|Printer and Photocopier Troubleshooting and Repair Collection : Apple Laserwriter IINT 'clicks' with int..
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"I have a LaserWriter IINT with an intermittent fuser error. When the printer
is switched on, sometimes it cycles normally and works fine; but sometimes,
the startup cycle sound is followed by a soft click, and a few moments later
the green light gives way to double blinking red. I have attached a voltmeter
to the fuser lamp contacts; when the soft click is heard, no voltage reaches
(From: Tony Duell (firstname.lastname@example.org).)
The click is almost certainly the fuser protection relay dropping out. This
relay is located in the AC input block assembly at one end of the fuser, under
the main cooling fan.
This relay is on the lower board in that module, and is driven by the
protection circuit (a few transistors, not hard to trace out if needed) on the
upper board. It operates if the fuser drive signal from the DC controller is
active for too long at a time - it prevents the fuser from overheating if one
of the CPUs on the DC controller goes crazy
OK, things to check:
- Look for dry joints on both boards in the AC input block. They are VERY common here.
- Check the thermistor in the fuser. Clean it, check for dry joints, check
that it is pressing against the fuser roller.
- Reseat all the connectors on the DC controller board associated with the
fuser and AC input block.
- If that doesn't cure it, you'll need to hang a scope off the fuser drive
signal (one of the 4 wires from the DC controller to the AC block - the
other 3 are ground, +24 V and fan speed control) and see if the fault is in
the DC controller (Signal does stick high) or the AC block.
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