Warning: Many wholesalers will try to sell their $50, untested HP-85s for the same price as collector quality computers, that have been restored. You must know what you are buying. Phrases like "working" or "powers up" are code for "not tested and fully working." If it is 100% functional, it should say that the "tape drive works" or the "printer tested and works." Anything that is vague, should be assumed to be "not working."

HP-85 Tape drives almost never work. The tape drive capstan rubber dissolves. If you buy one in unknown condition, it will not work and you will have to spend $200+ to have someone fix it, unless you do it yourself. A seller can easily test this, even without a tape. A simple visual check of the rubber capstan will tell if it's bad. If it is sticky, soft or tacky, it is bad. If in doubt, count on it being bad.

There are basically 3 things that make an HP-85 valuable: The model, The cosmetic appearance and functionality.

• HP-85A - The HP-85A is marked HP-85, in most cases. The "A" model is a Basic 16K computer. You will likely need a Mass Storage ROM for the "A" to use an HP-IB interface, as this is not built-in. This model can use a 16K RAM plugin. An "A" with a 16K plugin and the Mass Storage ROM, is nearly the same as a "B" model.

• HP-85B - The "B" model is a 64K computer (32K Program RAM, 32K EDISC) and has the Mass Storage ROM built into the computer. It also includes a built-in Electornic Disc. This ED makes the "B" model a slightly higher performer than the "A" model. This model cannot use the 16K RAM module.

• Cosmetic appearance - Cosmetic appearance is very important. Very little can be done to correct fading or other uglies that have been added with time. I put high value on excellent cosmetics.

• Functionality (Tape drive) - I have yet to find an HP-85 that has a working tape drive. The rubber on the capstan dissolves with time and most wholesale HP-85 have this problem. Ones that start off working usually fail within hours of use with a tape. These are very costly to fix, if you have someone do it for you. Another thing that goes bad with these is the end of tape light. This light burns out and the tape will spool off the end of the reel.

• Functionality (Printer) - Print heads can fail. This causes missing lines on your printout. If this happens, you will have to purchase another machine to find spare print head as these are no longer made. But the most common failure is in the printer drive belts. These, too, get crumbly and fail. There are two belts that often need replacing.

Recommendation: Do NOT blindly believe everything that is in the description. Working should mean 100% working. Ask questions. Ask for more photos. If a calculator is Mint, Brand New, or Unused, it should be no different from one that just came off the assembly line. It is a lot easier to believe your own eyes.

Questions you should ask: (Be wary of vague or incomplete answers)

• Is(are) the photo(s) shown, actually, of the calculator being sold
• Is the HP-85 tested and known to be 100% functional (including tape and printer)
• Have all accessories (included) been tested in this system
• Is the tape drive tested and working 100%
• Has the tape drive capstan been recently replaced
• Does the printer work?
• Does every print line work and does it feed properly
• Have the printer belts been recently replaced
• Is there any branding with personal names or other personal ID marks
• Are there any faded areas that are not shown
• Is there anything that is broken or missing on the HP-85
• Don't assume what might be included. If not stated, it's not included. ASK!

Finally, even with all these precautions, you can sometimes still be fooled. But at least you have enough information to know what to look for and what to ask. Without photos, you have more risk and have to trust the seller's word. Check the feedback. Check for repeat customers. Check what other items the seller sells. If he appears to deal in HP products, the "not tested" should raise a flag and should mean "possibly not working."

About me: I an a long-time HP collector. I have owned just about every calculator that HP has ever made, including most of the vintage computer line. I am also an Electronic Circuit Designer, with 28+ years experience. I have a great deal of experience in restoring old HP computers and calculators. But I still learn something every week about these.

My HP-85 computers: - are 100% tested and known to work. I replace the tape capstan rubber (if needed) with brand new rubber. So, there is never a question about my tape drives working. I also replace both printer drive belts (if needed) with brand new printer belts. With my systems, you avoid the need to make repairs to the two most common failure areas of the HP-85. Drives and printer are always tested.