PTC Secrets
For my curiosity I have decided to open and see inside the PTC thermistor and what are modes of its failure. I took one damaged PTC to check what is exactly in side. This is 3 legs PTC
Inside Look
Further dissection……
There are two types of the PTC
1) 3 leg with two Resistor elements inside and
2) 2 leg with single Resistor elements in side.
Circular Resistor element showing 242Ω on testing and Square Resistor element showing 14Ω.
The cause of failures are usually due to mechanical separation between the Resistor element and the lead material, caused by handling damage, excessive heat, thermal mismatch, etc. The second most common failure mode is drift in resistance value as the thermistor ages or parameter change. This results in inaccurate temperature measurements, thereby causing the thermistor circuit to provide incorrect thermal compensation as it ages.
When I opened this PTC both the resistor elements are fall down because of loose connection could be reason for failure of this PTC.
This article was prepared for you by Yogesh Panchal who works as a Computer Hardware Engineer in Mumbai India.
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Note: You can check his previous repair articles in the link below:
https://www.electronicsrepairfaq.com/200-ohm-resistor-open-circuited-in-sunwa-360tre-meter
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Jestine Yong works as an Electronics Repair Lecturer in Kuala Lumpur Malaysia and his training website is http://www.NoahtechElectronicsTraining.com. You can check out his repair blog at http://www.JestineYong.com
17 comments on “PTC Secrets”
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PTC THERMISTOR SECRETS:I saw the mechanical parts from pictures you posted they’re amazing, but can you repair it?
Charles,
No this can not be repaired because Resistor element get broken due to over Heat.
Thanks for the sneak peek, Yogesh.
Your welcome! Sir.
Nice detailed information. Likely a 3 legged PTC from an old TV degaussing circuit. I would like to know if the 2 resistor parts still were within spec and matched the top marking that shows 150M 9817 ML TDK. But they probably were. Couldn’t find the TDK datasheet.
Here is an example datasheet of such a dual PTC type with functional circuit:
http://www.datasheetspdf.com/pdf/699579/ETC/MZ73-9RM/4
Albert,
Thank you!
Thanks for sharing, good information.
Your Welcome ! James.
“What is a PTC???” – spell it out. I have worked in electronics for over 40 years and still have a problem with acronimes. I guess it is some kind of theromocouple or temp measurement device -spell it out – then I can understand your repair.
I agree with you that too many useless new acronimes enter our dayly lives. Like waste containers that are called PMD (for Plastic, Metal and Drink cartons) and so on. WTF are they thinking? But it is the opposite of the NTC resistor. The old standard lightbulb had a filament with PTC characteristics. The resistance of the filament was higher when it got hot. Hence why lightbulbs in cold rooms mostly burned open after the much higher current rushed in the low ohmic filament. So Positive Temperature Coefficent.
Hank,
PTC (Positive Temperature Coefficient).
Thank you for the technical informaton! It’s helpful to repair works if knowing the inside of the component as well as checking whether it was fault by multimeter.
Lau Darie,
You are right.
Thanks for sharing so valuable information.
Humberto,
Your Welcome!
Nice article Yogesh,these devices used to catch me out a number of times,when they’d blow smps fuse i eventually discovered that they do get short circuit…Thanks again Yo
In fact your article is so fantastic, I am so much impressed.
Please, sir.
What is the main function of the PTC IN TV and what is the implication when get fault?
Thanks