Mystery component in Sam's PhotoFact

[j]

There's a schmatic symbol in Sam's PhotoFacts # 2908 and 2753-1
(covering JVC TV sets av-2749s, av-2759s, and av-2779s) that I don't
recall ever having seen before. It's NOT listed in the parts section
so I have no original or replacement numbers for reference.

Here's my attempt to describe it for those without access to the
PhotoFacts that I mentioned. It looks like a circle with a vertical
line running through the middle. On the upper left half of the circle
there's what appears to be a "black pie" section extending from a
point in the middle of the circle with an angle from about 11 to 12
o'clock. It almost touches the circumference. On the lower right half
of the circle there's a simular "black pie" section, with an angle
from about 5 to 6 o'clock. There's no line where the two "pie
sections" meet so it doesn't appear to be some sort of dual diode
device. It also isn't a spark gap.

If anyone knows what it is, please let me know. I have researched
electronic schematic symbols on the web and in books but have not
found the symbol or what it represents.

 

[Jamie]

There's a schmatic symbol in Sam's PhotoFacts # 2908 and 2753-1
(covering JVC TV sets av-2749s, av-2759s, and av-2779s) that I don't
recall ever having seen before. It's NOT listed in the parts section
so I have no original or replacement numbers for reference.

Here's my attempt to describe it for those without access to the
PhotoFacts that I mentioned. It looks like a circle with a vertical
line running through the middle. On the upper left half of the circle
there's what appears to be a "black pie" section extending from a
point in the middle of the circle with an angle from about 11 to 12
o'clock. It almost touches the circumference. On the lower right half
of the circle there's a simular "black pie" section, with an angle
from about 5 to 6 o'clock. There's no line where the two "pie
sections" meet so it doesn't appear to be some sort of dual diode
device. It also isn't a spark gap.

If anyone knows what it is, please let me know. I have researched
electronic schematic symbols on the web and in books but have not
found the symbol or what it represents.

irradiation sensor?

 

[Phil Allison]

** Grope alert ?

There's a schmatic symbol in Sam's PhotoFacts # 2908 and 2753-1
(covering JVC TV sets av-2749s, av-2759s, and av-2779s) that I don't
recall ever having seen before. It's NOT listed in the parts section
so I have no original or replacement numbers for reference.

Here's my attempt to describe it for those without access to the
PhotoFacts that I mentioned. It looks like a circle with a vertical
line running through the middle. On the upper left half of the circle
there's what appears to be a "black pie" section extending from a
point in the middle of the circle with an angle from about 11 to 12
o'clock. It almost touches the circumference. On the lower right half
of the circle there's a simular "black pie" section, with an angle
from about 5 to 6 o'clock. There's no line where the two "pie
sections" meet so it doesn't appear to be some sort of dual diode
device. It also isn't a spark gap.

If anyone knows what it is, please let me know. I have researched
electronic schematic symbols on the web and in books but have not
found the symbol or what it represents.

** It wouldn't have hurt you to say where in the schematic the symbol
appears.




........ Phil

 

[j]

** It wouldn't have hurt you to say where in the schematic the symbol
appears.

I apologize for that omission. It's in the grid (G1) circuit of the
CRT.

Perhaps a circuit description would help for those who don't have
access to the PhotoFacts I mentioned. It starts out with a 200 Volt
DC source connected to a 1 M ohm Resistor. A 10 uF cap is connected
in parallel with the R. The other side of the R is connected to the
anode of a 1N4007 diode, whose cathode is connected to ground.
Connected in parallel with the diode is the mystery component. Also
connected to the anode of the diode is a 1k ohm R, whose other side is
finally connected to the spark gap and grid of the CRT.

 

[Phil Allison]

Connected in parallel with the diode is the mystery component.

** Err - what does it look like ??

Any labelling

What colour is it?



...... Phil

 

[Lionel]

There's a schmatic symbol in Sam's PhotoFacts # 2908 and 2753-1
(covering JVC TV sets av-2749s, av-2759s, and av-2779s) that I don't
recall ever having seen before. It's NOT listed in the parts section
so I have no original or replacement numbers for reference.

Here's my attempt to describe it for those without access to the
PhotoFacts that I mentioned. It looks like a circle with a vertical
line running through the middle. On the upper left half of the circle
there's what appears to be a "black pie" section extending from a
point in the middle of the circle with an angle from about 11 to 12
o'clock. It almost touches the circumference. On the lower right half
of the circle there's a simular "black pie" section, with an angle
from about 5 to 6 o'clock. There's no line where the two "pie
sections" meet so it doesn't appear to be some sort of dual diode
device. It also isn't a spark gap.

Are you 100% sure about that? - Because your description sure sounds
like one of the most common symbols for a spark gap. Given that you
say it's on a TV schematic, if it's on the neck-board you can be
certain that it's a spark gap. (Less likely, it might be a gas-filled
spark arrestor, which is sometimes used for the same purpose, but the
usual symbol for them is two horizontal bars with a circle around
them, & a big dot inside the circle.)

If it is a spark gap, & you can't find it on the PCB, it might be just
a really narrow slot cut into a big pad on the PCB, which is a trick
I've seen used sometimes on really cheap TVs & CRT displays. Another
odd looking variety is a rectangular block (a little like an old
fashioned bakelite capacitor) with a very narrow slot cut into it.

 

[Phil Allison]

"Lionel"

If it is a spark gap, & you can't find it on the PCB, it might be just
a really narrow slot cut into a big pad on the PCB, which is a trick
I've seen used sometimes on really cheap TVs & CRT displays.

** Darn YOU !

You beat me to the punch line !!!

The alleged mysterious " component " is not in the BOM - simply because
it is printed on the PCB !!




........ Phil

 

[Lionel]

I apologize for that omission. It's in the grid (G1) circuit of the
CRT.

Perhaps a circuit description would help for those who don't have
access to the PhotoFacts I mentioned. It starts out with a 200 Volt
DC source connected to a 1 M ohm Resistor. A 10 uF cap is connected
in parallel with the R. The other side of the R is connected to the
anode of a 1N4007 diode, whose cathode is connected to ground.
Connected in parallel with the diode is the mystery component. Also
connected to the anode of the diode is a 1k ohm R, whose other side is
finally connected to the spark gap and grid of the CRT.

Ah. Betcha it /is/ a gas-filled arrestor. Do you have access to the
PCB, or a photo of it? If so, look for a tiny glass cylinder with
metal disks at each end, either with leads coming out of the disks, or
it'll be sitting in a plastic holder, soldered into the PCB.

 

[Lionel]

"Lionel"



** Darn YOU !

You beat me to the punch line !!!

The alleged mysterious " component " is not in the BOM - simply because
it is printed on the PCB !!

<grin>

Good to see I learned something from all those years I spent salvaging
parts from TVs & suchlike as a kid.

 

[j]

On 22 Feb 2007 15:30:06 -0800, "j" <[email protected]> wrote:

Are you 100% sure about that? - Because your description sure sounds
like one of the most common symbols for a spark gap...

To Lionel and Phil:

I'm 99% sure it's not a spark gap. The Photofact symbol for a spark
gap has remained the same since at least 1981 and they print the words
"spark gap" next to each symbol on the schematic. You mention a gas-
filled spark arrestor but your description is way different than mine
from a 1991 Photofact schematic. In addition the device is not
directly connected to the grid (G1) of the CRT, it goes thru a 1k ohm
resistor first.

Stay tuned. I'll provide a physical description next.

 

[Lord Garth]

To Lionel and Phil:

I'm 99% sure it's not a spark gap. The Photofact symbol for a spark
gap has remained the same since at least 1981 and they print the words
"spark gap" next to each symbol on the schematic. You mention a gas-
filled spark arrestor but your description is way different than mine
from a 1991 Photofact schematic. In addition the device is not
directly connected to the grid (G1) of the CRT, it goes thru a 1k ohm
resistor first.

Stay tuned. I'll provide a physical description next.

Can't you scan it and post the image to A.B.S.E?

 

[JeffM]

There's a schmatic symbol in Sam's PhotoFacts # 2908 and 2753-1

Rather than using the selfish and inefficient multi-posting technique
http://groups.google.com/groups/sea...awEp1Wot8mUGa9h3i3SmjGmAJbX05nZ-8fQ&scoring=d
it's time you learned to cross-post.

The last half of this thread
http://groups.google.com/group/sci....ups+*-*-*-*-two-groups-*-*-aren't-*-different
explains how and why.
The last post in that thread hints at
why multi-posting is so reviled by the majority of Usenet readers.

The concise version:
http://en.wikipedia.org/wiki/Cross-post

 

[j]

Note: I'm trying to cross-post this to sci.electronics.repair, hope
it works. If not, I'll try to post the info that's there, over to
here.

Here's the physical description:

It's about 1/4" in diameter and 1/8" thick. The 2 leads are about
1/4" apart. The color is black with white charactors, which I next
describe. It has a triangle laying on it's base (ie, pointing up).
The corners of the triangle appear to have some detail, perhaps
looking like arrowheads. I suspect it's the manufacturers logo which
I think I've seen before, but I don't know which manufacturer. Below
the triangle are the charactors "K271" and below that "99".

 

[j]

Note: I'm trying to cross-post this to sci.electronics.repair, hope
it works. If not, I'll try to post the info that's there, over to
here.

Here's the physical description:

It's about 1/4" in diameter and 1/8" thick. The 2 leads are about
1/4" apart. The color is black with white charactors, which I next
describe. It has a triangle laying on it's base (ie, pointing up).
The corners of the triangle appear to have some detail, perhaps
looking like arrowheads. I suspect it's the manufacturers logo which
I think I've seen before, but I don't know which manufacturer. Below
the triangle are the charactors "K271" and below that "99".

 

[j]

Looking thru this site, the logo looks like it's Matsushita/Panasonic.

http://www.dialelec.com/semiconductorlogos.html

 

[Phil Allison]

"j" <[email protected]

Here's the physical description:

It's about 1/4" in diameter and 1/8" thick. The 2 leads are about
1/4" apart. The color is black with white charactors, which I next
describe. It has a triangle laying on it's base (ie, pointing up).
The corners of the triangle appear to have some detail, perhaps
looking like arrowheads.

** That is the Matsushita logo:

http://members.chello.nl/~h.dijkstra19/image/matsushita logo.jpeg

aka National / Panasonic

I suspect it's the manufacturers logo which
I think I've seen before, but I don't know which manufacturer. Below
the triangle are the charactors "K271" and below that "99".

** Its a 270 volt MOV.

Similar to these, but the older K series.

http://industrial.panasonic.com/www-data/pdf/AWA0000/AWA0000CE2.pdf



...... Phil