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need a fuse resistor

looxuser

Dec 28, 2015
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Anybody have or know where i can get hold of an 82ohm 0.5W 5% fused resistor please in the uk. I'm really struggling here. Thanks, Andy
 

davenn

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Sep 5, 2009
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have you tried Farnell, Maplin, Digikey
to name 3 sources
 

looxuser

Dec 28, 2015
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Thanks for your response, yes tried most places with no joy. Guess I could make one up with 0.5w resistors in series and perhaps put a 0.5w zero Ohm resistor in series that would act as a fuse? I did find a 0.75w but that would i assume be to high a value to protect the circuit?
 

looxuser

Dec 28, 2015
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Haha, you're nearly right Martin, but I did check them but must have missed it or not searched with the correct terms. Anyway after the forums help, I have still have a dilemma...

The failed resistor I've removed is shown on the circuit diagram as a 56Ohm 1/2w fusible resistor yet the one ive removed is definitely and 82Ohm with bands grey red black gold. So, happy days hey, well not quite because in my search I did find a supplier of the original aiwa component 87-029-030-010 in the US who quote this as a 82Ohm fine but as a 1/4w???!!!. So I know its definately a 82Ohm I want but at what rating 1/4w or 1/2w? Do I go with the part description or the circuit diagram? Admittedly the Ohm value was wrong on the circuit diagram so i guess the wattage could also be wrong. Is the size of the resistor a good indicator of its wattage would you say, its about 7mm in length and 2mm diameter. I assume they get bigger according to wattage? regards to all, Andy
 

Martaine2005

May 12, 2015
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6 to 7mm x 2mm is probably 1/4 watt. But newer resistors are of similar size with a higher wattage rating.
Your colours are an 82Ω resistor 20% tolerance.
The wattage rating can always be increased without a problem. Just means it wont have to dissipate as much heat, which is a good thing!.

Martin
 

looxuser

Dec 28, 2015
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Thanks martin i thought the wattage dictated the level of protection i.e the point the fusible bit blows, but I suspect thats wrong and all these are designed to blow with a high current flow anyway so it make little difference, and like you say better heat dissipation?
 

cjdelphi

Oct 26, 2011
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Wouldn't it be easier to buy the 83ohm (1/4 1/2 watt etc) then a regular 10cents fuse?

Or take the old one remove the fuse, test to see if it measures 86ohms, cut the fuse out, replace with new one...
 

Colin Mitchell

Aug 31, 2014
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"Guess I could make one up with 0.5w resistors in series and perhaps put a 0.5w zero Ohm resistor in series that would act as a fuse?"
This is a complete misunderstanding of how a resistor works.

However 82 ohms will pass a current of 80mA and produce a voltage drop of about 6v6 and stay warm for years.
The current needs to rise by at least 50% for the resistor to start to fail and in most cases it will fall off the board before it changes resistance.
However it will go up in smoke if a short-circuit occurs and then you will have to find the shorted component too.
 
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looxuser

Dec 28, 2015
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guys thanks for your help i managed to source an 82 r .75w 5% fusible so i.m away with that. on a separate note on the circuit diagram some resistors are shown in a rectangular box i.e the standard sybol of a zigzag line is within a rectangle. what does that mean please?
 

Colin Mitchell

Aug 31, 2014
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"I managed to source an 82 r .75w 5% fusible"

You have no idea what you are doing.
82 r .75w 5% fusible will never blow.
See my discussion on talkingelectronics.com website.
 

looxuser

Dec 28, 2015
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Hi Colin, i am merely trying to replace the resistor i know is open circuit and getting a value from the colour bands grey red black gold. The circuit diagram says a 56R .5w resitor is used but what was fitted was a 82r. You are right i am not sure what i am doing but am willing to learn. This hifi was never tampered with so thats how it came from the factory over twenty years ago. In their wisdom they chose to fit this value. Would welcome your thoughts on why you think they were wrong to do that.

Bottom line is my problem is that the sound level is very quiet on this hifi on both channels regardless of volume level, its is very old now so I've read elsewhere that the capacitors in the circuit could have aged and failed. I blew the fusible resistor with a slip of my meter probe, and now its doesn't power up consistently so i need to replace that first and get back to where i was in diagnosing the problem. Alas in the area i live the electronics repairers are well gone / retired so i'm diy/ having to teach myself with the help of forum members.

Many thanks, Andy
 

Colin Mitchell

Aug 31, 2014
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If you damaged the resistor, it is a completely different story.
You can fit the other resistor as it has never blown.
Just put in any 82R as a start.
 

looxuser

Dec 28, 2015
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Thanks Colin, i'll give that a try to get me back to the original fault of low volume output and go from there.
 
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