80 Series Selection:
|Product Number: 85
|Ad: Click to see, Click to see
|Original Price: $2750
|Catalog Reference: 1981, page 620
|Donated by: Paul Jones, Victoria.
The 85A was a small, low-cost, fully integrated computer with built in six inch CRT display, tape drive and thermal printer. The display (and printer) had a graphics resolution of 256 x 192 dots and displayed 16 rows of text, with up to 32 characters per row. The cartridge mass storage tapes could hold 210K data. The computer came standard with 16K RAM, upgradeable to 32K. The 85B replaced the 85A in 1983. It came standard with 64K RAM, expandable to 544K using pluggable ROM modules. The 85B also came standard with the mass storage ROM built in. The 85 was a very successful product for HP.
The 85B was obsoleted in November of 1987.
The HP-85 is a terrific little computer. It's small, easy to use and very reliable. Of the dozen or more units that the museum has processed, all have worked. The paper-advance and printhead drive (timing) belts decay, but they are easy to replace. The paper advance drive belt has 80 teeth and is 162.56mm long. A belt width of either 3.175mm or 6.35mm will work. One supplier of this belt can be found here. The printhead drive belt has 175 teeth, is 355.6mm long and 3.175mm wide. One supplier of this belt can be found here. Be careful about spending too much time removing and replacing the internal assemblies. The ribbon connectors that connect the modules are very fragile; we are not aware of a replacement source.
The only problem with the 85 is the tape drive. Very few of these drives are operational. Although the gooey capstan wheel can be replaced, other components are failure-prone. Regardless of whether the drive works, the old tapes are now very marginal. They are subject to breaking easily; it is also common for the magnetic substrate to flake off (even with brand new tapes). So, it's best to get any programs or data that you want to keep onto disc as soon as possible (this also makes the programs easy to archive). The 85 is easy to program and the small screen is surprisingly adequate.
Click here for a technique to replace gooey capstan wheels on the tape drive. Click here to view a YouTube video on how to repair the gooey capstan wheel.
Click here to visit Larry Atherton's HP-85 refurbishment site. Larry completely rebuilds HP-85 computers , replacing the tape drive with a reliable QIC drive.
Click here to see CuriousMarc's 16-volume video series on testing and repairing different parts of the HP-85.
For a detailed tutorial on restoring HP-85 tape drives and tapes, be sure to visit the hp9845.net site. Here.^ TOP
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