Go Back TV - Video - Vintage Television & Radio Forums > Vintage TV & Radio Tech Forum

We appreciate your help

in keeping this site going.
Thread Tools Display Modes
Old 05-10-2017, 04:51 PM
Jon A.'s Avatar
Jon A. Jon A. is offline
Don't mess with Esther.
Join Date: Jun 2013
Location: Canada
Posts: 4,070
Choosing a thermistor

I need to replace a 60-ohm PTC thermistor. I can't find a 60 so I'm wondering if a 50 can be used instead. If my guess is correct, the degaussing coil will just stay on a trifle longer with no ill effect.
Reply With Quote
Old 05-10-2017, 07:48 PM
Findm-Keepm's Avatar
Findm-Keepm Findm-Keepm is offline
Followin' the Rules...
Join Date: Jun 2007
Posts: 2,826
Considering most PTC/Posistor degaussing thermistors have a 20% tolerance to start with, no problemo.

Just don't use a posistor from a 36" set in a 13" set. Big difference in thermal/resistive "hysteresis" that'll cook a d-coil on a smaller set. I saw this once with a Samsung 13" set serviced by someone else. No degaussing, so I replaced the positor, only to find an open d-coil - melted aluminum winding...

Tip to those saving posistors (little boxy thermistors for modern set degaussing) from junked sets - mark the screen dimensions on the posistor, as there is no cross reference for the markings on the units - some Murata ones have a partial part number, but most are house marked, so you have no idea if a 617-40 or an A28-2 will replace a DAF40.....
USN RET (Avionics / Cal)
CET- Consumer Repair and Avionics ('88)
"Capacitor Cosmetologist since '79"

When fuses go to work, they quit!
Reply With Quote
Old 05-14-2017, 05:22 AM
Jon A.'s Avatar
Jon A. Jon A. is offline
Don't mess with Esther.
Join Date: Jun 2013
Location: Canada
Posts: 4,070
I didn't know degaussing coils could open, I assumed they would just get so hot they would trip a breaker or start a fire. I used a coil from a 19" set in a pinch when I had to do some manual degaussing. I ran it at probably less than half of line voltage but still it got too hot to handle in about 10 seconds. Buried the needle on the Powerite too.

I looked over the chassis of a junk 25V Hitachi for a posistor but couldn't spot one. Of course it seems Hitachi used some weird engineering, much more complex than I care to dig into. I got its oversized coil anyway so now I can mock up a decent manual degaussing coil. I hear a 100-watt light bulb makes a good current limiter for those.
Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT -5. The time now is 08:37 AM.

Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
ęCopyright 2012, All rights reserved.