Repair 82002A charger?

[Marcel Samek]

I have a non-functioning 82002a charger and have no electrical engineering skill. (I do own a multimeter though). Measuring the output of the charger (at the connector) when its plugged in, I get 0 volts on one side of the triple connector and approximately -.2 volts on the other.

While I have found the schematic for the circuit, I was wondering if someone could tell me what the readings should be at various points in the circuit so that I could identify the bad component.

[Paul Berger (Canada)]

Well at the end, unloaded, between the center (Gnd) and the + there should be about 16V and from Gnd to the unmarked pin 5V and you should see similar voltages inside where the wires connect to the little board. Have you ruled out a broken wire? I would think this would be the most common fault, I find them using the continuity check on the meter, or lowest resistance range to first check the wires end to end and if you find one is open, I locate the break point by pushing a needle through the insulation at various point along the wire, the most likely break points are near the body of the adapter or near the connector. One that I repaired recently had a break in the ground wire near the connector.

If it is not a broken wire let me know and I can take some measurements for you.

[Marcel Samek]

Thanks for the quick response. I did just check the continuity between the connector and the soldered connection on the board and all three wires are good.

The adapter has the sliding switch for 110/220 and it was a little iffy making sure that that was making decent contact while I had the charger open to check the voltages inside. I got the same readings of < 1 volt when checking on the circuit board.

I certainly won't turn down your generous offer to have you take some measurements. If you have some other suggestions on things relatively easy to check first - I can do that too. I don't mind playing with my multimeter even if I don't exactly understand the circuit I am poking at!

What is it that usually goes wrong on chargers like this?

Thanks!

[Paul Berger (Canada)]

Well aside from broken wires my number one suspect would have to be the 400uF electrolytic cap if it went short it would pull down everything. Looking at the circuit diagram again the only thing that really makes sense is that 400uF cap, so I would suggest that the first thing you do is remove it and see if you get any output don't worry about plugging it in without that cap it won't hurt anything but the dc voltage might measure a bit lower. I guess it is possible that the transformer has failed too or a couple of the rectifiers have gone open. Does you meter have a diode check function?


CAUTION be careful poking around in there with the adapter plugged in oriented as described above, at the bottom of the board the line input prongs come through the board and the rivets there are live as well.


The transformer used in these probably cannot produce a lot of current. Does it get warm when it is plugged in? I did take a few measurements, with the top off, board facing you, and output cable at the top. The 400uF caps is to the left of the cable and beyond that there is a tab transistor that you cannot conveniently get to the pins, on the right is another transistor flat on the board under an aluminum rod. The diodes that make up the bridge rectifier are on either side of the transformer to measure the AC output of the transformer connect to the bottom end of the diodes against the transformer on either side it should be about 14VAC



You can connect to ground at the top of the diode on the right side adjacent to the transformer, or since tour cable is good it may be just as easy to pick up DC ground at the end of the cable. To the right of the transformer on the outside there is a 470R resistor and a diode that join at the top the voltage here should be about 5.2Vjust above them is the transistor that lies flat the center pin should be about 16V and either outside pin about 5.2V. The tab on the transistor next to the 400uF cap should be about 16V as well. That is about all that is really convenient to check.

At http://www.keesvandersanden.nl/calculators/chargers.php there is a schematic for an 82010A which would seem to be the same except it seems to have a fuse in one leg of the output side of the transformer.

With the adapter oriented as above, the tab transistor on the left would be Q2, the small transistor next to it Q3, and the components below them from the inside out would be D3, R3, R2, D1. The 400uF cap is C1. The transistor on the right is Q1 and below it again from inside out D4, D2, D5, ad R1.