Commodore PET 2001 Capacitor Replacement Guide: Difference between revisions
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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: | |||
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, | * stabilises the +5 V / +12 V rails used by the logic and VIC video section, | ||
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* protects irreplaceable ICs such as the '''6502''', the twin '''6520/6522 PIA/VIA''' I/O chips, and the early mask ROM/SRAM devices. | * 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). | * '''Bulging or domed tops''' – particularly the two large 4 700 µF smoothing cans (C9 & C10). | ||
* '''Brown crust''' or green verdigris at the rubber bungs. | * '''Brown crust''' or green verdigris at the rubber bungs. | ||
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If any of the above are present, _replace the whole set_ – piecemeal swaps often lead to repeated strip-downs. | 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 | 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'''. | ||
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) === | === 🔌 Main Power / Logic Board (all 2001 revisions) === | ||
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''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;" | {| class="wikitable styled-table" style="width:100%; text-align:center;" | ||
|+'''9″ Monitor / Deflection Section''' | |+'''9″ Monitor / Deflection Section''' | ||
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|} | |} | ||
'''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. | 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. | ||
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# Run the PET for '''30 min burn-in'''; touch-test that the 7805 < 65 °C and C101/C102 remain cool. | # 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) | * Temperature-controlled '''soldering iron''' (fine 1 mm conical tip) | ||
* '''Desoldering wick''' 2 mm & spring pump | * '''Desoldering wick''' 2 mm & spring pump | ||
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* '''Kevlar gloves / eye protection''' for CRT section work | * '''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. | The PET’s PSU has no trimmer; voltage is set by the transformer and 7805. | ||
If +5 V is low after recapping, check: | If +5 V is low after recapping, check: | ||
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The '''monitor''' focus & vertical-height pots (_on the video board_) may drift after fresh caps—re-adjust for crisp text with a plastic tool. | 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. | * 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. | * Early _“blue label”_ PETs (with 6540 ROMs) omit C11; later logic boards include it—verify before ordering. | ||
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[[Category:Commodore Systems]] | [[Category:Commodore Systems]] | ||
[[Category:Capacitor Replacement Guides]] | [[Category:Capacitor Replacement Guides]] | ||