Re: Please help with component Identification

Stan wrote:

On Feb 15, 2:07 pm, "Stan" <g...@xxxxxxxxxxxxxxxxxxxxx> wrote:

Hi, I posted on here a few days ago but so far have no response. I now
have photo's available athttp://www.stanleyes.ndo.co.uk/.

If anyone can ID this component i'd appreciate it.

There is more info in my previous posting "Help Component ID, TVS??"

Thanks
Stan


Tom & HJS

Tom is correct, Z801 is the label for the mystery glass cased
component. It is labelled both top and bottom of the board and is
furthest from the relay. Just to be pedantic..you seem to be
mistakingly referring to R802 which is not in the photo's, i think you
mean R803. Also, unless i'm very much mistaken R803 (the big red blob)
is not a MOV but a PTC Thermistor (Posistor). I have removed this from
the PCB and at room temperature it has a resistance of 8Ohm. If i
leave it sat on a heater for a while and retest it had changed to
80Ohm. I believe this 10x range is what you would expect from a
Thermistor/Posistor.( I guess this blows the theory that the red blob
is a MOV and the labels have been switched.)
I think this is pretty standard degauss circuitry, On activating
degauss, relay RL801 closes allowing AC current to flow through the
degauss coil, current flows through the circuit causing heating in the
thermistor, this causes the thermistor resistance to gradually
increases reducing the current flow.... Its just this Z801 i'm not
sure about, it could be functioning perfectly OK but i'm not used to
observing sparks in a component even if they are small and contained.
As you can see on the bottom of the board, the mystery Z801 is
connected across one pair of NO relay contacts. I think this makes it
likely the device is some kind of suppression device.

Robert

Please note the photo's were taken before i removed any components
from the board so the chances that the two components have been
switched are minimal. Also note that the pad layout's match the
components, Z801 pads are in line to match the mystery glass
component, R803 has offset pads matching the offset legs of the
thermistor.

Baron

Was your suggestion tongue in cheek? No offence if not, but the name
sounds too close a match to my previous description for it to be true.
I hope i'm wrong, but searching for "spark gap surge suppressor" on
google returns very few hits.

My thoughts are that it could be:

1. A bipolar TVS. But the glass casing is unusual, i can't find
anything similar on TVS manufacturers websites.
2. A resistor, again in unusual packaging. If its burnt out the
voltage could be causing the sparks seen jumping across the inner
cylinder.
3. Dare i say it "spark gap suppressor"? Who manufacturers such
devices?

Thanks everyone, any more thoughts are gratefully received.
Stan

I agree, that glass encapsulation is rare and unusual.
The "most recent" glass encapsulated resistors i saw was about 30 or so years ago, and those were Victoreen gigohm and up resistors for ionization chamber electronics and similar very low current tube devices.
.

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