Osborne 1 Troubleshooting Guide: Difference between revisions

(One intermediate revision by the same user not shown)

Line 1:

[[File:Osborne 1 (photo).jpg|thumb|right|300px|Osborne 1. Source: Wikimedia Commons.]]

Line 152:

Line 153:

** Test for continuity in ribbon cable.

** Suspect PIA (Peripheral Interface Adapter, e.g. 6821) if keyboard matrix fails.

== ⚠️ Power supply ==

Recap the Osborne 1 supply before relying on it. The mains-side '''RIFA-type suppression capacitors''' crack and fail with '''smoke and loud bangs''' shortly after power-on, and the large filter electrolytics dry out after 40+ years — prioritise the '''4700 uF, 2200 uF and 1000 uF''' filter capacitors. A faulty disk drive can also overload the '''+12 V''' rail and cause crashes, so check the drives if the supply sags under load.<ref name="osb">[https://www.classic-computers.org.nz/blog/2008-12-06-osborne-repair-1.htm Repairs to an old Osborne 1], Tezza's Classic Computers; [https://www.richardloxley.com/2018/04/03/osborne-restoration-part-3-servicing-the-psu-and-disk-drives/ Osborne Restoration: PSU and disk drives], Richard Loxley; and the [https://www.eevblog.com/forum/repair/osborne-1-repair/ EEVblog Osborne 1 repair thread]. Source for the PSU capacitor failures (RIFA smoke/bangs and the 4700/2200/1000 uF filter caps), the CRT/no-video checks, the disk-drive 12 V overload, the DRAM garbage-screen piggy-back test, and the socket/ribbon reseating.</ref>

== No video / CRT ==

The Osborne 1 has a small built-in CRT. For a dark screen: confirm the CRT filament glows faintly (in a dark room), check for EHT (high voltage) at the tube, and inspect the CRT/neck board for burnt resistors, a failed flyback transformer or a cracked neck board. A '''rolling''' display is set with the vertical/horizontal hold potentiometers; if adjusting them does nothing, suspect the timing ICs.<ref name="osb">[https://www.classic-computers.org.nz/blog/2008-12-06-osborne-repair-1.htm Repairs to an old Osborne 1], Tezza's Classic Computers; [https://www.richardloxley.com/2018/04/03/osborne-restoration-part-3-servicing-the-psu-and-disk-drives/ Osborne Restoration: PSU and disk drives], Richard Loxley; and the [https://www.eevblog.com/forum/repair/osborne-1-repair/ EEVblog Osborne 1 repair thread]. Source for the PSU capacitor failures (RIFA smoke/bangs and the 4700/2200/1000 uF filter caps), the CRT/no-video checks, the disk-drive 12 V overload, the DRAM garbage-screen piggy-back test, and the socket/ribbon reseating.</ref>

== Garbage screen / no boot ==

A non-boot with garbage characters is commonly a '''dynamic RAM (DRAM) failure'''. Piggy-back a known-good DRAM on each suspect chip to isolate the bad one, and replace it with anti-static precautions. Because the Osborne uses many socketed ICs and board-to-board ribbon cables that corrode, first '''reseat every socketed IC and every ribbon''' (especially the logic-to-CRT-board ribbon) and clean the pins with isopropyl alcohol.<ref name="osb">[https://www.classic-computers.org.nz/blog/2008-12-06-osborne-repair-1.htm Repairs to an old Osborne 1], Tezza's Classic Computers; [https://www.richardloxley.com/2018/04/03/osborne-restoration-part-3-servicing-the-psu-and-disk-drives/ Osborne Restoration: PSU and disk drives], Richard Loxley; and the [https://www.eevblog.com/forum/repair/osborne-1-repair/ EEVblog Osborne 1 repair thread]. Source for the PSU capacitor failures (RIFA smoke/bangs and the 4700/2200/1000 uF filter caps), the CRT/no-video checks, the disk-drive 12 V overload, the DRAM garbage-screen piggy-back test, and the socket/ribbon reseating.</ref>

== Disk drives ==

Both floppy drives and their controller take part in booting. At power-on, listen for drive spin-up and head movement, and check the drive power and data cables. A drive that is mechanically stuck or electrically shorted loads down the +12 V rail and takes the whole machine down with it.<ref name="osb">[https://www.classic-computers.org.nz/blog/2008-12-06-osborne-repair-1.htm Repairs to an old Osborne 1], Tezza's Classic Computers; [https://www.richardloxley.com/2018/04/03/osborne-restoration-part-3-servicing-the-psu-and-disk-drives/ Osborne Restoration: PSU and disk drives], Richard Loxley; and the [https://www.eevblog.com/forum/repair/osborne-1-repair/ EEVblog Osborne 1 repair thread]. Source for the PSU capacitor failures (RIFA smoke/bangs and the 4700/2200/1000 uF filter caps), the CRT/no-video checks, the disk-drive 12 V overload, the DRAM garbage-screen piggy-back test, and the socket/ribbon reseating.</ref>

== References ==

== Related Pages ==

@@ Line 1: / Line 1: @@
 <templatestyles src="Template:StyledTable/styles.css" />
+[[File:Osborne 1 (photo).jpg|thumb|right|300px|Osborne 1. Source: Wikimedia Commons.]]
 <templatestyles src="Template:StyledTable/styles.css" />
@@ Line 152: / Line 153: @@
 ** Test for continuity in ribbon cable.
 ** Suspect PIA (Peripheral Interface Adapter, e.g. 6821) if keyboard matrix fails.
+== ⚠️ Power supply ==
+Recap the Osborne 1 supply before relying on it. The mains-side '''RIFA-type suppression capacitors''' crack and fail with '''smoke and loud bangs''' shortly after power-on, and the large filter electrolytics dry out after 40+ years &mdash; prioritise the '''4700 uF, 2200 uF and 1000 uF''' filter capacitors. A faulty disk drive can also overload the '''+12 V''' rail and cause crashes, so check the drives if the supply sags under load.<ref name="osb">[https://www.classic-computers.org.nz/blog/2008-12-06-osborne-repair-1.htm Repairs to an old Osborne 1], Tezza's Classic Computers; [https://www.richardloxley.com/2018/04/03/osborne-restoration-part-3-servicing-the-psu-and-disk-drives/ Osborne Restoration: PSU and disk drives], Richard Loxley; and the [https://www.eevblog.com/forum/repair/osborne-1-repair/ EEVblog Osborne 1 repair thread]. Source for the PSU capacitor failures (RIFA smoke/bangs and the 4700/2200/1000 uF filter caps), the CRT/no-video checks, the disk-drive 12 V overload, the DRAM garbage-screen piggy-back test, and the socket/ribbon reseating.</ref>
+== No video / CRT ==
+The Osborne 1 has a small built-in CRT. For a dark screen: confirm the CRT filament glows faintly (in a dark room), check for EHT (high voltage) at the tube, and inspect the CRT/neck board for burnt resistors, a failed flyback transformer or a cracked neck board. A '''rolling''' display is set with the vertical/horizontal hold potentiometers; if adjusting them does nothing, suspect the timing ICs.<ref name="osb">[https://www.classic-computers.org.nz/blog/2008-12-06-osborne-repair-1.htm Repairs to an old Osborne 1], Tezza's Classic Computers; [https://www.richardloxley.com/2018/04/03/osborne-restoration-part-3-servicing-the-psu-and-disk-drives/ Osborne Restoration: PSU and disk drives], Richard Loxley; and the [https://www.eevblog.com/forum/repair/osborne-1-repair/ EEVblog Osborne 1 repair thread]. Source for the PSU capacitor failures (RIFA smoke/bangs and the 4700/2200/1000 uF filter caps), the CRT/no-video checks, the disk-drive 12 V overload, the DRAM garbage-screen piggy-back test, and the socket/ribbon reseating.</ref>
+== Garbage screen / no boot ==
+A non-boot with garbage characters is commonly a '''dynamic RAM (DRAM) failure'''. Piggy-back a known-good DRAM on each suspect chip to isolate the bad one, and replace it with anti-static precautions. Because the Osborne uses many socketed ICs and board-to-board ribbon cables that corrode, first '''reseat every socketed IC and every ribbon''' (especially the logic-to-CRT-board ribbon) and clean the pins with isopropyl alcohol.<ref name="osb">[https://www.classic-computers.org.nz/blog/2008-12-06-osborne-repair-1.htm Repairs to an old Osborne 1], Tezza's Classic Computers; [https://www.richardloxley.com/2018/04/03/osborne-restoration-part-3-servicing-the-psu-and-disk-drives/ Osborne Restoration: PSU and disk drives], Richard Loxley; and the [https://www.eevblog.com/forum/repair/osborne-1-repair/ EEVblog Osborne 1 repair thread]. Source for the PSU capacitor failures (RIFA smoke/bangs and the 4700/2200/1000 uF filter caps), the CRT/no-video checks, the disk-drive 12 V overload, the DRAM garbage-screen piggy-back test, and the socket/ribbon reseating.</ref>
+== Disk drives ==
+Both floppy drives and their controller take part in booting. At power-on, listen for drive spin-up and head movement, and check the drive power and data cables. A drive that is mechanically stuck or electrically shorted loads down the +12 V rail and takes the whole machine down with it.<ref name="osb">[https://www.classic-computers.org.nz/blog/2008-12-06-osborne-repair-1.htm Repairs to an old Osborne 1], Tezza's Classic Computers; [https://www.richardloxley.com/2018/04/03/osborne-restoration-part-3-servicing-the-psu-and-disk-drives/ Osborne Restoration: PSU and disk drives], Richard Loxley; and the [https://www.eevblog.com/forum/repair/osborne-1-repair/ EEVblog Osborne 1 repair thread]. Source for the PSU capacitor failures (RIFA smoke/bangs and the 4700/2200/1000 uF filter caps), the CRT/no-video checks, the disk-drive 12 V overload, the DRAM garbage-screen piggy-back test, and the socket/ribbon reseating.</ref>
+== References ==
+<references />
 == Related Pages ==