Olympia Electronics emergency light stays on all the time

[goodpsusearch]

Hello.

I feel completely lost with this thing. It is a 13 years old emergency light that stopped working. I took it apart and replaced the batteries with new ones only to see that the fluorescent lamp stays on even when the AC is connected.

I checked the 2 electrolytic capacitors and found them ok.

I tested all the diodes with the diode mode of my multimeter and found them ok.

I did the same with the testing button. No problem with it.

Then I proceeded to test all the resistors including the smd zero ohm resistors and everything was good.

There is a ZTX851 NPN transistor that, according to the datasheet, is suited for "Emergency lighting circuits". I tested it with the diode mode of the multimeter and the readings I got seem to be normal...

So what is wrong??? I am a bit desperate here. I feel like a fool for getting new batteries before making sure that the emergency light is good.

In the last picture there is a three leg smd part that I wasn't able to identify. I read "6Cp22" but I couldn't find anything about it. Do you know if it is responsible for the light not turning off? What values I should get when I test it with the meter?

[bluto]

Re: Olympia Electronics emergency light stays on all the time

Maybe try pulling the transistor and see if the light goes out? While it is out, test it to make sure that it is not shorted. Voltage test the input to the transistor to see it if goes on and off when you pull the plug. That's all I have

[goodpsusearch]

Re: Olympia Electronics emergency light stays on all the time

Thank you for the input.

Good and bad news...

The component here is responsible for the light going off when AC is back.

I think it is an NPN transistor. This is the pinout I found: https://www.badcaps.net/forum/attach...1&d=1350769582
I also found that circuit:

http://dc200.4shared.com/doc/BH3RzXks/preview.html

Check the "9v to 12v OUTPUT" section.

Even though this is not an emergency light circuit, there are 2 transistors, the first is the ZTX851 the emergency light uses and there is a BC547 NPN transistor that is used to stop the ZTX851 switching.

I attached the schematic.

Quote from link:

The BC 547 prevents the ZXT 851 oscillator transistor turning on when the voltage is slightly above 12v. The 10u on the output stores the "reference voltage" and keeps the BC 547 turned on during the time when the output voltage is above 12v. This effectively stops the oscillator, but as soon as the output voltage drops below 12v, the circuit
comes back into operation, "charge-pumping" the 10u on the output.
The 12v zener works like this: No voltage appears on the anode end (the end connected to the 100R resistor) until 12v is on the cathode. Any voltage above 12v appears on the anode and this voltage passes through the 100R to the base of the BC 547. For instance, if 12.5v is
on the cathode, 0.5v will appear on the anode. When the base sees 0.7v, the transistor turns on, so slightly more than 12.7v is needed to turn on the transistor.

The bad news is that somehow I managed to damage this transistor. I am going to try a replacement, but my knowledge is limited on that subject.

Can I substitute the burnt smd transistor with the BC 547? Do you know if they are compatible? I wonder if it is possible to buy an SMD transistor like the one it originally had. That would save me some time trying to solder it.

For example is this compatible?


Please feel free to recommend me anything that would do the job.

[goodpsusearch]

Re: Olympia Electronics emergency light stays on all the time

I fixed it.

- I replaced the smd transistor that I fried accidentally with a BC846.

- Ι replaced the 22uF 85°C cap with a 22uF 50V Teapo SEK 105°C.

- I removed the original led light and used one with lower voltage drop.


But the thing that did the trick and increased the voltage the BC846 gets is the removal of the 681ohm resistor that was in parallel with a 221ohm resistor. Those resistors gave 167ohm equivalent R and were placed between "base" of BC846 and ground.

I cannot explain why after 9 years of service that voltage dropped bellow 0.7V. Every part tested was found ok and the values I got were close to nominal.

[goodpsusearch]

Re: Olympia Electronics emergency light stays on all the time

Just wanted to say that the symptoms appeared again 9 months later!

The problem was the ZENER diode "Z2". Although I tested it with the diode mode of the multimeter multiple times and always got normal readings, it seems it had started to fail.. I replaced it and the emergency light now lights only when AC is out

[Kiriakos GR]

Re: Olympia Electronics emergency light stays on all the time

You will see and a lot more components to fail due those damaged batteries which are unable to charge and they overload the charging circuitry.
It is pointless to replace components with out searching the why? they did failed.

[goodpsusearch]

Re: Olympia Electronics emergency light stays on all the time

This zener diode had nothing to do with the charging circuit. The batteries are new, the old ones were indeed bad.

[Kiriakos GR]

Re: Olympia Electronics emergency light stays on all the time

Just of curiosity why you did not contact this Greek company so to get help and even parts from them?

[goodpsusearch]

Re: Olympia Electronics emergency light stays on all the time

From my experience with other Greek companies (Crypto), they are more interested to sell you a new product, rather than help you repair the old one.