zener diode info and ID ?

R

robb

Guest
i have a suspect zener diode from a PS . Zener, because the PCB
says it is (ZD901)

it looks like a small signal diode and it has a 16 and 2 printed
on opposite sides.

to test/replace --- the 16 is for ? volts ? and the 2 is ?
*OR* are the ###s short hand for some other 1N4### value ?

and the best test is to measure V across it ?

thanks for any helpful replies,
robb
 
"robb" <some@where.on.net> wrote in message
news:wNOdnUbb-dLVum7XnZ2dnUVZ_uGdnZ2d@earthlink.com...
i have a suspect zener diode from a PS . Zener, because the PCB
says it is (ZD901)

it looks like a small signal diode and it has a 16 and 2 printed
on opposite sides.

to test/replace --- the 16 is for ? volts ? and the 2 is ?
*OR* are the ###s short hand for some other 1N4### value ?

and the best test is to measure V across it ?

thanks for any helpful replies,
robb
Click to expand...
If you can post a picture to a photo hosting service, someone might
recognise the type.

If the zener is faulty, measuring its voltage won't tell you anything
useful.

A home brew zener tester I use for checking salvaged zeners works well
enough, but its not for the faint hearted.

Start with 2 identical mains rectifier/reservoir electrolytics, typically
220/330uF and 385V for European supplies. assuming you get the caps from
scrap monitors, one of them will also donate a bridge rectifier.

Wire the 2 caps in series, connect the + terminal of the top cap to the +
terminal of the rectifier and the - terminal of the bottom cap to the -
terminal of the rectifier, then connect the junction between the 2 caps to
one of the ac terminals of the rectifier - this makes a voltage doubling
rectifier that will give you a maximum of about 600V on a European supply.

On the ac input to the rectifier that you connected to the +/- junction of
the caps, connect in series 2 resistors between 33 & 56k rated at 2W - this
is the current limited live input. The other ac terminal is the neutral
terminal.

To avoid blowing components under test, you will need a shorting switch to
completely discharge the caps between tests. If you just use a switch, the
charge in the caps will blow the contacts to smithereens first time they're
closed. Search a scrap PSU or monitor mains input section for the inrush
surge limiting ntc thermistor - put this in series with the shorting switch.

The large capacitors cause the voltage to rise fairly slowly as the current
limiting resistors are comparatively large, I have used mine to test not
only zeners but the reverse leakage voltage of ordinary diodes like the
1N4148 etc.

Note that *both* output leads are potentially live when its operating, so
I'd recommend a 2 pole isolating switch for the mains input so you can
safely change the component under test.
 
"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:KCHIm.82638$KU2.48491@newsfe26.ams2...
"robb" <some@where.on.net> wrote in message
news:wNOdnUbb-dLVum7XnZ2dnUVZ_uGdnZ2d@earthlink.com...
i have a suspect zener diode from a PS . Zener, because the PCB
says it is (ZD901)

it looks like a small signal diode and it has a 16 and 2 printed
on opposite sides.

to test/replace --- the 16 is for ? volts ? and the 2 is ?
*OR* are the ###s short hand for some other 1N4### value ?

and the best test is to measure V across it ?

thanks for any helpful replies,
robb


If you can post a picture to a photo hosting service, someone might
recognise the type.

If the zener is faulty, measuring its voltage won't tell you anything
useful.

A home brew zener tester I use for checking salvaged zeners works well
enough, but its not for the faint hearted.

Start with 2 identical mains rectifier/reservoir electrolytics, typically
220/330uF and 385V for European supplies. assuming you get the caps from
scrap monitors, one of them will also donate a bridge rectifier.

Wire the 2 caps in series, connect the + terminal of the top cap to the +
terminal of the rectifier and the - terminal of the bottom cap to the -
terminal of the rectifier, then connect the junction between the 2 caps to
one of the ac terminals of the rectifier - this makes a voltage doubling
rectifier that will give you a maximum of about 600V on a European supply.

On the ac input to the rectifier that you connected to the +/- junction of
the caps, connect in series 2 resistors between 33 & 56k rated at 2W -
this is the current limited live input. The other ac terminal is the
neutral terminal.

To avoid blowing components under test, you will need a shorting switch to
completely discharge the caps between tests. If you just use a switch, the
charge in the caps will blow the contacts to smithereens first time
they're closed. Search a scrap PSU or monitor mains input section for the
inrush surge limiting ntc thermistor - put this in series with the
shorting switch.

The large capacitors cause the voltage to rise fairly slowly as the
current limiting resistors are comparatively large, I have used mine to
test not only zeners but the reverse leakage voltage of ordinary diodes
like the 1N4148 etc.

Note that *both* output leads are potentially live when its operating, so
I'd recommend a 2 pole isolating switch for the mains input so you can
safely change the component under test.
Click to expand...
That is a DANGEROUS circuit and not required to test a little zener diode.

All you need is a variable power supply, a resistor to limit the current to
the zener under test, and a volt meter across the zener.
Watch the volt meter, turn up the power supply and watch the volt meter
reading as you reach it's operating voltage.

Before you do this check the zener with a VOM to see if it is still 0.6 to
0.7 volt ( out of circuit) on diode test in the forward direction. This way
you'll know it's still a diode and not shorted or open.

Shaun
 
Shaun wrote:
"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:KCHIm.82638$KU2.48491@newsfe26.ams2...

"robb" <some@where.on.net> wrote in message
news:wNOdnUbb-dLVum7XnZ2dnUVZ_uGdnZ2d@earthlink.com...

i have a suspect zener diode from a PS . Zener, because the PCB
says it is (ZD901)

it looks like a small signal diode and it has a 16 and 2 printed
on opposite sides.

to test/replace --- the 16 is for ? volts ? and the 2 is ?
*OR* are the ###s short hand for some other 1N4### value ?

and the best test is to measure V across it ?

thanks for any helpful replies,
robb


If you can post a picture to a photo hosting service, someone might
recognise the type.

If the zener is faulty, measuring its voltage won't tell you anything
useful.

A home brew zener tester I use for checking salvaged zeners works well
enough, but its not for the faint hearted.

Start with 2 identical mains rectifier/reservoir electrolytics, typically
220/330uF and 385V for European supplies. assuming you get the caps from
scrap monitors, one of them will also donate a bridge rectifier.

Wire the 2 caps in series, connect the + terminal of the top cap to the +
terminal of the rectifier and the - terminal of the bottom cap to the -
terminal of the rectifier, then connect the junction between the 2 caps to
one of the ac terminals of the rectifier - this makes a voltage doubling
rectifier that will give you a maximum of about 600V on a European supply.

On the ac input to the rectifier that you connected to the +/- junction of
the caps, connect in series 2 resistors between 33 & 56k rated at 2W -
this is the current limited live input. The other ac terminal is the
neutral terminal.

To avoid blowing components under test, you will need a shorting switch to
completely discharge the caps between tests. If you just use a switch, the
charge in the caps will blow the contacts to smithereens first time
they're closed. Search a scrap PSU or monitor mains input section for the
inrush surge limiting ntc thermistor - put this in series with the
shorting switch.

The large capacitors cause the voltage to rise fairly slowly as the
current limiting resistors are comparatively large, I have used mine to
test not only zeners but the reverse leakage voltage of ordinary diodes
like the 1N4148 etc.

Note that *both* output leads are potentially live when its operating, so
I'd recommend a 2 pole isolating switch for the mains input so you can
safely change the component under test.




That is a DANGEROUS circuit and not required to test a little zener diode.

All you need is a variable power supply, a resistor to limit the current to
the zener under test, and a volt meter across the zener.
Watch the volt meter, turn up the power supply and watch the volt meter
reading as you reach it's operating voltage.

Before you do this check the zener with a VOM to see if it is still 0.6 to
0.7 volt ( out of circuit) on diode test in the forward direction. This way
you'll know it's still a diode and not shorted or open.

Shaun
Click to expand...
That'll do it, provided your variable supply goes high enough
for the zener being tested. Ian mentioned taking parts from
an old monitor. I made a zener tester, using parts from an
old monitor, that runs from a 9V battery and produces up to
170 volts across the zener at regulated low current. You just
connect your meter across the zener with the zener connected
to the tester. When you press the test button, your meter
reads the zener voltage. No dangerous current, no caps to
discharge, no need to adjust a supply, no need for a
variable supply for a wide range of voltage.

I'll post the schematic on abse. The circuit is generic - oscillator
& xformer make a HV source, which feeds a current regulator. All the
parts were scrounged from an old monitor - I designed it around the
parts I got from it. The same circuit will work with different parts.
You need to be sure that ratings for the parts you use won't be
exceeded. Example: output transistors (Q2, Q3) handle the high voltage
at the transformer secondary so need to be rated accordingly.

Ed
 
ehsjr <ehsjr@nospamverizon.net> wrote in
news:hd07dk$igs$1@news.eternal-september.org:

All you need is a variable power supply, a resistor to limit the
current to the zener under test, and a volt meter across the zener.
Watch the volt meter, turn up the power supply and watch the volt meter
reading as you reach it's operating voltage.

Before you do this check the zener with a VOM to see if it is still 0.6
to 0.7 volt ( out of circuit) on diode test in the forward direction.
This way you'll know it's still a diode and not shorted or open.

Shaun





That'll do it, provided your variable supply goes high enough
for the zener being tested. Ian mentioned taking parts from
an old monitor. I made a zener tester, using parts from an
old monitor, that runs from a 9V battery and produces up to
170 volts across the zener at regulated low current. You just
connect your meter across the zener with the zener connected
to the tester. When you press the test button, your meter
reads the zener voltage. No dangerous current, no caps to
discharge, no need to adjust a supply, no need for a
variable supply for a wide range of voltage.

I'll post the schematic on abse. The circuit is generic - oscillator
& xformer make a HV source, which feeds a current regulator. All the
parts were scrounged from an old monitor - I designed it around the
parts I got from it. The same circuit will work with different parts.
You need to be sure that ratings for the parts you use won't be
exceeded. Example: output transistors (Q2, Q3) handle the high voltage
at the transformer secondary so need to be rated accordingly.
Click to expand...
Neat idea. Any chance there's an easy safe mod of a small disposable camera
flash to do this? As they are, they do have a risk of a heavy discharge, but
the basic idea is very similar, and most of the parts are there.
 
Lostgallifreyan wrote:
ehsjr <ehsjr@nospamverizon.net> wrote in
news:hd07dk$igs$1@news.eternal-september.org:


All you need is a variable power supply, a resistor to limit the
current to the zener under test, and a volt meter across the zener.
Watch the volt meter, turn up the power supply and watch the volt meter
reading as you reach it's operating voltage.

Before you do this check the zener with a VOM to see if it is still 0.6
to 0.7 volt ( out of circuit) on diode test in the forward direction.
This way you'll know it's still a diode and not shorted or open.

Shaun





That'll do it, provided your variable supply goes high enough
for the zener being tested. Ian mentioned taking parts from
an old monitor. I made a zener tester, using parts from an
old monitor, that runs from a 9V battery and produces up to
170 volts across the zener at regulated low current. You just
connect your meter across the zener with the zener connected
to the tester. When you press the test button, your meter
reads the zener voltage. No dangerous current, no caps to
discharge, no need to adjust a supply, no need for a
variable supply for a wide range of voltage.

I'll post the schematic on abse. The circuit is generic - oscillator
& xformer make a HV source, which feeds a current regulator. All the
parts were scrounged from an old monitor - I designed it around the
parts I got from it. The same circuit will work with different parts.
You need to be sure that ratings for the parts you use won't be
exceeded. Example: output transistors (Q2, Q3) handle the high voltage
at the transformer secondary so need to be rated accordingly.



Neat idea. Any chance there's an easy safe mod of a small disposable camera
flash to do this? As they are, they do have a risk of a heavy discharge, but
the basic idea is very similar, and most of the parts are there.
Click to expand...
Dunno. The transformer in the camera may be too wimpy to provide
the current. But it seems worth trying - so what if the transformer
fails, you haven't lost anything. :) Just be sure to remove
the stuff (except the diode) from the secondary of the transformer
before adding the current regulator.

Ed
 
On 2009-11-05, ian field <gangprobing.alien@ntlworld.com> wrote:

Start with 2 identical mains rectifier/reservoir electrolytics, typically
220/330uF and 385V for European supplies. assuming you get the caps from
scrap monitors, one of them will also donate a bridge rectifier.

Wire the 2 caps in series, connect the + terminal of the top cap to the +
terminal of the rectifier and the - terminal of the bottom cap to the -
terminal of the rectifier, then connect the junction between the 2 caps to
one of the ac terminals of the rectifier - this makes a voltage doubling
rectifier that will give you a maximum of about 600V on a European supply.
Click to expand...
you missed out the isolating transformer to run this device off...


I use a flyback converter built round the 5V standby transformer from
an on PC powersupply running as a blocking oscilator, I run it from
2.5V (2x AA rechargable cells) and it produces at peak a little over
200V

the 200V charges a capacitor (10uF or so) and then flows through a
resistor into the diode I'm testing.

anthing that starts conducting at over 100V is probably not a zener,
my 1N914's start at around 120V.
 
"ehsjr" <ehsjr@nospamverizon.net> wrote in message
news:hd0hck$dor$1@news.eternal-september.org...
Lostgallifreyan wrote:
ehsjr <ehsjr@nospamverizon.net> wrote in
news:hd07dk$igs$1@news.eternal-september.org:
All you need is a variable power supply, a resistor to limit the
current to the zener under test, and a volt meter across the zener.
Watch the volt meter, turn up the power supply and watch the volt meter
reading as you reach it's operating voltage.

Before you do this check the zener with a VOM to see if it is still 0.6
to 0.7 volt ( out of circuit) on diode test in the forward direction.
This way you'll know it's still a diode and not shorted or open.

Shaun





That'll do it, provided your variable supply goes high enough
for the zener being tested. Ian mentioned taking parts from
an old monitor. I made a zener tester, using parts from an
old monitor, that runs from a 9V battery and produces up to
170 volts across the zener at regulated low current. You just
connect your meter across the zener with the zener connected
to the tester. When you press the test button, your meter
reads the zener voltage. No dangerous current, no caps to
discharge, no need to adjust a supply, no need for a
variable supply for a wide range of voltage.

I'll post the schematic on abse. The circuit is generic - oscillator
& xformer make a HV source, which feeds a current regulator. All the
parts were scrounged from an old monitor - I designed it around the
parts I got from it. The same circuit will work with different parts.
You need to be sure that ratings for the parts you use won't be
exceeded. Example: output transistors (Q2, Q3) handle the high voltage
at the transformer secondary so need to be rated accordingly.



Neat idea. Any chance there's an easy safe mod of a small disposable
camera flash to do this? As they are, they do have a risk of a heavy
discharge, but the basic idea is very similar, and most of the parts are
there.

Dunno. The transformer in the camera may be too wimpy to provide
the current. But it seems worth trying - so what if the transformer
fails, you haven't lost anything. :) Just be sure to remove
the stuff (except the diode) from the secondary of the transformer
before adding the current regulator.
Click to expand...
Most cheap camera flash inverters use a blocking oscillator with the
capacitor charging circuit in the feedback loop, this is designed to give
the most rapid charging possible to the discharged capacitor, as the
capacitor charges the feedback current falls away and a point is reached
where the secondary winding no longer produces enough voltage to drive
sufficient base current to maintain oscillation.

There shouldn't be any problem using such an inverter to provide high
voltage for zener testing but don't use the inverters own regulation
system - if you're ripping parts from an old monitor, I'd suggest using a
salvaged video output transistor to make a current source.
 
"Jasen Betts" <jasen@xnet.co.nz> wrote in message
news:hd0m81$gpd$3@reversiblemaps.ath.cx...
On 2009-11-05, ian field <gangprobing.alien@ntlworld.com> wrote:

Start with 2 identical mains rectifier/reservoir electrolytics, typically
220/330uF and 385V for European supplies. assuming you get the caps from
scrap monitors, one of them will also donate a bridge rectifier.

Wire the 2 caps in series, connect the + terminal of the top cap to the +
terminal of the rectifier and the - terminal of the bottom cap to the -
terminal of the rectifier, then connect the junction between the 2 caps
to
one of the ac terminals of the rectifier - this makes a voltage doubling
rectifier that will give you a maximum of about 600V on a European
supply.

you missed out the isolating transformer to run this device off...
Click to expand...
I did say "not for the faint hearted".
 
"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:KCHIm.82638$KU2.48491@newsfe26.ams2...
"robb" <some@where.on.net> wrote in message
news:wNOdnUbb-dLVum7XnZ2dnUVZ_uGdnZ2d@earthlink.com...
i have a suspect zener diode from a PS . Zener, because the
PCB
says it is (ZD901)

it looks like a small signal diode and it has a 16 and 2
printed
on opposite sides.

to test/replace --- the 16 is for ? volts ? and the 2 is ?
*OR* are the ###s short hand for some other 1N4### value ?

If you can post a picture to a photo hosting service, someone
might
recognise the type.

If the zener is faulty, measuring its voltage won't tell you
anything
useful.

A home brew zener tester I use for checking salvaged zeners
works well
enough, but its not for the faint hearted.
[trim zener tester]
Click to expand...

Thanks Ian,
I'll look into the zener tester.

robb
 
"Shaun" <rowl@nomail.com> wrote in message
news:A3JIm.22044$1g6.13836@newsfe10.iad...
"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:KCHIm.82638$KU2.48491@newsfe26.ams2...

"robb" <some@where.on.net> wrote in message
news:wNOdnUbb-dLVum7XnZ2dnUVZ_uGdnZ2d@earthlink.com...
i have a suspect zener diode from a PS . Zener, because the
PCB
says it is (ZD901)
it looks like a small signal diode and it has a 16 and 2
printed
on opposite sides.
to test/replace --- the 16 is for ? volts ? and the 2 is ?
*OR* are the ###s short hand for some other 1N4### value ?
and the best test is to measure V across it ?
[trim]

All you need is a variable power supply, a resistor to limit
the current to
the zener under test, and a volt meter across the zener.
Watch the volt meter, turn up the power supply and watch the
volt meter
reading as you reach it's operating voltage.

Before you do this check the zener with a VOM to see if it is
still 0.6 to
0.7 volt ( out of circuit) on diode test in the forward
direction. This way
you'll know it's still a diode and not shorted or open.

Shaun
Thanks for reply and help Shaun,
Click to expand...
robb
 
"ehsjr" <ehsjr@nospamverizon.net> wrote in message
news:hd07dk$igs$1@news.eternal-september.org...
Shaun wrote:
"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:KCHIm.82638$KU2.48491@newsfe26.ams2...

"robb" <some@where.on.net> wrote in message
news:wNOdnUbb-dLVum7XnZ2dnUVZ_uGdnZ2d@earthlink.com...
i have a suspect zener diode from a PS . Zener, because the
PCB
says it is (ZD901)
it looks like a small signal diode and it has a 16 and 2
printed
on opposite sides.
to test/replace --- the 16 is for ? volts ? and the 2 is ?
*OR* are the ###s short hand for some other 1N4### value ?
and the best test is to measure V across it ?

If you can post a picture to a photo hosting service, someone
might
recognise the type.

If the zener is faulty, measuring its voltage won't tell you
anything
useful.

A home brew zener tester I use for checking salvaged zeners
works well
enough, but its not for the faint hearted.

[trim zener tester circuit]
All you need is a variable power supply, a resistor to limit
the current to
the zener under test, and a volt meter across the zener.
Watch the volt meter, turn up the power supply and watch the
volt meter
reading as you reach it's operating voltage.

Before you do this check the zener with a VOM to see if it is
still 0.6 to
0.7 volt ( out of circuit) on diode test in the forward
direction. This way
you'll know it's still a diode and not shorted or open.
Shaun


That'll do it, provided your variable supply goes high enough
for the zener being tested. Ian mentioned taking parts from
an old monitor. I made a zener tester, using parts from an
old monitor, that runs from a 9V battery and produces up to
170 volts across the zener at regulated low current. You just
connect your meter across the zener with the zener connected
to the tester. When you press the test button, your meter
reads the zener voltage. No dangerous current, no caps to
discharge, no need to adjust a supply, no need for a
variable supply for a wide range of voltage.

I'll post the schematic on abse. The circuit is generic -
oscillator
& xformer make a HV source, which feeds a current regulator.
All the
parts were scrounged from an old monitor - I designed it around
the
parts I got from it. The same circuit will work with different
parts.
You need to be sure that ratings for the parts you use won't be
exceeded. Example: output transistors (Q2, Q3) handle the high
voltage
at the transformer secondary so need to be rated accordingly.

Ed
Click to expand...
Thanks for the help Ed,
robb
 
"robb" <some@where.on.net> wrote in message
news:8ZadnccmAsGQ0GnXnZ2dnUVZ_oidnZ2d@earthlink.com...
"ian field" <gangprobing.alien@ntlworld.com> wrote in message
news:KCHIm.82638$KU2.48491@newsfe26.ams2...

"robb" <some@where.on.net> wrote in message
news:wNOdnUbb-dLVum7XnZ2dnUVZ_uGdnZ2d@earthlink.com...
i have a suspect zener diode from a PS . Zener, because the
PCB
says it is (ZD901)

it looks like a small signal diode and it has a 16 and 2
printed
on opposite sides.

to test/replace --- the 16 is for ? volts ? and the 2 is ?
*OR* are the ###s short hand for some other 1N4### value ?

If you can post a picture to a photo hosting service, someone
might
recognise the type.

If the zener is faulty, measuring its voltage won't tell you
anything
useful.

A home brew zener tester I use for checking salvaged zeners
works well
enough, but its not for the faint hearted.
[trim zener tester]

Thanks Ian,
I'll look into the zener tester.
Click to expand...
If you're not experienced with handling live circuitry you might be better
off with the blocking oscillator method being discussed elsewhere on the
thread.

The zener tester I described certainly works, but its a risky design - as
someone else suggested, an isolating transformer would be a very good idea
if you have one.
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top