Sony
Interactive Flowchart Sony PlayStation 1 (PS1 / PSone)
PU-7 / PU-8 / PU-18 / PU-22 / PU-23 & PSone PM-41 — 32-Bit R3000A + GPU + SPU + KSM-440 CD-ROM mainboards
Complete Diagnostic Flowchart: Capacitive Load, ESR & Power Rail Ripple Diagnostic Tree (Universal Retro Mainboards (C64, Amiga, ZX Spectrum, Game Gear, Consoles))
STEP 1: Measure 100Hz/120Hz Peak-to-Peak AC Ripple on the +5V / +12V Bulk Filter Cap
[node-1]
Set your oscilloscope to AC Coupling, 200 mV/div, and 2.5 ms/div (20 MHz bandwidth limit ON). Probe directly across the main bulk filter capacitor (e.g. C19 2200µF / C88 1000µF on C64, or C303/C304 on Amiga) under full system load. Measure the peak-to-peak sawtooth ripple amplitude (mVpp).
Expected Reading: < 50 mVpp clean regulated rail (post-regulator) or < 350 mVpp on raw unregulated bulk DC before the 7805/7812.
STEP 2: Check Linear Regulator (7805 / 7812) Input-to-Output Dropout Margin
[node-2]
Switch oscilloscope or multimeter to DC Volts and measure Pin 1 (Input) of the 7805 (+5V) or 7812 (+12V) regulator at the bottom of the ripple trough. Verify that Input Voltage remains at least 2.0V above the regulated output (e.g. ≥7.2V into a 7805, ≥14.2V into a 7812).
Expected Reading: 7805 Input ≥ 7.2V DC; 7812 Input ≥ 14.2V DC. Below this dropout threshold, ripple punches straight through to the logic rail.
STEP 3: Check Local IC Decoupling & Audio/Video AC Coupling Capacitors
[node-3]
Probe audio output coupling caps (e.g. C91 100µF on C64 SID Pin 27, or C324/C334 22µF SMD on Amiga Paula) — compare upstream vs. downstream signal amplitude. Inspect SMD electrolytic pads (Amiga 600/1200, Game Gear, DMG-01) under magnification for fishy odor, dull grey solder corrosion, or lifted copper traces.
Expected Reading: Full audio/video swing across the coupling capacitor with zero DC leakage on the output side and clean, shiny solder pads.
[ISOLATED FAULT: RES-BULK-CAP] Fault Isolated: High-ESR Bulk Filter Capacitor (>100 mVpp Rail Ripple)
VERDICT
Excessive 100/120Hz sawtooth ripple on the DC rail confirms that the primary reservoir/filter electrolytics have dried out and lost effective capacitance.
[ISOLATED FAULT: RES-REG-DROPOUT] Fault Isolated: Linear Regulator Dropout / Bridge Rectifier Diode Open
VERDICT
The pre-regulator DC rail is sagging below the minimum 2V dropout headroom required by the 7805/7812 regulator.
[ISOLATED FAULT: RES-COUPLING-CAP] Fault Isolated: Open/Leaky Audio or Video Coupling Capacitor & Trace Corrosion
VERDICT
Signal attenuation, muffled audio, or DC offset hum across the coupling stage indicates dried-out or leaking coupling capacitors.
[ISOLATED FAULT: RES-RAILS-HEALTHY] Verification Passed: Power Rails, Ripple & Coupling Capacitors Within Spec
VERDICT
All measured DC supply rails, AC ripple levels (<50 mVpp), and coupling stages pass bench specification. If performing a preventive recap, use the verified board BOM below.
Summary
On original Sony PlayStation 1 boards (PU-7 to PU-23) and especially the slim PSone (PM-41), leaking surface-mount 220 uF video coupling capacitors right behind the Multi-AV port cause dark, dim, or washed-out green video, while aging CD servo SMD caps cause FMV skipping and disc read failures.
Interactive Bench Oscilloscope — Verify Pre- & Post-Recap Waveforms
Open Full Signal Visualizer →Click any test point below to compare a healthy recapped rail or clock against high-ESR electrolytic capacitor ripple and droop:
Safety & Warnings
Discharge the internal PSU primary capacitor on SCPH-100x to SCPH-900x fat models
The left-hand open-frame power supply board carries live mains voltage on the primary side. Also check the miniature SMD ICP fuses PS601-PS605 on the mainboard if controller vibration or CD spindle power is missing.
Is This Your Board?
- Board revision (PU-7, PU-8, PU-18, PU-20, PU-22, PU-23, or PM-41 on PSone) is silkscreened in large white letters on the mainboard.
Verified
Check
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.
PS1 Mainboard (PU-8 / PU-18 / PU-22) & PSone (PM-41)
| Ref | Value | Voltage | Type | Function | Notes | Confidence |
|---|---|---|---|---|---|---|
C514 / C515 (Video) |
220 uF | 6.3 V | SMD (D) | Multi-AV Composite & S-Video Luma output coupling | Prime failure on PSone PM-41 (causes dark or dim green screen). | Verified |
C516 - C518 (RGB) |
220 uF | 6.3 V | SMD (D) | Multi-AV Red/Green/Blue coupling (early boards) | Verified | |
C408 / C409 (Audio) |
10 uF | 16 V | SMD (B) | AKM / SPU Left & Right stereo audio coupling | Verified | |
C704 / C705 (CD Servo) |
47 uF | 10 V | SMD (C) | CD RF amplifier & focus/tracking servo filter | Drying servo caps cause FMV stuttering and failure to read discs. | Verified |
C102 (Power) |
100 uF | 10 V | SMD (C) | +3.5V logic rail decoupling | Verified |
PS1 Mainboard (PU-8 / PU-18 / PU-22) & PSone (PM-41) — shopping list
- 2 x 220 uF 6.3 V SMD (D)
- 1 x 10 uF 16 V SMD (B)
- 1 x 47 uF 10 V SMD (C)
- 1 x 100 uF 10 V SMD (C)
PS1 Internal Switched-Mode Power Supply (SCPH-100x - 900x)
| Ref | Value | Voltage | Type | Function | Notes | Confidence |
|---|---|---|---|---|---|---|
C005 (Primary) |
68 uF | 400 V | Radial | Mains HV DC primary reservoir | Verified | |
C101 |
1000 uF | 10 V | Radial (Low-ESR) | +3.5V logic rail output filter | Verified | |
C102 |
470 uF | 16 V | Radial (Low-ESR) | +7.5V / +8V CD motor & rumble rail filter | Verified |
PS1 Internal Switched-Mode Power Supply (SCPH-100x - 900x) — shopping list
- 1 x 68 uF 400 V Radial
- 1 x 1000 uF 10 V Radial (Low-ESR)
- 1 x 470 uF 16 V Radial (Low-ESR)
Whole-Machine Shopping List
- 2 x 220 uF 6.3 V SMD (D)
- 1 x 10 uF 16 V SMD (B)
- 1 x 47 uF 10 V SMD (C)
- 1 x 100 uF 10 V SMD (C)
- 1 x 68 uF 400 V Radial
- 1 x 1000 uF 10 V Radial (Low-ESR)
- 1 x 470 uF 16 V Radial (Low-ESR)
Recap Tips
- Always recap the CD RF/servo SMD capacitors on PU-8 and PU-18 boards before adjusting the KSM-440 laser pot - weak servo capacitors mimic a dying laser!
Related Symptoms
- Very dim, dark or green-tinted picture on PSone (SCPH-101) Leaked 220 uF SMD video coupling capacitors right in front of the Multi-AV port on the PM-41 board.
Sources & References
- Console5 TechWiki - Sony PlayStation PU-7 to PM-41 capacitor schedules.