Battery Charger Repair

[Robert Anderson]

I am trying to repair a 20 something year old 10 amp Cliplight 12V charger. There are 2 components on the circuit board inside the charger that look like resistors, but are dark grey in color with 2 black bands. One end looks like it may be white. These components are 6 mm long and about 1.5 mm in diameter with a slight bulge on each end. One of the 2 grey components is obviously burned. I think this component is likely the problem. Printed on the circuit board below the failed component is "W1". Below the non-failed components is printed "W3". For what it's worth - resistors on the circuit board are brown in color and labeled "R1", "R2", etc.

I do not know what the abbreviation "W" means and cannot find it on any list of electronic component abbreviations. I removed both grey components from the board to measure their resistance. The one in good condition reads 0.1 ohm in both directions. The failed one reads 19.3 kohm in both directions.

What are these grey components? How would I determine the rating of a replacement?

 

[Gryd3]

I am trying to repair a 20 something year old 10 amp Cliplight 12V charger. There are 2 components on the circuit board inside the charger that look like resistors, but are dark grey in color with 2 black bands. One end looks like it may be white. These components are 6 mm long and about 1.5 mm in diameter with a slight bulge on each end. One of the 2 grey components is obviously burned. I think this component is likely the problem. Printed on the circuit board below the failed component is "W1". Below the non-failed components is printed "W3". For what it's worth - resistors on the circuit board are brown in color and labeled "R1", "R2", etc.

I do not know what the abbreviation "W" means and cannot find it on any list of electronic component abbreviations. I removed both grey components from the board to measure their resistance. The one in good condition reads 0.1 ohm in both directions. The failed one reads 19.3 kohm in both directions.

What are these grey components? How would I determine the rating of a replacement?

Can you post a picture? Of the board. Clear, both sides straight on without a flash.
It almost sounds like a jumper. But could also be a resistor to provide a reference voltage for the system.

 

[Robert Anderson]

Here are some photos. Could these things be thermal overloads? The are connected to the 120 VAC line.

 

[Robert Anderson]

Here are some photos. Could these things be thermal overloads? The are connected to the 120 VAC line.

Correction to my last post: These components are not in the 120 VAC line, they are in series with what I think is a 12 VAC circuit breaker.

 

[Bluejets]

Looks to me like your red and black are output and the 2 black are the input from a transformer with W1 to W4 making up a bridge rectifier.
Are there any other parts to this ??

 

[KrisBlueNZ]

The other "W" reference components on that board, W5, W6 and W7, are diodes, with the line marking the cathode.

If diodes were fitted in the W1~4 positions, they would have formed a bridge rectifier, but it's clear from the original solder that nothing was originally installed in the W2 and W3 positions. This would be consistent with the board being powered from a DC source instead of an AC source.

The thick copper areas beneath the W1~W4 positions indicate that the designer expected them to generate significant heat. The copper is supposed to help radiate heat and protect the PCB from heat damage.

Also, C1 appears to be missing, but was never installed either. This capacitor doesn't seem to be directly across the output of the bridge rectifier, but still, it may have been omitted because the board was being powered from a DC source.

The charred components from the W1 and W4 positions do not look like diodes though; they look like resistors that have been forced to dissipate too much power over a medium to long period of time. This would happen if the charger passed too much current, or if the wrong values were chosen for those resistors at the time when the changes were made for DC input to the board.

That might also happen if an AC supply was accidentally used with the board. Not a high-voltage AC supply like the mains, though; just a low-voltage AC supply. I'm just suggesting this as a possibility; I don't think it's likely.

If you want to go further with the board, we need a lot more information.

What is connected to the two black wires that connect into the W1~W4 area? Show us a photo.

Does the battery connect at the corner?

What are the markings on the 3-pin device attached to the heatsink? Show us a photo. Has it been replaced, or just resoldered? Did you resolder it? If so, get a smaller soldering iron and some 60/40 rosin-cored solder!

Also take some more photos of the board so we can read the markings on the transistors (TR1~4) and the electrolyic (C2). Most of the other component values are readable in the photo in post #3.

 

[Bluejets]

If diodes were fitted in the W1~4 positions, they would have formed a bridge rectifier, but it's clear from the original solder that nothing was originally installed in the W2 and W3 positions. This would be consistent with the board being powered from a DC source instead of an AC source.
.

Or half wave rectifier...?

 

[KrisBlueNZ]

Or half wave rectifier...?

No, I don't think so. You only need one diode for a half-wave rectifier, and anyway, the charred parts don't look like diodes. I've never seen a diode with end caps like that!