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P4 verification: real documentation page — identifies the sheet from its own title block, records that sheet 1 of every set is drawing 320130, and links the parts lists and display-assembly documents
Rewrite from the drawings: sheet 2 has the board's power input (J8, CR1-CR3, VR3-VR6, TP1-1..4); asterisk note is '8K machine only'; 555 at UDE9 is the reset timer; transformer and 23,000 uF cap are in the case; cite PET-Shack wiring and zimmers source
 
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'''Commodore drawing #320135''', the complete three-sheet main logic schematic for '''PET 2001 board assembly #320137''', Commodore Business Machines, Inc., Palo Alto, California. Three A-size sheets, scanned at 400 dpi.
'''Schematic 320135''' is Commodore's main logic schematic for the static [[Commodore PET 2001]] board assembly 320137, the version fitted with 2316B ROMs and 2114 RAM. The hosted PDF is a colour scan of the three drawings by Commodore Business Machines, Inc., Palo Alto, California, one 11 × 17 inch page per sheet. The same file, and separate monochrome scans of sheets 2 and 3, are in the PET 2001 schematics directory at zimmers.net.<ref name="zimmers">{{cite web |url=http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/2001/ |title=/pub/cbm/schematics/computers/pet/2001/ |website=zimmers.net |access-date=2026-10-01}} Directory listing: the four board PDFs (dated 2020-02-20), the 1998 GIF scans of sheets 2 and 3 for each board, and 320130-1.gif, described as sheet 1 of 3, "applies to all" four static boards.</ref>
 
Assembly 320137 is the static PET 2001 board fitted with '''2316B ROMs and 2114 RAM'''.


== The three sheets ==
== The three sheets ==
<templatestyles src="Template:StyledTable/styles.css" />
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table"
{| class="wikitable styled-table"
! Sheet !! Drawing number in the title block !! Title !! Separate page
|-
|-
! Sheet !! Drawing number in the title block !! Title !! Also on this wiki as
| 1 of 3 || 320130 || ''PET Computer Main Logic'', "Circuitry common to all PET computers" || [[Schematic 320130 (Sheet 1 of 3, Static PET)]]
|-
| 1 of 3 || '''#320130''' — not #320135 || ''PET Computer Main Logic'' — "Circuitry common to all PET computers" || [[Schematic 320130 (Sheet 1 of 3, Static PET)]]
|-
|-
| 2 of 3 || #320135 || ''PET Computer Main Logic — Memory Section'', pertaining to board assembly #320137 || [[Schematic 320135 (Sheet 2 of 3, Board 320137)]]
| 2 of 3 || 320135 || ''PET Computer Main Logic, Memory Section'', "pertaining to board assembly #320137" || [[Schematic 320135 (Sheet 2 of 3, Board 320137)]]
|-
|-
| 3 of 3 || #320135 || ''PET Computer Main Logic — Video Logic'', pertaining to board assembly #320137 || [[Schematic 320135 (Sheet 3 of 3, Board 320137)]]
| 3 of 3 || 320135 || ''PET Computer Main Logic, Video Logic'', "pertaining to board assembly #320137" || [[Schematic 320135 (Sheet 3 of 3, Board 320137)]]
|}
|}


'''Sheet 1 is the same drawing in all four sets.''' Its title block reads #320130 whichever board's PDF you open, which is why this wiki holds only one copy of it. Sheets 2 and 3 are the board-specific drawings and carry #320135.
Sheet 1 is the same drawing in all four board sets and always carries number 320130; only sheets 2 and 3 carry 320135. The wiki holds one separate copy of sheet 1.


== The four static board assemblies ==
== The four static board assemblies ==
<templatestyles src="Template:StyledTable/styles.css" />
Sheets 2 and 3 of every set carry Commodore's note: "All locations are same on all boards; only the specific components will differ on boards numbered 320132, 320081, 320137, 320008. The identifying board number is in upper left corner." A component position read from one set therefore applies to all four boards; only the fitted part changes.
 
{| class="wikitable styled-table"
{| class="wikitable styled-table"
! Board assembly !! Drawing (sheets 2–3) !! Program ROMs (H1–H7) and character generator (A2) !! Program RAM (rows I and J) and screen RAM (C3, C4)
|-
|-
! Board assembly !! ROMs !! RAM !! Drawing number for sheets 2–3
| 320008 || 320026 || 6540 || 6550
|-
|-
| 320008 || 6540 || 6550 || 320026
| 320081 || 320082 || 2316B || 6550
|-
|-
| 320081 || 2316B || 6550 || 320082
| 320132 || 320130 || 6540 || 2114
|-
|-
| 320132 || 6540 || 2114 || 320130
| 320137 || 320135 || 2316B || 2114
|-
| 320137 || 2316B || 2114 || 320135
|}
|}


Commodore's note is printed on sheets 2 and 3 of every set: '''"All locations are same on all boards; only the specific components will differ on boards numbered 320132, 320081, 320137, 320008. The identifying board number is in upper left corner."''' So a component location read off one of these drawings is valid for any static PET 2001 board; only the fitted part changes.
== What the sheets show ==
Sheet 1 is the processor and input/output section. It has the 6502 at F3, the 6520 PIAs at G8 (PIA 1) and B8 (PIA 2), the 6522 VIA at A5 and three MC3446 IEEE-488 transceivers at A7–A9. The LM555 at UDE9, timed by R15, R16 (1 MΩ) and C5 (1.0 µF tantalum), drives the reset line through inverter D9. The two cassette motor drivers are TIP29 transistors Q1 and Q4, switched by 2N4401s (Q2, Q5) and 2N3904s (Q3, Q6) with 7.2 V zeners VR1 and VR2, and run from the rail marked "+9V UN REG".


== What these sheets contain ==
Sheet 2 is the memory section. The seven 2316B ROMs H1–H7 occupy C000–E7FF and F000–FFFF. The sixteen 2114 RAMs are in two rows: I1–I8 carry data bits D0–D3 and J1–J8 bits D4–D7, two chips to each 1 KB from 0000 to 1FFF. The chips for 1000–1FFF (I1–I4 and J1–J4) are marked with an asterisk, and the handwritten note beside the title block reads "All ckts marked * are for 8K machine only". A link on the SEL1 line is labelled "Jumper for 8K only".
* '''Sheet 1''' — the 6502 at UF3, both 6520 PIAs (UB8, UG8), the 6522 VIA (UA5), the three MC3446 IEEE-488 transceivers at UA7–UA9, the LM555 retrace timer, the cassette interface with its TIP29 motor drivers and 7.2 V zeners, and the keyboard matrix pull-ups. '''No regulator''' — the board takes +5 V and +9 V unregulated from elsewhere in the machine.
* '''Sheet 2, Memory Section''' — the ROM and RAM array for this assembly specifically, which is what distinguishes the four boards.
* '''Sheet 3, Video Logic''' — character generator, video timing and the display output.


Some circuits on sheets 2 and 3 are marked with an asterisk and annotated '''"all ckts marked * are for BC machine only"''' — the business-keyboard variant.
Sheet 2 also carries the logic board's power input. Connector J8 feeds rectifiers CR1–CR3 (1N5402), C50 and C51 (0.02 µF 500 V), C11–C13 (1.0 µF 25 V) and four three-terminal regulators, VR3–VR6. Each regulator has a 47 µF 16 V output capacitor (C7–C10) and a test point, TP1-1 to TP1-4. The regulator type is not printed on the drawing.


== What these sheets do not contain ==
Sheet 3 is the video logic: the 8 MHz crystal Y1, the 2316B character generator at A2 feeding a 74LS165 shift register at B2, the two 2114 screen RAMs at C3 and C4, and connector J7, which takes video, horizontal drive and vertical drive to the display board.
* '''No parts list.''' Values appear on the drawing where the drawing carries them. For the full component list with Commodore part numbers see [[System Board Parts List (1 of 3)]] and [[Commodore PET 2001 Service Documentation]].
* '''No power supply and no display circuitry.''' The mains transformer, the rectifiers, the 4700 µF reservoir and the flyback are all on the '''display assembly''' — see [[Video Board Schematic]] and [[Video Board Parts List (1 of 3)]].


Each sheet carries Commodore's 1970s trade-secret notice down the left edge. It is of historical interest only.
== What the sheets do not contain ==
There is no parts list. Values are written beside the parts where Commodore gave them. Commodore's part numbers are in the ''Main Logic Assembly Parts Cross Reference'', held here as [[System Board Parts List (1 of 3)]] (an earlier Palo Alto issue, three images) and [[2001 Main Logic Assembly]] (a later Santa Clara issue, one PDF). That list does not include VR3–VR6, C50 or C51, which appear only on sheet 2.
 
The transformer and the display are not on these sheets. PET-Shack's console wiring drawing puts the power switch, a 1.8 A fuse, the mains transformer and a 23,000 µF capacitor in the case, with a 15.7 V AC centre-tapped winding to the logic board and a 16.2 V AC winding to the video monitor.<ref name="bundle">PET-Shack (P.S. Software House), PET 2001 schematic and data-sheet bundle, c. 1978, hosted at [[:File:PET-Shack PET 2001 Bundle.pdf]], PDF p. 4, "PET console wiring": power switch, 1.8 A fuse, transformer with a 16.2 V AC winding "to video monitor" and a 15.7 V AC centre-tapped winding to the logic board connector, and a 23,000 µF capacitor. Third-party, not a Commodore document.</ref> The display board has its own bridge rectifier, 4700 µF reservoir (C1) and 7812 regulator (VR1); its T1 is the horizontal driver transformer and T2 the flyback.<ref name="video">Commodore Business Machines, ''Schematic, Service, Display Circuit'', hosted as [[:File:Video-1.gif]] (see [[Video Board Schematic]]). Low-voltage AC enters at the board connector into bridge CR19–CR22 (1N5402), reservoir C1 4700 µF 25 V and regulator VR1 (78/12) for +12 V; T1 is the horizontal driver transformer and T2 the flyback (+10 kV).</ref>


== Related pages ==
== Related pages ==
* [[Commodore PET 2001]] · [[Commodore PET 2001 Service Documentation]] · [[Commodore PET 2001 Capacitor Replacement Guide]] · [[Commodore PET 2001 General Maintenance]] · [[Commodore PET 2001 Troubleshooting]]
* [[Commodore PET 2001]]
* The other three board sets: [[Schematic 320026 (Complete, Board 320008)]] · [[Schematic 320082 (Complete, Board 320081)]] · [[Schematic 320130 (Complete, Board 320132)]]
* [[Commodore PET 2001 Service Documentation]]
* [[Commodore PET 2001 Capacitor Replacement Guide]]
* [[Commodore PET 2001 General Maintenance]]
* [[Commodore PET 2001 Troubleshooting]]
* The other board sets: [[Schematic 320026 (Complete, Board 320008)]], [[Schematic 320082 (Complete, Board 320081)]], [[Schematic 320130 (Complete, Board 320132)]]


<pdf> File:320137.pdf </pdf>
<pdf> File:320137.pdf </pdf>


Download: [[:File:320137.pdf|320137.pdf]]
Download: [[:File:320137.pdf|320137.pdf]]
== References ==
<references />


[[Category:Commodore PET 2001 Schematics]]
[[Category:Commodore PET 2001 Schematics]]
[[Category:Commodore Documentation]]
[[Category:Commodore Documentation]]
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