Posts: 1,162
Threads: 26
Joined: Aug 2005
I took my 9915 tape drive apart recently -- AFIAK it's the same unit as in the HP85. Although there are some small rollers, etc that will fall out if you take the top section apart, it's easy to remove the capstan without doing that. All you do is remove the tape drive from the machine, disconnect the tachometer lamp leads from the PCB (some machines have these soldered in place -- my 9115 did, others have them plugged into little pin sockets on the PCB).
Unplug the motor wiring from the PCB. Remove the 4 screws round the motor on the underside of the unit. Remove the motor and capstan complete. Undo the 2 Allen screws (0.050" key) holding the capstan to the spindle, and pull it off. Take great care not to damage the tachometer disk.
I need to rebuild the capstan in this drive (and in some other similar HP drives I have here) -- can you tell me what the outside diameter of the capstan should be?
Posts: 265
Threads: 29
Joined: Jan 1970
Here's how I fixed the tape drive on my 9815:
In the plumbing department at Home Depot I found some stuff called Magic Wrap, it's a roll of very thin rubber 1" x 16'. I cut a 2" x 1/4" piece of this stuff stretched it out to about the width of the roller then wrapped it around (several turns) the cleaned off roller as tight as I could. Then I smoothed it out by spinning the drive wheel at high speed and grinding down the rubber with an emery board. This sort of melts the rubber and fusses it to itself getting rid of the overlap and making the whole thing perfectly symmetric. To spin the drive wheel I disconnected one of the motor leads and put it on a variable power supply. You can use up to 12 volts but I found 5 or 6 volts ran the wheel plenty fast with tons of torque. Basically, you want to use it like a lathe and I found that the tape head makes a good tool rest!