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Michael, Technician
Category: Consumer Electronics
Satisfied Customers: 9568
Experience:  Over 25 years experience in the field of electronics repair, TV, VCR and computer repair.
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What is done in the panasonic PQLV219 power adaptor to enable

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What is done in the panasonic PQLV219 power adaptor to enable the panasonic KX-TG6441 base station to connect/disconnect from the phone line? I find that simply supplying 6.5 volts D.C. from a different source results in failure to enable line disconnect. (Cannot "Hang Up" the phone, unless using the genuine panasonic adaptor, but I wish to be able to use a battery to enable operation of the base station during power outages! (I AM electronically knowledgeable and skilled)

Hi that isnt due to some special part.
It has to do with usually the exact specs.
Please make sure that the new power cube supplies, the same polarity, amperage at least equal to or higher and voltage to be exact.
Also make sure that it is either AC or DC whatever that phone base calls for.
Also let me ask, is the 6.5 VDC source you are speaking of your battery?
Customer: replied 4 years ago.

The power source is a battery, through a well filtered, and adjustable regulating circuit, and the output voltage MATCHES the panasonic adaptor, and my device has current capacity that is more than adequate, with no voltage sag.There appears to be a unique circuit inside the Panasonic adaptor!

Hi that would be the first I have heard of that.
What you can try, is not regulating the supply and see if that helps. You know electronics sometimes act peculiar with different circuits. As far as i can tell that battery pack should work.
Try that and let me know if that helps I will research this further for you as well in the mean time.
Thank you for your patience.
Tech Michael
Customer: replied 4 years ago.

As stated, there IS a special circuit inside the adaptor! (I opened one up, and the adaptor seems to consist of a regulated switching power supply, fed from an internal bridge rectifier off the AC line, probably switching around 100 khz, into a ferrite transformer, which is 1/2 wave rectified and filtered, feeding the regulated 6.5 volts through a winding of about 3 or 4 turns, wound around the OUTSIDE of the ferrite transfomer, seemingly as to affect CORE SATURATION? with D.C. current variation? This very likely causes some sort of "Current related voltage shift" on the part of this adaptor! I need details on this aspect of its operation, it is NOT "Just a 6.5 volt supply!"---Do you have acess to the Panasonic schematic for the model PQLV219 adaptor?--I want to efficiently power this phone base during power outages, using a 12 volt battery through a "Buck Convertor" type regulated supply.


Hi since I have never seen that be the case i will refer this question to another expert who may know.
Thank you for your patience.
Customer: replied 4 years ago.

OK, it appears to be an oddball. If you have access to a panasonic KX-TG6441 base and handset, you can readily see the problem yourself, by connecting an alternate 6.5 volt source, and observing the failure to enable a "Line disconnect" when (Attempting) hanging up!--I did try deliberately setting the voltage 1/2 volt higher and lower than normal, without success. VERY oddball situation!

It sure is an oddball.
Wish I new but I am trying to find a schematic of that cube power supply.
Customer: replied 4 years ago.

There is a 680 ufd, 16 volt capacitor, directly accross the output of the supply leads going to the phone, so whatever happens must NOT involve high requencies, or very fast rise/fall times! The insides look fairly straightforward, EXCEPT for the 3 turn winding, around the OUTSIDE of the ferrite core transformer, and it seems that the 6.5 volt load current is routed through this winding, before the output capacitor! (As stated earlier, I broke an old adaptor open, to SEE what was inside!)--My phone# XXXXX XXXXX

Customer: replied 4 years ago.

Hello again! I decided to do more testing, and found that the
Panasonic "6.5 volt D.C. output" AC adaptor has an unloaded output of approximately 7.5 volts D.C., and only gets near 6.5 volts at /near its 500 ma full load rating. With this in mind, I reset MY supply to 7.5 volts D.C. output, and connected it in place of the Panasonic unit, and the base unit seemed to connect and disconnect properly!--BUT: I THEN reduced the voltage back to 6.5 volts, and even as low as 5.0 volts, and it STILL seems to work! I am going to test some more, this is very strange!--Why did it fail to hang up before, at the 6.5 volt level???--Stay tuned!

Customer: replied 4 years ago.

So far, at 11:07PM, tuesday night, 30 Oct.2012, the phone seems to work just fine from MY supply or the panasonic unit!--I tried voltages from 4.0 all the way up to 8.0 volts, and ALL settings WORKED today, wheras yesterday at 6.5 volts it worked but would NOT allow me to hang the phone up, unless the genuine panasonic supply was used! I will leave MY battery-powered supply, set at 6.5 volts, connected tonight, and see if it continues to work properly. It all seemed to work after I raised my supply to 7.5 volts and tried that, but now it works at almost ANY voltage, at least from 4.0 to 8.0 volts!--Very unusual, but if it will continue to operate from my battery-backed 6.5 volt source, I will be happy!

Customer: replied 4 years ago.

EUREKA!--I found the problem!! I continued wondering WHY the failure to "Hang Up" occured yesterday but not today, and realized todays test was NOT quite the same, as the 12 volt battery was not connected to its CHARGER as it was yesterday! After reconnecting the system, my phone supply set at 6.5 volts as yesterday, AND connecting the battery charger, failure to disconnect returned!-To shorten a long story, the CHARGER has a resistive path to the AC GROUND terminal from its negative terminal, and this pulls in the telephone circuit, keeping it in an "OFF HOOK" condition! An ISOLATED charger for my battery SOLVED the problem! (I still do not know what the strange connection inside the panasonic adapter is doing, but I guess it is some sort of overload/short protection?) All is well now, with an isolated charger for my 12 volt battery. (The "Buck Converter" that reduces the voltage to 6.5 volts is NOT isolated from the DC input/battery side)-Sorry for the waste of time!--Robert Curry

LOL Im so glad you got it !
I knew it couldnt be an issue with the charger itself.
Have a great day!
Tech Michael
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