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Atari STE Capacitor Replacement Guide

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Revision as of 20:32, 27 March 2026 by Josh (talk | contribs) (Created page with "<templatestyles src="Template:StyledTable/styles.css" /> The '''Atari STE Capacitor Replacement Guide''' provides complete capacitor lists, board revision identification, and replacement procedures for the '''Atari 520STE''' and '''Atari 1040STE'''. Both models share the same motherboard and identical capacitor locations. The only factory difference between the two is installed RAM (520STE: 2× 256 KB SIMMs; 1040STE: 4× 256 KB SIMMs); all capacitor positions, v...")
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The Atari STE Capacitor Replacement Guide provides complete capacitor lists, board revision identification, and replacement procedures for the Atari 520STE and Atari 1040STE. Both models share the same motherboard and identical capacitor locations. The only factory difference between the two is installed RAM (520STE: 2× 256 KB SIMMs; 1040STE: 4× 256 KB SIMMs); all capacitor positions, values, and reference designators are the same on both machines.

For general maintenance procedures, see Atari STE General Maintenance. For fault diagnosis, see Atari STE Troubleshooting Guide.

Why Recap an STE?

The electrolytic capacitors used in Atari STE computers were manufactured in the late 1980s and early 1990s. After 30+ years, these capacitors degrade in several ways:

  • Increased ESR (Equivalent Series Resistance): The capacitor appears functional on a simple capacitance meter but cannot deliver or absorb current quickly enough. This is the most common failure mode in PSU capacitors and causes voltage ripple, random crashes, and video noise.
  • Reduced capacitance: The capacitor drifts below its rated value, reducing filtering effectiveness.
  • Electrolyte leakage: The electrolyte seeps out, potentially corroding nearby traces and pads. Visible as brown or white crystalline residue around the capacitor base.
  • Short circuit: Less common but catastrophic — the capacitor fails short, potentially damaging other components.

PSU capacitors degrade fastest due to thermal stress from the switching power supply. Motherboard capacitors degrade more slowly but are equally important — particularly the DMA audio coupling capacitors (C202, C204, C205, C215) and bulk filter capacitors (C103, C216).

Before You Begin

Tools Required

  • Temperature-controlled soldering iron (recommended 350°C / 660°F for through-hole work)
  • Solder wick (desoldering braid) and/or desoldering pump
  • 63/37 or 60/40 tin-lead solder (0.8–1.0 mm diameter)
  • Flush cutters
  • Multimeter with capacitance and ESR measurement capability
  • Isopropyl alcohol (99%+) and cotton swabs for flux cleanup
  • Anti-static wrist strap
  • Pen and paper to record original capacitor orientation before removal

Capacitor Selection

  • Use low-ESR, high-ripple-current rated capacitors for PSU replacements. Standard-grade electrolytics are insufficient for switch-mode PSU applications and will overheat.
  • Recommended brands: Panasonic FR/FC series, Nichicon HE/UHE series, Rubycon ZLH series. Avoid generic/unbranded capacitors.
  • Temperature rating: 105°C rated capacitors are preferred over 85°C, especially for PSU use.
  • Voltage rating: Match or exceed the original voltage rating. Using a higher voltage rating is acceptable and slightly improves reliability (e.g. replacing 16 V with 25 V).
  • Non-polarized (NP/bipolar) capacitors: Required at positions C202, C204, C205, and C215. These are in the audio signal path and must be non-polarized electrolytics or film capacitors. Do not substitute standard polarized electrolytics.
  • Physical size: Ensure replacements fit the PCB footprint. Modern low-ESR capacitors are often taller than originals at the same capacitance/voltage.

STE Motherboard Capacitor List

The following list applies to all known STE motherboard revisions: CA300779-001 REV 5.1, CA401177, and CA4003290. Reference designators and values are consistent across all three revisions.[1][2]

Power Section

Ref Value Voltage Type Circuit Area Notes
C100 10 µF 35 V Polarized Power regulation
C102 22 µF 16 V Polarized Power regulation Some board revisions use 10 µF / 35 V at this position
C103 4700 µF 16 V Polarized +5 V bulk filter Critical for system stability; replace with low-ESR type
C107 100 µF 16 V Polarized Power filtering
C110 100 µF 16 V Polarized Power filtering

Audio / DMA Sound Section

Ref Value Voltage Type Circuit Area Notes
C202 4.7 µF 35 V Non-Polarized DMA sound coupling Critical for DMA audio quality. Replace with NP electrolytic or film cap. Degradation causes high-pitched whistle.[3]
C204 4.7 µF 35 V Non-Polarized DMA sound coupling Same as C202 — audio path capacitor
C205 4.7 µF 35 V Non-Polarized DMA sound coupling Same as C202 — audio path capacitor
C215 4.7 µF 35 V Non-Polarized Audio path Audio coupling
C216 470 µF 35 V Polarized Audio power filter Large capacitor near audio section

Floppy / DMA Controller Section

Ref Value Voltage Type Circuit Area Notes
C415 470 µF 16 V Polarized Floppy/DMA power filter
C416 47 µF 16 V Polarized Floppy section
C417 100 µF 16 V Polarized Floppy section
C423 100 µF 16 V Polarized DMA controller area
C433 1 µF 50 V Polarized DMA section

CPU / Logic Section

Ref Value Voltage Type Circuit Area Notes
C508 47 µF 16 V Polarized Logic decoupling
C520 47 µF 16 V Polarized Logic decoupling
C525 47 µF 16 V Polarized Logic decoupling
C529 47 µF 16 V Polarized Logic decoupling
C535 47 µF 16 V Polarized Logic decoupling
C537 47 µF 16 V Polarized Logic decoupling
C541 47 µF 16 V Polarized Logic decoupling
C542 10 µF 35 V Polarized Logic section
C543 47 µF 16 V Polarized Logic decoupling
C544 47 µF 16 V Polarized Logic decoupling
C546 47 µF 16 V Polarized Logic decoupling
C547 47 µF 16 V Polarized Logic decoupling

Video / Output Section

Ref Value Voltage Type Circuit Area Notes
C558 100 µF 16 V Polarized Video/output filtering
C561 100 µF 16 V Polarized Video/output filtering
C564 100 µF 16 V Polarized Video/output filtering
C566 47 µF 16 V Polarized Video section
C567 47 µF 16 V Polarized Video section
C600 100 µF 16 V Polarized Output section

Summary Count (Motherboard)

Value Voltage Type Quantity
4700 µF 16 V Polarized 1
470 µF 35 V Polarized 1
470 µF 16 V Polarized 1
100 µF 16 V Polarized 7
47 µF 16 V Polarized 12
22 µF 16 V Polarized 1
10 µF 35 V Polarized 2
4.7 µF 35 V Non-Polarized 4
1 µF 50 V Polarized 1
Total 30

PSU Capacitor Lists

The STE uses the same internal PSU types as the later STFM models. Identify your PSU by the model number printed on the PSU PCB.

Mitsumi SR98 / SR118 / 68-4231A (220–240 V)

The most common PSU in European STE machines.[4][5]

Ref Value Voltage Notes
C104 47 µF 400 V Primary filter — HIGH VOLTAGE. Replace with 68 µF 400 V for improved filtering.
C201 2200 µF 10 V Secondary output filter. Replace with 4700 µF 16 V for improved performance.
C202 2200 µF 16 V Secondary output filter. Replace with 4700 µF 16 V.
C203 2200 µF 10 V Secondary output filter. Replace with 4700 µF 16 V.
C204 1000 µF 16 V Secondary output filter. Replace with 1500 µF 16 V.
C205 1000 µF 10 V Secondary output filter. Replace with 1500 µF 16 V.
C206 1 µF 50 V Feedback/compensation capacitor.

Additional SR98 modifications:

  • Replace the 2A bridge rectifier with a KBU1005 (10 A, 600 V) for improved reliability and lower voltage drop.
  • Replace the output diode (HRW34) with an STPS10H100CFP Schottky type for reduced ripple (500 mV → 200 mV measured improvement) and lower heatsink temperature (49°C → 39°C).
  • For improved peak current response (reduces video dimming during floppy access): replace R202 with 1 kΩ and R201 with 1.2 kΩ, then readjust the trimmer pot to 5.00 V on the +5 V rail.[6]

DVE DSP-508A / DSP-508AA

Ref Value Voltage Notes
C3 47 µF 250 V Primary filter — HIGH VOLTAGE
C4 47 µF 250 V Primary filter — HIGH VOLTAGE
C8 330 µF 25 V Secondary filter. Replace with 680 µF 25 V.
C9 1 µF 50 V Compensation.
C?? 100 µF 25 V In shrinkwrap near safety cap at board top.
C22 2200 µF 16 V Secondary output. Replace with 4700 µF 16 V.
C25 2200 µF 16 V Secondary output. Replace with 4700 µF 16 V.
C23 330 µF 25 V Secondary filter. Replace with 680 µF 25 V.
C20 330 µF 25 V Secondary filter. Replace with 680 µF 25 V.

The DVE PSU uses a BU508A switching transistor, which has superior voltage and current ratings compared to the SR98's 2SC2979. This PSU generally has better regulation and is considered one of the more robust STE PSU designs. Replace the bridge rectifier with a KBU1005 (10 A, 600 V) as with the SR98.[7]

ASTEC ASP34 / ASPF34

Ref Value Voltage Notes
C4 47 µF 250 V Primary filter — HIGH VOLTAGE. Replace with 47–68 µF 250 V.
C5 47 µF 250 V Primary filter — HIGH VOLTAGE. Replace with 47–68 µF 250 V.
C7 330 µF 25–35 V Secondary filter. Replace with 470–820 µF 35 V.
C9 100 µF 25 V Secondary filter.
C14 330 µF 25–35 V Secondary filter. Replace with 470–820 µF 35 V.
C15 330 µF 25–35 V Secondary filter. Replace with 470–820 µF 35 V.
C13 4700 µF 16 V Main +5 V filter.
C12 2200 µF 16 V Secondary filter. Replace with 4700 µF 16 V.

Uses BU508 switching transistor. Re-solder the transistor legs and any other components on the heatsink as a preventive measure.[8]

Board Revision Identification

Identify your STE motherboard revision by the part number silkscreened on the PCB, typically in a corner near the edge connectors.

Board Number Key Characteristics Cap List Differences
CA300779-001 REV 5.1 Early production STE board. Separate BLiTTER chip (PLCC-68). GST Shifter in DIP-64 socket (C300588). DIP-64 or PLCC-68 CPU. Standard cap list as above. C102 may be 10 µF / 35 V instead of 22 µF / 16 V.
CA401177 Mid-production board. Some units have surface-mounted MC68000 CPU. Standard cap list. No known capacitor value differences.
CA4003290 Later/final production STE board. Most commonly encountered. Used in both 520STE and 1040STE. Standard cap list. No known capacitor value differences.

Note: Despite different board numbers, all three STE motherboard revisions use the same capacitor reference designators and values. The Console5 cap kit "Atari 520STE/1040STE Computer Cap Kit (Main STE PCB)" covers all revisions.[9]

Replacement Procedure

Motherboard Recap

  1. Photograph the motherboard before starting. Record the polarity orientation of each capacitor — the negative (−) stripe on the capacitor body should match the marking on the PCB silkscreen. For non-polarized capacitors (C202, C204, C205, C215), orientation does not matter.
  2. Remove the old capacitor: Heat one lead while gently pulling the capacitor away from the board. When one lead is free, heat the other. Alternatively, cut the capacitor body away and remove each lead individually.
  3. Clean the through-hole pad: Apply solder wick to remove old solder from both holes. The holes should be clear enough to pass a new component lead through. If a pad lifts, it can be repaired with a small wire jumper soldered to the nearest trace.
  4. Install the new capacitor: Insert leads through the PCB holes, observing polarity markings. The longer lead is positive (+). Solder both leads. Trim excess leads flush with the solder joint.
  5. Inspect each joint: A good joint is shiny and concave. Re-flow any dull, blobby, or cold-looking joints.
  6. Clean flux residue with IPA and a brush after completing all replacements.

PSU Recap

WARNING: PSU primary-side capacitors (C104, C3, C4, C5 depending on model) are rated at 250–400 V. Ensure all capacitors are fully discharged before working on the PSU. Discharge through a 10 kΩ 2 W resistor held across the capacitor terminals, not by shorting.

  1. Follow the same removal and installation procedure as the motherboard.
  2. Take extra care with high-voltage primary capacitors. These have higher lead spacing and require capacitors rated for high ripple current.
  3. Re-solder the main switching transistor legs (BU508 or 2SC2979) while the PSU is open.
  4. Re-solder the bridge rectifier terminals.
  5. Consider upgrading the bridge rectifier to a KBU1005 (10 A, 600 V) on all PSU models. The original 2 A rectifiers are marginal.

Post-Recap Voltage Checks

After completing the recap, reconnect the PSU to the motherboard and power on. Verify the following voltages:

Rail Expected Acceptable Range Measurement Point Action if Out of Range
+5 V 5.00 V 4.75–5.25 V Across C103 (4700 µF); joystick port pin 7 to ground Adjust PSU trim pot. If no trim pot or unable to adjust, PSU may need further repair.
+12 V 12.00 V 11.40–12.60 V Floppy drive power connector +12 V pin Trim pot adjustment (if available). Some PSUs regulate only +5 V; +12 V is semi-regulated.
−12 V −12.00 V −10.80 to −13.20 V MC1489 pin 14 Derived from +12 V via inverter circuit. If absent, check inverter components.

Ripple check (oscilloscope): Measure AC ripple on the +5 V rail at C103. Expected results after a proper recap:

  • Mitsumi SR98: ≤400 mV (≤200 mV with output diode upgrade to Schottky type)
  • DVE DSP-508A: ≤200 mV (excellent regulation)
  • ASTEC ASP34: ≤500 mV

If ripple exceeds these values after recap, check for a failed opto-coupler, incorrect capacitor values, or a failing switching transistor.

DMA Audio Verification

After replacing the audio-path capacitors (C202, C204, C205, C215, C216), verify DMA sound quality:

  1. Boot the STE to the GEM desktop.
  2. Run a DMA sound test program (e.g. fenarinarsa's ste_dmatest from https://github.com/fenarinarsa/ste_dmatest/releases/).
  3. Listen for:
    • Clean playback without high-pitched whistles (confirms C202/C204/C205 replacement was successful).
    • No crackling or popping (if present, see DAC latch fixes in Atari STE Troubleshooting Guide).
    • Balanced stereo output on both RCA channels.
  4. Test Microwire volume control by adjusting master volume — the LMC1992 should respond smoothly.

Capacitor Kit Sources

See Also

References

  1. ↑ Atari ST Cap Lists — STE section, Console5 TechWiki—link(accessed 2026-03-27)
  2. ↑ 1040 STE capacitors, Atari-Forum—link(accessed 2026-03-27)
  3. ↑ STe high pitched whining sound, Atari-Forum—link(accessed 2026-03-27)
  4. ↑ Atari ST Cap Lists — Mitsumi SR98, Console5 TechWiki—link(accessed 2026-03-27)
  5. ↑ The LaST Upgrade — SR98 repair, exxos—link(accessed 2026-03-27)
  6. ↑ The LaST Upgrade — SR98 peak current update, exxos—link(accessed 2026-03-27)
  7. ↑ The LaST Upgrade — DVE DSP-508A, exxos—link(accessed 2026-03-27)
  8. ↑ The LaST Upgrade — ASP34, exxos—link(accessed 2026-03-27)
  9. ↑ Atari 520STE/1040STE Cap Kit, Console5—link(accessed 2026-03-27)


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