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Amiga 2000 Maintenance Guide

From RetroTechCollection
Inside an Amiga 2000, revision 6.2

Routine care for the Amiga 2000: the clock battery, the internal power supply, the fuses and jumpers that cause confusing faults, and the sockets. For fault-finding see the Amiga 2000 Troubleshooting Guide; for capacitor lists see the Amiga 2000 Capacitor Replacement Guide.

Clock battery

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Commodore's parts list gives the clock battery as BT800, a 3.6 V 60 mAh NiCd, part 380393-01, next to the MSM6242B clock chip at U801.[1] The board charges it while the machine is on.[2] Model A boards used square Varta batteries; B and C boards use barrel-shaped ones.[3]

These batteries leak. Repairers report:

  • Green corrosion on pins 1 to 6 of the 68000 socket, which had to be replaced.[2]
  • A circle of corroded parts about 5 cm across round the battery, with the CPU's legs turned green.[4]
  • Boards needing new CPU, Kickstart and Agnus sockets and the electrolytics near the corrosion.[5]
  • A clock that does not keep time, and a mouse that does not work or a jumpy pointer, as the usual symptoms of corrosion from the battery.[6]

To deal with it:

  1. Remove the battery whether or not it has leaked. One method is to cut one leg and rock the battery until it comes off the board.[7]
  2. Clean the area. I Like 8 Bits used vinegar on its board.[4] Follow Battery Explosion, Capacitor or Corrosion Damage for neutralising and cleaning, then check the tracks round the battery, the CPU socket and the CIAs for continuity.
  3. Replace corroded sockets and any capacitors that the electrolyte reached.[5]
  4. If you want the clock, fit a new rechargeable cell, or a CR2032 lithium cell with a diode so that the board cannot try to charge it.[2] Shop-made adapters that take a coin cell at BT800 include their own charge protection.[8]

The clock is optional. Jumper J500 normally stays closed; opening it disables both the 512 KB of RAM at $C00000 and the real-time clock.[9]

Power supply

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Warning: the A2000 supply is a mains switch-mode unit with large primary reservoir capacitors that hold their charge after unplugging. Discharge them before working inside.

A2000 supply outputs (Ian Stedman)[10]
Rail Rating
+5 V 20.5 A
+12 V 8.0 A
−5 V 0.3 A
−12 V 0.3 A

Faults found by restorers:

  • A RIFA mains filter capacitor that failed with a lot of smoke on a barn-find machine.[11] World of Jani's recap list includes the X2 and Y capacitors and says RIFA parts should be replaced as soon as possible.[12]
  • A shorted switching transistor (BUV48A, Q2) in an Ismet 380708-01 supply.[13]
  • Zorro cards that stopped being recognised once the machine was warm; the supply was at fault.[14]

The supply's capacitor lists are on the capacitor page. The original fan is noisy; World of Jani fitted a quiet 80 mm three-pin fan, noting that the connector's pin order differs and the red and black wires must be matched.[12]

The supply also sends the 50/60 Hz TICK signal to the board on pin 14 of the 14-way connector.[15] Jumper J300 selects TICK or the video vertical sync as the CIA time base, and the system will not run properly without one of them. Set J300 to vertical sync if you fit a replacement supply that has no TICK output.[9]

Fuses and jumpers

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Several A2000 faults that look like chip failures are fuses and jumpers. From Ian Perry's chart:[7]

  • Mouse pointer does not move on a Rev. 6 or later board: F1, a 4 A pico fuse.
  • Internal or external floppy drive not recognised: F3 or F4, also 4 A pico fuses.
  • Second internal drive (DF1) not recognised: jumper J301 must be fitted. l8r.net explains that J301 provides the drive ID that internal drives lack.[9]
  • Keyboard dead: R914, a 1 Ω 1/2 W resistor that supplies the keyboard's 5 V.

Sockets

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Agnus sits in a PLCC socket. LinuxJedi cleaned a tarnished one with a fibreglass pen.[11] Check the CPU, Kickstart and Agnus sockets carefully on any board that has had battery leakage.[5]

Floppy drives

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Commodore's major parts list includes 3.5-inch Panasonic and 5.25-inch ALPS and Chinon drive assemblies.[1] The Chinon FB-354 3.5-inch drive has three 22 µF and one 1 µF electrolytic.[16] See Floppy Drive Repair.

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References

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  1. ↑ 1.0 1.1 Commodore Business Machines, System Schematics A2000, PN-314135-01, August 1990, parts list for PCB assembly #312720-01, PDF pp. 8-9, hosted at Amiga 2000 System Schematics (314135-01).
  2. ↑ 2.0 2.1 2.2 Amiga 2000 battery repair—link(accessed 2026-10-01)
  3. ↑ Commodore A2000—link(accessed 2026-10-01)
  4. ↑ 4.0 4.1 Fixing the Amiga 2000 (part 1)—link(accessed 2026-10-01)
  5. ↑ 5.0 5.1 5.2 Amiga of Rochester, Amiga 2000: 4 board repair, 22 May 2020—link(accessed 2026-10-01)
  6. ↑ RTC battery replacement—link(accessed 2026-10-01)
  7. ↑ 7.0 7.1 Commodore Amiga problems—link(accessed 2026-10-01) Includes Ian Perry's Amiga Troubleshooter chart (1993) with A2000 designators.
  8. ↑ AmigaStore, Amiga lithium coin cell clock battery adapter—link(accessed 2026-10-01) Fits "BT800 (Amiga 2000 and 1500)"; "Battery holder PCB contains protection circuit to prevent charging of the coin cell."
  9. ↑ 9.0 9.1 9.2 A2000 jumpers—link(accessed 2026-10-01)
  10. ↑ Ian Stedman, Amiga power supply guide—link(accessed 2026-10-01)
  11. ↑ 11.0 11.1 LinuxJedi, Restoration of a barn find Amiga 2000: part 1—link(accessed 2026-10-01)
  12. ↑ 12.0 12.1 Amiga 2000 PSU recap / capacitor list, 21 May 2021—link(accessed 2026-10-01)
  13. ↑ Andrea Mazzai, A2000 Rev. 4 PSU—link(accessed 2026-10-01)
  14. ↑ [Solved][A2000] no more autoconfig cards when hot—link(accessed 2026-10-01)
  15. ↑ Amiga 2000 power supply 14 pin—link(accessed 2026-10-01)
  16. ↑ Nightfall Crew, Chinon FB-354 recap (Amiga floppy drive), 31 August 2017—link(accessed 2026-10-01)
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