HP Forum Archive 08

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Battery chargers in need of repair Message #1 Posted by Alfredo Bezara on 11 May 2002, 8:02 p.m. I have two inoperative battery chargers for my HP models 45 and 55. The model number is 82002A. Does anyone know where to get these chargers repaired? Also any of you know what usually goes wrong with them? Thanks for any help.

Re: Battery chargers in need of repair Message #2 Posted by David Smith on 12 May 2002, 5:00 p.m., in response to message #1 by Alfredo Bezara I would say 90 percent of HP classic charger problems are broken wires in the plug. 7 percent are bad filter caps. 2 percent are dirty voltage selector switch contacts, 1% are other. If you are careful you can slice the top off of the plug, rerpair the broken wires, and glue it back together again.

Re: Battery chargers in need of repair Message #3 Posted by Tony Duell (UK)_ on 12 May 2002, 5:16 p.m., in response to message #1 by Alfredo Bezara The 'classic series' charger provides separate outputs for charging the battery (constant current -- 55mA or so) and for running the machine (constant voltage -- 4.2V). So 'inoperative' can mean 'Will run the machine, but won't charge a battery' or 'will charge a battery but won't run the machine' or 'does neither'. Inside the charger there are 3 main parts to the circuity : an unregulated PSU (transformer, rectifier, smoothing capacitor), a constant current regualtor (2 transistors) and a constant voltage regulator (zener + transistor). Fairly obviously, the unregulated PSU needs to be working for anything else to work, but one of the regulators can fail and only affect one of the outputs. The most common problem, though, is broken wires in the calculator cable, particularly inside the moulded socket connector that fits into the calculator. You can check this with an ohmmeter (check for continuity between the contacts on the socket and the wires inside the charger itself) and you can sometimes repair it by slicing open the socket. Other common problems are the smoothing capacitor (400uF electrolytic), the intenral picofuse (if fitted, it rarely seems to be!), and occasionallu one of the transistors fails. I think you can get a schematic from the CUCPS web site (do a google search for CUCPS and look around) if you want to try fixing it yourself.

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