Mystery component in Sam's PhotoFact

J

j 19 years ago

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.

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J

Jamie 19 years ago

irradiation sensor?

"I\'m never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5

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Phil Allison 19 years ago

** Grope alert ?

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

....... Phil

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J

j 19 years ago

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.

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Phil Allison 19 years ago

** Err - what does it look like ??

Any labelling

What colour is it?

..... Phil

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L

Lionel 19 years ago

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.

W "Some people are alive only because it is illegal to kill them." . | ,. w , \\|/ \\|/ Perna condita delenda est ---^----^---------------------------------------------------------------

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Phil Allison 19 years ago

"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 !!

....... Phil

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L

Lionel 19 years ago

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.

W "Some people are alive only because it is illegal to kill them." . | ,. w , \\|/ \\|/ Perna condita delenda est ---^----^---------------------------------------------------------------

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L

Lionel 19 years ago

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

W "Some people are alive only because it is illegal to kill them." . | ,. w , \\|/ \\|/ Perna condita delenda est ---^----^---------------------------------------------------------------

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J

j 19 years ago

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.

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L

Lord Garth 19 years ago

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

>

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J

JeffM 19 years ago

Rather than using the selfish and inefficient multi-posting technique

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it's time you learned to cross-post.

The last half of this thread

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*-*-*-*-*-*-*-*-appear+*-proper-answer-*-*-*-given+much-easier-*-*-*-*-*-*-*+*-frowned-on+*-correcting+*-Followup-To-*+*-*-_perfect_-*-*-*-*+*-*-*-too-lazy-*-*-*-*-*-appropriate-*+*-polite-*-mention-*-*-*-*-*-*-*+Just-because-*-*-*-*-*-*-*-*-does-not-mean-*-*-*-*-*-*+mark-*-*-*-*-all-*-groups+*-*-*-*-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:

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J

j 19 years ago

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".

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J

j 19 years ago

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".

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J

j 19 years ago

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

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Phil Allison 19 years ago

"j" Here's the physical description:

** That is the Matsushita logo:

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aka National / Panasonic

** Its a 270 volt MOV.

Similar to these, but the older K series.

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..... Phil

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Mystery component in Sam's PhotoFact

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