AMP9 - Polyfuse mod

[Scratchy]

I used an 8A Polyfuse to replace the AMP9-Basic schottky protection diodes:

P1030491a.jpg

[krilli]

Hmm, that's interesting. Can you explain the purpose and benefits?

[V-bro]

You could extend the mod with a big to220 diode over the rail voltage in non conducting direction. That way if you connect the power up the wrong way the polyfuse will break circuit...

Then did you check the polyfuse datasheet? You have to make sure the trip current is ok. Usually they specify the holding current on the package and the trip current is usually twice of that! So an 8A polyfuse trips at 16A!!

[Scratchy]

@Krilli, I'm just following V-bro's advice:
http://www.41hz.com/forums/showthrea...6514#post16514
http://www.41hz.com/forums/showthrea...1071#post21071

@V-bro;
I thought of using a reversed diode across the input after the polyswitch, but figured the forward bias voltage would be high enough to still cause damage the the TA4100A before the polyswitch blows, but perhaps if worth a test?

I did some polyfuse searching before deciding on this one:
http://www.tycoelectronics.com/catal...0?RQPN=RUEF800
Yes, you are correct it trips at 16A after some 20 seconds.
This basically only provides short circuit protection.

[mr-busy]

thx for the link, informative. only one thing needed: how much are they?

Found it. less then 1 Euro. Makes it interesting!

[Scratchy]

I bought 3 from Digi-key.
I chose the 30V models because I will also use it for my home AMP9-Basic which I will run at 24V.
The AHRF600 is more appropriate for automotive use.
It is rated 6A hold, 12A trip current @ 16V.

The AMP3 kit actually uses a SMD polyswitch instead of a fuse (thanks to V-bro).