hp 45 charger


i have a hp-45 with a broken charger and wish to buy one. anyone can hepl?


This might help:



thanks Thomas


Don't start cutting it apart assuming it is a failure of the plug. The easiest check is to measure the resistance from the center pin to either outer pin. If either measurement is infinite, yes, the wire has most likely failed at the plug. But, it is just as common for the 400uf capacitor to fail. There is a schematic online here:

Classic charger schematic

PS: If repair is out of the question, list a want to buy in the classifieds here. Beyond that, eBay is about the only source.

Edited: 4 July 2009, 4:30 p.m.


thanks Randy


I repaired the AC charger for my HP-55 quite easily. In this case, the charger would run the 55 on AC but never charge the battery. I bought a generic PNP power transistor (I would have to go home to look) from Radio Shack, traced out the schematic from the circuit board layout and replaced it. You do have to be care for the Base, Emitter and Collector layout as the replacement part is different from the original. There is plenty of space inside of the case for the new part. Now it works great.

If the cord is bad at the connector end, I have seen replacement cord kits show up on eBay periodically. I got one for when my cord fails. If the cord it bad at the PS side, then just cut out the bad section and re-solder. As Randy suggests, do some continuity tests first to figure out where the problem is.

Oh, I almost forgot, when you pull the power supply case apart, be sure to keep track of the 120v/240v switch parts so you can put it back together properly. I think some people have hard-wired the switch to 120v, but I think that reduces the value of the PS. I just cleaned the contacts for more reliable operation.

I'll look up the parts I bought and post them.

Good Luck,



Not long ago I would've sold you one cheaply, but as I am left with only two I want to keep both (one to use, one as backup) to charge my 45, 65, 67, and 80.

These adapters are fortunately not rare and can be had for a price via The Auction Site That Must Not Be Named.

I advice against cutting these things open, as Randy can attest, given that he usually is the one to correct my "experiments". Unlike many here, I am dangerous with a soldering iron.


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