Power supply

So, first rule of thumb: before you go switching out Paula and other chips, please make sure you have a +12V and a -12V on your power supply. If not, then there’s where you need to start. Most common errors are not the chips that are defective.


Second: remove old batteries from your Amiga

Leaking battery (source)

There are 3 types of batteries:

  • Coin battery
  • Standard AA/AAA batteries
  • Barrel batteries (the welknown Varta types)

These need to be removed from your Amiga. They will leak and eat your motherboard. Especially the barrel batteries. Best thing to do is to cut the one leg and wiggle the battery until it comes right of the board. You can replace them if you want, but it’s not really neccessary. The only thing they do is hold the date and time. So it’s up to you if you like to replace the battery.


A simple-to-use symptomatic guide for diagnosing faulty IC components on Amiga computers
(includes all version of the A500/1500/2000/2500)
Credits are at the bottom of this page.



  • About 1/2 second delay
  • Disable and clear all interrupts
  • Dark grey screen
  • If ROM bad, screen red
  • Temporary exception processing: If artificial exception occurs, screen yellow.
  • Configure memory: If bad, screen green.
  • Custom IC registers. If bad, screen blue.
  • Restore screen change to light grey, then workbench prompt.


  1. No workbench prompt:
    Screen goes from dark grey to light grey but does not display

    • 8520 U7 Odd CIA (U300 A2000)
    • 8364 U3 Paula (U200 A2000)
    • EMI 1301 1 ohm resistor (R309 Rev. 6A/7 boards; R200 A2000)
    • 8370 – 8372/8375 U2 Fat Agnus (U101 A2000)
    • 74LS32 U37 (chip select) U301 A2000)
    • U2 socket
  2. No power up (black screen)
    • Substitute a known good power supply to eliminate it as a possible source of the problem.
    • 68000 U1 (Check for excessive heat. If it is too hot to touch, it is bad) (U100 A2000)
    • 8370 – 8372/8375 U2 (U101 A2000)
    • X1 Crystal (no clocks)
    • U3 and U33
  3. Green screen
    • 8370 – 8372/8375 U2 (U101 A2000)
    • 501 or similar RAM expansion
    • 5719 U5 Gary (U102 A2000)
    • RAM on motherboard (Check for excessive heat. If it is too hot to touch, it is bad.
    • U2 socket (U101 A2000)
    • U7 and U8


  1. If the caps lock light on the keyboard is flashing when power up, note the number of times it flashes:
    • 1 flash: 6570-036 keyboard controller
    • 2 flashes 6570-036 keyboard controller
    • 3 flashes 555/74LS123/74LS27

The above chips are located on the keyboard. If you cannot reset computer [control-lamiga-ramiga], the most probable cause is Q2. The next most likely cause, 74LS27

  1. If the keyboard is determined not to be the problem, the defect is most likely on the main PCB (A500/A2000 motherboard). The most problematic chips are:
    • U7 Odd CIA (KBdata Pin 39 – KBclock Pin 40) (U300 A2000)
    • 8370 – 8372/8375 (U101 A2000)
    • 5719 Gary U5 (U102 A2000)
    • R914 1 ohm 1/2 watt resistor A2000 (supplies 5 volt to the keyboard)


A known good mouse and joystick should be used to eliminate them as the source of the problem. If it is determined that the mouse and joystick are okay, the most likely causes are:

  1. Mouse does not move, left and right mouse buttons okay, joystick okay:
    • EMI 1401 5.1 ohm resistor (supplies 5 volt to mouse). A2000 Rev.6 and up: F1 4 amp pico fuse.
    • 8362 U4 (U201 A2000)
    • 74LS157 U15 (U202 A2000)
  2. Mouse or joystick not working:
    • 74LS157 U15 (U202 A2000)
    • 8362 U4 (U201 A2000)
    • 74F04 U33 (U107 A2000)
  3. Left mouse button and fire button on joystick not working:
    • 8520 U7 Odd CIA (U300 A2000)
  4. Right mouse button not working
    • 8364 U3 Paula (U200 A2000)


  1. Screen breaks up (scrambles) after running for 15 to 30 minutes.
    Probable causes are:

    • 8370 – 8372/8375 U2 Fat Agnus (U101 A2000)
    • 8362 U4 (U201 A2000)
    • U2 Socket (U101 A2000)
  2. System locks up when double clicking icon:
    • 8370/8375 U2 (U101 A2000)
    • 8362 U4 (U201 A2000)
    • 8520 U7 Odd CIA (U300 A2000)
    • 74LS32 U37 (U302 A2000)
  3. Scrambled video loss of composite sync.
    • 8370 – 8372/8375 U2 (U101 A2000)
    • 74HC245 U41 (74HCT244 U205 A2000)
    • RP403
  4. Incorrect colors (loss of red, green or blue):
    • 8362 U4 (U201 A2000)
    • 74HC245 U40-U41 (74HCT244 U205-U206 A2000)
    • Video Hybrid
  5. No video (black screen)
    • R405 4.7 ohm resistor
    • R406 4.7 ohm resistor
    • 8362 U4 (U201 A2000)
    • Video Hybrid
    • 74HC245 U40-U41 (74HCT244 U205-U206 A2000)


  1. Modem will not transmit. Most likely causes are:
    • 1488 U38 (transmit) (U304 A2000)
    • 8364 U3 Paula (U200 A2000)
    • 8520 U8 Even CIA (U301 A2000)
  2. Modem or serial port will not receive:
    • 1489 U39 (receive) (U305 A2000)
    • 8364 U3 Paula (U200 A2000)
    • 8520 U8 Even CIA (U301 A2000)

NOTE: Computer will function with no -12 volts but serial port will not work.


A known good printer should be substituted to eliminate it as the source of the problem.

  1. Printer not working correctly or not working at all. The most likely causes are:
    • 8520 U8 Even CIA (U301 A2000)
    • EMI 1501 47 ohm resistor (R318 A2000)
  2. Prints incorrectly
    • 8520 U7 Odd CIA (U300 A2000)


Clean heads and check for excess dust in drive. Clean out dust and try again. This may eliminate the problem. In the followings tests, a known good drive should be substituted to eliminate the drive as the source of the problem.

  1. Internal/external drive not recognized. Probable causes:
    • 8520 U8 Even CIA (U301 A2000)
    • F4 4 amp pico fuse bad (A2000)
    • F3 4 amp pico fuse bad (A2000)
  2. Motor problem
    • 8520 U8 Even CIA (U301 A2000)
    • 5719 U5 Gary (U102 A2000)
    • 74LS38 U 36 (U203 A2000)
  3. Not recognizing disk change:
    • 8520 U7 Odd CIA (U300 A2000)
  4. Write protect problems:
    • 8520 U7 Odd CIA (U300 A2000)
  5. Read/Write errors:
    • 8364 Paula U3 (U200 A2000)
    • 68000 U1 (U100 A2000)
    • 8370 – 8372/8375 U2 (U101 A2000)
  6. DF1 A2000 not recognized:
    • J301 open (must have jumper installed)
    • 8520 U301
    • 74F00 U900
    • 74LS74 U108


Problems with left, right or both channels:

  • 8364 U3 Paula (U200 A2000)
  • LF347/TL084 OP-amp U14 (U204 A2000)
  • Q331 or Q321 F.E.T. (Q200 or Q201 A2000)
  • CN3 or CN4 (cold solder connection) (CN205 or CN204 A2000)
  • EMI 1303 or 1302 (R243-R233 1k ohm A2000)
  • Bad connecting cable.

NOTE 1: Remove all external add ons: extra memory, hard drive, external disk drive printer, modem. This eliminates them as a source of the problem. If computer works normally when all add ons have been removed, start adding devices on, one at a time, until the problem comes back. Then determine which is at fault, the device or the computer.

NOTE 2: Substitute a known good disk drive and power supply so as to to eliminate them as the source of the problem


Amiga problems: screen colors and their meaning (errors)

When you boot up your Amiga you are always greeted with a series of flashing screen colors. On most days the screen will change from dark gray to a couple lighter shades then white before marching on. On bad days, it flicks over to an actual color of the rainbow, each with its own heart-stopping meaning.

What do those colors mean? And what is the Amiga doing during the boot-up process in the first place?

The following is a collection of ancient and excellent information compiled from various sources.

During boot-up, the Amiga is going through a series of system checks and routines.

  1. Clear all chips of old data
  2. Disable DMA and interrupts during the selftest.
  3. Clear the screen.
  4. Check the hardware ….checks to see if 68000 processor is working.
  5. Change screen color.
  6. Do a checksum test on all ROMS.
  7. Change screen color.
  8. Beginning of system startup.
  9. Check RAM at $C0000 and move SYSBASE there
  10. Test All CHIP RAM.
  11. Change screen color.
  12. Check that software is being executed.
  13. Change screen color.
  14. Setup CHIP RAM to receive data.
  15. Link the libraries
  16. Check for additional memory and link it (FAST RAM)
  17. Turn the DMA and interrupts back on.
  18. Start a default task.
  19. Check for 68010, 68020, 68881 or other processor upgrades (accellerator / math co processor).
  20. Check to see if there is an exception or processor error
  21. If so do a system reset.

During this system test the Amiga is sending vital information to the screen with colors. If the system checks out ok, you will see the following sequence that you have seen so many times.

DARK GRAY:  The initial hardware tested OK. the 68000 is running and the registers are readable.
LIGHT GRAY: The software is coming in and seems OK.
WHITE: The initialization test have passed and the system is ready to boot.

The failure mode screen colors:

  • Turquoise (0x0CC) (A1000 only): RAM failure in the Kickstart WCS
  • Green (0x0F0) error in the lowest 256 bytes of Chip RAM. Possible causes, defective CIA-A IC or defective Agnus IC.
  • Yellow (0xFE5) an unexpected processor exception before the appropriate system failure message was prepared. This could mean defective hardware or an attempt to access a RAM address where no RAM exists.
  • Red (0xF00) invalid KickStart ROM checksum.
  • Magenta (0xF0F) single-task or cold-start initialization failed.

These problems could be caused by a number of things such as a loose chip or board.
The red screen may be caused by a loose Kickstart chip that can be fixed by pressing down on the ROM to check it is fitted correctly. Another cause could be a connection problems between the chip and socket that can be solved by straightening an bent pins.

Alternatively, the green screen could be caused by a loose memory board, SIMM, or a loose RAM chip on the memory board. If reattaching these chips do not solve the problem, try them on another Amiga.

Another listing of screen color interpretations:

RED Kickstart ROM error Two ICs in A1200, A3000, A4000
BLUE Custom chip problem Denise Paula Agnus
YELLOW Above problems combined
LIGHT GREEN CIA (U7/U300) problem
BLACK CIA (U7/U300) problem If not booting
DARK GRAY Hardware tested OK
LIGHT GRAY Software tested OK
LIGHT GRAY CIA (U8/U301) problem Stops at gray, CIA defective
No video R406 or R215 open R406=1 ohm R215=4.7 ohm
Video scrambled Agnus or Denise defective


The keyboard also has its own processor, RAM, and ROM. It also has a selftest that performed on power up in the following sequence.

  1. Performs checksum on ROM’s
  2. Checks 64 bytes of RAM.
  3. The timer is tested.
  4. Performs handshake with computer and gives results of self-test.

If the keyboard does not pass the test, it will tell you through the blinking of the caps lock light.

If the Amiga caps lock key LED blinks repeatedly at boot up, another series of error messages must be consulted:

  • One blink: keyboard ROM checksum error
  • Two blinks: RAM failure
  • Three blinks: watchdog timer failure
  • Four blinks: A short between two lines or the special control keys. 
  • No Blinks: No Flashes = Main PCB faultREAD THIS (please). Don’t panic if your keyboard flashes once when you switch on. THIS IS PERFECTLY NORMAL. Every Amiga in the entire universe does this.

If something is wrong with your system, you may see the following:

  • RED: Error was found in ROMS.
  • GREEN: Error found in the CHIP RAM.
  • BLUE: Error was found in the custom chips.
  • YELLOW: If 68000 found an error before the error trapping software (GURU) was running.

Guru Meditations

It’s not always obvious why your Amiga guru’s. With the codes below, you can break the meaning down to its basic components and get to the bottom of things.

Probably all Amiga owners have seen the guru at one time or another. The guru meditation is what your Amiga does when the low level error trapping routines catch an error before the computer crashes. When the higher-level routines detect the error you are given a requestor saying: ‘Software Failure. Task held. Finish ALL disk activity’, with two gadgets saying retry and cancel. Retry usually does nothing and cancel causes a guru.

The proper term for the guru is an alert. The alerts give you some useful information about why the Amiga crashed and what program caused the program to crash.


D: This indicates whether or not the software failure is recoverable or not (with the current OS none are really). A zero means that it is recoverable and any non-zero value means that it isn’t.

S: This (together with D) indicates the subsystem that generated the alert. The various subsystems are (DS):

00 .. Processor or none
01 .. Exec.Library
02 .. Graphics.Library
03 .. Layers.Library
04 .. Intuition.Library
05 .. Math.Library
06 .. Clist.Library
07 .. DOS.Library
08 .. RAM.Library
09 .. Icon.Library
10 .. Audio.device
11 .. Console.device
12 .. GamePort.device
13 .. Keyboard.device
14 .. Trackdisk.device
15 .. Timer.device
20 .. CIA.resource
21 .. Disk.resource
22 .. Misc.resource
0A .. Expansion.Library
30 .. Bootstrap
31 .. Workbench
32 .. Diskcopy

Ge: This indicates the general error. Basically telling you what went wrong. The various defined General Errors are (Ge):

01 .. No memory
02 .. Make Library
03 .. Open Library
04 .. Open Device
05 .. Open Resident
06 .. I/O Error
07 .. No Signal

Code: This gives more detail as to what went wrong. The value that appears here depends on the subsystem and general error.

TAddress: This is the Address of the task that caused the guru (where applicable).

Quite often the processor with trap an error. The operating system will then display a guru. These errors will only contain two digits (the right-most two digits in ‘Code’) and their meanings are:

00000000 Reset (SP). /Technically, these shouldn’t occur, but
00000001 Reset (PC). /they do pop up occassionally
00000002 Bus Error (memory doesn’t exist)
00000003 Address error (usually odd address access) A program probably made a jump to somewhere it shouldn’t have
00000004 Illegal instruction
00000005 Divide by zero. A program has attempted to divide a number by zero (a mathematical impossibility).
00000006 CHK instruction (Check register against boundaries)
00000007 TRAPV instruction (Trap on overflow)
00000008 Privilege violation. A program in user mode attempted to execute a privileged Instruction.
00000009 Trace (debugging)
0000000A Op Code 1010 (unimplemented instruction)
0000000B Op Code 1111 (unimplemented instruction)
0000000A & 0B A & F Line Emulation. Used with some coprocessors. Usually program is out of control.
00000018 .. Spurious interrupt.
00000019 to 1F .. Auto-Vector Interrupts – These should not happen as the OS uses them to detect what is going on with the hardware, but as with all others they do appear sometimes.
00000020 to 2F .. Trap Vectors – Usually a program is out of control.
00000030 to 3F .. These are reserved by Motorola. Any program causing these is probably out of control.
00000040 to FF .. User Interrupt Vectors – Usually a program is out of control.

AmigaDos error messages

If you enter a command and comes back with an error message, typing WHY will display more
information about it. Use the FAULT command to display the error message that applies to a error

Typical AmigaDos error messages are:

Code Description Solution
103 Insufficient free store . Free up some memory by quiting other programs
105 Task table full Shutdown some programs
120 Argument line invalid or too long Check command arguments using `?`
121 File is not an object module Try setting ‘e’ or ‘s’ protection flag.
122 Invalid resident library during load
202 Object in use Exit program, unassign assign or close directory windows.
203 Object already exists.
Cannot move the program as it exists elsewhere. Delete the original first
204 Directory not found Retype directory name
205 Object not found Retype file name
206 Invalid window description
Re-enter correct window description for NEWCLI or NEWSHELL
209 Packet request type unknown
210 Stream name component invalid
211 Invalid object lock Recheck filename
212 Object not of required type Recheck file
213 Disk not validated Wait until disk is validated first.
214 Disk write-protected Ensure write tab is closed.
215 Rename across devices attempted Use copy instead
216 Directory not empty Must delete its contents first. Use DELETE ALL.
218 Device (or volume) not mounted Check device name and reinsert disk
219 Seek failure Check position in file
220 Comment too big Use shorter description in FILENOTE
221 Disk full Delete some files or use a new disk.
222 File is protected from deletion Enable Delete flag with Protect
223 File is write protected Enable Write flag with Protect
224 File is read protected Use PROTECT to set ‘r’ flag.
225 Not a valid DOS disk. Disk is unformatted or a protected game disk
226 No disk in drive Use correct device name or insert disk
232 No more entries in directory Directory is full, delete files or move files into new sub-dirs.

Lotharek HxC

You can use a Gotek to read floppy disk images for your Amiga, but it’s also possible to use Lotharek HxC. Below you can find the jumper settings for your Lotharek HxC:

If you need this Lotharek HxC information for an Acorn Risc PC / Archimedes, check out this link (in Dutch)


(just preserving your great information guys, thanks for this! it helps our retro computer community a lot)


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