Ryobi 12v Li-Ion Battery Charger dead

[sambul83]

Re: Ryobi 12v Li-Ion Battery Charger dead

Did you mean D201 on the smaller heatsink right behind the transformer? This one has 3 legs and looks like SMPS IC.

As to C3E H62 (IC203), I already mentioned it was 16V at every pin, but now:

Left pin = 9.8 mV (its mV, not V)
Center pin = 27.1 mV
Right pin = 25 mV
Tab = 27.1 mV

Yet the question remains, how a charger can possibly die without being used, unless an electrolytic cap is at fault - or its a time bomb?

[budm]

Re: Ryobi 12v Li-Ion Battery Charger dead

Sorry, typo, it is D201 mounted on the heatsink.

Hmm, no voltages at all, I will need to trace out the connections, so far I cannot find the spec of the ATMEL IC to get the VCC pin out.

[redwire]

Re: Ryobi 12v Li-Ion Battery Charger dead

About IC203, SMD marking code "C3E" S-812C HV CMOS voltage regulator 5V Just in case, similar SMD marking code "C3Q" UA78M33 3.3V 500mA vreg

[budm]

Re: Ryobi 12v Li-Ion Battery Charger dead

OK, I traced out the board, this is what I come up with.
I would check Q209, ZD2???.
Also check the resistance between the two legs of C203, C205 to make sure there is no shorts to ground.
Check the Voltages without the battery in place.
REDWIRE, thanks for finding the regulator spec.

[sambul83]

Re: Ryobi 12v Li-Ion Battery Charger dead

Transistor c1815 gr8e (Q209) What should I measure here, under power?
Did you mean Q209 on your sketch (not Q202 - can't find it)?
Zener unknown (ZD203). Its 750mV in one direction, and 790mV continuity in the other with power off.

I checked resistance btw caps legs with power off, and for C203 (L-Tec 220Uf 16V SM85C) its near 0 (beep on continuity check), and for C205 its higher than 20+MOhm.

Its getting hotter now...

[Agent24]

Re: Ryobi 12v Li-Ion Battery Charger dead

You should check the parts out of circuit... the zener should not show continuity both ways, but if you tested in-circuit you may be getting some false reading.

[budm]

Re: Ryobi 12v Li-Ion Battery Charger dead

It is Q209 as shown in your picture:
https://www.badcaps.net/forum/attach...4&d=1429208748
If C203 shows 0 Ohms then that is not right, use Ohm mode and check it both ways with your probes, no power to the unit of course.
BTW, Q209 and the Zener is just a simple linear regulator, the 4.5VDC as you measured is kind of low to feed two regulator, but that low Voltage reading may be due shorts that you find across C203.
What is the voltage rating of C202?

[sambul83]

Re: Ryobi 12v Li-Ion Battery Charger dead

Q209 measures 1-3 750mV, 1-2 715mV, 2-3 740mV with power off, where 1 is emitter
ZD203 is 750mV in one direction, and 790mV in the other
C203 is 0.2 Ohm both ways
C202 (L-Tee 100uF 35V 110c(M)) is 4.3V now may be due to outlet power fluctuations

But... IC203 was showing 16V to the ground on all legs, and now its near 0. Does it say anything to you?

[budm]

Re: Ryobi 12v Li-Ion Battery Charger dead

"C203 is 0.2 Ohm both ways" Right now this is the key to the problem, it is either the cap C203 is shorted, or the very small SMD (MLCC) cap C207 that is connected in parallel with the C203 is shorted, or the regulator IC203 has shorted input, I suspect the SMD cap C207.
So basically you will have to start removing parts connected to the + leg of C203.

"But... IC203 was showing 16V to the ground on all legs, and now its near 0. Does it say anything to you?" That does not make sense because you were getting in mV on C203 which is connected to the input pin of the IC203 regulator and C203 also show 0.2 Ohms.
I cannot speculate as to hwy the unit failed without being used for a long time, but looking that very simple transistor/Zener linear regulator circuit it should be working and not showing 0.2 Ohms across the cap's legs.
I hope it is not your measurement errors.

[sambul83]

Re: Ryobi 12v Li-Ion Battery Charger dead

With C203 there is no error, its 0.2 Ohm. I think you mean small C204 (not C207), but how I can remove this thing, and more important, what it can be replaced with? Right now it also beeps on continuity check.

What do you think of the above Q209 and ZD203 readings? Do they make sense to you? I watched through a lens and checked everything 3 times, and also each time I calibrate on a next working part to see if there is any difference that makes sense.

[budm]

Re: Ryobi 12v Li-Ion Battery Charger dead

"With C203 there is no error, its 0.2 Ohm" I do not understand what you mean, are you saying that with C203 removed the 0.2 Ohms is still there in the board?
Sorry it is C204 (C207 is parallel with the filter cap for the output of the IC regulator).
To remove C204 (you cannot reuse it once it is removed because it can easily be damaged) you use wide tip soldering iron and add more solder to both ends of the cap and move the soldering tip back and forth while pushing on the body of the cap with screw driver. C204 can be left out for now if it is bad, for replacement you can use 0.1uF 16V Ceramic disc cap through hole type since the board has lots of room.

[sambul83]

Re: Ryobi 12v Li-Ion Battery Charger dead

I mean no measurement error. OK, I took C203's out, and it measures 250uF on multimeter (rated 220uF), and resistance fluctuates 30 kOhms - 2 mOhms.

C204 measures 14kOhm both ways when C203 is out. Should I remote C204?

I tested the board withoutC203, and here we go:

Red led is lit now!!!
Voltages:
C106 6.7V (charger power side), C201 4.7v (why dropped from 16V - because the battery is not attached?), C202 11V, C205 5.7V

IC203
Left pin = 0V
Center pin = 10V
Right pin = 5.7V
Tab = 10V

[sambul83]

Re: Ryobi 12v Li-Ion Battery Charger dead

I put the battery in, the charger now recognizes it, but the flashing pattern isn't right. Hopefully, it'll improve once C203 is replaced. Is it the only thing for now?

Does it mean that Q209 and ZD203 are OK? Is it possible that defective Q209 caused C203 damage? Any other test I can do with Q209, if some reading below seems too low?

ZD203 3.7 mOhms / 17 mOhms @ power off

Q209
Emitter to base 2+ mOhms
Base to emitter 135 kOhms
Emitter to collector 2+ mOhms
Collector to emitter 133 kOhms
Collector to base 1.5 kOhms
Base to collector 1.5 kOhms


My bad caps collection is growing.

[budm]

Re: Ryobi 12v Li-Ion Battery Charger dead

I would replace C203 first and see what happen, without that high capacitance in place the circuit may be oscillating.
The question is 0.20 Ohms reading went away?

[sambul83]

Re: Ryobi 12v Li-Ion Battery Charger dead

I'll get C203 cap replacement. Yes, its 0.2 Ohms reading went away once removed from the board, but... I can't say what it is now. Once out and fully discharged, it measures from 30 kOhms slowly growing to 2 mOhms, then suddenly drops back to 15-30 kOhms, and start growing again towards mOhms. Is it normal for caps? I assume its bad, since without it the charger shown signs of life?

[redwire]

Re: Ryobi 12v Li-Ion Battery Charger dead

I was thinking this might have been tin whiskers around the cap?
It would explain why it died in storage and why the shorted cap tests ok out of circuit.

[budm]

Re: Ryobi 12v Li-Ion Battery Charger dead

I just wish the OP will came back with the follow-up after all the helps (tracing the board, drew up the diagram, give the test points) we gave.

[sambul83]

Re: Ryobi 12v Li-Ion Battery Charger dead

Sorry I didn't have a chance to complete this repair yet. Now I re-tested the removed cap, and it shown 0 Ohms in both directions, and also meter emitted sound on "short" test both ways. Does it confirm "tin whiskers" theory? I don't see them on the board. Despite all this, it measured 250uF stable capacitance versus 220uF rated. How is it possible?

Open question however remains, why did it die prematurely without being used...

[budm]

Re: Ryobi 12v Li-Ion Battery Charger dead

"Now I re-tested the removed cap, and it shown 0 Ohms in both directions" is this reading on the cap or on the pads on the board where the cap was?

[sambul83]

Re: Ryobi 12v Li-Ion Battery Charger dead

Since I don't do repairs electronics for leaving, I keep these bad caps as souvenirs, so the reading is definitely on the detached cap. Its still alive despite fully shorted!

And the reading on its board pads is 14.6 kOhms. I'm quite inventive in various theories, so it looks like surface of its charged element is large, and the short is only in a small area so the discharge is not immediate. That allows this cap to keep charge and show stable capacitance when connected to a meter as current source, while being short. When in-circuit, voltages are higher, so discharge is faster, and it stays short.