Amiga 500
Rev 3 / Rev 5 — Early A500 mainboard
Summary
The Rev 3 and Rev 5 boards are the early A500 mainboards, usually paired with Kickstart 1.2 and the 8370 Agnus. They share the Rev 6A designators but use different values at C307 and the C811 group, and they have no C816.
Safety & Warnings
Check the A501 trapdoor expansion before anything else
If a 512 KB A501 RAM expansion is fitted in the trapdoor, remove it and inspect it now. The A501 carries a NiCd barrel battery that leaks and destroys the expansion board, and the corrosion creeps toward the trapdoor connector. Desolder the battery even if the board still looks clean - this is the single most destructive fault on an A500.
The two 3300 uF cans hold a charge
C401 and C402 are the largest capacitors on the board. Let the machine sit unplugged before you work on the power section, and check across them with a meter rather than assuming they are discharged.
Higher voltage ratings are always safe
You can fit a higher voltage rating than original as long as the can physically fits under the keyboard and shielding. Never fit a lower rating. Capacitance should stay at the original value.
Single-source list. Every row below is flagged for checking because only one independent capacitor list for the Rev 3 / Rev 5 board was available at the time of writing - unlike the Rev 6A, which two sources agree on. Read the value off each can before you order, and treat this page as a shopping guide rather than gospel.
The 16 V ratings shown at C307 and the C811 group are what distinguishes these boards from the 50 V parts used at the same designators on the Rev 6A / 7.
Height matters on an A500. The keyboard sits directly above the board, so check the can height of replacements for C401 and C402.
Is This Your Board?
- The revision is silkscreened on the mainboard, usually near the edge connectors. Look for "Rev 3" or "Rev 5".
- Decisive test against the later boards: the C811 group stops at C815 on Rev 3 / Rev 5. If there is a can at C816, you have a Rev 6A or Rev 7.
- C307 is 100 uF on these boards and 470 uF on the Rev 6A / 7 - worth checking before you order.
- Early boards commonly carry the 8370 Agnus limited to 512 KB chip RAM.
Verified rows are agreed by two or more independent sources. Check rows are revision-dependent or single-sourced — confirm the value against your own board before ordering.
Mainboard
| Ref | Value | Voltage | Type | Notes | Confidence |
|---|---|---|---|---|---|
C303 |
22 uF | 50 V | Radial | Check | |
C304 |
22 uF | 50 V | Radial | Check | |
C306 |
10 uF | 50 V | Radial | Check | |
C307 |
100 uF | 16 V | Radial | 100 uF on this revision. The Rev 6A / 7 uses 470 uF 25 V here. | Check |
C324 |
22 uF | 50 V | Radial | Check | |
C334 |
22 uF | 50 V | Radial | Check | |
C401 |
3300 uF | 25 V | Radial | One of the two largest cans on the board. Watch the height under the keyboard. | Check |
C402 |
3300 uF | 25 V | Radial | One of the two largest cans on the board. | Check |
C712 |
10 uF | 50 V | Radial | Check | |
C811 |
100 uF | 16 V | Radial | 100 uF here, while C812 to C815 are 47 uF - do not assume the whole group is one value. | Check |
C812 |
47 uF | 16 V | Radial | Check | |
C813 |
47 uF | 16 V | Radial | Check | |
C814 |
47 uF | 16 V | Radial | Check | |
C815 |
47 uF | 16 V | Radial | Last of the group on this revision - there is no C816. | Check |
C821 |
47 uF | 16 V | Radial | Check | |
C822 |
47 uF | 16 V | Radial | Check |
Mainboard — shopping list
- 4 x 22 uF 50 V Radial
- 2 x 10 uF 50 V Radial
- 2 x 100 uF 16 V Radial
- 2 x 3300 uF 25 V Radial
- 6 x 47 uF 16 V Radial
Recap Tips
- All sixteen are through-hole, so a temperature-controlled iron and solder wick is all you need - no hot air required.
- Use 105 C low-ESR parts. Panasonic FR or FC and Nichicon PW or HE series are the usual bench choices.
- Do the A501 trapdoor board at the same time if one is fitted. Its battery damage is a far bigger threat to the machine than any capacitor on the mainboard.
- Because this list is single-sourced, photograph the board before you desolder anything. The photo settles any argument about original values later.
Related Symptoms
- No boot / blank screen On an Amiga the Kickstart diagnostic screen colours tell you far more than a capacitor inspection - check those first.
- Distorted or missing audio Coupling capacitors in the audio path are a genuine suspect here, unlike most no-boot faults.
Sources & References
- Retro Rewind - Amiga 500 Cap List The only per-designator Rev 3 / Rev 5 list used here. Its Rev 6/6A list is corroborated by a second source, which is why the Rev 6A page carries verified rows and this one does not.
- Commodore A500 / A2000 Technical Reference Manual (PDF) Contains the official parts list for PCB assembly 312510 Rev 5 - the primary source to settle any row below.