At 03:24 PM 12/22/02 -0500, Charles wrote:
The power module cable is a problem though. The wires in the cable seem
to break at the molded connector on the calculator end. I have two
calculators and three power modules. I can only get one of the power
modules to work most of the the time. I will have to try rebuilding the
battery packs. All of them I have are shot.
Are you talking about HP-35 type claculators or HP-25s? I've never seen a cable
problem on the chargers for the HP-25 but I've seen lots of problems with the HP-35
type chargers that use three wires. But they can be fixed. First you need to open the
charger and figure out exactly which wire (or wires!) are broken. They will almost
certainly be broken where the wires enter the molder plastic plug. You'll have to cut
back the plug and slit open the wire insulation until you find the break. The break is
usually easy to find because the wire will be very flexible at the break. Then I cut the
insulation back about 1/8" past the broken ends and solder a short piece of very
flexible wire to the ends. (I use a J hook to make they have a good connection that will
resist the pull on the wires.) After I get them working, I wrap the joint with unwaxed
dental floss (high strength nylon cord) and coat it liberally with the plastic potting
compound that's used to coat plier handles. I zig zag the dental floss back and forth
past the joint to try and give the joint some reinforcement. You can't go far on the
molded plastic plug but you can wrap the cord over the bulges so that it has some place to
attach. I've fixed DOZENS of chargers this way and my success rate is about 98%.
Both the HP 35 type calculators (aka classic series) and the HP-25 type both use AA size
NiCads and are fairly easy to rebuild. But you'll have to reuse the contacts on the 35
type packs and they need to be spot welded to the cell so you'll probably have to find
someone that has a battery spot welder. Anyone that builds or rebuilds battery packs
should have one. Batteries Plus is one company that comes to mind. They seem to be wide
spread. Beware of some of these companies. Some of their prices are outragous. I went to
an Interstate battery store a couple of weeks ago and they quoted me almost $100 to
rebuild a five cell battery! I told them they were out of their minds. That job
shouldn't cost more than $20. The battery wholesaler that I use to do business with
charged about $2.50 each for AA size Sanyo NiCads and $.50 for each strap that they welded
on. That would come to about $11.50 for a HP-35 type battery and that's using GOOD
Japanese made Sanyo cells.
Batteries. I INSIST on Japanese made Sanyo cells! I've tried a lot of other brands
and found most of them are JUNK! I haven't found ANY good American made, Chinese made
or Mexican made cells including the Mexican made Sanyos. I've heard that some of the
other Japanese made cells are good but I haven't tried them. I've had EXTREMELY
good luck with the Japanese made Sanyos. I've rebuild hundreds of battery packs with
them and I think I've only had one cell fail. I've also got a set of four AA
Sanyos that I bought in Thailand in 1973 and they're still working fine!
Joe