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Apple ProFile Capacitor Replacement Guide

From RetroTechCollection
The power supply sits under the controller board (Apple owner's manual, 1983)

The electrolytic capacitors in the power supply of the Apple ProFile, from the component listings in Apple's 1982 Astec power supply service package. ProFile supplies were made by Astec: the package covers the AA11770, AA11770/A and AA11771 used in the ProFile for Apple III, and Apple's later ProFile supply specification names the AA11771.[1][2] Read the Astec number on your supply before ordering parts; the two main versions differ.

The Level II service manual also contains Apple's schematic 050-5009, "120V/240V Switchable Power Supply". It is not covered here; if your supply does not carry an Astec AA1177x number, check it against that schematic.[3]

Safety

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The supply runs from the mains, selected for 115 or 230 V by a jumper on the board.[2] Its four 47 µF 250 V capacitors (C6-C9) hold a charge after the drive is unplugged; discharge them and measure before touching the board. Check the voltage jumper before reconnecting the supply. See Capacitor Failure Symptoms.

Astec AA11770

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Astec AA11770 electrolytic capacitors[1]
Ref Value Voltage Tolerance Part number
C6, C7, C8, C9 47 µF 250 V +100/−10% 057-47020040
C10 220 µF 10 V +50/−10% 057-22120080
C13, C15, C24 1000 µF 10 V +100/−10% 057-10220020
C16 330 µF 16 V ±20% 057-33120120
C20 1000 µF 25 V +50/−10% 057-10220040
C21, C22 470 µF 25 V +50/−10% 057-47120110

C14, C17 and C23 have no part listed. The other capacitors on the board are film, metallised paper and ceramic types (C1-C5, C11, C12, C18, C19, C25).[1] The AA11770/A version adds a monitor board whose list includes two 10 µF 25 V tantalum capacitors (C3, C4).[1]

Astec AA11771

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Astec AA11771 electrolytic capacitors[1]
Ref Value Voltage Tolerance Series Part number
C6, C7, C8, C9 47 µF 250 V +100/−10% 057-47020040
C10 220 µF 10 V ±20% SXA 057-22120300
C13 1000 µF 16 V ±20% SXA 057-10220180
C16 100 µF 25 V ±20% SXA 057-10120270
C20, C21 1000 µF 16 V ±20% SXA 057-10220180
C22 100 µF 25 V ±20% SXA 057-10120120
C24 2200 µF 10 V ±20% SXA 057-22220120

The AA11771 list continues with C25-C32, which include two 10 µF 25 V tantalum capacitors (C28, C29); the rest are film and ceramic.[1]

Output rails

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Apple's specification for the ProFile supply gives +5 V ±2% at 2.0 A, +12 V ±6% at 1.5 A (3.5 to 4.0 A for 10 to 14 seconds while the disks spin up) and −12 V ±6% at 0.1 A, with ripple and noise of 50 mV peak to peak on +5 V and 100 mV on +12 V. The +5 V output has a crowbar for over-voltage protection.[2] The Astec component lists do not say which capacitor sits on which output; follow the schematic in the Astec package before choosing replacements with a different voltage rating.[1]

Procedure

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  1. Remove the cover, disconnect the LED cable and take out the controller board.[3]
  2. Unplug the small white connector between the power supply and the HDA, turn the drive over and remove the four screws holding the supply to the bottom of the case.[3]
  3. Turn the drive back over, remove the longer outer rear plate (two screws) and the four screws holding the supply to the inner rear plate, and lift the supply out.[3]
  4. Discharge C6-C9, note the polarity of every electrolytic, and replace them one at a time with parts of the same capacitance and at least the same voltage rating.
  5. Refit the supply with its two cables facing the HDA, reconnect the two-pronged power cable behind the orange Mylar cable, and reassemble.[3]

After the repair

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Measure the supply at connector P3 on the controller board with at least one module connected, as Apple's troubleshooting chart requires: +5 V ±0.1 V on pin 1, +12 V ±1.2 V on pin 2, Power OK at +5 V ±0.3 V on pin 3 and −12 V ±1.2 V on pin 4.[4] Then let the drive complete its power-on scan; see Apple ProFile Troubleshooting Guide.

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References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Apple Computer, Apple Products Information Package: Astec Power Supplies, originator Larry Sovulewski, 6 August 1982, hosted as File:Apple Astec Power Supplies Service Package 1982.pdf (see Apple Astec Power Supplies Service Package). Contents p. 1; ProFile III schematics and layouts pp. 7-10; component listings AA11770 pp. 21-24, AA11770/A p. 25, Apple monitor board 656-0104 p. 25a, AA11771 pp. 26-31.
  2. ↑ 2.0 2.1 2.2 Apple Computer, Power Supply, ProFile, specification 062-0074-C and drawing 699-0059-B, hosted as File:Apple ProFile Power Supply Specification 062-0074.pdf. The purchased supply is Astec AA11771, mechanically equivalent to Apple 656-5102, with monitor circuitry equivalent to Apple 656-4106.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Apple Computer, ProFile Level II Service Manual, 072-0116, update 1 of 12 October 1984, Table of Contents (Appendix E schematics) and Service Procedures, Power Supply p. 2.11, hosted as File:Apple ProFile Level II Service Manual 072-0116 (1984).pdf.
  4. ↑ ProFile Level II Service Manual, main troubleshooting flowchart sheet 2, Figure 3, p. 1.6 (PDF p. 18), and note p. 1.7 (PDF p. 19), hosted as File:Apple ProFile Level II Service Manual 072-0116 (1984).pdf.


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