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Old 15th June 2013, 08:06 PM   #1
SonyES is offline SonyES  United Kingdom
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Default Help identifying a component and its value

I believe this is a thermistor but I am unsure of its value, looking it up has not brought up much via google:
Writing on the component says:
PTH
AR0R5M
MURATA

Any help appreciated!
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Old 15th June 2013, 08:40 PM   #2
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It looks like a resettable fuse, maybe 0.5A of 5A.
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Old 15th June 2013, 09:10 PM   #3
SonyES is offline SonyES  United Kingdom
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The Sony p/n from the service book is 1-808-65-11 Thermistor, Positive, but not giving many clues on the amperage or such like.
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Old 15th June 2013, 09:53 PM   #4
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It's just an inrush current limiter, and it is perfectly ok to bypass it with straight wire.
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Old 16th June 2013, 02:23 PM   #5
DF96 is offline DF96  England
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Could it be a PTC thermistor (the opposite of an NTC inrush limiter)?

What is its cold resistance? How does it change if you warm it between your fingers? What role does it play in the circuit?
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Old 16th June 2013, 02:42 PM   #6
Mooly is offline Mooly  United Kingdom
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I think it could be a "positor" which is used in place of a fuse. At currents within its operating range it has a very low resistance, when the current is exceeded the resistance rises dramatically and suddenly.

These devices have to be replaced with one of the correct characteristics for continued protection as they are chosen on voltage as well as current.

Are you sure its faulty ? Have you measured its resistance when cold.
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Old 16th June 2013, 03:59 PM   #7
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Current Murata datasheet suggests the initial character string denotes case style, and AR means 120C. The 0R5 may be its resistance @ 25C. For specification another parameter is required linking power dissipation to temperature, I assume.

The datasheet, available for example from RS, may help selection of a suitable replacement. I don't know enough about PTC thermistors to make a suggestion.
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Old 16th June 2013, 04:45 PM   #8
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Hi,
I found not too long ago the attached PDF Posistor application manual that may help you to find what it is. I think they list the PTH in the last line to the right in the variety list. If I am not wrong they used it in motor starters. Good luck.
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Old 17th June 2013, 02:40 PM   #9
SonyES is offline SonyES  United Kingdom
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Thanks for your inputs, I cant be sure if its faulty or not but it certainly isn't letting any voltage pass through (highlighted is the two areas where these components sit) it any more than 0.3-0.5v.
The parts in the schematic are PS951 and PS952

I have attached a schematic of the area I am working on, if I am reading correctly there should be 11.9v with the power on between the feeder leg and leg 1 of IC950, currently there is no voltage.

At the Reds to Black (gnd) there is a fluctuation between 11-26 milivolts, should it be this low from a direct feed from the main traffo?
Starting to think now it might be a traffo issue, what's the best way to test?

Oranges both read 26.8v to GND.
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Old 17th June 2013, 03:14 PM   #10
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Hi,
Read the AC voltage at the bridge. If you do not have voltage remove the transformer wires to the bridge and read the voltage. If you have voltage then the bridge it is bad. If you do not read voltage then the trafo it is bad
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