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Help ID'ing diodes?

D

DaveC

Jan 1, 1970
0
Have a couple of fried glass-body diodes in what is probably an old dimmer
circuit that I've used for years as my soldering iron variable-heat
controller.

Circuit consists of main pot, trim pot, diodes, choke, a few caps, and a
3-term semi device (sort of TO-220, only smaller -- SCR?).

The diodes have no markings save these: one has a blue stripe around exactly
the middle of the body, and one lead where it meets the body is slightly
flared (cathode?). The other has no markings at all on the body, save a
barely visible black mark on one end. Both are the traditional copper color
under the glass.

Both measure infinite cont. in both directions.

Presuming this was originally a 100 watt light dimmer (I'm using it to
control a 35 watt iron), are there some generic diodes I can use as
replacements? Can I use 1N400x here?

The controller quit when I tried to connect my scope's ground lead to 120 vac
(there goes another lead clip!)

Thanks,
 
D

DaveC

Jan 1, 1970
0
The controller quit when I tried to connect my scope's ground lead to 120
vac (there goes another lead clip!)

Scope ground lead, that is...
 
T

The Al Bundy

Jan 1, 1970
0
DaveC said:
How does one troubleshoot this type of device? A simple continuity test won't
do it, it seems.

Maybe it's not these that are at fault, at all. Maybe it's the triac? Guess
I've gotta put those devices back in circuit, fire it up and see...

What should I see at these device's term?

Thanks,
--
DaveC
[email protected]
This is an invalid return address
Please reply in the news group

A diac conducts at a certain voltage and current can flow in both
directions.

It is used to trigger the gate of the triac. This triggering is done by
charging up a capacitor with a potentiometer. When the voltage across the
capacitor is high enough (the spec of the diac) the diac will conduct and a
current flows into the gate (to cathode) of the triac. The triac will then
conduct until the sinewave of the mains goes through zero. The Triac stops
with conducting and the capacitor charges again, etc etc.

What you control basically is how late the triac must switch on after the
sinewave went through zero.

A diac you can test by putting some voltage across with a series resistor.
This voltage has to be high enough to let the diac conduct. So just
measuring the resistance of the diac should give high or infinitive
readings.

Hope this helps a bit,

Al
 
DaveC said:
Have a couple of fried glass-body diodes in what is probably an old dimmer
circuit that I've used for years as my soldering iron variable-heat
controller.

Circuit consists of main pot, trim pot, diodes, choke, a few caps, and a
3-term semi device (sort of TO-220, only smaller -- SCR?).

The diodes have no markings save these: one has a blue stripe around exactly
the middle of the body, and one lead where it meets the body is slightly
flared (cathode?). The other has no markings at all on the body, save a
barely visible black mark on one end. Both are the traditional copper color
under the glass.

Both measure infinite cont. in both directions.

Presuming this was originally a 100 watt light dimmer (I'm using it to
control a 35 watt iron), are there some generic diodes I can use as
replacements? Can I use 1N400x here?

The controller quit when I tried to connect my scope's ground lead to 120 vac
(there goes another lead clip!)

Thanks,
--
DaveC
[email protected]
This is an invalid return address
Please reply in the news group

Probably blew the triac. Try replacing it with
whatever you have or whatever you order. There should
be nothing critical about it, so you don't need an
identical replacement.
 
D

DaveC

Jan 1, 1970
0
Probably blew the triac. Try replacing it with
whatever you have or whatever you order. There should
be nothing critical about it, so you don't need an
identical replacement.

The catalog I looked in (NTE) lists them by voltage (50, 100, 200, 300,
higher) and max forward current (1A to 8A):

http://www.nteinc.com/Web_pgs/TRIACs.html

Do you think an NTE5629 would work, here? See something better?

Thanks,
 
W

Watson A.Name - Watt Sun, Dark Remover

Jan 1, 1970
0
Have a couple of fried glass-body diodes in what is probably an old dimmer
circuit that I've used for years as my soldering iron variable-heat
controller.

Circuit consists of main pot, trim pot, diodes, choke, a few caps, and a
3-term semi device (sort of TO-220, only smaller -- SCR?).

The diodes have no markings save these: one has a blue stripe around exactly
the middle of the body, and one lead where it meets the body is slightly
flared (cathode?). The other has no markings at all on the body, save a
barely visible black mark on one end. Both are the traditional copper color
under the glass.

Both measure infinite cont. in both directions.

One is probably a DIAC, and would normally measure infinite in both
directions. In any case a new 300W dimmer is dirt cheap, so buy one
and use it or the parts.
Presuming this was originally a 100 watt light dimmer (I'm using it to
control a 35 watt iron), are there some generic diodes I can use as
replacements? Can I use 1N400x here?

The controller quit when I tried to connect my scope's ground lead to 120 vac
(there goes another lead clip!)

Thanks,

--
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W

Watson A.Name - Watt Sun, Dark Remover

Jan 1, 1970
0
How does one troubleshoot this type of device? A simple continuity test won't
do it, it seems.

Maybe it's not these that are at fault, at all. Maybe it's the triac? Guess
I've gotta put those devices back in circuit, fire it up and see...

What should I see at these device's term?

Well, if you use your scope, be (again!) prepared for a surprise.

You had better use an isolation transformer.

--
@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@,@@[email protected]@[email protected],@@[email protected]@[email protected]@[email protected]@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@
 
DaveC said:
The catalog I looked in (NTE) lists them by voltage (50, 100, 200, 300,
higher) and max forward current (1A to 8A):

http://www.nteinc.com/Web_pgs/TRIACs.html

Do you think an NTE5629 would work, here? See something better?

It'll work fine, but it costs more than a BTA06-400. I'd
order a few BTA06's, just to have some on hand. By the way,
the 06 means 6 amps, and the 400 means 400 volts. You can
get them up to 40 amps! I keep a few BTA16's on hand.
See http://www.mouser.com/ and put triac in the search box.
 
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