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[[File:Macintosh Centris 650 (photo).jpg|thumb|300px|Macintosh Centris 650 (photo: Benoît Prieur, CC0)]]
This guide covers capacitor replacement for the '''Macintosh Centris 650''' and '''[[Macintosh Quadra 650]]'''. These systems share the same logic board and power supply design.
Capacitor diagnosis and replacement for the '''Macintosh Centris 650''' and the [[Macintosh Quadra 650]], which Apple services together in one ''Service Source'' volume.<ref name="ss650">Apple Computer, ''Centris 650/Quadra 650 Service Source''. Hosted as [[:File:Quadra.centris_650.pdf]]; see [[Centris 650/Quadra 650 Service Source]].</ref> On this machine the logic board is not the recap job; the power supply is.


== Important: Logic Board Uses Tantalum Capacitors ==
<templatestyles src="Template:StyledTable/styles.css" />


Unlike most Macintosh computers from the early 1990s, the '''Centris/Quadra 650 logic board uses tantalum capacitors instead of electrolytic capacitors'''. This is significant because:
== Safety ==
The power supply is a mains-rectified switching supply. Its primary side is at mains potential and the two large reservoir capacitors hold a lethal charge after the machine is unplugged.
# Switch off and unplug the mains lead.
# Discharge each large reservoir capacitor through a 1 kΩ, 5 W resistor across its terminals, then confirm with a meter that it reads near zero before touching anything.
# Do not probe a powered primary side without an isolation transformer.


* '''Tantalum capacitors do not leak''' – They won't cause the corrosive damage seen in systems like the Macintosh IIsi or LC series
The system unit has no CRT. Apple's displays contain their own tube and supply; see [[CRT Discharge Procedure]] when working on one.
* '''Preventive recapping is not required''' – You don't need to replace the logic board capacitors as a maintenance measure
* '''Tantalum caps can fail differently''' – When they fail, they may short-circuit, sometimes with smoke or flame (rare)


The '''power supply unit (PSU)''', however, contains standard electrolytic capacitors that may need replacement.
The supply accepts 100–240 V AC at 50–60 Hz with no voltage selector, and Apple rates the machine at 112 W maximum, not including display power.<ref name="ss650el">''Centris 650/Quadra 650 Service Source'', Specifications, Electrical, p. 9 (PDF p. 13).</ref>


== Capacitor Inspection ==
== What fails ==
* The logic board has no surface-mount aluminium electrolytics: Retro Viator found only tantalum and ceramic capacitors on a Quadra 650 logic board, which is the same board.<ref name="rv">{{cite web |url=https://retroviator.com/2021/09/02/apple-macintosh-quadra-650/ |title=Apple Macintosh Quadra 650 |publisher=Retro Viator |date=2021-09-02 |access-date=2026-09-30}}</ref> Check your own board.
* Solid tantalums most often fail short. A shorted filter tantalum pulls its rail down, and the supply shuts down or its fuse blows.<ref name="tdtant">TinkerDifferent forum thread [https://tinkerdifferent.com/threads/tantalum-vs-electrolytic-can-i-just-always-use-tantalum.4077/ "Tantalum vs Electrolytic. Can I just always use tantalum?"], January 2025. Secondary source for the 50 % voltage derating of solid tantalums and their short-circuit failure mode.</ref> Look for a cracked or scorched moulded body.
* The power supply does use aluminium electrolytics.<ref name="c5smp" />


Even though the logic board doesn't need preventive recapping, inspect both the logic board and power supply periodically:
Apple published no capacitor values for this machine. The ''Service Source'' has no capacitance, voltage-rating or designator data; power faults in its symptom charts end at "Replace power supply".<ref name="ss650ts">''Centris 650/Quadra 650 Service Source'', Troubleshooting, pp. 1-14 (PDF pp. 17-30).</ref>


=== Logic Board Inspection ===
== Identifying the power supply ==
Apple's service part number for the supply is 661-0758.<ref name="ss650ev">''Centris 650/Quadra 650 Service Source'', Exploded View (PDF p. 81).</ref> Apple's developer note says it is the same physical size as the Quadra 700's supply but delivers up to 112 W.<ref name="dn9">Apple Computer, ''Developer Note: Macintosh Centris 610, Macintosh Centris 650, and Macintosh Quadra 800 Computers'' (1993), "Power Supplies", p. 9 (PDF p. 21). Hosted as [[:File:Macintosh Centris 610 Centris 650 and Quadra 800 Developer Note.pdf]].</ref> Apple Rescue of Denver lists the same supply as Apple 614-0009 (service part 661-0758), 112 W, made by Delta (SMP-120EB) or ASTEC (AA16870), and fitted to the Centris and Quadra 650, IIvi, IIvx, Performa 600 and Power Macintosh 7100.<ref name="arod">{{cite web |url=https://applerescueofdenver.com/products-page/macintosh-to-powerpc/shop-by-model-desktop/macintosh-iivi-iivx-power-mac-7100-quadra-650/quadra-650-iivi-iivx-power-mac-7100-performa-600-power-supply/ |title=Quadra 650, IIvi, IIvx, Power Mac 7100, Performa 600 – Power Supply |publisher=Apple Rescue of Denver |access-date=2026-09-30}} "Apple 614-0009, 661-0758. 112w. ... Delta SMP-120EB, Astec AA16870."</ref><ref name="mlapsu">68kMLA forum thread [https://68kmla.org/bb/threads/compact-desktop-power-supply-capacitor-lists-by-make-and-model.35890/ "Compact Desktop Power Supply Capacitor Lists (by make and model)"]. Secondary source for the 614-0009 makers and models.</ref> Two makers means two different capacitor lists: open the supply and read the maker and board markings before ordering.


* '''Burn marks''' – Look for discoloration or charring near tantalum capacitors
== Power supply capacitors ==
* '''Failed tantalum caps''' – May show visible damage or burn marks
Console5 lists fifteen electrolytics in the Delta SMP-120EB version of the supply. It has no list for the ASTEC AA16870 version; read the markings on that one.<ref name="c5smp">Console5 Tech Wiki, [https://wiki.console5.com/wiki/Delta_SMP-120EB "Delta SMP-120EB"], capacitor list (page revision 7206, retrieved 2026-10-01). Secondary source; Console5 sells the parts as a kit.</ref>
* '''Corrosion''' – Check for PRAM battery leakage (different from cap leakage)


=== Power Supply Inspection ===
{| class="wikitable styled-table" style="width:60%;"
 
|+'''Delta SMP-120EB electrolytics (Console5)'''<ref name="c5smp" />
* '''Bulging Tops''' – Capacitors with domed tops have failed and must be replaced
! Designator !! Value
* '''Leaking Electrolyte''' – Brown or black residue around capacitor bases
|-
* '''Corrosion or PCB Staining''' – Electrolyte may spread across the PCB
| C1, C2 || 470 µF 200 V (680 µF on some revisions)
* '''Swelling''' – Any expansion of the capacitor body indicates failure
 
== Power Supply Capacitor Replacement ==
 
The power supply contains electrolytic capacitors that degrade over time. If your Centris/Quadra 650 exhibits power issues, PSU recapping may be necessary.
 
'''Warning:''' The power supply contains high-voltage capacitors that can retain dangerous charge. Discharge the supply properly before servicing.
 
=== Common PSU Capacitor Values ===
 
Exact values vary by PSU revision. Common capacitors found include:
 
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''Typical Power Supply Capacitors'''
|-
|-
! Capacitance !! Voltage !! Type !! Notes
| C103 || 2200 µF 10 V
|-
|-
| 1000µF || 10V || Electrolytic || Secondary filtering
| C104, C153, C154 || 1000 µF 16 V
|-
|-
| 470µF || 25V || Electrolytic || Secondary filtering
| C252 || 470 µF 25 V
|-
|-
| 220µF || 25V || Electrolytic || Various
| C253 || 470 µF 16 V
|-
|-
| 100µF || 25V || Electrolytic || Various
| C302, C522, C612, C684 || 10 µF 50 V
|-
|-
| 47µF || 50V || Electrolytic || Various
| C505 || 2.2 µF 50 V
|-
|-
| 10µF || 50V || Electrolytic || Various
| C551 || 1000 µF 35 V
|-
|-
| 1µF || 50V || Film/Ceramic || Replace with equivalent
| C807 || 470 µF 35 V
|}
|}


'''Note:''' Open your specific PSU and document the capacitor values before ordering replacements. Values may differ between PSU revisions.
=== The 200 V reservoir pair ===
C1 and C2 are 200 V parts on a supply that accepts 240 V mains, which rectifies to about 340 V DC; a single 200 V capacitor cannot hold that, so the two work as a series pair across the rectified bus. Replace both together with matching parts of the same value and at least the same voltage rating, and never fit a single 200 V capacitor in place of the pair.


== Logic Board Tantalum Capacitors ==
== Logic board capacitors ==
There is no routine work to do here. If a tantalum has failed:
# Find it: look for a cracked, split or scorched body, and for a rail that measures as a short to ground with the supply disconnected.
# Note its orientation. The bar on a tantalum marks the positive end, the opposite of an aluminium electrolytic's stripe.
# Remove it with hot air, or by alternating a fine iron between the two terminations.
# Fit a replacement of the same capacitance, derated by 50 %: a part on the 5 V rail wants a 10 V or higher rating, and one on 12 V wants 25 V.<ref name="tdtant" /> Some restorers use solid polymer electrolytics instead.<ref name="tdtant" />


The logic board uses surface-mount tantalum capacitors. These do '''not''' need preventive replacement. If one fails (rare), replace only the failed component.
For the signs of failure in general see [[Capacitor Failure Symptoms]].


=== Signs of Tantalum Capacitor Failure ===
== Replacement procedure ==
# Discharge the supply as above and confirm with a meter.
# Photograph each board before removing anything. The supply is built from stacked sub-boards.
# Desolder with a temperature-controlled iron and a pump or wick. The reservoir capacitors sit on heavy copper and need more heat.
# Clean the pads with isopropyl alcohol.
# Fit the replacements the right way round; the stripe on an aluminium electrolytic marks the negative lead.
# Trim leads, then check for bridges and stray clippings.
# Test the supply on a dummy load before connecting it to the logic board.


* System won't power on (dead short)
Use 105 °C, low-ESR parts suited to switching supplies. See [[Recommended Tools]].
* Visible burn marks on or near the capacitor
* Burning smell when system is powered
* Smoke from logic board (power off immediately!)


=== Tantalum Replacement Procedure ===
== Battery ==
Apple's check: set a voltmeter to the 10 V DC range, measure the battery in its holder (positive end marked "+" on the logic board), and replace it if it reads below 3.2 V. The holder has a latched cover; prise the latch with a small flat-blade screwdriver and lift the battery out.<ref name="ss650batt">''Centris 650/Quadra 650 Service Source'', Additional Procedures, Battery Verification and Battery Replacement, pp. 1-5 (PDF pp. 60-64).</ref> If it has leaked, see [[Battery Explosion, Capacitor or Corrosion Damage]].


If a tantalum cap fails and must be replaced:
== Apple's symptom charts and the power supply ==
 
Apple's charts include "Replace power supply" among the cures for:<ref name="ss650ts" />
# '''Identify the failed capacitor''' – Look for burn marks or measure with ESR meter
* no power, black screen, fan not running and LED off;
# '''Note polarity''' – Tantalum caps are polarized; mark orientation before removal
* clicking, chirping or thumping (power supply first, then logic board);
# '''Remove with hot air or soldering iron''' – Use appropriate SMD rework technique
* intermittent shutdown, after checking the air vents (thermal protection can shut the machine down for 30 to 40 minutes), the power cord and the battery;
# '''Clean pads''' – Remove residue with flux and solder wick
* intermittent crashes or lock-ups, after software, SCSI and SIMM checks;
# '''Install replacement''' – Observe correct polarity
* a dark screen with no sound and no drive activity while the fan runs and the LED is lit, after removing peripherals and NuBus cards and trying DRAM and VRAM;
# '''Use quality replacements''' – Consider polymer tantalum or equivalent-value ceramic capacitors
* no CD-ROM icon on the desktop.
 
== Power Supply Capacitor Replacement Procedure ==
 
# '''Discharge the PSU''' – Wait 24+ hours after unplugging, or use a discharge tool
# '''Document capacitor locations''' – Photograph before removal
# '''Remove old capacitors''' – Use desoldering pump or wick
# '''Clean pads''' – Remove residue with isopropyl alcohol
# '''Install replacements''' – Observe '''correct polarity''' (stripe indicates negative on electrolytics)
# '''Use quality capacitors''' – Nichicon, Panasonic, Rubycon, or equivalent
# '''Solder securely''' – Ensure good solder flow
# '''Inspect work''' – Check for solder bridges or cold joints
# '''Test before reassembly''' – Verify voltages before connecting to logic board
 
== Recommended Tools ==
 
* Temperature-controlled soldering station (adjustable 300-400°C)
* Desoldering pump or desoldering braid
* Fine solder (0.5-0.8mm diameter, leaded preferred for vintage work)
* Isopropyl alcohol (90%+) and ESD-safe brushes
* Flux (no-clean or water-soluble)
* Multimeter with capacitance testing
* ESR meter (optional but helpful)
* Safety glasses
* Heat-resistant gloves
* Capacitor discharge tool or resistor (for PSU)
 
== Voltage Verification After Recap ==
 
After recapping the PSU, verify output voltages before connecting to the logic board:
 
* '''+5V rail:''' 4.85V – 5.15V
* '''+12V rail:''' 11.9V – 12.7V
* '''-12V rail:''' -11.9V – -12.7V
 
== Additional Tips ==
 
* '''Order extra capacitors''' – Having spares saves time
* '''Match or exceed voltage ratings''' – 25V cap can be replaced with 25V or higher
* '''Match capacitance exactly''' – Don't substitute higher or lower values
* '''Consider cap kits''' – Some vendors sell complete recap kits
* '''Work in a well-ventilated area''' – Soldering fumes should be exhausted
* '''Take your time''' – Rushing leads to mistakes
 
== Related Maintenance Pages ==


== Related pages ==
* [[Macintosh Centris 650]]
* [[Macintosh Centris 650]]
* [[Macintosh Centris 650 Troubleshooting]]
* [[Macintosh Centris 650 Troubleshooting]]
* [[Macintosh Centris 650 General Maintenance]]
* [[Macintosh Centris 650 General Maintenance]]
* [[Macintosh Quadra 650]]
* [[Macintosh Quadra 650]]
* [[Capacitor Failure Symptoms]]
* [[Recommended Tools]]
== References ==
<references />
{{Navbox-AppleVintage|state=collapsed}}


[[Category:Apple Vintage Computers]]
[[Category:Apple Vintage Computers]]
[[Category: Capacitor Replacement Guides]]
[[Category:Capacitor Replacement Guides]]
Retrieved from "https://wiki.retrotechcollection.com/Macintosh_Centris_650_Capacitor_Replacement_Guide"