Not very happy with LEDs.

[ClydeCrashKop]

I checked one that was still working on my home transformer that puts out 31 volts but has big capacitors in it. (I don't remember the uf) It was drawing 65 mA and getting warm.
The boards are epoxy/fiberglass.

 

[audioguru]

I checked one that was still working on my home transformer that puts out 31 volts but has big capacitors in it. (I don't remember the uf) It was drawing 65 mA and getting warm.
The boards are epoxy/fiberglass.

A transformer has an AC output and does not have capacitors. Maybe you have a DC power supply that has big filter capacitors and an output of 31VDC?

 

[MrAl]

I tried them on 12 volts and they were very dim.
We are using 24 volt transformers but I put full wave bridge rectifiers on their outputs, just in case and to bring the 26 or 27 volts down a little. But that is well below the 32 VDC they claim.
All of the diodes have blisters on the clear coat.
The 6 pin IC is numbered 40??

View attachment 100933

Hi,

Can you show the other side of the board too?

What is on the other side opposite those diodes?
Did you ever try replacing them?

SMD parts are a little different than through hole parts. SMD parts like diodes need a certain amount of copper real estate in order to function to the power level they were intended for. In fact, even some regular through hole diodes require copper board area to help dissipate the heat. Maybe they did not provide enough copper surface area.

All just guessing though until we see the circuit schematic. If you can create one we can wrap this up, but if not it's guess guess guess from now until October

 

[JimB]

if not it's guess guess guess from now until October

Oh MrAl, you are such a spoil sport!

Lack of information is no hindrance to wild guessing and speculation, which seem to be the favourite pastime on this and most other electronic discussion boards.

Focussed discussion based on hard facts...
We cannot have that!

JimB

 

[ClydeCrashKop]

A transformer has an AC output and does not have capacitors. Maybe you have a DC power supply that has big filter capacitors and an output of 31VDC?

This is a 1.5 kva transformer that I use for my CNC. I used 100 amp diodes to make the rectifier and the highest mfd capacitors that would fit in the box. The ones on the boat are 6" high & 4" square with a 7 amp fuse.

All just guessing though until we see the circuit schematic. If you can create one we can wrap this up, but if not it's guess guess guess from now until October

Somehow I think if I put better diodes in them or bypassed them altogether, (since we have DC now) they might be okay. Although 140 lights at $21.99 is a lot of money and so is 140 lights at $7.00 that we are going to replace them with, we consider them a fire hazard. The price here isn't all that important. Mainly, I am just complaining.

 

[audioguru]

We are just guessing about what those diodes are for. The sales sheet says the LED discs are powered by DC and does not mention AC.
The diodes might protect the circuit if the polarity of the 24VDC is backwards.

 

[alec_t]

The diodes might protect the circuit if the polarity of the 24VDC is backwards.

True. But a single diode could do that. It's unlike a manufacturer to add extra components just for the helluvit. As you say, we're just guessing.

 

[ClydeCrashKop]

The diodes might protect the circuit if the polarity of the 24VDC is backwards.

The diodes make the polarity right no matter which way you plug it in.
They work either way.
I did that on one of my products to make it fool proof.

 

[RODALCO]

You need to backwards engineer the circuit and make a drawing to avoid the wild guessing of how the circuit works.

 

[bountyhunter]

It looks like the rectifier diodes are failing first, not the LEDs. Maybe the diodes become shorted then the entire circuit becomes destroyed.

That was my first guess. Exceeding the peak reverse voltage, pop the rectifiers and then they cook.

 

[bountyhunter]

I think the defective (insert any word here) came from ebay.

Yeah. Never buy anything off ebay you can't just write off.....

 

[bountyhunter]

The problem with linear constant current sources is they must dump VI product in heat for every volt above threshold.

yeah Switcher would be more efficient.

 

[MrAl]

Oh MrAl, you are such a spoil sport!

Lack of information is no hindrance to wild guessing and speculation, which seem to be the favourite pastime on this and most other electronic discussion boards.

Focussed discussion based on hard facts...
We cannot have that!

JimB

Hi Jim,

Ha ha, yeah, sorry for trying to clear up the confusion

Someone on another site asked an interesting question about if it would help to add more LED's to a China LED light. I guess that could help if the LED's were overdriven and it was not a constant current driver.

The problem i see with the 'bad diode' conjecture is that if there was only 65ma it's hard to believe they could burn out. Of course we dont know that much about the circuit yet and that's what we really need to know in order to solve this.
With my Streamlight i just added a larger resistor in series with all the LED's, and left the original very small LED's intact for balancing the current through each LED, but then later i changed the LED's to a single Luxeon Star and used that for several years after that. Now i have so many LED lights that i dont need that one anymore

I've obtained several now from China based manu's and find most of them work pretty well. I dont get anything from Ebay though as i have heard too many complaints about wayyyy too many electronic boards and parts. Maybe more people need to invoke the refund policy they have, or at least i think they have. Probably not many people do that.

 

[KeepItSimpleStupid]

I might agree that the first thing to look at is power quality. AC operation is never good. Adding a TVS isn't a bad thing. Instead of actually taking out the bridge, it may actually be taking out the IC first.

You may have some cooling issues too.

Try to ascertain any markings on the IC and the diodes.

I remember a thermocouple scanner which kept breaking. The schematic I obtained had a whole bunch of unpopulated parts missing. All I added was a transorb. I definately had reason to believe transients were the cause. It was an unregulated DC made from AC that IR lamps were being controlled by a temperature controller.

 

[ClydeCrashKop]

I cleaned off the diodes with acetone. All that is on top is || BB . I'm sure the bars are just for orientation. Would there be anything on the bottom?

 

[Nigel Goodwin]

The schematic I obtained had a whole bunch of unpopulated parts missing. All I added was a transorb. I definately had reason to believe transients were the cause.

It used to be common in TV's, in the UK there were loads of parts missing in the mains side of the PSU's, as the mains quality here is so high they aren't needed. In countries with poorer mains they fitted lot's of extra components for filtering and spike/surge suppression.

I've seen many Sky boxes brought back from Spain for repair, with the PSU 'blown up', and very commonly the reservoir capacitor was exploded as well - this never happens to the boxes in the UK, even though our mains is 20V higher.

 

[Tony Stewart]

This is a 1.5 kva transformer that I use for my CNC. I used 100 amp diodes to make the rectifier and the highest mfd capacitors that would fit in the box. The ones on the boat are 6" high & 4" square with a 7 amp fuse.


Somehow I think if I put better diodes in them or bypassed them altogether, (since we have DC now) they might be okay. Although 140 lights at $21.99 is a lot of money and so is 140 lights at $7.00 that we are going to replace them with, we consider them a fire hazard. The price here isn't all that important. Mainly, I am just complaining.

LED lamps are only CDN1$/W here ,more and less, if you make your own it's USD$0.1/W in volume. You can pay more if there is something about it you like , such as PFC , efficacy , dimmable , colour control with yellow LED added or CCT values etc.

 

[Tony Stewart]

I once had halogen lamps on front wood deck steps with a 200W transformer, so I converted 12Vac to DC inside the unit and replaced a pair with 1x4 LED Alum Clad boards cut down from scrap boards made for Ambulence flashers that were 1x16. Then made a dozen for along the fence line and added to the few in front. There were all running in parallel due to good quality matching in 1W chips fed from 13Vdc using AWG18 wire.

Later in the current residence , ( no pun intended ) I put all these 1x4 same LEDs in a 12.0V regulated wall supply.
Installed into $1 Chinese lanterns sprayed with Urethane and LEDs installed. It's been 3 yrs since they were installed.
and the LEDs were almost free from an Alum. Scrap dealer who got them from Solectron. Note the season is winter, but I use all year round.

 

[throbscottle]

According to the 2007 Turuta codebook, the diodes could be any of the following:
BZT52H-C5V1 zener SOD123F
BZX399-C5V1 zener SOD-323
BZX884-C6V2 zener SOD-882
SC016-2 GP, Rectifier, 200V, 1A, Vf<1,1V(2A) DO-214
SD833-04 Schottky Barrier Rectifier, 60V, 3A, Vf<0,58V(2,5A) PowDI123
UDZ5V1B zener SOD-323
ZMS5800 Schottky Rectifier, 50V, 1A, 250mW, Vf<410mV(1mA) SOD-323

Hopefully the package will give away which one.

For the chip I get several possibilities, mostly LDO regulators and various kinds of FET and diodes, but I also found:
BCR420U which is an LED driver, but the package looks wrong.
Is it not possible to make out what the ?? part of the marking is?
(edit) Ahhhh would you look at that ... my nice columns all gone

 

[throbscottle]

All just guessing though until we see the circuit schematic. If you can create one we can wrap this up, but if not it's guess guess guess from now until October

What happens in October?