HP-65, 45, 80 On/Off Switch Problems

[jeejohn]

I have been working on selling my collection, but these 3 pose a little problem.

All 3 are having problems with intermittent power to the calculator. The 65 will work with the switch about 1/2 to 2/3rds of the way "on". With the switch all the way over to "on", it has no power. Otherwise, the 65 is in excellent condition. The 45 is bad, as it won't work with NiCds, but somewhat with alkalines (in a waterhosko battery pack). The 80 is similar to the 65.

I have searched the forums and found out about the lubricant that is between the switch and an internal contact.

I really like to get these working good. I am wondering if there is some way of fixing the problem short of having to open the calculators. If not, then are there instructions someplace about the process? I notice that the 65 has a different body than the others, so might require some different instructions?

[rprosperi]

The simplest thing to try is to just put a drop or two of DeOxit (Red) into the power-switch slot and work it back and forth gently 10-20 times (remove batteries while cleaning). Most likely, this will clean the contacts inside and the switch behavior will return to normal.

If so, then it is good to use something like Lubriplate DS-ES for long-term switch lubrication and contact health (though this latter action might be something you leave to the buyer, as he/she can decide if they want to open the case to this the "right" way).

https://www.amazon.com/CAIG-Laboratories...B0002BBVN2

[teenix]

The switch should feel fairly tight when sliding OFF - ON or WPGM / RUN and with a higher resistance felt in between as the switch moves across a plastic hump which holds the switch either left or right.

What has most likely happened is the original switch lubricant has deteriorated over the years and is causing problems. It usually ends up a dark brown color and has a thick waxy consistency.

The problem may also be that due to lack of lubricant over the years, the switch contacts have eroded so much that a only very poor connection is being made and cleaning won't do. It is also possible that if the switch feels sloppy to use, the spring contact may have lost some tension and might require some small mechanical adjusting to make it rub harder against the circuit board contacts.

In my opinion then, and I know you really don't want to, the best way is to open up the calculators and give the switch contacts a good clean, both the actual contact and the circuit board pads which it rubs on. Isopropyl alcohol will do. Applying some good quality contact lubricant will keep them working for a long time. If you don't want to spend money, then a "tiny" dab of petroleum jelly.

Contact cleaner may dissolve some of the gunk, but it still resides inside the calculator and may end up elsewhere like under the keyboard contacts.

cheers

Tony