator circuit using a 7905 or equivalent, to generate -5V
+5V @ 17.25A
+12V @ 3.00A
-5V @ 0.2A
-12V @ 0.3A
Note: This system requires a 'tick' circuit which provides a 50/60Hz +/-10% reference signal to the video chipset. Changing motherboard jumper connect across pins 2-3 to ensure that the machine generates the TICK signal from the VSYNC signal.
Would require a simple linear regulator circuit using a 7905, to generate -5V
Information taken from A4000 PSU schematics
Information taken from A4000T specifications
Measured Amiga power consumption
The following measurements have been made on Amiga systems
The most commonly available, high power supply is the ATX power supply. There are two distinct variants, the original rectangular box type and the picoPSU type:
Original ATX power supply, widely available
This type of supply is best suited to towered or big box Amigas. The +5V line can supply 15A or more and the +12V line will be of similar capacity.
picoPSU originally from Mini-box.com, available from multiple suppliers
The picoPSU uses an external mains to 12V power adaptor. The +12V is switched through and the +5V, +3V3 and -12V, as provided by the original, larger ATX power
Both supplies require the PS-ON signal (green wire) to be grounded to switch on the power supply. This can be achieved by wiring between the two signals or using an adaptor board, sold on this website.
This is a popular power supply for the 'wedge' Amigas as it is small enough to fit inside the Amiga and is silent.
picoPSU power ratings
The picoPSU is available in six power ratings, the specifications are below:
Spotting fake picoPSU adaptors
In response to comments from fellow Amiga users, I have provided some information on spotting fake picoPSU supplies. First lets take a look at a couple of genuine parts.
The genuine 80W converter
The genuine 90W converter
What to look for in a genuine picoPSU
Take a look at the following fakes, found on ebay
This fake pico PSU does not have the coloured connector or inductors and uses cheaper electrolytic silver can capacitors.
This one also does not have the yellow connector or inductors. The design uses Tantalum capacitors(yellow colour)
instead of the lower ESR black OSCCON, this variant will have more ripple on the output supplies.
Another 'PICO-BOX' supply
See the comments for Fake #1
This has a yellow power connector, like the original but does not have the coloured inductors. Again this has the cheap,
high ESR Tantalum capacitors, they increase the ripple and noise on the supply outputs.
It is worth noting that modern, high current ATX power supplies, have minimum load requirements. If you do not
provide the minimum load on each power rail, the voltage outputs may be outside of the specification. Trying to locate
actual minimum loading data was not easy, what the author did manage to locate is below.
Corsair, Evga and XFX did not provide minimum loads in their documentation.
A good ATX PSU test guidehttp://www.antec.com/pdf/article/info_DIYArticle1.html
+12V 'bias' of modern ATX power supplies and the Amiga
Reading various Amiga forums, the author has seen a number of comments that modern ATX power supplies, with the bulk of their power, coming from the +12V supply being
less suited to the Amiga. This is not quite true. To meet the increasing power requirements of high end graphics cards in the PC and avoid changing the wire gauges, the modern PC PSU provides higher currents on the +12V lines but they can still supply more than enough for the Amiga on the +5V rail.
The following came from the Antec NeoPower 550W supply
Perhaps you would like a smaller alternative to an ATX power supply, well there are a number of alternatives.
Fellow Amiga user, Chris Edwards emailed me to say that he has succesfully used a Meanwell P50A13D-R1B
power supply. It has the following specifications:
+5V @ 4A
+12V @ 2A
-12V @ 0.2A
The original Amiga power lead is required and the DIN plug of the new, Meanwell, supply needs to be cut off.
It is available direct from Meanwell and from Mouser.
Have not tried this but it does work
+5V @ 4A
+12V @ 2A
-12V @ 0.5A
Sold by Mouser, www.mouser.co.uk/ProductDetail/Mean-Well/RPT-60B/?qs=V9a8iPeg90y32GHaWpmkvA%3d%3d
Check local suppliers.
With the exception of the A500/A600/A1200 with their specific square DIN plugs you can still purchase
power connectors for the other Amigas. In this section the relevant part numbers and more importantly suppliers,
RS Components http://rswww.com
Rapid Electronics http://www.rapidelectronics.co.uk
The ATX connectors are from the Molex Mini-Fit Jr. range.
If you are making a wired lead (with no PCB) to adapt an ATX PSU to an Amiga, you will require this connector.
20 way dual row panel mount plug RS 418-0150
Molex part number 3901-2201
You will also require the crimp contact, RS 324-8003 or Rapid 22-3850
These are expensive (£11 for 100)!
If you are connecting into a PCB or wish to (carefully) solder onto the tabs, the part is:
20 way dual row vertical header RS 172-8923
the authorhave personally bought and used all these connector types successfully.
Amiga A500/A600/A1200 connectors
The user 'mech' at Eniglish Amiga Board (EAB) has connectors in stock, http://eab.abime.net/showpost.php?p=989238&postcount=10
Alternatively you can chop the lead of your old PSU and wire it up to your new PSU using the guide detailed here
Amiga A2000 connectors
Amiga A3000 connectors
AMP part. 172171-1 (Plug), and 170366-1 (Terminals)
Amiga A4000 Mate-N-Lok connectors
The A4000 power supplyÂ connectors are from the Amp Mate-N-Lok range.
To make up a new power supply lead you will require:
6-way Mate-N-Lok housingRS 848-874/ Rapid 22-4608
AMP part number is 1-480704
Mate-N-Lok pin 14-20 AWG RS 849-085/Rapid 22-4672
AMP part number is 926894-1
Note: you have to buy the Mate-N-Lok connectors in packs of 100 pieces.
You will require the above items to make a new power connector for your A4000 desktop motherboard.
If you want to fit a new motherboard connector you will require this part:
Mate-N-Lok 6 pin PCB RS 129-5221/ Rapid 22-4644
AMP part number is 350711-1
ATX to AT power adaptor
the authorfound this whilst hunting through the RS catalogue, an ATX to AT adaptor, perfect for the A4000T and
some bridgeboards, RS part number 214-739 and at £4.13 cheap too. It converts the ATX power lead to
the P8/P9 leads required by your system.
Re-wiring the original power lead for the A500, A600 and A1200
Required tools & parts
A pair of wire cutters,
A pair of pliers,
A small flat blade screwdriver,
A terminal block connector,
Optional, a Soldering Iron + solder
You will have to cut the lead off your Amiga PSU. This is easily done with a pair of cutters. Strip the ends of the wires
As Commodore never used a standard wiring scheme for their PSU's you need to ascertain which PSU pin connects to
This picture of the power plug should help.
For reference, this is how the author wired up my Amiga PSU. I used a blue wire to connect the -12V from the Motherboard connector
to the Amiga PSU cable
If you own a CD32, you can easily make a power lead up. All you need is a 4 pin DIN plug and to wire it up as shown here
and for ease of use use a PC 'Y' cable to connect it.
For reference, here is the pinout of the CD32 when looking at the connector:
CDTV power adaptor
The easiest solution for the CDTV is to purchase a CDTV power adaptor and use a picoPSU power supply, as shown here
To utilise the existing CDTV remote on/off switch requires an adaptor circuit to invert the polarity of the PSU-ON signal, which
the CDTV adaptor provides.
Wiring details for A1500/A2000
The main issue issue you will encounter with the A2000 is connecting to the Motherboard. You can either cut off your original power lead and re-use the existing lead or buy a new one. A new connector is an Molex 2139 (KK) 3.96 MM 14 way connector.
In addition you need to change jumper J300 to cover pins 2-3, so that the TICK signal is provided internally by the VSYNC signal.
NOTE: Originally the information I had suggested J200 should be connected across pins 2-3, this was incorrect, as J200 control the light pen input. The information above has been corrected to U300, which does in fact select the clock source for the TICK input.
An alternative method to generate the Tick signal is by using this circuit on Aminet: Tickit.lha, be warned this circuit connects directly to
the 220V AC mains, do not build unless you are competent in working with the AC mains, if in doubt do not build it.
After some research the authorfound that the +5V_USER supply can be safely connected to the normal +5V supply as it is only used to provide
+5V to the mouse and joystick ports.
Control the PS-ON (ATX pin 14) either by using my circuit shown above or by connecting it to ground via a switch, which ever is easier for you.
Here is the wiring list from an ATX plug to your A2000
The first choice you will face when adding a new PSU is how to connect it to the Motherboard, you can either chop off the original lead or
buy a new connector. The A3000 desktop PSU uses a an AMP #172171-1 connector with size TBD inserts.
Similar to the A2000, the +5V_USER/+5V_VID supply can be connected to the system +5V wiring.
To ensure that the A3000 works, connect jumper J350 across pins 2-3 to ensure that the machine generates the TICK
signal from the VSYNC signal.
Control the PS-ON (ATX pin 14) either by using my circuit shown above or by connecting it to ground via a switch,
which ever is easier for you.
The A3000T takes a power FAIL signal from the original PSU which indicates when the power rails are operating out of tolerance,
when connecting to an ATX PSU you must connect this wire to the PWR_OK (pin 8) of the ATX PSU or your A3000T
will not power up.
Wiring list to connect an ATX PSU to an A3000D
Wiring details for A4000/A4000T
The A4000 desktop machine is not too difficult to wire a new PSU upto, it only has 6 wires.
Importantly, the A4000 requires the ATX PWR_OK signal to function, if you do not connect this, it will not work.
Note: PWR_GOOD=PWR_OK. A logic 1 level indicates that the PSU is operating normally.
This is the wiring list:
What voltages should the +5V, +12V, -12V rails be at?
±5% of the nominal line voltage, or in plain english:
What is the -12V supply on the Amiga used for?
It is used for the RS232 transceiver chips and to power the Op-Amps in the audio circuits.
What is the shield wire for?
In the original Amiga PSU, it is used to reduce the radiated emissions of the power lead. Inside the Amiga, the shield
Â pin is connected to the Amiga system ground and back at the original PSU. When you re-wire the lead as shown in
Â this guide, you will have maybe a 1 metre length of unshielded cable going from the PSU to you Amiga lead. This will
Â radiate noise. Connecting the shield will make no difference to the radiated or picked up noise.
What is crowbar protection?
To reduce the risk of you totally screwing your system!
If you short a power rail to ground, circuitry inside the PSU will operate to reduce the outputs to a safe level
(typically less than 1 volt) until power is removed. The idea is to reduce the chance of blowing up a PCB when
you short circuit something (lower voltage, lower current). DO NOT RELY ON THIS SAVING YOUR SYSTEM
IT IS NOT 100%.
How much current can the peripheral connector (HDD/CDROM power cable) take?
I checked one of my adapter leads and it uses 18AWG wire. Referring to the Electronic Engineers handbook
Â for this cable type and derating, I found that it was rated at up to 8Amperes per wire!
More than enough to power your Amiga mainboard.
How much current can the Floppy drive connector of the Amiga FDD supply?
As best I can measure it, the tracking here is approximately 50 thou (1.27 mm). Assuming Â½Oz copper, Mil Standard 275
rates this at 1.5 Amperes. It should only be used to power the floppy drive, not a PPC accelerator.
What is the best way to power my PPC accelerator?
Use another Peripheral connector (HDD/CDROM power cable) and adapt the plugs.
This article was created with reference to the following sources:
Commodore Amiga A500/A600/A1200/A3000 & CD32 schematics from my personal collection.
Big Book of Amiga hardware, http://www.amiga-hardware.com
The Hardware book, http://www.hardwarebook.net
The A3000 technical guide by Calum, Tsang, http://peach.mie.utoronto.ca/people/tsangc/amiga-index.html
Building an A3000 into an ATX case project, http://www.liukuma.net/amiga/A3000atx/buildingdescription.html
The A4000 hardware guide by Warren Block, http://wonkity.com/~wblock/a4000hard/main.html
The A2000 tower guide V1.1 by Bill toner, from Aminet, http://main.aminet.net/hard/hack/A2000T.lha
The ATX specification from Intel, http://www.intel.com/design/motherbd/atx.htm
Tickit, an alternative Tickit circuit, http://main.aminet.net/hard/hack/TickIt.lha
AC Alternating Current
ATX AT eXtended
DC Direct Current
CD-RW CD Re-writable
FDD Floppy disk drive
HDD Hard Disk Drive
IDE Integrated Drive Electronics
PC Personal Computer or Piece of Crud ;)
PCI Peripheral Component Interconnect
PPC Power PC microprocessor
PSU Power Supply Unit
RAM Random Access Memory
ROM Read Only Memory
SCSI Small Computer System Interface
Updated 08 July 2017