Cordless drill battery charger

[Mr.C]

Might be the wrong forum but here goes. I`ve 2 Parkside drill/drivers 10.8v not had a lot of use but come in handy because they are quite small and do the job. Problem is I`ve lost one of the chargers and the remaining one has given up. I`ve inserted a pic of the circuit board, no sign of any overheating or visible damage any chance someone might have an idea of which component has died or where to start testing, a longshot I know...……..

 

[DPG]

Impossible to be certain. However, bearing in mind it is a switch mode power supply and there is no obvious damage then I would suspect that the electrolytic capacitor that starts the supply has dried up. Do any of the capacitors look domed on top?

 

[Deleted member 26818]

I would suspect the transformer.

 

[Lucien Nunes]

There are many possible failure modes. The snag with troubleshooting SMPSUs is that if you don't change all the faulty parts, and there are often several, then the next time you switch it on for testing, the ones you replaced fail again. There are ways round this, such as with a lamp limiter, but fixing even a simple little supply like this can be fiddly and annoying, even with experience.

I personally don't suspect the reservoir capacitor or the transformer, as it has not had many power-on hours (caps are usually the first thing to fail in SMPSUs that are on 24/7 though). I can't see the power switching device but that, and the IC that drives it, the startup resistor (if fitted) and current-feedback parts are common causes of random failures.

I'd check for dry joints, check the DC output for shorts (which could be the output rectifier or reservoir) and any obviously vulnerable items such as current feedback resistor, other fusible resistors, startup circuit, output transistor and efficiency diode. If all looks OK I'd energise through a lamp limiter and isolating transformer to make sure there is 340V DC on the input reservoir that is reaching the transistor. OTOH if it's a monolithic IC, I'd pull it, test around it again e.g. up the opto-coupler for domino-effect faults, replace, then repeat from top.

Actually, no. I wouldn't bother, and I have loads of experience fixing SMPSUs. It probably isn't worth the agro.

 

[DPG]

For a few pence it's always worth a go (in my opinion) at changing the capacitor. Have repaired countless ones where it has dried out and has bad ESR. Usually they place them next to a heatsink as well for reasons best known to the designers!!

 

[Lucien Nunes]

Sure, there's no harm in swapping the reservoir cap, it's not usually part of a domino failure chain so if it was bad, it might be the only bad part. I know what you mean about 'thermally undesirable' locations that electrolytics seem to find themselves in.

 

[casperLennon]

Buy a new one. They are dirt cheap

 

[Squid]

As Lucien mentioned check for dry joints also check the fuse in the plug top then see if you are getting power to the unit, I'd do this first.

 

[telectrix]

i have twice found that it's the SCR (or transistor) failed. that's the bugger on the large alloy heatsink. about £1.50 from cpc. had this in a lithium charger and a washing machine.

 

[Lucien Nunes]

The device on the heatsink looks bigger than a TO220 package so I suspect it might be an all-in-one PSU IC rather than a discrete transistor. It's a prime suspect, either way. I referred to it as the 'power switching device' for lack of clearer identity.

 

[DPG]

I'm still going to go with the small electrolytic being dried out. OP let us know if you do try anything and have any success!!

 

[Mr.C]

First thanks to everyone for the replies, didn`t expect that many, firstly I would have replaced it if I could find one, tried everywhere including Ebay. Not worth spending a lot, don`t know how long the batteries will last anyway. Had a look for similar drill/driver but being a tight old sod couldn`t find one at the right price, the Parkside ones were only £15 and like all their kit is good enough for a diy`er and got a 3 year warranty to boot. I`ve a friend who is a bit more savvy than me I`ll see if he can check the things mentioned.
Thought about a 3.6v screwdriver but no good for drilling, not enough torque, might have to bite the bullet and spend...…………….
If I get a result with the charger I`ll come back with what the problem was, thanks again.

 

[Andy78]

First thanks to everyone for the replies, didn`t expect that many, firstly I would have replaced it if I could find one, tried everywhere including Ebay. Not worth spending a lot, don`t know how long the batteries will last anyway. Had a look for similar drill/driver but being a tight old sod couldn`t find one at the right price, the Parkside ones were only £15 and like all their kit is good enough for a diy`er and got a 3 year warranty to boot. I`ve a friend who is a bit more savvy than me I`ll see if he can check the things mentioned.
Thought about a 3.6v screwdriver but no good for drilling, not enough torque, might have to bite the bullet and spend...…………….
If I get a result with the charger I`ll come back with what the problem was, thanks again.

Could this be the simple answer ?

 

[telectrix]

aldi have a reasonable cordless and impact driver set for £99.95. 3 year warranty.

 

[freddo]

One of my Milwaukee chargers has just gone with a loud bang.
SMPS control chip has a hole in it, same thing failed in my other one. A replacement got that working again, so I have ordered a replacement IC for this one for £3. It's a tiny little thing for a power component.

 

[Mr.C]

Where the power cable enters on the board is a note saying that for continued fire protection the fuse must be replaced with the same type, a T2AL 250vac. Is that not a glass type fuse, if so I can`t find one……………………..or have I got it wrong ?

 

[DPG]

I would expect a fuse somewhere, although it may rely on the fuse in the plug top. Maybe they have changed (cost- reduced!) the design at some point but forgotten to amend the text.

Confirm you have 350VDC approx at the large reservoir capacitor. Do this carefully.

 

[GeorgeCooke]

As Lucien mentioned check for dry joints also check the fuse in the plug top then see if you are getting power to the unit, I'd do this first.

Plug tops don't have fuses. Plugs do.

 

[GeorgeCooke]

As Lucien mentioned check for dry joints also check the fuse in the plug top then see if you are getting power to the unit, I'd do this first.

Plug tops don't have fuses. Plugs do.

 

[DPG]

Thanks for your ever useful input George. You are a credit to the forum. I have a question about MR16 bulbs as well.