RetroTechCollection - User contributions [en]

Commodore PET 2001 Capacitor Replacement Guide

2025-08-01T22:06:22Z

JoshTest:

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The first-generation '''PET 2001''' (1977 – 1979)—assemblies 320008 / 320081 / 320132—uses a simple linear supply together with an internal 9" monochrome CRT. After forty-plus years, the original electrolytic capacitors are at (or past) their design life. Re-capping:

* stabilises the +5 V / +12 V rails used by the logic and VIC video section,
* removes vertical “jail-bars”, shimmering, or ticking noises caused by dried-out CRT filter caps, and
* protects irreplaceable ICs such as the '''6502''', the twin '''6520/6522 PIA/VIA''' I/O chips, and the early mask ROM/SRAM devices.

'''''Tip ►''' The PET will usually still boot with tired capacitors—but voltages sag as it warms up, causing random lock-ups and screen collapse. Fix the caps before chasing “mystery” digital faults.''

== Visual Inspection ==
* '''Bulging or domed tops''' – particularly the two large 4 700 µF smoothing cans (C9 & C10).
* '''Brown crust''' or green verdigris at the rubber bungs.
* '''‘Fishy’ smell''' when the board warms up – electrolyte seepage.
* '''White salt deposits''' around the CRT board’s high-voltage electrolytics.

If any of the above are present, _replace the whole set_ – piecemeal swaps often lead to repeated strip-downs.

== Capacitor Reference Tables ==
Values are taken from Commodore parts sheets '''parts-3.gif''' (system board) and '''parts-6.gif''' (video board) for the PET 2001 series. Board lettering differs slightly between early 6540/6550 “static” boards (320008) and later 2316B/2114 “dynamic” boards (320132); positions are therefore given as '''silkscreen “Cx” + functional description'''.

=== 🔌 Main Power / Logic Board (all 2001 revisions) ===
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''Power & Regulator Section'''
! Designator !! Location / Function !! Capacitance !! Voltage !! Notes
|-
| C9 || 5 V rail smoothing (after bridge) || 4 700 µF || 25 V || Axial can, glue-mounted
|-
| C10 || 5 V rail secondary filter || 4 700 µF || 25 V || Identical to C9
|-
| C11 || 12 V booster reservoir || 2 200 µF || 25 V || Generates +12 V for VIC/audio
|-
| C12 || 5 V pre-reg filter || 1 000 µF || 25 V || Near 7805 regulator heatsink
|-
| C13 / C14 || Logic decoupling bulk caps (left & right board edges) || 220 µF || 16 V || 2 pcs
|-
| C16 – C27 || Local bypass (scattered across DRAM/ROM rows) || 10 µF || 16 V || 12 pcs
|}

''Use '''105 °C low-ESR''' parts for C9–C13—they run hot next to the transformer.''

=== CRT (Video/Deflection) Board ===
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''9″ Monitor / Deflection Section'''
! Designator !! Function !! Capacitance !! Working V !! Qty
|-
| C101 || B+ rail reservoir || 220 µF || 200 V || 1
|-
| C102 || Horizontal output stage || 100 µF || 200 V || 1
|-
| C103 || Vertical sweep supply || 47 µF || 160 V || 1
|-
| C108 || Video amplifier decouple || 10 µF || 50 V || 1
|-
| C110 / C111 || Sync & oscillator timing || 1 µF || 160 V || 2
|-
| C115 || Heater/filament filter || 100 µF || 25 V || 1
|-
| C120 – C123 || Frame-store / blanking filters || 22 µF || 50 V || 4
|}

'''Safety!''' C101 & C102 sit at ~160 V DC. Discharge them _with a 100 kΩ 2 W resistor_ before desoldering.

=== Optional Dynamic-RAM Board (PET 2001-8 upgrade) ===
Early 2001-8 machines add a small plug-in board carrying four 2114 SRAMs and four 10 µF / 16 V electrolytics (C201–C204). Replace these at the same time.

== 🛠️ Replacement Procedure ==
# '''Isolate power''' & remove the 2 A slo-blo fuse.
# '''Disassemble''' – take out the motherboard (4 screws) and pivot the monitor/keyboard assembly.
# '''Document''' with photos; note capacitor polarity (square pad = positive on PET PCBs).
# '''Desolder''' using braid or a spring pump. PET boards are single-sided—lifted pads are common; be gentle.
# '''Clean pads''' with isopropyl alcohol; scrape away corroded lacquer if necessary.
# '''Fit new capacitors'''; keep lead length minimal and apply fresh thermal compound to the 7805 if removed.
# '''Re-assemble''', checking that C9/C10 do not short against the case bottom.
# '''Power-on with series-bulb limiter''' (or bench-supply) and verify rails:
## +5 V = 4.95 – 5.10 V at the 6502 (pin 8 = GND, pin 40 = Vcc)
## +12 V ≈ 11.6 – 12.6 V at VIC pin 18
# Run the PET for '''30 min burn-in'''; touch-test that the 7805 < 65 °C and C101/C102 remain cool.

== Tooling Checklist ==
* Temperature-controlled '''soldering iron''' (fine 1 mm conical tip)
* '''Desoldering wick''' 2 mm & spring pump
* '''ESR meter''' or capacitance tester (optional but recommended for pre-check)
* '''100 kΩ / 2 W resistor lead''' for safe high-voltage discharge
* Non-acidic '''IPA (99 %)''' & ESD brush
* '''Kevlar gloves / eye protection''' for CRT section work

== Post-Recap Adjustments ==
The PET’s PSU has no trimmer; voltage is set by the transformer and 7805.
If +5 V is low after recapping, check:

* bridge rectifier D1–D4 for heat damage,
* continuity of the power-switch contacts, and
* correct mains-tap wiring (120 V vs 240 V).

The '''monitor''' focus & vertical-height pots (_on the video board_) may drift after fresh caps—re-adjust for crisp text with a plastic tool.

== Additional Notes ==
* C9/C10 sometimes leak _inside_ the aluminium can and look fine externally—always meter for ESR.
* Early _“blue label”_ PETs (with 6540 ROMs) omit C11; later logic boards include it—verify before ordering.
* If you plan a modern '''switch-mode 5 V module''' in place of the 7805, you may down-rate C9/C10 to 2 200 µF 16 V low-ESR; ripple is dramatically lower.

== 🔗 Related Pages ==
* [[Commodore PET 2001 Troubleshooting|Commodore PET 2001 Troubleshooting Guide]]
* [[Commodore VIC-20 Capacitor Replacement Guide]]

[[Category:Commodore Systems]]
[[Category:Capacitor Replacement Guides]]

User:JoshTest

2025-05-10T17:46:48Z

JoshTest: Created page with "This is User:Josh's Test Account 😊"

This is [[User:Josh]]'s Test Account 😊

Category:Apple Vintage Computers

2025-05-10T17:33:58Z

JoshTest:

__NOTOC__
{{CategoryHeaderBox
| title = Apple Vintage Computers
| subtitle = Preserving and Maintaining Apple's Legacy Machines
}}
{{cmbox
| type = notice
| text = The Apple Vintage Computers category is still under construction, some pages are missing, or, not complete. The category page is also incomplete. '''If you wish to contribute, please do!'''
}}

[[File:Apple Computer Inc Logo.svg|349x349px|right|frameless]]
Welcome to the '''Apple Vintage Computers''' category! This section is dedicated to maintenance, restoration, diagnostics, and historical documentation for classic Apple Macintosh computers. Each system features:
* Detailed maintenance guides (cleaning, recapping, preventative care)
* Troubleshooting resources for analog/logic board faults
* Capacitor replacement specifications and diagrams
* RAM upgrades and logic board variants

== 🖥️ Macintosh 128K & 512K ==
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|-
! Model !! Maintenance !! Troubleshooting !! Capacitor Guide
|-
| [[Macintosh 128K]] || [[Macintosh 128K/512K General Maintenance]] || [[Macintosh 128K/512K Troubleshooting]] || [[Macintosh 128K/512K Capacitor Replacement Guide]]
|-
| [[Macintosh 512K]] || [[Macintosh 128K/512K General Maintenance]] || [[Macintosh 128K/512K Troubleshooting]] || [[Macintosh 128K/512K Capacitor Replacement Guide]]
|}

== 💾 Macintosh Plus ==
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|-
! Model !! Maintenance !! Troubleshooting !! Capacitor Guide !! Memory Upgrade
|-
| [[Macintosh Plus]] || [[Macintosh Plus General Maintenance]] || [[Macintosh Plus Troubleshooting]] || [[Macintosh Plus Capacitor Replacement Guide]] || [[Macintosh Plus Memory Upgrade Guide]]
|}

== 🖥️ Macintosh SE ==
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|-
! Model !! Maintenance !! Troubleshooting !! Capacitor Guide !! Memory Upgrade
|-
| [[Macintosh SE]] || [[Macintosh SE General Maintenance]] || [[Macintosh SE Troubleshooting]] || [[Macintosh SE Capacitor Replacement Guide]] || [[Macintosh SE Memory Upgrade Guide]]
|}

== 🖥️ Macintosh SE/30 ==
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|-
! Model !! Maintenance !! Troubleshooting !! Capacitor Guide !! Memory Upgrade !! Logic Board
|-
| [[Macintosh SE/30]] || [[Macintosh SE/30 General Maintenance]] || [[Macintosh SE/30 Troubleshooting]] || [[Macintosh SE/30 Capacitor Replacement Guide]] || [[Macintosh SE/30 Memory Upgrade Guide]] || [[Macintosh SE/30 Reloaded Logic Board]]
|}

== 🖥️ Macintosh Classic ==
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|-
! Model !! Maintenance !! Troubleshooting !! Capacitor Guide !! Memory Upgrade
|-
| [[Macintosh Classic]] || [[Macintosh Classic / Classic II General Maintenance]] || [[Macintosh Classic / Classic II Troubleshooting]] || [[Macintosh Classic Capacitor Replacement Guide]] || [[Macintosh Classic Memory Upgrade Guide]]
|}

== 🖥️ Macintosh Classic II ==
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|-
! Model !! Maintenance !! Troubleshooting !! Capacitor Guide !! Memory Upgrade
|-
| [[Macintosh Classic II]] || [[Macintosh Classic / Classic II General Maintenance]] || [[Macintosh Classic / Classic II Troubleshooting]] || [[Macintosh Classic II Capacitor Replacement Guide]] || [[Macintosh Classic II Memory Upgrade Guide]]
|}

== 🖥️ Macintosh Color Classic ==
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|-
! Model !! Maintenance !! Troubleshooting !! Capacitor Guide !! Memory Upgrade
|-
| [[Macintosh Color Classic]] || [[Macintosh Color Classic General Maintenance]] || [[Macintosh Color Classic Troubleshooting]] || [[Macintosh Color Classic Capacitor Replacement Guide]] || [[Macintosh Color Classic Memory Upgrade Guide]]
|}

== 🖥️ All Apple Computers ==
{{Navbox-AppleVintage|state=expanded}}

== 🧠 Sad Mac Errors & Diagnostics ==
* '''[[Sad Mac Error Codes]]''' – Comprehensive reference of system error codes and boot chimes.
* '''[[Diagnostic Serial Console]]''' – Serial-based diagnostic mode for SE and SE/30 systems.
* '''[[Diagnostic Flowcharts]]''' – Visual logic for narrowing down hardware faults (coming soon).

== 💾 Drives & Storage ==
* '''[[Macintosh Floppy Drive Maintenance]]''' – Repair, lubrication, and alignment of Apple floppy drives.
* '''[[Macintosh HDD Maintenance]]''' – Restoration and longevity practices for SCSI-based drives.
* '''[[Apple Hard Disk 20 Maintenance]]''' – Maintenance for Apple’s early external hard disk system.

== 🌟 Retrobrite (Plastic Whitening) ==
* '''[[Retrobrite]]''' – Safe and effective techniques to reverse yellowing on plastic enclosures.

== 🧪 Tools & Procedures ==
* '''[[Recommended Tools]]''' – Essential gear for restoration, soldering, cleaning, and diagnostics.
* '''[[CRT Discharge Procedure]]''' – Critical safety process for working inside compact Macintosh CRTs.
* '''[[Capacitor Failure Symptoms]]''' – Recognizing common symptoms of failing or leaking electrolytic capacitors.

== 🔧 Maintenance & Repair Resources ==
* [[:Category:Apple Service Source|Apple Service Manuals]] – Official Apple service documentation.
* [[:Category:Apple Documentation|Apple Books, Guides & Technical Notes]] - Aggregated repair literature, diagrams, and other books.

== 🛠️ Planned Models (Coming Soon) ==
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|-
! Model !! Maintenance !! Troubleshooting
|-
| [[Macintosh IIci]] || (Planned) || (Planned)
|-
| [[Macintosh IIsi]] || (Planned) || (Planned)
|-
| [[Macintosh LC]] || (Planned) || (Planned)
|-
| [[Macintosh Portable]] || (Planned) || (Planned)
|}

== 🔍 See Also ==
* '''[[List of Apple Macintosh models by CPU type]]'''
* '''[https://forum.retrotechcollection.com/index.php#apple-vintage-computers.10 RTC Community Forum – Apple Section]'''
* [[:Category:Macintosh Memory Upgrades|'''Macintosh Memory Upgrades''']]

[[Category:Vintage Computers]]