Help needed with fried SWMPS - RING RSC612/RESC612

[madan1]

Hello everyone.

Just got from ebay a dead ( *almost ) smart auto-battery charger. It turned out that the mains part of the SWMPS is fried.
It looks like there has been an arc between NTR1, C6, JP24 and the resistor near them. Part of the jumper wire has been evaporated.
The resistor goes to leg3 of the optocoupler O3 ( which seems to be dead open on that side ).
On the other side of the board, there is a hole in the optocoupler path to the resistor, most likely caused by an arc between it and the nearby leg of C10.
Also there is an exploded transistor(?) marked N5.
The pcb lacquer over the path next to the main positive rail fell when I was using the pen.
So far I have found the following parts to be dead:
F1, on the input, right next to C1
D3 - one of the diodes to the negative rail has shorted
O3 - open on the transistor side
Z3 - shorted
N5

The charger is RING RSC612/RESC612
The board is WYH6859J-A6.PCB
The main SWMPS IC is UC3842B with UCS3842B
The secondary/standby SWMPS is RCP 36R DB(?)

So any schematics will be appreciated.. or at least any ideas with what to substitute the exploded N5... also, which other components are very likely to have lost their magic smoke?
Thanks in advance.

*almost dead, because the smart part should have some functionality when a battery is connected ( TEST mode ).. at least according to the seller.

[budm]

Re: Help needed with fried SWMPS

How about the power MOSFET mounted on the big heastink in the HOT side,?
Did you test to find out if the MOSFET is shorted?
MOSFET Q3 for 12V1A power supply section tested OK?
Please also provides the top and bottom pictures of the board without your making on them?
Photo Transistor in the opto should show open circuit, it will not be turned on unless you drive the LED side on.

[madan1]

Re: Help needed with fried SWMPS

Tested both ( primary and secondary ) transistors in circuit on diode mode and they are not shorted. Once I start replacing components, I might test them out of the circuit.

[budm]

Re: Help needed with fried SWMPS

I just updated my post #2.

[madan1]

Re: Help needed with fried SWMPS

The main mosfet and q3 seem to be fine - no shorts and the expected voltage drops.
On the other two optos I get a voltage drop in one direction, so expected to see the same here.. but that could just be something else in the circuit. I guess I wrote it off as soon as I saw the burn hole on its path and the burnt resistor ( which still shows some resistance, will have to compare it to its color code tho ). Probably testing it with voltage on the other side will not hurt and might save some work.

Let me know what photos you need and will make them. For now I have uploaded 4 - top and bottom of the whole board and top and bottom of the hot part ( free of markings ).

[budm]

Re: Help needed with fried SWMPS

https://www.badcaps.net/forum/attach...4&d=1595803171
Where do you see the board number?
"The board is WYH6859J-A6.PCB"
I see the prints on the board showing the name 'CENTURY' and above that there are two lines of printed numbers and letter but I cannot see them clearly.

[madan1]

Re: Help needed with fried SWMPS

There you go.

[madan1]

Re: Help needed with fried SWMPS

So did some more tests today - no other resistors or diodes seem to have failed.
The SMPS ICs also have no shorted pins.

The exploded transistor(?) seems to belong to the start current circuit of the secondary/standby swmps and probably the primary.
There are few other components labeled "N#" ( all on the secondary side of power supply ) and they are marked as:
1x
BV
51
( bigger than the others and with 4 pins )
3x
K1P
F8
(the same physical size as the exploded one )

For K1P google returned MMBT2222A NPN transistor.
What do you think.. does one of those fit in the schematics for the exploded N5?


If we count the legs of N5 as:
---1---
-2---3-

leg 3 goes to the primary ground rail
leg 2 goes to the opto and then through a resistor to the primary ground
leg 1 - through a couple of resistors ( ~110K which might vary due to Q9 ) to the "startup/aux rail"

K1P pinout is:

---c---
-b---e-

[budm]

Re: Help needed with fried SWMPS

2N2222 NPN should be OK for N5.
I am still surprised that the MOSFET's did not shorted out and cause the 3A Fuse to blow when 230VAC arc over to the jumper.
See the attached picture that I marked up the connection.

[madan1]

Re: Help needed with fried SWMPS

Thank you, budm.
Just checked again - no shorts on both mosfets. I guess the majority of the power was contained between the 3 ( or probably 4 ) arced components. By the way, what would be your best guess about the cause for this?
Which component failed first? Could it be the short where the burn hole on the path to the opto is.. or probably the rectifier?

[budm]

Re: Help needed with fried SWMPS

I really do not know but it has to be pretty large amount flows through that jumper wire to make it melts like, that why I am surprised that more traces are not blown when jumper wire which is bigger conductor than copper traces.

[madan1]

Re: Help needed with fried SWMPS

And to close the thread - replaced the rectifier, the zener, the fuse and the mystery "N5" component ( with 2N2222 ) and fixed the jumper wire. That seems to have fixed the problem.
Now the unit powers up and seems to be charging the battery ( at least reads properly the battery voltage and shows "real-time' charging current values ). Didn't have time for more extended test, but the things look good.
Some words about the quality - total shit! As soon as any serious heat is applied and the copper paths pop.
About the product - the idea is good.. has several testing and charging modes, and up to 12A charging current. I guess useful product for a repair shop or someone with lots of cars/bikes and batteries. For average Joe with a couple of cars and with some knowledge about car electrics, these are $100 of another unnecessary gadget.

[budm]

Re: Help needed with fried SWMPS

Glad to hear you got it working.
I still wonder how the arc jump that far to the jumper wire and melted that wire, may be something conductive fell into the case and shorted out.
$100 is a lot for a charger.

[madan1]

Re: Help needed with fried SWMPS

Glad to hear you got it working.
I still wonder how the arc jump that far to the jumper wire and melted that wire, may be something conductive fell into the case and shorted out.
$100 is a lot for a charger.

It is a "smart" charger and that's the price on which it is sold on amazon - https://www.amazon.co.uk/Ring-RSC612.../dp/B00S8969OG
and probably if you are taking care of 10-20 vehicles, it could be very useful and can save money from dead batteries.

I also thought that something from outside caused the arc, but there was nothing left inside the case ( very carefully looked inside for the exploded top of the transistor ). Of course it is possible to have been previously opened for inspection ( the seller had few of those for sale, so probably part of a job lot of warranty returns ).
Also, the ventilation holes are not that big...

By, the way, what about a power surge?

[budm]

Re: Help needed with fried SWMPS

I see blue MOV just above the black fuse, so if bad surge comes along it should conduct and blow the main fuse.

[jnkcrowther@gmail.com]

Re: Help needed with fried SWMPS

Hi. I'm chasing a fault on a Ring RSC612 as well. Mine lights up and does all the diagnostics but won't charge, even though it has no fault codes. Can anyone tell me what the two To-220 packaged semiconductors are on the corner of the board opposite the power supply corner. The heat sinks are soldered directly on the printed circuit track. I can't make out any numbers on them. Thanks.

[tyrex]

Re: Help needed with fried SWMPS - RING RSC612/RESC612

New here and not an expert, but found this thread on Google and wanted to add my experience.

Now about to get my third RSC612 under warranty. The two I've had seem to fail in the same way - completely dead on the mains (and charging) side but light up when connected to the battery.

Standard support always asks whether mains fuse has blown - it always has. I use 3A on 240V/50Hz main.

My car is permanently on charge (irregularly used sports car which is garaged most of the time) so I guess could be a power surge, but nothing else in the house has ever been fried.

They're great little chargers, but looks like something on the mains side is pretty weak.

[Dedgey]

Re: Help needed with fried SWMPS - RING RSC612/RESC612

Hello All,
I too have a Ring smart charger that the mains side of it is dead, but the 12v battery side still seems to work correctly in test mode.

Thus far I have found R26 is blown, and F1 is open circuit. I think the resistor is about 2W 0.2 ohm, and the fuse a 3.15A 250v. I cannot see any other damage to components or board.

The charger was left overnight charging a 110Ah leisure battery that was already about 95% charged, but the battery did not seem to want to go any higher. It had been heavily discharged and I was hoping the smart charger could save it.

I have looked but cannot find a schematic diagram, and I think the unit has 3 photo switches, which seems rather a lot! No you tube explanations of computer type power supplies seem to have as many photo switches??

So, does anyone know where i can find a schematic diagram for the board please, and given F1 and R26 have blown where would be next to check? Or, would replacing the fuse and resistor then seeing if it turns on on mains be a reasonable next step? I am assuming R26 was faulty or overworked, and that blowing took out F1. Would that be a reasonable first guess?

[PeteS in CA]

Re: Help needed with fried SWMPS - RING RSC612/RESC612

If R26 is a very low value part and in the source circuit of the switch MOSFET it probably is for current sense and the MOSFET shorted, blowing the resistor and the fuse.

[R_J]

Re: Help needed with fried SWMPS - RING RSC612/RESC612

Check if the resistor is indeed open, it may just have the coating cracked off due to heat over time.