HP9825 lights and drive wheels



#2

Previously, I have contacted Etienne Victoria with thanks for a method of refurbishing the drive wheel of the tape recorder. Where I work we have a number of HP 9825's and most have the sticky wheel problem. His method is good but with the addition of a Dremel routing table to hold the drill and glueing the sandpaper to a square piece of wood, the necessary sizing can be accomplished. Material to shape can be pressure cones (slip joint washers) for toilet tank water supplies or electrical grommets with almost any size preselected. I used a 932 dremel grinding stone to hold the slip joint (Danco STK no 38805B or 38808B), since the 9825B cleaned wheel was very close to 3/8 of an inch of the stone. A finely divided metal ruler and patience (don't try to rush) in shaping does the job. I don't have a web site yet to post linking pictures (but am willing to send JPGs of what I did, but give me an indication of the resolution you would like). The final dimensions (in inches) are: ID = 0.375 OD = 0.410 and width 0.150. Dremel has other dimensions of stones or a larger one could be dressed down to hold the proper ID. I thought I would have mine well tested by now, but I noticed no light in the tape transport. To make a long story short, I discovered that not all 9825's have a visible light. This one had an infrared diode (part number F5D1) which I thought was an incandescent bulb (with part number F501) when I emailed Etienne Victoria. So be careful, not all nonvisible lights are burnt out. I also found out my digital camera can take a picture of the active diode and shows up pink in the picture. I have not tried yet (discovery was today Jan. 24, 2006) to detect the IR in an assembled 9825. Oh, the 9825Bs with the diode also have an 82 ohm resistor connecting it to the +5 volt supply thereby limiting the current to about 45 milliamps. Tony Duell may want to show this on his schematics if it not sown there already. I have ordered them but they have not yet arrived. If anyone has replaced an incandescent bulb I would be interested to know if the hole size is different than the F5D1 (T0-48 package) made by Fairchild. I also have taken many pictures during the disassembly process.

Eugene Royer


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