irwin@A.CS.UIUC.EDU (Al Irwin) (01/24/86)
We have two of the Ricoh print engines from Imagen, known as the 12/300s. Today while working on them, we discovered an interesting thing about them. In the rear, there are two fans. When viewed from the rear, the one on the lower right corner has an air filter, which can be accessed by removing the service panel which has two large screws holding it in place. We removed the panel to check the filter and found that it had dust on the <inside>, indicating that the fan was installed backwards, and air was being filtered as it <left> the printer, not as it entered. The one in the upper left is the exhaust fan and the one on the lower right is the <inlet> fan, but ours was installed at the factory in reverse order in both units, so as a result, we had four outlet fans in our two printers and no inlet fans. The air that they moved managed to leak in through all of the various cracks between cabinet sections, etc. The metal panel that the fan is bolted to can be removed by removing the two screws at the right end and one screw at the left end. If the fusing drawer is unlatched and slid back about an inch, there is just enough room to tilt the top of the fan panel out at the top, so it can be removed. Go slowly, there is a fan AC power lead that plugs into the printed circuit board that is behind the panel. You will have to unplug it, and then you can completely remove the fan panel and reverse the fan if yours is also backwards. I would bet that ours is not the only units in the field that have this error. The air flow is supposed to be a positive air system, one pushing air in and the other pulling it out. Behind the inlet fan, there is a large heat sink on the circuit board that is to be cooled by the fan. In our case, there was no direct air flow on it, with the fan backwards. This did not cause us a failure, but could have lead to one, as the air filter <looked clean> from the outside, but when removed, it was clogged on the inside where the dirt was not visable, at first glance. I hope this info serves to point someone else to a potential problem, before it happens. I would be interested, if anyone else discovers that their fans are wrong, after being alerted by this notice. Al Irwin U of Illinois Computer Sci Dept Urbana, Il 61801
MELNYK.WBST@XEROX.COM (01/30/86)
Al you may be quite right about the fan being reversed on your Ricoh print engines from Imagen. But I suggest that you double check with the manufacturer. I am not familiar with this machine, but in general, xerographic machines including laser printers, filter the exhaust air to remove the dry ink powders. Higher speed copiers/printers even use special (activated charcoal) filters to remove ozone generated by the corona charging before exhausting into the room. The intake of this air is usually filtered, but that depends on the design. The flow path is first through the optics path at the photoreceptor (to keep the window cleen on the laser ROS) then past the corotron charging and out between charging and the cleaning housing (to remove stray ink leaking out of the cleaner). This airflow is separate from the cooling for the electronics but may not be in a low cost design. Andy Melnyk