Panasonic PNLC-1029 charging cradle repair

by Updated: Mar 2, 2021diy-miscellaneous0 comments

Panasonic PNLC1029 charging cradle

How to fix and repair by Avi

This post relates to Panasonic charging cradle, charger unit model PNLC-1029, PNLC1029 OR PNLC-1035, which charges the handset model KX-TGA470 or alike.

Those cradles were supplied with telephone set models:
KX-TG7731, KX-TG7732, KX-TG7733 and possibly with other models as well such as:
KX-TG7741, KX-TG7742, KX-TG7743, KX-TG7745, KX-TG8561E, KX-TG8562E, KX-TG8563E, KX-TG8564E, KX-TG254SK, KX-TG294SK etc.

The symptoms, the fault:
The Panasonic handset does not charge as expected. The battery charging indicator does not show any level increase after few hours of charging nor does it show “Fully charged” status on its display.

Panasonic handset display charging mode

DISCLAIMER – Important!

A. Check first:

First to check is the voltage over the cradle’s charging points.
If you get a reading that is different from 5.5VDC (much less or high), check and /or replace the power adapter (*). Proper voltage is 5.5VDC measured both on the power adapter’s DC plug and over the cradle’s contact points.

(*) In case you need to replace the power adapter, get the Panasonic PNLV226XX.
XX stands for different models of plugs and mains voltage (input). Select one that is suitable to your local mains voltage and plug. If you pick a non-Panasonic adapter, beware that it might transmit interference to your system, especially if used in the base unit. For using it with the charging unit only it might be OK.

Panasonic cradle PNLC-1029 contact points

Voltage is not the only parameter that counts. It can be OK while still not charging.
The problem in this case is with the amperage draw.
When measuring the draw amperage of a non-charging faulty cradle, the result is much lower than the correct ~200mA draw and  this is usually the cause for a non charging cradle.

B. The fix

1. exclaim2  Disconnect the power adapter from the mains and disconnect the cradle unit from the power adapter!

2. Remove the single screw on the cradle’s bottom part.

Panasonic cradle PNLC-1029 bottom screw

3. Open and separate the cradle’s housing parts in a rotational move.

4. The opened cradle reveals a small PCB model TH165B PNLB2081ZA-IG with 4 components:
A fuse marked F1, 2 resistors marked R1 and R2 and a diode marked D1

Panasonic cradle PNLC-1029 PCB

In most cases the cause for the charging malfunction is a bad D1 diode solder contacts or a faulty diode.

5. The D1 diode is an SMA/SMD type marked M2S with a package size of 4.0×2.7mm (the preceding numbers are manufacturing date).
According to Panasonic’s service manual of model KX-TG7731, the diode part number is B0ECKM000008. I couldn’t locate any official document of its specifications. 

Panasonic cradle PNLC-1029 PCB diode

6. First try to fix it by re-solder the diode contacts.

7. Re-assemble the cradle’s parts and charge your handset for several hours to test if it works OK.
If it is charging OK and reached to 3-lines battery icon with “fully charged” display note, you have fixed the fault and this is all you need to do.

But if it does not charge, follow next steps:

8. Replace the diode.
You can use a replacement M2 SMA/SMD diode or use a through hole 1N4002 diode which you’ll need to bend and trim its legs in order to fit the existing PCB’s pads.
See this datasheet for the specs of SMA diodes by SYC for example.
See this datasheet for the specs of through hole diodes by Fairchild for example.
Remove / desolder the existing diode and solder the new diode to existing PCB’s pads.

M2 and 1N4002 diodes

exclaim2  NotePay attention to the diode polarity. It is clearly marked on the PCB.

thumbUP_gifanim Tip: If you can’t obtain the needed M2 or 1N4002 diode, you may use M1 or 1N4001 instead. That will work OK as well.

9. Re-assemble the cradle’s parts and charge the handset for several hours to test if it works OK and reaches 3-lines battery icon with “fully charged” display note.
If it did, you have fixed the fault.

If after ~7 hours of charging the charging level did not increase or increased but did not reach the 3-lines level nor the “fully charged” state is displayed, replace the batteries and try again to charge it.

exclaim2  Note: Use only 2x AAA Ni-MH rechargeable batteries.

A simple and very low cost fix which will allow your Panasonic charging cradle to work properly for years to come.

Enjoy your phone,
Avi clapup_gifanim

For more How-To guides by Avi, Visit the main DIY page

You might find there useful guides such as :

Grohe cistern repair
Westinghouse ceiling fan fix and upgrade
Microwave oven circuit breaker trip fix

and more…

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1. This product contains electronics and/or electric parts.

Any modification made to your product may cause damage to your equipment and harm to yourself or to others. 
Any modification made to your product AND/OR to a 3rd party attached accessories will void manufacturer warranty.
None of the following steps is recommended by me nor by the manufacturer. 
This post show only my personal experience and know-how.
If you follow any of the steps, you do it on your own risk and responsibility.

2. Copyright © 2003 Avi. All rights reserved. 

Content including all text and images in part or in whole may not be reproduced, retransmitted, stored, distributed, disseminated, sold, published, broadcast or circulated in any medium
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