On Friday, November 2, 2012 9:28:28 AM UTC-7, KenO wrote:
> Have a Sylvania Model 72032 LED Lite that stopped working.
...
> Did some checking and seems the batteries go bad
If the battery is bad, replace it. The typical 'emergency lighting' appliance has to be tested
from time to time, and commercial units recommend
battery replacement every ten years, regardless of test.
So, figure a battery has 10 year mean time between failure.
There might be 10% of the batteries that fail in the first year,
and another 10% that are good after fifteen years.
Collecting anecdotes over the internet isn't going to be
very useful in this kind of situation. Maintaining your
emergency lighting, IS very useful. So, do it.
> Was thinking of using a wrench to try to twist off but am afraid of shattering these parts.
> Am wondering about de-bonders?
> Ken
It's not that expensive at $14. I would take a very sharp/brand-new
utility knife to the seams and carefully cut the unit at all the
visible seams, like in a circle around where the clear lens fastens to
the body, and elsewhere that you can find anything that looks like
where two pieces of plastic were joined together. Superglue is great
at re-attaching these separate pieces after you have fixed it.
Finally got the non working Sylvania Model 72032 LED Lite apart and checked the battery and fuse and they were OK but a component next to the fuse showed burn marks so am guessing this was what gave out.
While it is sold in USA as the Sylvania Model 72032 LED Lite, it is actually manufactured by LOMAK and inside the plastic shell is marked T4-1.
Did some searching using both Sylvania Model 72032 and LOMAK Model 72032 but to date have been unable to find either a parts list or schematic for it.
Would be interested in any suggestions how to find either the parts list or schematic.
Alternatively would be interested in trying to determine what the burnt component is.
I have taken some photos and would be glad to post if there is interest.
"I'm interested...Franc Zabkar...Please remove one 'i' from my address when replying by email."
Franc,
I did not see a way to post the Sylvania Model 72032 LED Lite Photos on the forum so tried sending them to you but got error message The message To: Cc: or Bcc: field contains a malformed email address.
If there is a way to post photos on forum please tell me how.
On Tue, 13 Nov 2012 07:51:10 -0800 (PST), KenO <kenithol...@yahoo.com>
put finger to keyboard and composed:
>I did not see a way to post the Sylvania Model 72032 LED Lite Photos on the forum so tried sending them to you but got error message The message To: Cc: or Bcc: field contains a malformed email address.
>If there is a way to post photos on forum please tell me how.
This is a text-only forum. You could upload your photos to a file
sharing service.
As for my email address, it is valid, but you need to remove one "i"
...
- Franc Zabkar
-- Please remove one 'i' from my address when replying by email.
The component below the fuse looks like it may be a series resistor
for the zener diode (ZD1). Together they would constitute a crude
zener regulated DC supply.
Measure the voltage across the zener and compare it against the
markings on the zener's body. This should tell you if the supply is
working correctly. I expect that there would be a filter capacitor on
the reverse side of the PCB (could we see that as well?).
- Franc Zabkar
-- Please remove one 'i' from my address when replying by email.
"Measure the voltage across the zener and compare it against the markings on the zener's body. This should tell you if the supply is working correctly."
Am a electronics beginner which is the reason I am interested in trouble shooting this LED Lite.
On Fri, 23 Nov 2012 10:02:08 -0800 (PST), KenO <kenithol...@yahoo.com>
put finger to keyboard and composed:
>"Measure the voltage across the zener and compare it against the markings on the zener's body. This should tell you if the supply is working correctly."
>Am a electronics beginner which is the reason I am interested in trouble shooting this LED Lite.
>How do I "Measure the voltage across the zener"?
With respect, voltage measurement is a very basic task. If you have to
ask this question, then you shouldn't be working on this device. There
are lethal AC voltages inside.
That said, here is the zener regulated supply:
Vin o-- R --|----|---o Vout
| |
Z C
| |
0V o-------|----|---o
Z = zener diode
C = electrolytic capacitor on reverse side
R = series resistor
Measure Vin with respect to 0V, and also measure the voltage between
Vout and 0V.
Examine the markings on the zener.
- Franc Zabkar
-- Please remove one 'i' from my address when replying by email.
"With respect, voltage measurement is a very basic task. If you have to
ask this question, then you shouldn't be working on this device. There
are lethal AC voltages inside."
Agree, which is why I have not plugged in this LED Lite to AC.
Had hoped I could do the measurements without plugging it in!
"Examine the markings on the zener." What am I looking for? From your looking at the photos I sent what are the possible variations?
Thanks again for your detailed explanations and help!
We will discuss both tests in this article.
Test a Zener Diode with an Ohmmeter of a Multimeter
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.
So we take the ohmmeter and place it across the leads of the diode. The orientation is very important.
Anode-Cathode Diode Resistance Test
We first take the ohmmeter and place the positive probe on the anode of the diode (the black part of the diode_ and the negative probe on the cathode of the diode (the black strip), as shown above. In this setup, the diode should read a moderately low resistance, maybe a few hundred thousands of ohms. For example, you may read around 450KΩ.
Zener Diode Anode to Cathode Resistance Test
Cathode-Anode Diode Resistance Test
Now take the ohmmeter and switch the probes around so that the positive probe of the multimeter is now on the cathode of the diode and the negative lead on the anode. In this setup now, the diode should read a much higher resistance, well over 1MΩ. A typical reading may, for example, be 2.3MΩ. The multimeter may even indicate 'OL' for an open circuit, since the resistance is so high.
Zener Diode Cathode to Anode Resistance Test
If you read a moderately low resistance with the leads on the zener diode one way and a high resistance with the leads the other, this is a sign that the zener diode is good. A zener diode should read relatively low resistance in the forward biased direction and very high resistance in the reverse biased direction.
Open Diode
If a zener diode reads high resistance in both directions, this is a sign that the diode is open. A diode should not measure very high resistance in the forward biased direction. The diode should be replaced in the circuit.
Shorted Diode
If the zener diode reads low resistances in both directions, this is a sign that the diode is shorted. A diode should not measure low resistance in the reverse biased direction. The diode should be replaced in the circuit.
How to Test a Zener Diode with a Voltmeter of a Multimeter
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."
> 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.
On Sat, 24 Nov 2012 12:42:17 -0800 (PST), KenO <kenithol...@yahoo.com>
put finger to keyboard and composed:
>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
-- Please remove one 'i' from my address when replying by email.
