Resistor ID

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riggler

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Joined
Jan 24, 2006
Messages
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Location
Pennsylvania, USA
Hi guys, working on the phantom supply on my Ramsa WR-T820.

I have a relatively small blue colored power resistor here (R901 on the board):

Brown, Black, Black, Gold, White

My eyes are not great. It's hard to see the colors. There's another resistor that looks the same to me elsewhere in the circuit (R931). That one measures 10R.

I am guessing my candidate is also 10R, it's open.

My question is regarding the White band. Is that a power rating possibly?

I guess it could be a temperature marking?...
 
Hi John, I guess what I am really asking is, what power rating do I need? It measures 9mm x 2.5mm

I measure 70VDC on the output of the bridge rectifier that this is connected to. I wish I had a schematic for this.

Also, I am trying to find a replacement for this D837A. I can't find a datasheet on it, but I believe it's a regulator. There are Base, Collector, and Emitter markings on the board thankfully!

I am testing with the resistance function on my analog meter. I pulled it out of the circuit:

D837A:
+ on C, - on E : 3 ohms  ***This means the transistor is bad, right?
+ on E, - on C : infinite ohms
+ on B, - on E : infinite ohms
+ on E, - on B : about 60 ohms
+ on B, - on C : infinite ohms
+ on C, - on B : 4 ohms

The other transistor is a C1318. It checks out as follows:

C1318:
+ on C, - on E : infinite
+ on E, - on C : infinite
+ on B, - on E : infinite
+ on E, - on B : 5 ohms
+ on B, - on C : infinite
+ on C, - on B : 5 ohms

So I *think* this one is good.

I attached a pic!
 

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riggler said:
Hi John, I guess what I am really asking is, what power rating do I need? It measures 9mm x 2.5mm
That size sounds like perhaps 1/4- 1/2W?? perhaps flameproof
I measure 70VDC on the output of the bridge rectifier that this is connected to. I wish I had a schematic for this.
What matters is V drop the resistor sees in use.
Also, I am trying to find a replacement for this D837A. I can't find a datasheet on it, but I believe it's a regulator. There are Base, Collector, and Emitter markings on the board thankfully!

I am testing with the resistance function on my analog meter. I pulled it out of the circuit:

D837A:
+ on C, - on E : 3 ohms  ***This means the transistor is bad, right?
+ on E, - on C : infinite ohms
+ on B, - on E : infinite ohms
+ on E, - on B : about 60 ohms
+ on B, - on C : infinite ohms
+ on C, - on B : 4 ohms

The other transistor is a C1318. It checks out as follows:

C1318:
+ on C, - on E : infinite
+ on E, - on C : infinite
+ on B, - on E : infinite
+ on E, - on B : 5 ohms
+ on B, - on C : infinite
+ on C, - on B : 5 ohms

So I *think* this one is good.

I attached a pic!

The ohms measure for diode junctions can vary between different meters, but yes the first one definitely looks squirrely.

Surely there is a service schematic somewhere for this...

JR
 
2SD837A  http://www.datasheetcatalog.org/datasheet/panasonic/2SD837.pdf
Darlington transistor with protection diode. Your measurements look OK as you are measuring the diode forward volt drop. Your meter has the polarity reversed when measuring Ohms.
i.e. Red lead actually has a negative voltage on it. Very common with analogue meters.

2SC1318  http://www.datasheetcatalog.org/datasheet/panasonic/SJC00100CED.pdf
 

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