Make NEDA-213 rechargeable battery for Emerson 838 hybrid radio.

Using battery tube radio , the B battery can be expansive. I found a way to make it into rechargeable battery. For the A battery the original battery using mercury battery which is 4V and there is Lithium ion 22430 can fit very well . Lithium ion battery when fully charge is 4.2V slightly higher , it will be ok..

for B battery i using Ni-MH 20mAH battery button cell, it come with 4 cell in one pack which give 4.8V , by parallel 10 of them make 48V battery pack.

The new Empty plastic shell/case for make 9V rechargeable battery.

I found the empty case sell in china taobao i think they are for make rechargeable battery. I cut and join them together and the length is exactly same as NEDA-213

After soldier all battery and using super glue to glue together.

I add a heat shrink tube to make it look nicer.

To charge this battery , i can use a 230VAC 5W lamp as current limiting go to a bridge diode and connect to battery.. the lamp as current limiting.. the battery is 20mAH is good to charge by 10mA no more then 20mAH for better life span.

I still have some battery leave so i use it to make 28.8V battery .

28.8V 20mAH battery.

Emerson 838 schematic..

After i plug in new battery i realize my Emerson 838 have very weak output sound.. i check everything look work fine.. then i found the input transformer primary is open. I try to remove and check luckly the secondary is wind inner layer and primary wire wind at outer layer. So i try to re-wind by myself.

The input transformer after remove the core.

Input transformer after remove the label.

Input transformer after remove primary , the primary wire is very fine. i cant count exactly how many turn.

The motor winder i use to wind the input transformer.. with 0.08mm magnet wire, it look close to the original wire .

I wind about 1900turn which look almost full so i stop it.

Measure primary resistance 329.6 ohm.

After connect back the original wire and label this is how it look like

After assembly the core i dip into Bees Wax .

After bees wax

It look as good as original.

First power up , Malaysia dont have MW station so i only can receive noise and hum it now sound good and loud.

Test the radio with my DIY MW modulator

I go to car park i can barely receive thailand station..

Another video about 28.8V battery i make and test.

I also write it in Antique Radio forum Click