M
Michael
- Jan 1, 1970
- 0
Hi All,
I have a 220VAC drop in charger for a Motorola GP68 two-way radio. The
bottom of the charger indicates 220VAC input and 10VDC output at 100mA and
170mA in rapid charge mode. I would like to replace the transformer to use
this charger on 120V mains.
Looking at the discrete 12 component circuit, it looks a fullwave rectifier
circuit using a 220V CT step down transformer. The CT is tied to the gnd
bus and both ends of the secondary winding are connected to a 1N4004 diode.
There is a 5 resistor series-parallel network (22 / 82 / 33K / 220 / 10
Ohms) used to switch between normal and rapid charge modes using one side of
a DPDT slide switch. Along with 2 LEDs: one for charge mode indication and
the other for charging status. The negative DC charging lead is tied to
gnd via a 1N4004. The positive DC charging lead is picked off at a point
that is separated from the gnd via 33K resistor and a LED.
I've got a Radioshack power transformer (part # 2731365) with the following
specs:
* Input: 120VAC / 60 Hz
* Output (load): 12VAC C.T. @ 450mA
* Output (no load): 14VAC
* Current (load): 80mA max
* Current (no load): 45mA max
This 120VAC transformer's loaded current rating is only 80mA yet the loaded
output rating indicates 12VAC @ 450mA. How do I interpret these ratings
correctly? The chargers DC output current is 100mA/170mA Knowing nothing
else about this circuit (and no schematics or further info online that I
could find) and being a newbie, what is the best approach to tackling this
project while ensuring a safe solution.
Any and all info would be appreciated!
Thanks in advance,
Mike
I
I have a 220VAC drop in charger for a Motorola GP68 two-way radio. The
bottom of the charger indicates 220VAC input and 10VDC output at 100mA and
170mA in rapid charge mode. I would like to replace the transformer to use
this charger on 120V mains.
Looking at the discrete 12 component circuit, it looks a fullwave rectifier
circuit using a 220V CT step down transformer. The CT is tied to the gnd
bus and both ends of the secondary winding are connected to a 1N4004 diode.
There is a 5 resistor series-parallel network (22 / 82 / 33K / 220 / 10
Ohms) used to switch between normal and rapid charge modes using one side of
a DPDT slide switch. Along with 2 LEDs: one for charge mode indication and
the other for charging status. The negative DC charging lead is tied to
gnd via a 1N4004. The positive DC charging lead is picked off at a point
that is separated from the gnd via 33K resistor and a LED.
I've got a Radioshack power transformer (part # 2731365) with the following
specs:
* Input: 120VAC / 60 Hz
* Output (load): 12VAC C.T. @ 450mA
* Output (no load): 14VAC
* Current (load): 80mA max
* Current (no load): 45mA max
This 120VAC transformer's loaded current rating is only 80mA yet the loaded
output rating indicates 12VAC @ 450mA. How do I interpret these ratings
correctly? The chargers DC output current is 100mA/170mA Knowing nothing
else about this circuit (and no schematics or further info online that I
could find) and being a newbie, what is the best approach to tackling this
project while ensuring a safe solution.
Any and all info would be appreciated!
Thanks in advance,
Mike
I