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Posted to uk.d-i-y
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Drill charger diagnostics
On 18/05/2019 17:49, wrote:
On Saturday, 18 May 2019 11:44:50 UTC+1, D.M. Procida wrote:
I have an old B&D cordless drill; the batteries don't charge.
Either the batteries or the charger are faulty.
I've opened up the charger. At the input of the transformer, I
measure 240V. At the output, 0V (I'd expect 18V or so).
I assume this means that the transformer itself is broken - at
least, I can't think that anything in the circuit after the
transformer could be responsible.
I haven't desoldered the transformer from the circuit board, but I
guess that would be a way of being sure.
Is that correct?
Daniele
The transformer is generally the least likely item to fail, but it
looks like it has. Measure the resistance of the secondary winding to
be sure (with power disconnected)
I can't agree. Thermal fuses age, plus if the regulation circuit is
faulty that can apply a larger than designed load on the transformer its
going to go pop.
As an example, I have in front of me a charger with a transformer.
Strangely the 3A plug fuse is o/c, and when replaced there is no output
from the transformer. The PCB has some beefy diodes, but the PCB below
these is blackened from heat.
I bought a new (old stock) charger and measured the transformer output
to find 30Vac. This charger is for Bosch 7.2V to 24V battery packs.
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