can't get a 9825T tape drive to work

[phe78]

Hi folks,

I recently acquired a 9825T (similar to the 9825B, with full travel keys, but with added internal ROMs I believe), and as expected the tape cartridge was faulty, returning "error 43" to any cassette I was inserting, including reliable several 3M DC1000A that work fine on my HP85.

I checked the wheel and actually it has been replaced previously, the gum was looking new and the cassette was spinning smoothly. Okay, so then I took the drive apart and discovered the tachometer light bulb was dead. Cool I thought, I found the issue, I purchased a set of bulb from ebay, soldered one in, and got the "error 43" again.

So time to investigate further... I tool apart the motor and realized the tachometer radial lines that are printed on a plastic cover on top of the photodiode were almost erased. The radial pattern on the capstan wheel look used but still OK. I decided to move the plastic piece on top of the photodiode so that a better-looking portion of "radial lines" faces the sensor. Same result.

This is not the first time I see these tachometers disks worn out, the printed pattern being erased by the friction with the spinning disk. Has anyone in this forum face a similar issue ? How did you get this fixed ?

Another question : I could not find any schematic of the 9825 tape drive, and reference voltage, waveforms etc like I have for the HP85. If someone has such a documentation, I would be interested to look at it.

thanks in advance for your feedback
Philippe

[cruff]

Look at http://www.hpmuseum.net for schematics of various models, along with the service handbooks.