Source or replacement for WG K6100 PTC?

aramis

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Hi all,

I'm rebuilding a K6100 and it is missing the PTC. On my Tempest, this part is marked PTH451C 35M17. I know this is not a common part...but does anyone happen to know of a source or replacement for one? I only need one. :)

Or, has anyone had any luck using a disc style thermistor (or two) as a substitute?

Thanks!
 
That ebay part has a different resistance value than the original, even though both are PTH451C parts. It looks to be ~14 ohms compared to the original ~3 ohms. I actually think that would be OK, but am not sure how that affects the timing for degaussing.

The thermistor will act like a short until it heats up and then it becomes a resistor to cut the current flow. In a super critical application, getting to 3 ohms at a certain slope vs. getting to 14 ohms at a certain slope may be important, due to the overall time it takes to get there. I can't believe that the degaussing timing would be that critical but I don't know for sure.

Or, maybe the higher resistance part would act to shut off the coil like a switch, when the original may allow it to gradually decay (depending on the temperature it reacts at).

I am probably overthinking this...
 
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I've got some spare K6100 boards (non working). Help a me identify which component that may be and I could pull it for you.

It's the black plastic "cube" that's about halfway up the left hand side. I'd hate for you to pull it and doom a board though, if there's no replacement known.
 
Hi all,

I'm rebuilding a K6100 and it is missing the PTC. On my Tempest, this part is marked PTH451C 35M17. I know this is not a common part...but does anyone happen to know of a source or replacement for one? I only need one. :)

Or, has anyone had any luck using a disc style thermistor (or two) as a substitute?

Thanks!

The ones on ebay are the wrong impedance.
 
That ebay part has a different resistance value than the original, even though both are PTH451C parts. It looks to be ~14 ohms compared to the original ~3 ohms. I actually think that would be OK, but am not sure how that affects the timing for degaussing.

The thermistor will act like a short until it heats up and then it becomes a resistor to cut the current flow. In a super critical application, getting to 3 ohms at a certain slope vs. getting to 14 ohms at a certain slope may be important, due to the overall time it takes to get there. I can't believe that the degaussing timing would be that critical but I don't know for sure.

Or, maybe the higher resistance part would act to shut off the coil like a switch, when the original may allow it to gradually decay (depending on the temperature it reacts at).

I am probably overthinking this...

It can't be critical. Just keep the proper ratio between the thermistor and the power resistor across the load. If the R1/R2 ratio is the same, then D106/D107 will still drop below their conduction threshold as the PTC heats up and it's R1 value changes. The R2 in this circuit is 22ohms.

Millions of televisions were manufactured with this exact same circuit for 50 years.
 
Assuming I'm reading the resistances correctly (original is 3.5 and ebay is 14), would that then mean increasing R2 from 22 ohms to 88 ohms in order to use the ebay part? Or am I thinking about that all wrong?

But, I think that I worded my thermistor description all wrong, and that it's not a short that becomes rated resistance, but instead is the rated resistance (at zero power) that then becomes 'open' as it heats up.

Have you taken one apart by any chance to know why there are 3 legs?
 
It can't be critical. Just keep the proper ratio between the thermistor and the power resistor across the load. If the R1/R2 ratio is the same, then D106/D107 will still drop below their conduction threshold as the PTC heats up and it's R1 value changes. The R2 in this circuit is 22ohms.

Millions of televisions were manufactured with this exact same circuit for 50 years.

The impedance of the degauss coil matters too.
 
If the coil on this monitor reads 4 ohms, does that sound right? If so, any idea on what would be a suitable PTC replacement?

Is it internally 2 positive slope thermistors, that I could buy individually from digikey or someplace? (Not sure why it has 3 legs)

On my Tempest, pin 1 to 3 and pin 2 to 3 of the PTC each read 3.5 ohms, so I assume that is what I'm looking for...?
 
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I also find this thread pertinent currently, as I am building my Mouser order for my P9K repro PCB buildup and need a 451C as well. It has been advised in the threads relating to that, and other repro vector PCB projects, to scavenge one from a TV, other chassis, or eBay.

However, upon closer inspection, I am finding myself in the same quandary as the OP. And according to this datasheet, HudsonArcade is, of course, correct : http://www.paulswan.me/arcade/datasheets/PTH451C.pdf

It does note that a 451A has two mounting legs, and C has three, to answer that question. As for the rest, I am curious as to what will work as well.

A quick glance at some nearby chassis reveals the following part #'s :
WG6100 : 35M19
Amplifone : 35M25
Sanyo EZ : 05M09
Sanyo EZ : 05M25

Clearly resistance (the first #) is important... Possibly pairing the degauss coil with the donor chassis' PTH when harvesting used? But what then of the new part (sold by Syracuse on eBay)? Haven't a bunch of people here already bought and used NOS ones off eBay for other repro vector PCB's already? Presumably the Syracuse ones, or some other unknown or unconsidered resistance?

:confused:
 
quite similar, but it may be a lower voltage (or WG oversized theirs.). According to the Amplifone manual, that monitor uses a 3 ohm (+/- 10%) 60V PTC. It is also a 3-pin package. Even though the schematics have pins "1", "2" and "3" labeled differently I'd guess it's the same PTH451C package.
 
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