Macintosh Quadra 840AV Troubleshooting: Difference between revisions

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See the [[Macintosh Quadra 840AV Capacitor Replacement Guide]] for recapping information.

== ⚠️ PRAM battery — remove it now ==

The Quadra 840AV carries a 3.6 V 1/2AA lithium PRAM battery. These leak and can '''burst''', spraying corrosive electrolyte across the logic board and destroying nearby components — often while the machine simply sits in storage. '''Remove the PRAM battery from any un-serviced unit.''' If one has leaked, neutralise and clean the residue and repair corroded traces and vias before troubleshooting.<ref name="mac2_batt">[https://68kmla.org/bb/threads/warning-exploding-maxell-pram-batteries.25169/ "Warning! Exploding Maxell PRAM Batteries"], 68kMLA; and [https://macdat.net/macintosh/macii/macintosh_iicx.html MacDat — Macintosh II family]. Source for the leaking/exploding lithium PRAM battery that destroys nearby components.</ref>

== Logic board (tantalum capacitors) ==

Unlike the LC and Mac II surface-mount-electrolytic boards, the 68040-family Quadra 840AV logic board uses '''tantalum''' capacitors, which do not leak with age — the '''logic board does not normally need recapping'''. If the board misbehaves, look to leaked-PRAM-battery corrosion, socket/connector contacts and the power supply rather than to board capacitors.<ref name="quadra_tant">[https://retroviator.com/2021/09/02/apple-macintosh-quadra-650/ "Apple Macintosh Quadra 650"], Retro Viator; and the Apple Macintosh Quadra/Centris 650 Service Source. Source for the 68040-family logic boards using tantalum capacitors (no logic-board recap needed) while the power supply uses electrolytics that do need replacing.</ref>

== Power supply ==

The power supply uses electrolytic capacitors that fail with age (fails to power on, unexpected power-off, clicking when plugged in). '''Recap the power supply''' and confirm the rails.<ref name="mac2_psu">[https://68kmla.org/bb/threads/compact-desktop-power-supply-capacitor-lists-by-make-and-model.35890/ "Compact/Desktop Power Supply Capacitor Lists (by make and model)"], 68kMLA; and [https://www.bigmessowires.com/2016/04/21/capacitor-replacement-in-a-vintage-power-supply/ "Capacitor Replacement in a Vintage Power Supply"], Big Mess o' Wires. Source for the shared desktop PSU form factor (IIci/IIcx/IIvi/IIvx/Performa 600/Quadra 650/Quadra 700), the electrolytic failure symptoms and the PSU capacitor lists.</ref>

== AV features ==

The Quadra 840AV adds the AT&T DSP3210 digital signal processor and video in/out. If the machine boots but AV functions (video capture/out, enhanced sound) fail, confirm the AV software/extensions are installed and check the DSP and the AV connector before suspecting the main logic.

== References ==

== Related Pages ==

@@ Line 243: / Line 243: @@
 See the [[Macintosh Quadra 840AV Capacitor Replacement Guide]] for recapping information.
+== ⚠️ PRAM battery — remove it now ==
+The Quadra 840AV carries a 3.6&nbsp;V 1/2AA lithium PRAM battery. These leak and can '''burst''', spraying corrosive electrolyte across the logic board and destroying nearby components &mdash; often while the machine simply sits in storage. '''Remove the PRAM battery from any un-serviced unit.''' If one has leaked, neutralise and clean the residue and repair corroded traces and vias before troubleshooting.<ref name="mac2_batt">[https://68kmla.org/bb/threads/warning-exploding-maxell-pram-batteries.25169/ "Warning! Exploding Maxell PRAM Batteries"], 68kMLA; and [https://macdat.net/macintosh/macii/macintosh_iicx.html MacDat &mdash; Macintosh II family]. Source for the leaking/exploding lithium PRAM battery that destroys nearby components.</ref>
+== Logic board (tantalum capacitors) ==
+Unlike the LC and Mac II surface-mount-electrolytic boards, the 68040-family Quadra 840AV logic board uses '''tantalum''' capacitors, which do not leak with age &mdash; the '''logic board does not normally need recapping'''. If the board misbehaves, look to leaked-PRAM-battery corrosion, socket/connector contacts and the power supply rather than to board capacitors.<ref name="quadra_tant">[https://retroviator.com/2021/09/02/apple-macintosh-quadra-650/ "Apple Macintosh Quadra 650"], Retro Viator; and the Apple Macintosh Quadra/Centris 650 Service Source. Source for the 68040-family logic boards using tantalum capacitors (no logic-board recap needed) while the power supply uses electrolytics that do need replacing.</ref>
+== Power supply ==
+The power supply uses electrolytic capacitors that fail with age (fails to power on, unexpected power-off, clicking when plugged in). '''Recap the power supply''' and confirm the rails.<ref name="mac2_psu">[https://68kmla.org/bb/threads/compact-desktop-power-supply-capacitor-lists-by-make-and-model.35890/ "Compact/Desktop Power Supply Capacitor Lists (by make and model)"], 68kMLA; and [https://www.bigmessowires.com/2016/04/21/capacitor-replacement-in-a-vintage-power-supply/ "Capacitor Replacement in a Vintage Power Supply"], Big Mess o' Wires. Source for the shared desktop PSU form factor (IIci/IIcx/IIvi/IIvx/Performa 600/Quadra 650/Quadra 700), the electrolytic failure symptoms and the PSU capacitor lists.</ref>
+== AV features ==
+The Quadra 840AV adds the AT&T DSP3210 digital signal processor and video in/out. If the machine boots but AV functions (video capture/out, enhanced sound) fail, confirm the AV software/extensions are installed and check the DSP and the AV connector before suspecting the main logic.
+== References ==
+<references />
 == Related Pages ==