Looking to Cross ref a Diac & Triac set

T

Tim

Guest
Hello again, I have a circuit for an electronic Variac that uses a Diac
and Triac to control the output. It looks like a glorified dimmer
circuit. Anyways it uses part # MAC2-4 for the triac and MPT-28 for the
trigger diode (diac). I haven't been able to cross reference these
puppies on the net. I hav checked the usual sources, but came up empty.

Any help would be appreciated.

Thanks,

- Tim -
 
"Tim" <tim@tim.tim> wrote in message
news:MPG.208f0ad45cebc0ae98974e@allnews.nbnet.nb.ca...

Hello again, I have a circuit for an electronic Variac that uses a Diac
and Triac to control the output. It looks like a glorified dimmer
circuit. Anyways it uses part # MAC2-4 for the triac and MPT-28 for the
trigger diode (diac). I haven't been able to cross reference these
puppies on the net. I hav checked the usual sources, but came up empty.
Click to expand...
What load and operating voltage?

Generally a 10 amp triac and any 'normal' diac will do. This isn't precision
engineering.
 
Tim,
The triac is not critical almost any will work but the diac is one that
triggers at 28 volts + or - 4 volts.
Ray


"Tim" <tim@tim.tim> wrote in message
news:MPG.208f0ad45cebc0ae98974e@allnews.nbnet.nb.ca...
Hello again, I have a circuit for an electronic Variac that uses a Diac
and Triac to control the output. It looks like a glorified dimmer
circuit. Anyways it uses part # MAC2-4 for the triac and MPT-28 for the
trigger diode (diac). I haven't been able to cross reference these
puppies on the net. I hav checked the usual sources, but came up empty.

Any help would be appreciated.

Thanks,

- Tim -
Click to expand...
 
Tim wrote:

Hello again, I have a circuit for an electronic Variac that uses a Diac
and Triac to control the output. It looks like a glorified dimmer
circuit. Anyways it uses part # MAC2-4 for the triac and MPT-28 for the
trigger diode (diac). I haven't been able to cross reference these
puppies on the net. I hav checked the usual sources, but came up empty.
Click to expand...
They're ancient, that'll be the problem !

Graham
 
In article <46256ABB.11328C3B@hotmail.com>,
rabbitsfriendsandrelations@hotmail.com says...
Tim wrote:

Hello again, I have a circuit for an electronic Variac that uses a Diac
and Triac to control the output. It looks like a glorified dimmer
circuit. Anyways it uses part # MAC2-4 for the triac and MPT-28 for the
trigger diode (diac). I haven't been able to cross reference these
puppies on the net. I hav checked the usual sources, but came up empty.

They're ancient, that'll be the problem !

Graham


Hmmm, this circuit was drawn in 2005, August 18th to be exact. It's
Click to expand...
strange that the guy used old parts in the design. It also appears that
he has spec'd and drawn a triac, but the pins are marked cathode, anode
and gate, like an SCR. I think it should have MT1, MT2 and gate for a
triac.

The schematic is here;
http://homebrewradio.tripod.com/id58.html

- Tim -
 
In article <b8dVh.14422$GV5.8278@edtnps89>, nobody@nowhere.com says...
"Tim" <tim@tim.tim> wrote in message
news:MPG.208f0ad45cebc0ae98974e@allnews.nbnet.nb.ca...

Hello again, I have a circuit for an electronic Variac that uses a Diac
and Triac to control the output. It looks like a glorified dimmer
circuit. Anyways it uses part # MAC2-4 for the triac and MPT-28 for the
trigger diode (diac). I haven't been able to cross reference these
puppies on the net. I hav checked the usual sources, but came up empty.

What load and operating voltage?

Generally a 10 amp triac and any 'normal' diac will do. This isn't precision
engineering.





Yes, I figured I'd use the parts I have kicking around the shop, and I
Click to expand...
thought mebbe someone would reconize the parts and tell me the ratings
on 'em.

The schematic is here if you are interested in the project;
http://homebrewradio.tripod.com/id58.html
 
In article <pQdVh.11956$qB4.11493@bignews3.bellsouth.net>,
rayjking@bellsouth.net says...
Tim,
The triac is not critical almost any will work but the diac is one that
triggers at 28 volts + or - 4 volts.
Ray


"Tim" <tim@tim.tim> wrote in message
news:MPG.208f0ad45cebc0ae98974e@allnews.nbnet.nb.ca...
Hello again, I have a circuit for an electronic Variac that uses a Diac
and Triac to control the output. It looks like a glorified dimmer
circuit. Anyways it uses part # MAC2-4 for the triac and MPT-28 for the
trigger diode (diac). I haven't been able to cross reference these
puppies on the net. I hav checked the usual sources, but came up empty.

Any help would be appreciated.

Thanks,

- Tim -



So is that what the -28 is for? Kinda makes sense. I am planning on
Click to expand...
using some TO-220 15A triacs I have here. I'll be sure to get a 28v diac
tho.

The schematic is here if you are curious as to the application;
http://homebrewradio.tripod.com/id58.html


Thanks for the info,

- Tim -
 
Tim,

Is this a diode on the ac input of of this circuit? Also is the load a
transformer? If either is true then the circuit will not work. You can not
control the primary of a transformer with a triac or two scr's at least over
the full range. you can go from zero to aproximately 75% depending on the
inductance vs the load and wheather or not the load is resistive or
rectified with a cap filter.

Ray



"Tim" <tim@tim.tim> wrote in message
news:MPG.208f5f8373e2c5c298974f@allnews.nbnet.nb.ca...
In article <46256ABB.11328C3B@hotmail.com>,
rabbitsfriendsandrelations@hotmail.com says...


Tim wrote:

Hello again, I have a circuit for an electronic Variac that uses a Diac
and Triac to control the output. It looks like a glorified dimmer
circuit. Anyways it uses part # MAC2-4 for the triac and MPT-28 for the
trigger diode (diac). I haven't been able to cross reference these
puppies on the net. I hav checked the usual sources, but came up empty.

They're ancient, that'll be the problem !

Graham


Hmmm, this circuit was drawn in 2005, August 18th to be exact. It's
strange that the guy used old parts in the design. It also appears that
he has spec'd and drawn a triac, but the pins are marked cathode, anode
and gate, like an SCR. I think it should have MT1, MT2 and gate for a
triac.

The schematic is here;
http://homebrewradio.tripod.com/id58.html

- Tim -
Click to expand...
 
I had intended to use this as a variac to lower the operating voltage to
an RCA TV, to allow me to reset it's eeprom. The set uses a switching
power supply inside. It's a trick that some guru came up with to solve
the eeprom programming issue without a proper chip programmer.
Apparently these sets had a problem with this chip getting scrambled due
to bad grounds, bad soldering, and power flucuations.

I don't have access to a real variac, nor the funds to buy one, even if
one was available locally.

- Tim -

In article <E1gVh.5575$Pq5.1492@bignews6.bellsouth.net>,
rayjking@bellsouth.net says...
Tim,

Is this a diode on the ac input of of this circuit? Also is the load a
transformer? If either is true then the circuit will not work. You can not
control the primary of a transformer with a triac or two scr's at least over
the full range. you can go from zero to aproximately 75% depending on the
inductance vs the load and wheather or not the load is resistive or
rectified with a cap filter.

Ray



"Tim" <tim@tim.tim> wrote in message
news:MPG.208f5f8373e2c5c298974f@allnews.nbnet.nb.ca...
In article <46256ABB.11328C3B@hotmail.com>,
rabbitsfriendsandrelations@hotmail.com says...


Tim wrote:

Hello again, I have a circuit for an electronic Variac that uses a Diac
and Triac to control the output. It looks like a glorified dimmer
circuit. Anyways it uses part # MAC2-4 for the triac and MPT-28 for the
trigger diode (diac). I haven't been able to cross reference these
puppies on the net. I hav checked the usual sources, but came up empty.

They're ancient, that'll be the problem !

Graham


Hmmm, this circuit was drawn in 2005, August 18th to be exact. It's
strange that the guy used old parts in the design. It also appears that
he has spec'd and drawn a triac, but the pins are marked cathode, anode
and gate, like an SCR. I think it should have MT1, MT2 and gate for a
triac.

The schematic is here;
http://homebrewradio.tripod.com/id58.html

- Tim -
Click to expand...
 
"Ray King" <rayjking@bellsouth.net> wrote in message
news:E1gVh.5575$Pq5.1492@bignews6.bellsouth.net...

Is this a diode on the ac input of of this circuit? Also is the load a
transformer? If either is true then the circuit will not work. You can not
control the primary of a transformer with a triac or two scr's at least
over the full range. you can go from zero to aproximately 75%
Click to expand...
You can with the right design. Fan controllers do it.
 
Yes,

Fan motors are high slip and less inductive and more resistive. This similar
to a transformer with a full resistive load ( pure resistive). The fan motor
does not have as much mutual/leakage reactance that looks inductive to the
primary as the transformer with a pure resistive load.
Ray

"Homer J Simpson" <nobody@nowhere.com> wrote in message
news:wviVh.14492$GV5.569@edtnps89...
"Ray King" <rayjking@bellsouth.net> wrote in message
news:E1gVh.5575$Pq5.1492@bignews6.bellsouth.net...

Is this a diode on the ac input of of this circuit? Also is the load a
transformer? If either is true then the circuit will not work. You can
not control the primary of a transformer with a triac or two scr's at
least over the full range. you can go from zero to aproximately 75%

You can with the right design. Fan controllers do it.
Click to expand...
 
On Tue, 17 Apr 2007 20:50:12 GMT, Tim <tim@tim.tim> put finger to
keyboard and composed:

Hello again, I have a circuit for an electronic Variac that uses a Diac
and Triac to control the output. It looks like a glorified dimmer
circuit. Anyways it uses part # MAC2-4 for the triac and MPT-28 for the
trigger diode (diac). I haven't been able to cross reference these
puppies on the net. I hav checked the usual sources, but came up empty.

Any help would be appreciated.

Thanks,

- Tim -
Click to expand...
MPT-28 is a 28V diac:
http://www.nteinc.com/specs/6400to6499/pdf/nte6407.pdf

I don't see a MAC2-4 in either my 1984 Motorola catalogue or my NTE
1990-91 catalogue, but the "-4" appears to refer to a 200V device.
FWIW, the MAC20-4 is a 200V, 15A triac.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
 
There is a very good circuit for controlling the primary of any inductive
load. It consists of a switch in series with the ac input to the transformer
that pwm's the load. During the off time a second switch turns on in
parallel with the load. Each switch consists of fets or IGBT's either in
anti series or across the output ( + and - ) of a 4 diode bridge( fast
diodes ) . The fets/igbts are transformer driven ( both switches are driven
with the same transformer ) This will prevent the two switches from
conducting at the same time ( shoot through ). The output can be filtered so
the output looks like the output of a variac. The use of scr/triacs can not
be filtered very well and reek havoc with the switchers with cap input
filters.
Ray


"Ray King" <rayjking@bellsouth.net> wrote in message
news:%6jVh.10552$XU4.6424@bignews8.bellsouth.net...
Yes,

Fan motors are high slip and less inductive and more resistive. This
similar to a transformer with a full resistive load ( pure resistive). The
fan motor does not have as much mutual/leakage reactance that looks
inductive to the primary as the transformer with a pure resistive load.
Ray

"Homer J Simpson" <nobody@nowhere.com> wrote in message
news:wviVh.14492$GV5.569@edtnps89...

"Ray King" <rayjking@bellsouth.net> wrote in message
news:E1gVh.5575$Pq5.1492@bignews6.bellsouth.net...

Is this a diode on the ac input of of this circuit? Also is the load a
transformer? If either is true then the circuit will not work. You can
not control the primary of a transformer with a triac or two scr's at
least over the full range. you can go from zero to aproximately 75%

You can with the right design. Fan controllers do it.
Click to expand...
 
I have a 1979 mot catalog that does not list the MAC2-4 ----I have looked in
a 1981 D.A.T.A. BOOK with no results. The lowest numbers for the MAC is
MAC15-4.
Ray


"Franc Zabkar" <fzabkar@iinternode.on.net> wrote in message
news:7cfb23h7trh8ftqg192umadeqqaoc3sdu0@4ax.com...
On Tue, 17 Apr 2007 20:50:12 GMT, Tim <tim@tim.tim> put finger to
keyboard and composed:

Hello again, I have a circuit for an electronic Variac that uses a Diac
and Triac to control the output. It looks like a glorified dimmer
circuit. Anyways it uses part # MAC2-4 for the triac and MPT-28 for the
trigger diode (diac). I haven't been able to cross reference these
puppies on the net. I hav checked the usual sources, but came up empty.

Any help would be appreciated.

Thanks,

- Tim -

MPT-28 is a 28V diac:
http://www.nteinc.com/specs/6400to6499/pdf/nte6407.pdf

I don't see a MAC2-4 in either my 1984 Motorola catalogue or my NTE
1990-91 catalogue, but the "-4" appears to refer to a 200V device.
FWIW, the MAC20-4 is a 200V, 15A triac.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
Click to expand...
 
Tim wrote:

rabbitsfriendsandrelations@hotmail.com says...
Tim wrote:

Hello again, I have a circuit for an electronic Variac that uses a Diac
and Triac to control the output. It looks like a glorified dimmer
circuit. Anyways it uses part # MAC2-4 for the triac and MPT-28 for the
trigger diode (diac). I haven't been able to cross reference these
puppies on the net. I hav checked the usual sources, but came up empty.


Hmmm, this circuit was drawn in 2005, August 18th to be exact. It's
strange that the guy used old parts in the design.
Click to expand...
It mnay simply be what he had in his box of bits !


It also appears that
he has spec'd and drawn a triac, but the pins are marked cathode, anode
and gate, like an SCR. I think it should have MT1, MT2 and gate for a
triac.
Click to expand...
It should.


The schematic is here;
http://homebrewradio.tripod.com/id58.html
Click to expand...
They are non-critical as previously mentioned by others. Choose a triac to suit
your load. It's basically a triac based dimemr. Check any other similar designs
online for comparison.

Did you spot the deliberate mistake btw ?

Graham
 
Tim wrote:

I had intended to use this as a variac to lower the operating voltage to
an RCA TV, to allow me to reset it's eeprom. The set uses a switching
power supply inside.
Click to expand...
That may not work very well actually.

Graham
 
In article <4625F9AA.322BB4C3@hotmail.com>,
rabbitsfriendsandrelations@hotmail.com says...
Tim wrote:

rabbitsfriendsandrelations@hotmail.com says...
Tim wrote:

Hello again, I have a circuit for an electronic Variac that uses a Diac
and Triac to control the output. It looks like a glorified dimmer
circuit. Anyways it uses part # MAC2-4 for the triac and MPT-28 for the
trigger diode (diac). I haven't been able to cross reference these
puppies on the net. I hav checked the usual sources, but came up empty.


Hmmm, this circuit was drawn in 2005, August 18th to be exact. It's
strange that the guy used old parts in the design.

It mnay simply be what he had in his box of bits !


It also appears that
he has spec'd and drawn a triac, but the pins are marked cathode, anode
and gate, like an SCR. I think it should have MT1, MT2 and gate for a
triac.

It should.


The schematic is here;
http://homebrewradio.tripod.com/id58.html

They are non-critical as previously mentioned by others. Choose a triac to suit
your load. It's basically a triac based dimemr. Check any other similar designs
online for comparison.

Did you spot the deliberate mistake btw ?

Graham


Deliberate mistake? In the drawing? I can't see anything obvious...
Click to expand...

- Tim -
 
Eeyore wrote:
Did you spot the deliberate mistake btw ?

Graham
Click to expand...
I don't think it's a deliberate mistake. I suspect
it is just poor drawing of what is supposed to be
the output connector.

Ed
 
I got the TV set re-programmed without needing the variac thing. I
pulled the chip and re-programmed it in my eprom programmer using data
from a fellow tech on the net.

I did not need to build the circuit after all, but I appreciate
everyone's input on the project.

- Tim -

In article <MPG.208f0ad45cebc0ae98974e@allnews.nbnet.nb.ca>, tim@tim.tim
says...
Hello again, I have a circuit for an electronic Variac that uses a Diac
and Triac to control the output. It looks like a glorified dimmer
circuit. Anyways it uses part # MAC2-4 for the triac and MPT-28 for the
trigger diode (diac). I haven't been able to cross reference these
puppies on the net. I hav checked the usual sources, but came up empty.

Any help would be appreciated.

Thanks,

- Tim -
Click to expand...
 
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