Repair Sylvania Model 72032 LED Lite?

[tuinkabouter]

Franc,

A second test you can do to check to see whether a zener diode is defective or not is to measure its voltage with a voltmeter of a multimeter (or simply just a voltmeter if you have one.)

In order for this test to work, we must feed voltage to the zener diode in reverse bias in series with a resistor. The voltage must be higher than the rated zener voltage of the zener diode. In the circuit below, we feed the zener diode and a 1KΩ resistor 9 volts from a 9-volt battery. The zener diode is rated for 5.1V, well below the 9 volts, so the test will work wtih this diode. When measuring the voltage across the zener diode, it must measure a voltage near its rated zener voltage.

Zener Diode Voltage Test

If a zener diode reads a voltage near its rated zener voltage, VZ, then it is good.
Open Diode

If the diode reads a much higher voltage, of or near the voltage of the supply voltage feeding it, it is open and, thus, defective. It should be replaced.
Shorted Diode

If the diode is reading a much lower voltage than its rated voltage, such as near 0V, it is shorted internally and, thus, is defective and must be replaced."

What do you think?

Explane the readings when you connect the zener in reverse.

Wat are the readings when you use 9v AC instead of DC.

 

[amdx]

Have a Sylvania Model 72032 LED Lite that stopped working.

Did some checking and seems the batteries go bad. http://www.amazon.com/Sylvania-72032-Sensor-Failure-FAILURE/product-reviews/B000KJZNBW

Would like to replace it with a better battery if possible.

Appreciate any tips concerning repair of either the Sylvania Model 72032 LED Lite or LED lites in general.

Thanks

Ken

I have the same light, if you find a good battery for replacement,
please post it. I need three!
Mikek

 

[Franc Zabkar]

A very good test you can do is to check a zener diode with your multimeter set to the ohmmeter setting.

This is a simple test we can do to check whether it is good, open, or shorted.

What readings did you find? Did you also measure the resistance of R?
Note that when performing resistance measurements, you need to do so
in the absence of power.

To answer your other questions, I use isopropyl alcohol to clean PCBs
but I'd be wary of using it on device markings. Sometimes they rub
off.

The markings on the zener usually reflect its breakdown voltage.

The battery appears to have three cells. Is it a 3.6V type? Does it
have a mAH rating on the body?

I notice that there appears to be extensive galvanic corrosion at the
switch terminals. I expect that the associated copper traces may
eventually turn black.

- Franc Zabkar

 

[KenO]

Franc,

These are the results

Zener markings I could see N1 & A

power off R series resistor ~22M Ohms

Zener Test with Ohmmeter of Multimeter

Negative Probe on Cathode (Black Strip) ~140 K Ohms

Positive Probe on Cathode (Black Strip) ~167 K Ohms

power on

Vin ~111 V

Vout to 0 V ~200 mV

"If the diode is reading a much lower voltage than its rated voltage, such as near 0V"

From tests seems Zener is Shorted.

Since the zener was destroyed from a "power surge" what upgrade do you suggest to prevent this from happening?

Ken

 

[KenO]

"The battery appears to have three cells. Is it a 3.6V type? Does it have a mAH rating on the body?"

Was finally able to locate this LED Lite on the OEMs website.
http://www.lomak.com/product_lv3.php?id=255

It is listed as Model 33030008A

Bat info Ni-MH 3.6V 110 AH

Ken

 

[KenO]

Mikek & Everyone,

"I have the same light, if you find a good battery for replacement, please post it. I need three!"

I would like to convert them to rechargeable Li if possible.

Did a quick search and found http://www.gpbatteries.com/index.php?option=com_k2&view=item&layout=item&id=291&Itemid=120 which lists rechargeable Lithium Cylindrical, Lithium Prismatic, and Lithium Polymer.

Any suggestions concerning what is the best for LED lites and what is needed to convert this Ni-MH Lite to Li?

Thanks

Ken

 

[Franc Zabkar]

Zener markings I could see N1 & A

Sorry, I can't make anything out of that.

power off R series resistor ~22M Ohms

It looks like this is open circuit.

Zener Test with Ohmmeter of Multimeter

Negative Probe on Cathode (Black Strip) ~140 K Ohms

Positive Probe on Cathode (Black Strip) ~167 K Ohms

I'm not sure what you are doing here. You should connect one probe to
one end of the zener, and the other probe to the other end. If that's
what you were doing, then you should have used the diode test function
of your meter.

power on

Vin ~111 V

Vout to 0 V ~200 mV

This is consistent with an open circuited series resistor. The zener
is not shorted, as per your previous measurement.

That said, I'm surprised that Vin is so high. I can't imagine that the
zener voltage would be more than 10V, so this would mean that the
series resistor would need to drop a lot of voltage. It seems too
small for that kind of wattage. Something doesn't look right to me,
but I can't see the circuit clearly enough (too many components
obscuring the PCB). I don't think I can help you without a circuit
diagram.



- Franc Zabkar

 

[Franc Zabkar]

This is consistent with an open circuited series resistor. The zener
is not shorted, as per your previous measurement.

That said, I'm surprised that Vin is so high. I can't imagine that the
zener voltage would be more than 10V, so this would mean that the
series resistor would need to drop a lot of voltage. It seems too
small for that kind of wattage. Something doesn't look right to me,
but I can't see the circuit clearly enough (too many components
obscuring the PCB). I don't think I can help you without a circuit
diagram.

I'm wondering if there may be a series capacitor whose function it is
to losslessly reduce the supply voltage ...

C2
bridge 1uF
rectifier 250VAC
______ | | Vin
AC1 o--| |----| |----o-- R --+----+---o Vout
| | | | | |
||>| | ZD1 C
| | | |
AC2 o--| |-----------o-------+----+---o
|----| 0V


As for the zener voltage, perhaps we can guess at its value by
examining the battery charging circuit.


D1 100 ohm
Vout o---|>|---- R4 ----+-o
|
3.6V NiMH
110mAH battery
|
0V o------------------+-o


If we assume that the charging current is 11mA (mAH rating / 10), and
if we allow for a charging voltage of 4.5V, say, then Vout would be
....

4.5 + (100 x 0.011) + 0.6 = 6.2V


- Franc Zabkar

 

[Franc Zabkar]

I'm wondering if there may be a series capacitor whose function it is
to losslessly reduce the supply voltage ...

C2
bridge 1uF
rectifier 250VAC
______ | | Vin
AC1 o--|~ +|----| |----o-- R --+----+---o Vout
| | | | | |
||>| | ZD1 C
| | | |
AC2 o--|~ -|-----------o-------+----+---o
|----| 0V

Sorry, C2 should be on the AC side of the bridge, not the DC side.

- Franc Zabkar

 

[KenO]

Franc,

"It looks like this is open circuit.
Zener Test with Ohmmeter of Multimeter
Negative Probe on Cathode (Black Strip) ~140 K Ohms
Positive Probe on Cathode (Black Strip) ~167 K Ohms
I'm not sure what you are doing here. You should connect one probe to
one end of the zener, and the other probe to the other end. If that's
what you were doing, then you should have used the diode test function
of your meter.
power on
Vin ~111 V
Vout to 0 V ~200 mV

Redid the tests using the diode test function of the meter and got the same results.