Good evening,
I intend to repair if possible the PCB from a Sakura SS3630 6A 12V battery charger, else I will make a new control circuit.
The present PCB is very simple with 4 x 6A10 diodes and a small driver circuit for the 3 LED panel lights - 2 x 4.6K resistors and a little loop with a 75 ohm in series with a C13ST (13V) Zener diode, tapped into the PCB as per the pictures. These all test out fine and the transformer is also OK.

The burned out, and i do mean burned, component is in series with the positive DC output rail and as far as could see was a two leg 10mm x 10mm "bit" was was some type of (don't laugh) saftey device. I would have expected a fuse but this is, was, something else any ideas ?

Comments or advice appreciated

TC

 

Do you have any idea if the unit ever shut down temporarily due to overheating? Sometimes there is a kind of thermal switch or breaker.

 

I am afraid I don't know but whatever device was in series with the DC output burned !
The PCB pictured is the only control device.

 

Take a picture of the whole board, both component side and foil side.

Trace the two blue wires and the red and black wire. Let us know where they are connected.

Clean up that area before taking the pictures.

What test equipment do you own for troubleshooting?

The "load" on that point could have been a battery.

 

... betting that part was a Schottkey diode inserted for the purpose of reverse polarity protection, which is likely what caused it to vaporize. ... Guessing a 6 amp Schottkey diode would replace it, but thats only a guess.

 

Take a picture of the whole board, both component side and foil side.

Trace the two blue wires and the red and black wire. Let us know where they are connected.

Clean up that area before taking the pictures.

What test equipment do you own for troubleshooting?

The "load" on that point could have been a battery.

DearJoeJester,
Thank you for the repy and interest.
The pictures I posted are, believe it or not, cleaned ! it was black with soot when I opened the case, they are also the only PCB - the 4 pin header only goes to 3 LED indicators.
The Blue wires are from the transformer - this has only one pair from it and checks out on voltage and load
The Red and Black wires go the battery being charged.
In all it is a very basic circuit and all the remaining components have tested out fine.

Test Equipment :-
I have multimeters and can measure inductance, capacitance, frequency and duty cycle as well as the "normal" values. I also have a component tester that can do a range of components - Atmega 328P based and a small kit based oscilliscope

Regards,
TC

 

... betting that part was a Schottkey diode inserted for the purpose of reverse polarity protection, which is likely what caused it to vaporize. ... Guessing a 6 amp Schottkey diode would replace it, but thats only a guess.

Dear DRC_567,

I think you may well be right ! the charred remains of the component - which fell to pieces when i touched it were a TO-220 package but without heat sink.

Regards,
TC

 

DRC is correct.

You never mentioned that you incorrectly hooked up the cables incorrectly or you had received it that way. Make sure you have good contact with what remains of the traces.

 

DRC is correct.

You never mentioned that you incorrectly hooked up the cables incorrectly or you had received it that way. Make sure you have good contact with what remains of the traces.

I recieved it in this condition so I guess the previous owner connected it up reverse polarity to a battery !

I did a couple of further checks :-

AC from transformer 14.20V
Vf of combined rectifier bridge 1.15V
C13ST Zener diode Vf 0.83V for "fully charged" LED
So I guess I have about 13V before Schottkey diode

As recomended a Schottkey diode it shall be. Would a 10A 45V one be OK with or without a heatsink.

Regards,
TC

 

... The only question is if there could be momentary transient current peaks. Who knows?
Your suggestion sounds ok ... you'll just have to try it out. I would say do not heat sink it ... you want it to fail open if a reverse polarity accidentally occurs.

 

... The only question is if there could be momentary transient current peaks. Who knows?
Your suggestion sounds ok ... you'll just have to try it out. I would say do not heat sink it ... you want it to fail open if a reverse polarity accidentally occurs.

It just occured to me that, perhaps, the Schottky diode needs to sized for the battery amps rather than the chargers rated amps. Is that sensible

 

... It seems to make more sense to go with the charger rated amps, give or take a few. If it is an automotive battery charger, you would be looking at at least 10 times the charger rating, if not more. ... Suggest that you try the 10 amp Schottkey version and see if there are any problems. ... Should be in the ballpark range.

 

Good evening,
I intend to repair if possible the PCB from a Sakura SS3630 6A 12V battery charger, else I will make a new control circuit.
The present PCB is very simple with 4 x 6A10 diodes and a small driver circuit for the 3 LED panel lights - 2 x 4.6K resistors and a little loop with a 75 ohm in series with a C13ST (13V) Zener diode, tapped into the PCB as per the pictures. These all test out fine and the transformer is also OK.

The burned out, and i do mean burned, component is in series with the positive DC output rail and as far as could see was a two leg 10mm x 10mm "bit" was was some type of (don't laugh) saftey device. I would have expected a fuse but this is, was, something else any ideas ?

Comments or advice appreciated

TC

View attachment 177841
View attachment 177842

6A 100V diode...


https://www.futurlec.com/Diodes/6A02pr.shtml

 

Thank you for your advice, parts ordered and repair imminent

 

It's never that simple is it !
I repaired the +ve DC output using 10A 40V (10SQ45) and tested the DC output.

I did some checks :-

I get only 11.7V DC output with no load and it drops 10.1V with a 5A load (little compressor)
AC output no load 14.2V and when a 5A DC load is attached to the output it drops to 12.8V
I checked the DC output before and after the blocking Schottky diode I put in place and get a voltage drop of about 0.3V across it which seems OK.
I suspect that one of the original 6A10 diodes is faulty.
I have another 4 x 10SQ45 diodes left. Could I just replace all the original 6A10's with these ?

 

... don't know about replacement equivalency. The burn mark in the picture suggests that the adjacent diode might be questionable. If you can remove the original diodes without too much effort, you would be able to check and compare each diode by using a multi-meter that has the diode check function. See if one or two diodes are different. If you are not familiar with desoldering, get some solder-wick and a small bottle of resin based liquid flux ... things will go much better with a drop or two of the flux. Before removal, maybe mark a + and - on the board so there is no mix-up.

 

It's never that simple is it !
I repaired the +ve DC output using 10A 40V (10SQ45) and tested the DC output.
I
I did some checks :-

I get only 11.7V DC output with no load and it drops 10.1V with a 5A load (little compressor)
AC output no load 14.2V and when a 5A DC load is attached to the output it drops to 12.8V
I checked the DC output before and after the blocking Schottky diode I put in place and get a voltage drop of about 0.3V across it which seems OK.
I suspect that one of the original 6A10 diodes is faulty.
I have another 4 x 10SQ45 diodes left. Could I just replace all the original 6A10's with these ?

Yes replace all the diodes for new, and re test...

 

... don't know about replacement equivalency. The burn mark in the picture suggests that the adjacent diode might be questionable. If you can remove the original diodes without too much effort, you would be able to check and compare each diode by using a multi-meter that has the diode check function. See if one or two diodes are different. If you are not familiar with desoldering, get some solder-wick and a small bottle of resin based liquid flux ... things will go much better with a drop or two of the flux. Before removal, maybe mark a + and - on the board so there is no mix-up.

I de-soldered one of each pair so I could test them indiviually and you were correct the one closest to the burned PCB was faulty. It is academic but I wonder if the 6A10 died before the "burn out" or after the Scottky diode caught fire ! Anyway these 6A10's are inexpensive so I will replace them all like for like rather than use my extra Schottky diodes.

Regards,

TC

 

There are two ways diodes are used to protect from reverse polarity:

One is as a pass element (Source: https://www.allaboutcircuits.com/technical-articles/how-to-protect-your-circuits-using-only-a-diode/ ):



The other is as a fuse:


From the way yours burned out, it is likely to have been used as a fuse. If that's the case, using a lower rating versus a rating greater than the charger's capacity might be advised.