HP 37E - Battery charging issue

[johnlyles]

Good news!!! FIXED!!! There was no glaring problem, but several small problems. The good news is that after disassembling the 37E, thoroughly testing and cleaning the flex ribbon path to the DC-to-DC power module, and the charger connections, the unit is working great!!! Even the original battery pack has charged a bit, although I do not expect it to be usable. Here is what I found: the R1 resistor and D1 diode tested good. The connection points between that power module and the power leads on the back-side of the unit's motherboard appeared to be "hazy", as in oxidation. I used De-Oxit to clean those contacts. Also, the small board that provides the "+" and "-" contacts for the battery, and interfaces to the flex ribbon cable was loose, causing it to slightly cocked when the charger was plugged in, and therefore not properly aligned - perhaps a millimeter off. The two charger-connection leads on that module also looked hazy, so I also cleaned them thoroughly with Deoxit. One of the small rivets that secures the battery terminals to the flex ribbon cable was loose. I squeezed it as tight as possible. After tightening and cleaning everything, I noticed that my voltage readings were no longer jumping from one reading to another every second. I was surprised when a small chip fell off of the motherboard, but I used the schematic provided by the last poster, that included a "repair the 32E" link. In that document there was a picture showing the orientation of the TI chip(s). I read where HP received a patent for their method of clamping the chips to the motherboard. The most challenging part was removing the outer back cover from the calculator! I now need to polish up that seal at the base of the calculator. Thanks SO very much for the suggestions! John in Dallas