Author Topic: I could use some help indentifying a component in a audio reciever  (Read 1199 times)

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Offline BanthorsTopic starter

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This is the component in question r244fl on the schematic. I looked up all versions of the info written on it and nonthing comes up. Thank you guys
 

Offline james_s

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Re: I could use some help indentifying a component in a audio reciever
« Reply #1 on: May 20, 2022, 03:42:24 am »
It's a power resistor, although I've never seen one with 3 legs, and I've never seen that schematic symbol either.

https://www.made-in-china.com/showroom/kingwahoo/product-detaillqdJutsvbEcg/China-Cement-Resistor-MPR-Type.html
 

Offline octillion

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Re: I could use some help indentifying a component in a audio reciever
« Reply #2 on: May 20, 2022, 03:47:17 am »
It's two 0.27 ohm resistors in series, the center leg being the common tap.  These are frequently seen in push-pull audio amplifiers.
 
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Offline inse

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Re: I could use some help indentifying a component in a audio reciever
« Reply #3 on: May 20, 2022, 04:16:36 am »
Appears to me, they did not have this special resistor in their CAD library and used a sort of connector instead.
Done that myself too, but not for official schematics.
 

Offline TheMG

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Re: I could use some help indentifying a component in a audio reciever
« Reply #4 on: May 20, 2022, 06:31:47 pm »
Yup seen these things a lot, two 0.27 ohm resistors in a single package, with a common terminal.
 

Offline gamalot

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Re: I could use some help indentifying a component in a audio reciever
« Reply #5 on: May 20, 2022, 07:22:20 pm »
Not the exact same model, but for reference

http://www.oneresistor.com/wp-content/uploads/2013/07/MPR.pdf

Offline floobydust

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Re: I could use some help indentifying a component in a audio reciever
« Reply #6 on: May 20, 2022, 07:29:29 pm »
I recognize that as a dual rectangular 5W "plate resistor", like Fukushima Futaba MPC series or Koa BPR series.
They are commonly used in audio power amplifiers, low inductance flame-proof.
One problem is they can fuse and one or both can go open circuit if an output transistor fails, so check their resistance.
 

Offline CaptDon

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Re: I could use some help indentifying a component in a audio reciever
« Reply #7 on: May 21, 2022, 12:58:23 am »
Why does every designator have 'FL' after it?
Collector and repairer of vintage and not so vintage electronic gadgets and test equipment. What's the difference between a pizza and a musician? A pizza can feed a family of four!! Classically trained guitarist. Sound engineer.
 

Offline gamalot

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Re: I could use some help indentifying a component in a audio reciever
« Reply #8 on: May 21, 2022, 06:54:17 am »
Why does every designator have 'FL' after it?

"Front Left" I guess.

Offline Jeff eelcr

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Re: I could use some help indentifying a component in a audio reciever
« Reply #9 on: May 21, 2022, 10:13:47 am »
Although that picture is a .27 ohm resistor at 5W the schematic is showing a different part ? 4.7 ohm to the base of the transistor not an emitter resistor so I think there is a mismatch of part and location.
This is not a symbol I have seen used before. What brand is the unit?
Jeff
 

Offline mclute0

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Re: I could use some help indentifying a component in a audio reciever
« Reply #10 on: May 21, 2022, 07:15:01 pm »
It may not match the schematic spec due to manufacturing changes. If the factory runs out of a certain part and can't get replacements soon enough, they put in a part that will just 'work' and move on with production. As long as the device will last through any warranty period it will save them money.

I think the schematic symbol indicates a shielded resistor and the third leg is the shield going to ground, but you can easily test that with a DMM on one of the other similar resistors shown on the schematic. Third legs are also added to components that heat up to help stop solder joint separation from expansion/contraction.

good luck.
 

Offline Audiorepair

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Re: I could use some help indentifying a component in a audio reciever
« Reply #11 on: May 21, 2022, 08:17:25 pm »
Hang on a minute,

it was clarified earlier that this is a dual emitter resistor, commonly used in audio power amps.

That is 2 x 0.27 ohm resistors in one  package.
Both resistors share the same amplifier output connection in the circuit they are used in, so this is indeed a thing, and has been for decades.
 

Offline mikerj

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Re: I could use some help indentifying a component in a audio reciever
« Reply #12 on: May 21, 2022, 09:12:14 pm »
Although that picture is a .27 ohm resistor at 5W the schematic is showing a different part ? 4.7 ohm to the base of the transistor not an emitter resistor so I think there is a mismatch of part and location.
This is not a symbol I have seen used before. What brand is the unit?
Jeff

You are looking at R238FL/R239FL which is not the resistor the OP is referring to.  R244FL is connected to the emitters of both output transistors and doesn't have a value listed on the schematic.  It doesn't use a conventional resistor symbol, looks more like a connector.
 

Offline floobydust

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Re: I could use some help indentifying a component in a audio reciever
« Reply #13 on: May 21, 2022, 09:38:12 pm »
The emitter resistors are also test points for measuring bias current, so schematics can have arrow bubbles, circles, test points, connectors, pins etc. also drawn at them to make things seem even weirder.
 

Offline Jeff eelcr

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Re: I could use some help indentifying a component in a audio reciever
« Reply #14 on: May 22, 2022, 01:17:41 am »
Now I see what you mean, still what brand is this and what drew that schematic?
Thats two symbols I have never seen used in an audio product by any manufacturer.
Jeff
 


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