How do I test this charging circuit board, wall wart, battery pack?

lumen aeternum

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Joined
Sep 29, 2012
Messages
890
How do I test these items to know which is bad?

Have a very old (15+ years) Husky 3W spotlight that is not working.
Wall Wart puts out 7.5v 300mA
3 x AA NiMh battery pack, 400 mAh 3.6v

Substituting good batteries, it lights up. Don't have a "pack" or I'd just run it & see if it recharges.
Sticking my voltmeter probe in the wall wart output makes the needle deflect just a little, so I suppose its sending vDC.

So is the battery pack dead, or is the circuit board gone bad, or the wall wart?

How do I test ?
Pack reads 2.6 v and ought to be fully charged.

The board has a rats nest of red wires. Dunno where to put probe to check for vDC charging current. Touching D- and V+ does not move the meter, & I scraped the solder in case they coated it.

LED red wire # 1 to Pad alpha marked D+
Pad D+ to
1) a tiny diode, not the "striped side" (so INPUT, right?)
2) R10
R10 to Red wire #2 to "C" terminal of on/off switch

Switch "NO" terminal to red wire #3 to Pad beta
Pad beta has
1) to striped side of a diode
2) red wire #4 going to battery pack, thru hole marked V+

The black wires from the battery pack and the LED are joined together on a pad linking them to 2 resistors "E" & "B" -- which are part of a row of resistors labeled Gnd, E, B, C, C1.

And bunch of other components.
 

System1459

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Feb 17, 2018
Messages
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Um what? Can you post a pic of what you are talking about? "The needle jumps" you have an analog voltmeter? Wow haven't seen one of those in years. Haha you said you don't have a "pack" but then you ask if the pack is dead?? Yes VDC is what batteries provide and what they require to be charged.
 

lumen aeternum

Enlightened
Joined
Sep 29, 2012
Messages
890
Yea, analog. The OEM pack is soldered. I don't have one of those, I just shoved 3 cells in a row & held probes on the ends with the other ends alligator clipped to the battery leads, to power the LED for a moment. Don't have a place to post pics online.

Need to know where to put my probes on the board to measure the output of the charger going to the battery pack.
 

System1459

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Joined
Feb 17, 2018
Messages
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Ok, after a google image search I think I have a better understanding what you are doing. The charger is actually internal to the light? The wall watt plugs into the light itself? Really you just need to test where the battery pack attaches to the charger. But you won't know for sure if the charger is working without a ampmeter. I think most DMMs have that function up to 20a. If you have voltage where the battery connects you might be ok.
 

lumen aeternum

Enlightened
Joined
Sep 29, 2012
Messages
890
>The charger is actually internal to the light? The wall watt plugs into the light itself?

yes and yes.
BUT -- why doesn't it light up when plugged into the wall, even if the battery pack is dead?
Got a DMM somewhere, have to read the instructions...
 

System1459

Newly Enlightened
Joined
Feb 17, 2018
Messages
5
For the light to function while it being charged would mean the wallwart has to put out more power to be able to power both. To make this possible inside the light it would require an additional circuit inside the light. Those lights are only like $15 might be easier to just move on.
 
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