Correct volts out on HP-45 PSU - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Calculators (and very old HP Computers) (/forum-3.html) +--- Forum: General Forum (/forum-4.html) +--- Thread: Correct volts out on HP-45 PSU (/thread-20212.html)

Correct volts out on HP-45 PSU - Pennine_Lad - 07-21-2023 05:18 PM Hi Is anyone familiar with the HP-45 calculator PSU correct pin out voltages. Took a gamble and bought one declared not working with the HP PSU it came with. The calculator works fine on 3AA rechargeables. Checking the HP PSU it came with there's 12V on outer pins and 0V on the ones marked with + and -. The seller used this PSU to declare not working. Are these correct, 12V seems high for a unit that runs on 3AAs. If 12V is incorrect a bit surprised still working if 12V was delivered to it. Thanks. David RE: Correct volts out on HP-45 PSU - Steve Simpkin - 07-21-2023 10:41 PM The center pin is a common ground to the left and right outside pins. Center pin to left pin is used to charge the NiCad batteries and will be around 12-16V unloaded. Center pin to right pin is used to power the calculator circuitry and should be around 3.6-4.7V. See the following Museum link for more information on the voltages on the plug: https://www.hpmuseum.org/batts/battery.htm See the following Museum link for more information on power supply circuitry: https://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/articles.cgi?read=390 RE: Correct volts out on HP-45 PSU - Steve Simpkin - 07-21-2023 10:58 PM Here are links to more information about the changer. The HP-35's POWER UNIT: https://archived.hpcalc.org/laporte/HP35%20power%20unit.htm Making New Battery Packs for the HP-35 Calculator: http://homepage.divms.uiowa.edu/~jones/hp/battery/ RE: Correct volts out on HP-45 PSU - Pennine_Lad - 07-22-2023 08:14 AM Hi Many thanks for the info. The volts on the board do match those and have since found a break in the middle wire somewhere between board and plug. Any tricks of the trade to isolate to keep as much of good length as possible. Tried a sewing pin through middle cable for continuity check either end but too hit and miss as do not know if have touched wires. Perhaps shave a little off insulation so know touching and then heatshrink those when repaired. May not need many shaved areas, if do half way down wire, then half way down again the bad half and again on the bad quarter it may narrow down quickly. David