Apple II
Interactive Flowchart Apple IIe
Apple IIe Mainboard (820-0064 / 820-0087) & Astec AA11040 PSU — Standard, Enhanced & Platinum Apple IIe
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
Just like the BBC Micro, the Apple IIe uses an Astec switched-mode PSU (AA11040) containing two amber RIFA PME271M metallised paper mains filter capacitors (0.1 uF and 0.47 uF) that crack and erupt in foul-smelling smoke.
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
Replace the RIFA X2 capacitors in the Astec AA11040 PSU before plugging in!
Use safety-approved 275V/310V AC Class X2 polypropylene film capacitors for C1 (0.47 uF) and C2 (0.1 uF), and discharge the primary HV reservoir before working on the PCB.
Is This Your Board?
- Remove the gold anodized Astec AA11040 power supply case on the left side of the Apple IIe chassis and drill out or unscrew the bottom cover rivets.
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.
Astec AA11040 Switched-Mode Power Supply
| Ref | Value | Voltage | Type | Function | Notes | Confidence |
|---|---|---|---|---|---|---|
C1 |
0.47 uF (470 nF) | 275 V AC | Class X2 Film | Mains AC input X2 filter | Replaces large RIFA PME271M smoke bomb. | Verified |
C2 |
0.1 uF (100 nF) | 275 V AC | Class X2 Film | Mains AC secondary X2 filter | Verified | |
C11 |
2200 uF | 16 V | Radial (Low-ESR) | +5V DC output reservoir | Verified | |
C12 |
1000 uF | 16 V | Radial (Low-ESR) | +5V DC pi-filter | Verified | |
C13 |
1000 uF | 25 V | Radial (Low-ESR) | +12V DC output reservoir | Verified | |
C15 |
220 uF | 25 V | Radial | -12V DC output filter | Verified | |
C16 |
220 uF | 16 V | Radial | -5V DC output filter | Verified |
Astec AA11040 Switched-Mode Power Supply — shopping list
- 1 x 0.47 uF (470 nF) 275 V AC Class X2 Film
- 1 x 0.1 uF (100 nF) 275 V AC Class X2 Film
- 1 x 2200 uF 16 V Radial (Low-ESR)
- 1 x 1000 uF 16 V Radial (Low-ESR)
- 1 x 1000 uF 25 V Radial (Low-ESR)
- 1 x 220 uF 25 V Radial
- 1 x 220 uF 16 V Radial
Apple IIe Mainboard (820-0064 / 820-0087)
| Ref | Value | Voltage | Type | Function | Notes | Confidence |
|---|---|---|---|---|---|---|
C1 |
47 uF | 16 V | Axial | +5V mainboard entry filter | Verified | |
C18 |
22 uF | 25 V | Axial | +12V slot rail decoupling | Verified | |
C27 |
10 uF | 25 V | Axial | Speaker & cassette coupling | Verified |
Apple IIe Mainboard (820-0064 / 820-0087) — shopping list
- 1 x 47 uF 16 V Axial
- 1 x 22 uF 25 V Axial
- 1 x 10 uF 25 V Axial
Whole-Machine Shopping List
- 1 x 0.47 uF (470 nF) 275 V AC Class X2 Film
- 1 x 0.1 uF (100 nF) 275 V AC Class X2 Film
- 1 x 2200 uF 16 V Radial (Low-ESR)
- 1 x 1000 uF 16 V Radial (Low-ESR)
- 1 x 1000 uF 25 V Radial (Low-ESR)
- 1 x 220 uF 25 V Radial
- 1 x 220 uF 16 V Radial
- 1 x 47 uF 16 V Axial
- 1 x 22 uF 25 V Axial
- 1 x 10 uF 25 V Axial
Recap Tips
- Run the Apple IIe built-in diagnostic self-test by holding both Apple keys (Open-Apple + Closed-Apple) while powering on or pressing Control-Reset.
Related Symptoms
- Popping sound and white smoke from left rear PSU Blown C1 (0.47 uF) or C2 (0.1 uF) RIFA X2 mains filter cap in the Astec AA11040.
Sources & References
- Console5 TechWiki - Apple II PSU Astec AA11040 capacitor schedule.