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All posts for the month October, 2012

Panasonic Cordless Handsets Resetting KX-TGA650b KX-TGA450b

Posted by Ben on October 10, 2012
Posted in: Batteries, Fixit Troubleshooting & Repair, Panasonic Cordless Phones. 27 comments

Is your Panasonic cordless handset going dead? Resetting? Does the screen go blank for a few seconds then give you an error to move closer to the base?

Typically this happens only at the most inconvenient of times… (while you are using the phone of course!) Most phones with this problem will work just fine as long as you leave it alone on the table or in the charger where it’s as useless as a glass of sea water in the desert.

So what’s the deal? Unfortunately this is a very common problem in many models of Panasonic cordless phones. It is caused by a drop in available power to the phone. It’s more likely to happen when the phone needs the most power (when on a call) and when the phone is being moved (as you handle it during a call).

Open up your battery door. Does the battery just clip in without any wires or coiled springs? Are there just two metal flat contact plates for the battery connection??? Like this…..

Panasonic cordless phone battery connection

This type of battery connection works fine with a new battery… a properly designed battery… and new metal contacts free of dirt or oxidization (at the peak of their conductivity potential). After a few years of use, maybe with an older battery or an aftermarket copy… your phone is very likely to experience this power issue problem. The flat contacts are not a very powerful spring and under a microscope the flat metal plates are only touching in a few tiny locations. All the battery power running through one area causes oxidization and reduced conductivity…. and as you jiggle the phone (in normal use) the battery can bounce ever so slightly causing an additional drop in moving electrons.

Old batteries do not help the situation.


panasonic lcd battery display

Your phone is just guessing when it’s telling you the battery is fully charged. There is no easy way to test a battery and these phones do not have the circuitry for any more than a guess that relies on how long it’s been in use vs. how long it’s been on the charger.  Old batteries have less force to push out those electrons and there is just no way for your phone to alert you to the problem.

To make matters worse…. the poor battery connection doesn’t help the life of your battery. A poor connection can cause the phone to charge the battery when it does not need it. Over-charging is bad… not horribly bad… but over time it can really kill a battery. Also, never letting the battery fully drain to it’s potential isn’t so great for it either. Every time your phone resets because of a poor connection, it’s probably deciding that the battery is dead and needs a full charge, even if it just did that 15 minutes ago. You may even notice your phone getting warmer in the charger.

Could it get any more confusing?

It seems like a straight forward problem that should be easy to spot…. real world experience does not agree however. I’ve seen plenty of instances when one battery works fine in one phone but has power drops frequently in another. Swapping around batteries isn’t always a quick confirmation of the problem or validation of a good battery.  Improving the contacts with springs doesn’t fix old batteries which can and do offer up the same symptoms all on their own. Even new batteries can be junk… poorly made… weak cells… old stock… defective… or even more likely –> quickly damaged by a malfunctioning over-charging, under using, poor battery terminal phone.

What can you do about it??

A new battery might help but really you need better battery contacts. At p1repair we install springs in every model that uses this type of battery contact. We tried other solutions, like beefing up the contacts with added metal… copper fiber…. conductive glue… even lead. They all helped a little but they did not solve every issue or last reliably.
Known effected models:
KX-TGA650b, KX-TGA450b

 

Panasonic KX-TG4500b dead, no power

Posted by Ben on October 9, 2012
Posted in: Fixit Troubleshooting & Repair, Panasonic Cordless Phones. 2 comments

Do you have a dead Panasonic KX-TG4500b base station? 

The #1 cause of a dead base station is the power supply. The new switching power supplies are more energy efficient and they can provide more power in a smaller package than the the old transformer type wall-warts. The downfall is they break far more easily. This problem is rarely ever seen in the older systems that use transformer type supplies.

It’s easy to check
In this model (the 5.8gHz KX-TG4500b) the same power adapters are used for both the base station and the small cordless handset charger stands.  Try swapping the power supply and see if that solves the problem. If it does, that should get you by until you can locate a replacement power adapter.

For a replacement you can use either a switching power supply or an older transformer type. If you have a choice I recommend the transformer type as they rarely ever break.

Compatible power adapters
You need to know 4 things to match up your power adapter.

  1. Voltage
  2. Amps (or watts)
  3.  Plug size
  4. Plug polarity

The voltage should be the same output as your old power supply. Also make sure the type is the same (AC or DC). If you are replacing a 9vDC power adapter you want the same exact value and type

Amps (A, mA, or watts) needs to be the same or higher. Amps is the available power and the device will only use what it needs at any particular moment. You can replace a bad 9v 500ma (that’s half an amp) with a 9v 2A (2 full amps) but not a 9v 250ma (quarter of an amp). Watts is just (amps x volts) so if you are using the same voltage supply then you just need the same or greater wattage power supply. Most power adapters list power in amps.

Plug size is important. If it’s wrong your adapter will either not fit or it will be too loose and cause problems. Typical sizes are 5.5mm x 2.1mm and 5.5mm x 2.5mm. It’s hard to tell the difference by eye and most power supplies are not labeled so it can be difficult to match.

Plug polarity is also very important. With these typical barrel plugs it will either be center positive or center negative. There is almost always a little diagram on the label showing a + and a – with lines pointing to the center of a circle and another to the outside edge. This needs to match on your replacement supply.

What if it’s not the power adapter?
The next thing to try would be the reset button on the bottom of the phone. If that does not help I’m afraid you’ve run out of options and it will either have to be replaced or sent in for repair.