This guide is the result of years of experience in buying actively Hewlett-Packard vintage calculators on eBay. It concerns only pocket calculators and some peripherals, when they are available. It is made for everyone who is looking for a fine calculator or for the exigent collector. It is not made for traders who lose their precious time to make poor money on the back of collectors, buying and reselling immediately on eBay (often bad condition, not sufficiently described or tested and overpriced products) without thinking one minute about HP glory’s days.
I dedicate this guide to the HP Museum site which is a good introduction for HP calculator’s fans and to HP Corporation who represents a big part in my career in Information Technologies.
The HP vintage pocket calculators family
Between 1972 and the beginning of 90’s, HP produced different families of calculators. Each family could be identified by a series name:
The first series of calculators: The HP-35, HP-45, HP-55, HP-65, HP-67, HP-70 and the HP-80.
The HP-21, HP-22, HP25, HP-25C, HP-27, HP-29C.
The HP-31E, HP-32E, HP-33E, HP-33C, HP-34C, HP-37E, HP-38E, HP-38C.
The HP-10 and the HP-19C having a built in printer.
The HP-41C, HP-41CV and the HP-41CX.
The HP-10C, HP-11C, HP-12C, HP-15C, HP-16C.
Also called the Clamshell series: The HP-18C, HP-19B, HP-19BII, HP-28C and HP-28S.
The HP-20S, HP-21S, HP-22S, HP-27S, HP-32S, HP-32SII, HP-42S for the scientific models,
but also: The HP-10B, HP-14B, HP-17B, HP-17BII for the financial models.
- Titan, Kangaroo and Merlin
Respectively: The HP-71B, HP-75C and HP-75D.
Some recent models should also be considered regarding their power and application catalog:
- The HP-48S, HP-48SX, HP-48G, HP-48G+ and HP-48GX.
What you have to check before buying
Most of problem I experienced concern the description made intentionally or not ambiguous and/or incomplete by the sellers.
Here is what you have to check before to contract with the seller.
- Never buy a calculator described untested except if you are looking for some specific parts that can be clearly identified as fitting for your purposes on the pictures. Untested means in major cases not working just because as a working calculator is much more valuable, the seller has interests in specifying it. Furthermore, it is pretty easy to get the expected batteries for testing.
- Never buy a calculator if pictures are not supplied or if they are not enough clear. Scratches cannot be checked on a poor picture and have an impact on the price.
- If possible, ask for a front, back, and battery compartment picture.
- Ask if not specified what is included and avoid to buy a calculator without its original pouch just because if you want it later, you will have to pay more for it and add extra shipping costs. For calculators working with batteries, ask if they are supplied (even dead because it is easy to rebuild a battery pack) with the battery charger. As for the pouch, a battery charger sold alone can be expensive.
- Never consider a calculator announced protected by the Paypal protection program like insurance. I experienced situations where the seller took particular attention to disguise the reality or gave an ambiguous or fake description where Paypal was not enough competent on this field to give a good judgment,
- The original packaging (box, travel case, registration card, accessories list), an original owner’s manual, applications manuals, keyboard overlays or the quick reference guide, even if they are not necessary, are components that can have a big influence on the price, consider them carefully.
- Ask if not specified if the calculator is free from scratch, ding, crack or other cosmetic blemish like a name, social# or other inscription engraved or painted somewhere. Those things have a main influence on the market price. Take care that there was no attempt to hide a scratch or a crack with a repair (paint, glue …).
- Check for calculator’s rubber feet, battery cover, port covers if existing, presence and usage.
- For some models having a back label (showing diagram or explanations for example), check that it has not been removed or altered (removing attempts …). Those labels in most cases protect screws that give access to the internal; it is often a sign of repair and has a bad impact on market price.
- Ask for serial number and check on the HP Museum site that this serial number matches the model.
- Ask if not specified if battery compartment is corrosion free; if battery tabs are in perfect shape (not cracked, broken or missing) and if the calculator turns on with and without the battery charger (when the model can manage both ways).
- Check if there is no display problem (missing information like dot, segment or other indicator).
- Ask if the keyboard is perfectly working with no sticky or repeating key. HP calculator’s are know for their specific precision in the famous HP click.
Specific aspects regarding Classic series
Those old ladies need more attention than others. Here are specific aspects you have to consider:
- Battery contacts have to be shiny with no corrosion evidence. Most of the time, those ladies has been forgotten in the back of a closet for years without removing the battery pack.
- Battery door’s tabs are often incomplete missing the part avoiding the tab to get out of the rail.
- Like in Woodstock, Spice and Sting series, the LED display is sometime incomplete showing missing LED segments. Check with the seller that each digit segment, comma, dot, minus sign is present (all eight test: -8.888888888 -88). For some model, the display is soldered on the motherboard and it is impossible to change it easily.
- Take care to the back label more than other series.
- Take care about the key’s HP click aspect.
- Check if the seller used a metallic leafing pen to restore or emphasized the metallic like plastic border under the display (HP 45 V1 & V2 and HP 80 V1 & V2 have a real metallic band) and all around the calculator. Depending on your expectations, you can tolerate or not this practice.
- The battery pack is not mandatory as it can be easily found and rebuilt.
Specific aspects regarding Woodstock series
They belong to 70’s too and are sometime more than 30 years old then be careful of following:
- Battery contacts sometime have been broken inside or show some soldering evidence to enhance contacts with the battery.
- It is mandatory to own the battery pack because this battery pack and the battery door is one piece.
- Like for Classic, Spice and Sting series, the LED display is sometime incomplete showing missing LED segments. Check with the seller that each digit segment, comma, dot, minus sign is present (all eight test: -8.888888888 -88). The display can be replaced by a working one taken on another model of the same series.
- As the battery door is hard to open, there is often scratch on the back (door, case and bottom label).
- Ask for a complete working test (basic operations, display and keyboard responsiveness) because some people try sometime to use it just with the battery charger and without the battery pack damaging them.
Specific aspects regarding Spice series
Those models are relatively recent (80’s) and cost optimization started to enter in the production process. Here is what you have to verify:
- A poor conception of the battery compartment makes it impossible to receive standard AA batteries without breaking the 2 battery tabs. Even with the battery pack supplied, the risk exists and is emphasized by a sensibility to corrosion. It is essential to check that battery tabs are perfects and to ask to the seller to ship the calculator with the battery pack apart.
- Like for Classic and Woodstock series, the LED display is sometime incomplete showing missing LED segments. Check with the seller that each digit segment, comma, dot, minus sign is present (all eight test: -8.888888888 -88 obtained by pressing STO ENTER). The display can be replaced by a working one taken on another model of the same series.
- Check if there is no crack around the 2 screws present on the top inside of the battery compartment. It is a weakness point.
- The battery door can show some attempts to open it using a tool because when closed, it is hard to open it.
- Take care that the calculator works with the battery charger because the corrosion can have destroyed the feeding line that is just a very thin circuit band. This calculator should not be used with the battery charger and without the battery pack.
Specific aspects regarding Sting series
You have to check those aspects with this hard to find models:
- Be sure to have the battery door and the battery pack because they are hard to find as well as the pouch. If you can obtain some rolls of paper, it is a real goodies.
- Ask for the printer section checking because in most cases, they are some rows missing on the printing.
- Like for Classic, Woodstock and Spice series, the LED display is sometime incomplete showing missing LED segments. Check with the seller that each digit segment, comma, dot, minus sign is present (all eight test: -8.888888888 -88).
Specific aspects regarding Coconut series
The one I bought for my scholarship! Please check particularly:
- The battery contacts have to be perfect (shiny and not corroded) as well as the contacts in the 4 module’s extension ports. Those sections are pretty hard to repair then take care of it.
- Check if the battery tunnel and modules port covers are presents.
- Check that the ON, USER, ALPHA, PRGM keys work perfectly.
- The connection between the keyboard and motherboard is made by a central connector inside the calculator. Due to oxidation or other factors, the calculator could appear non working. Check with the seller that the calculator turns ON.
- If there is a card reader supplied, it does not work if it has not been repaired. Don’t think it will because you will be disappointed. The only thing is that it is easy to fix or find someone who can do it for you.
Specific aspects regarding Champion series
This series show some sign of a bad conception and you will have to check those points with the seller:
- The battery door is on the side (except for the 19BII V2) and the poor conception tends to break the battery door and the battery door area due to internal pressure of batteries.
Specific aspects regarding Pioneer series
The main points to verify are:
- The connection between the keyboard and motherboard is made by a central connector placed just below the display inside the calculator. Due to oxidation or other factors, you can experience key responsiveness problems. To check it, just press just below the display at the same time you press the defective key. If it works, you got the solution and will have to operate the calculator to clean and reinforce the pressure of the central connector with the motherboard. If you are not Mac Gyver, just check with the seller that every key work perfectly.
Speculated and overpriced models
The following recent and very common models are targeted by traders and proposed for an exaggerated price:
HP-48GX : The easy way to buy at $80 and to resell immediately for $220. Ridiculous.
Very rare models
Don’t expect some rationality about the final price of the auction regarding the following models, everyone is looking for them:
HP-35 V1: The first HP calculator with the famous red dot.
HP-70: A very hard to find model. Don’t expect to get it below $200 or you are the guy of the day!
HP-10C: Why so many people throw them away, they are hard to find now!
Coconut option 001: For those like me who collect all the variations of the Coconut series.
HP-27: I have actually no explanation but I have to say that we have not enough the occasion to see them on eBay.
HP-29C: Like for the HP-27, I would like more of them on the market.
Today’s good opportunities
Those models are actually below the market price regarding how much times we can find them on eBay or because we can currently find numerous:
The guide part 2 here: Guide - Part 2