AEX-300-0

[Hipocrates]

Greetings.

I'm looking for information regarding this AEX-300-0 posistor on the SA9900.
Does anyone know where to find the datasheet in order to get a replacement?

One is gone and the other one broken..

 

[zebulon1]

Correction: Pioneer part number AEX-003-0
Thermistor/Posistor
It's part of the protection. Maybe you can figure out a way to disable it? Is the amp operational other than the obvious?
Maybe MTF has some experience on this.

 

[Hipocrates]

Correction: Pioneer part number AEX-003-0
Thermistor/Posistor
It's part of the protection. Maybe you can figure out a way to disable it? Is the amp operational other than the obvious?
Maybe MTF has some experience on this.

Thanks for the correction man...

AFAIK, posistor is a Murata's brand for a PTC thermistor.
The amp is working, I just got it yesterday since all the boards are good with the purpose of rebuilt (and because is my second Pioneer ), it have a some other issues made by a muppet, fake differents outputs, chinese caps and resistors.
Checking AWH-037-A, (too many 2SC1451 and 2SA726) I found that one if the "posistors" (PR1 on the schematic) is not there, and the other one ( PR2 on the schematic) have a broken leg.
Looking the schematic still is not clear to me their purpose but that seems to be important, hence my question.
What PTC Thermistor can be used there?



Cheers!

 

[zebulon1]

There's only a gazillion Thermistors. Plus their in two forms NTC and PTC. That part can be figured out but the rating?
If the amp works with the Thermistors removed, then they must be NTC's.
Still Ratings?
Use a Decade box and dial the resistance down until the amp goes into protection. Record that resistance. The Knee should be near a temp that Pioneer felt was the heatsink limit. 165 to 185F?

 

[Hipocrates]

Understood, thank you.

 

[LesE]

These are a possibility.

THERMISTOR PTC 100OHM 90DEG PROB

https://www.digikey.ca/product-detail/en/epcos-tdk/B59901D90A40/495-7085-ND/651966

I ordered a few for my 9900 just in case I managed to break off a lead. Fortunately, I didn't need to use them.

These are 90 deg C devices but they also have 80C PTC thermistors available. The ones that I have on hand measure 60 ohms @ 20C which I believe is roughly the same as original PTC thermistor.

 

[Hipocrates]

THERMISTOR PTC 100OHM 90DEG PROB

This is awesome.... thank you!

 

[LesE]

You may also want to take a look at the characteristic curves in the datasheet when deciding between 80C vs 90C.

https://en.tdk.eu/inf/55/db/PTC/PTC_Sensors_D901_D1052.pdf

I figure that the relay will activate when the thermistor resistance is somewhere between 500 and 600 ohms. According to the curves, you should see relay activation at around 80C for the B59901D0080A040 and just under 90C for the B59901D0090A040 as compared to the spec of 85C.

 

[Hipocrates]

You may also want to take a look at the characteristic curves in the datasheet when deciding between 80C vs 90C.

https://en.tdk.eu/inf/55/db/PTC/PTC_Sensors_D901_D1052.pdf

I figure that the relay will activate when the thermistor resistance is somewhere between 500 and 600 ohms. According to the curves, you should see relay activation at around 80C for the B59901D0080A040 and just under 90C for the B59901D0090A040 as compared to the spec of 85C.

Great info, I will study it and I'll order both a make some experimentation too...