I am working on a pair of Allison CD-9 speakers and while recapping them, I cooked a polyfuse. So, I need to replace it but don't know the trip current. It's round, yellow, and labeled as follows:
XD
-115
823Q
The X could be the littlefuse logo. The polyfuse is way in the back of the cabinet, so this is my what it says to the best of my ability to read it: the D or Q could potentially be 0s, but I'm pretty sure I've got it right.
Can anyone identify this polyfuse?
Thanks!!
XD
-115
823Q
The X could be the littlefuse logo. The polyfuse is way in the back of the cabinet, so this is my what it says to the best of my ability to read it: the D or Q could potentially be 0s, but I'm pretty sure I've got it right.
Can anyone identify this polyfuse?
Thanks!!
Last edited:
They're on the negative sides of the drivers. One on the woofer and one shared by the tweeter and midrange. The woofer one is blown. I can't take a picture, I can barely get my hand back there. They are not easy cabs to work in.
I see, but it bears the question how you are going to replace it if you can't reach it.
Can't you take the woofer out?
I have been looking at your part numbers but can't find anything.
Are these fuses original? It's strange they don't appear on the crossover drawing.
Can't you take the woofer out?
I have been looking at your part numbers but can't find anything.
Are these fuses original? It's strange they don't appear on the crossover drawing.
I don't think the marking on the polyfuse (PTC resistor) will help much as different manufacturers use different codings.
However, I can provide a link to a calculator that allows the selection of a suitable PTC resistor according to the power handling and impedance of the driver it is intended to protect: https://www.lautsprechershop.de/hifi/ptc_en.htm
N.B. Read the "Input instruction (a guide line according to our experience)" section carefully.
Netlist, they're long, skinny speakers with a four inch hole for a mid driver in front or the cross over. I can get my hand in, hand a tool in to myself through the tweeter hole. I've gotten okay soldering in there. But it's not easy to get good pictures, and I've been reticent to remove the polyfuse (or any part) until I have the replacement because I might need to get creative fitting the replacement.
The woofer is about two feet below the crossover, it's harder to work through there.
I have reviewed that link, and did the math myself. I guess I'm struggling to figure out which one to use based upon the spec for the speaker. It's a 4z speaker with the power handling in the attached file.
To get the approximate times (1s at 190W, 10s at 90W), the data sheets for most current polyfuses would suggest a roughly 1.1A trip current. However, to get closer to 40-60 W continuous, I need somewhere closer to 3A. I'll revisit that link. Last I checked, it agreed with my math of about 3A.
I should also note that I was confused by that link as it states the rated voltage is 50V, then gives a rated voltage in the table, which I believe is perhaps rated current.
The woofer is about two feet below the crossover, it's harder to work through there.
I have reviewed that link, and did the math myself. I guess I'm struggling to figure out which one to use based upon the spec for the speaker. It's a 4z speaker with the power handling in the attached file.
To get the approximate times (1s at 190W, 10s at 90W), the data sheets for most current polyfuses would suggest a roughly 1.1A trip current. However, to get closer to 40-60 W continuous, I need somewhere closer to 3A. I'll revisit that link. Last I checked, it agreed with my math of about 3A.
I should also note that I was confused by that link as it states the rated voltage is 50V, then gives a rated voltage in the table, which I believe is perhaps rated current.
Yes, underneath "Rated voltage" it says I/A which I interpret as current in amps.
PTC resistors only go high resistance during continuous power overload and don't react to transient power peaks.
For this reason I'd be inclined to go for the "continuous or average at any frequency" power rating of 20 W.
20 W would suggest using the PTC designated SE160 (1.6 A) which switches off after 3 s at 23 W.
Note that you are highly unlikely to be listening at a continuous level of 20 W as most domestic listening is done at around 1 W.
P.S. I hesitate to say it, but your existing PTC labelled 115 could well indicate a current rating of 1.15 A, but that is by no means certain.
P.P.S. If you don't continuously listen to your music at ear-shattering levels, you probably don't need the PTC and could simply bypass it!