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Schematic Notes for Video Board: Difference between revisions

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Remove wrong claim that mains reaches the display board; quote the sheet; cite zimmers and the display schematic; copyedit
 
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'''''Supplement to Schematic for Display Circuit''''' — Commodore Business Machines, Inc. A single typed sheet giving '''the oscilloscope settings for each of the fourteen waveform photographs''' printed on the [[Commodore PET 2001]] display circuit schematic.
'''Schematic Notes for Video Board''' holds Commodore's ''Supplement to Schematic for Display Circuit'', a single typed page on Commodore Business Machines letterhead (901 California Avenue, Palo Alto, California). It gives the oscilloscope settings for the fourteen waveform photographs printed on the [[Commodore PET 2001]] display circuit schematic, held here as [[Video Board Schematic]]. The sheet opens: "The following data should accompany each of the photographs". The scan is notes-2.gif from the PET 2001 schematics directory at zimmers.net, which describes it as "Notes to go with video board schematic".<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}}</ref>
 
'''This is not a set of notes about the video board.''' It is one specific thing: the vertical sensitivity and timebase that go with each numbered waveform photograph on [[Video Board Schematic]]. Without it, those photographs cannot be compared against a real measurement, because the scale they were taken at is not printed beside them. The two documents are useless apart.


== The settings, as printed ==
== The settings, as printed ==
<templatestyles src="Template:StyledTable/styles.css" />
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table"
{| class="wikitable styled-table"
|-
! Picture !! Vertical !! Timebase !! Note
! Picture !! Vertical !! Timebase !! Note
|-
|-
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| 8 || 0.5 V || 20 µs ||
| 8 || 0.5 V || 20 µs ||
|-
|-
| 9 || 0.5 V || 20 µs || '''11.6 V peak'''
| 9 || 0.5 V || 20 µs || 11.6 V peak
|-
|-
| 10 || 0.2 V || 20 µs ||
| 10 || 0.2 V || 20 µs ||
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|}
|}


Commodore's sheet writes these as "mil sec" and "micro sec"; they are milliseconds and microseconds per division, and the voltage figures are volts per division. '''Picture 9 is the only one with an absolute figure against it: 11.6 V peak.''' That is the single measurable number in the document, and it is the only amplitude Commodore published for any of the fourteen test points.
Commodore writes each line as a voltage and a time ("1V 5 mil sec", "1V 20 micro sec") without saying "per division". Picture 9 is the only one with an amplitude against it, "11.6V peak".


== What it does not contain ==
== What it does not contain ==
It does not say '''where''' each photograph was taken — the numbered test points are on the schematic itself, not here. It carries no component values, no rail voltages and no fault information.
The page does not say where each photograph was taken. The numbered test points, circled 1 to 14, are marked on the display circuit schematic itself. The page has no component values, rail voltages or fault information.


{{Warning|The display assembly is the PET's power supply as well as its monitor. Mains voltage is present on it whenever the machine is plugged in, the CRT anode runs at roughly +10 kV from flyback T2, and C1 is a 4700 µF reservoir that stores real energy. Read [[CRT Discharge Procedure]] before working on this board.}}
{{Warning|The CRT anode runs at about +10 kV from flyback T2 on the display board, and the tube holds its charge after power-off. Read [[CRT Discharge Procedure]] before working on the display board.<ref name="video">Commodore Business Machines, ''Schematic, Service, Display Circuit'', hosted as [[:File:Video-1.gif]]. Shows the fourteen waveform photographs and the circled test points 1-14, the +10 kV output of flyback T2, bridge CR19-CR22, reservoir C1 4700 µF 25 V and regulator VR1 (78/12) for +12 V.</ref>}}


== Related pages ==
== Related pages ==
* [[Video Board Schematic]] — the sheet these settings belong to
* [[Video Board Schematic]], the drawing these settings belong to
* [[Video Board Parts Layout]] · [[Video Board Parts List (1 of 3)]]
* [[Video Board Parts Layout]]
* [[Commodore PET 2001 Service Documentation]] · [[Commodore PET 2001 Troubleshooting]] · [[CRT Discharge Procedure]]
* [[Video Board Parts List (1 of 3)]]
* [[Commodore PET 2001 Service Documentation]]
* [[Commodore PET 2001 Troubleshooting]]


[[File:notes-2.gif|thumb|600px|Commodore's ''Supplement to Schematic for Display Circuit'' — the oscilloscope settings for the fourteen waveform photographs.]]
[[File:notes-2.gif|thumb|600px|Commodore's ''Supplement to Schematic for Display Circuit'', the oscilloscope settings for the fourteen waveform photographs.]]


Download: [[:File:notes-2.gif|notes-2.gif]]
Download: [[:File:notes-2.gif|notes-2.gif]]
== References ==
<references />


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