Commodore 64
ASSY 250407 — Early breadbin "long board"
Summary
The 250407 is the early breadbin long board, fitted with eight 4164 DRAM chips. It carries more electrolytics than any later C64 revision - fifteen 10 uF decoupling cans plus four larger power-supply filters.
Safety & Warnings
Test the power supply first
A recap will not protect the machine from an original Commodore "black wedge" or beige brick. These fail with the 5 V rail drifting high and take out RAM, the CIAs, the PLA and the SID. Measure the 5 V rail under load before you fit a single new capacitor, and replace the brick with a modern regulated supply.
Confirm polarity against the board, not just the silkscreen
Align the negative stripe on each capacitor with the negative marking on the PCB. Commodore silkscreens of this era are occasionally ambiguous or reversed, so if a marking looks wrong, buzz the pad out to the ground plane with a continuity tester before soldering.
Higher voltage ratings are always safe
You can fit a higher voltage rating than original (25 V or 35 V in place of a 16 V part) as long as the can physically fits. Never fit a lower rating. Capacitance should stay at the original value.
The first C64 production runs used 50 V capacitors, most likely down to parts availability. Later runs and the later schematics specify 25 V. Either is correct for your board; the values below follow the later schematics.
Function and rail annotations are only shown on rows where the service manual or schematic confirms them. Rows without an annotation are decoupling capacitors whose exact role is not documented in the sources used here.
Is This Your Board?
- The assembly number is silkscreened on the mainboard, usually near the cartridge port or along the front edge. Look for "ASSY 250407".
- The 250407 has eight 4164 DRAM chips in a row. If your board has only two RAM chips it is a 250469 short board, not this one.
- The video connector (CN5) on the 250407 has 8 pins. Very early 326298 boards use a 5-pin video connector.
- Board revision letters (Rev A, B, C) are also printed on the PCB and matter for C88 - see the note on that row.
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 |
|---|---|---|---|---|---|
C8 |
10 uF | 25 V | Radial | Verified | |
C12 |
10 uF | 25 V | Radial | Fitted as an electrolytic on Rev B. Some revisions use a ceramic here - if yours is ceramic, leave it alone. | Check |
C13 |
10 uF | 25 V | Radial | Verified | |
C14 |
10 uF | 25 V | Radial | Verified | |
C15 |
10 uF | 25 V | Radial | Verified | |
C17 |
10 uF | 25 V | Radial | Verified | |
C19 |
2200 uF | 16 V | Axial | Largest can on the board. Both sources list this as the 2200 uF axial - it is not a 470 uF part. | Verified |
C24 |
10 uF | 25 V | Radial | Verified | |
C34 |
10 uF | 25 V | Radial | Verified | |
C57 |
10 uF | 25 V | Radial | Verified | |
C62 |
10 uF | 25 V | Radial | Verified | |
C65 |
10 uF | 25 V | Radial | Verified | |
C88 |
1000 uF | 25 V | Axial | 470 uF on Rev B and earlier, 1000 uF on Rev C and later. Both sources ship 1000 uF for every revision, which is safe to fit throughout. | Check |
C90 |
470 uF | 25 V | Axial | Verified | |
C91 |
100 uF | 16 V | Radial | Verified | |
C94 |
10 uF | 25 V | Radial | Verified | |
C102 |
10 uF | 25 V | Radial | Verified | |
C107 |
10 uF | 25 V | Radial | Rev C boards. Sits inside the VIC-II shielded area, so the shield has to come off to reach it. | Check |
C108 |
10 uF | 25 V | Radial | Rev C boards. Also inside the VIC-II shielded area. | Check |
Extra Parts (not failure items)
These are not electrolytic recap candidates. They are listed because the kit vendors include them for a known modification or fix — do not replace them as part of a routine recap.
| Ref | Value | Voltage | Type | Purpose | Notes |
|---|---|---|---|---|---|
C38 |
4.7 nF | - | Ceramic | RESTORE key fix | Not an electrolytic and not a failure item. Replacing the original 51 pF with 4.7 nF restores the soft-touch RESTORE key function. Both cap-kit vendors include this part for exactly that reason. |
Mainboard — shopping list
- 15 x 10 uF 25 V Radial
- 1 x 2200 uF 16 V Axial
- 1 x 1000 uF 25 V Axial
- 1 x 470 uF 25 V Axial
- 1 x 100 uF 16 V Radial
Recap Tips
- Work one capacitor at a time and keep the old part next to its pad until the new one is in - it is the cheapest insurance against a polarity mix-up.
- Use 105 C low-ESR parts. Panasonic FR or FC and Nichicon PW or HE series are the usual bench choices and keep ripple off the video and audio outputs.
- Check can diameter before ordering. The 2200 uF axial at C19 and the 1000 uF at C88 have to clear the RF shield and the case.
- This board is single-sided with generous pads, so it is a good first recap. Keep the iron at 320-340 C and do not linger - the laminate lifts pads if you dwell.
Related Symptoms
- Black screen / no video Start with the power rail tests before assuming a capacitor is at fault.
- Garbage video / character corruption More often DRAM or the PLA on this board than a capacitor.
Sources & References
- Console5 TechWiki - Commodore 64 Per-assembly capacitor lists compiled from real boards and later schematics.
- Retro Rewind - C64 Assembly 250407 Cap List Independent list that agrees with Console5 on every row used here.
- Commodore 64 Service Manual (PDF) Primary reference for schematic 251138 and the official parts list.