riggler

Resistor ID
« on: August 27, 2011, 07:40:50 PM »
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?...
Why does it happen? Because it happens - Roll the bones...


JohnRoberts

Re: Resistor ID
« Reply #1 on: August 27, 2011, 08:03:37 PM »
10 x 10^0 5% 9?    the white band (9) looks like some spare marking of some sort, but yes 10 ohm.

JR
Cancel the "cancel culture", do not participate in mob hatred.

riggler

Re: Resistor ID
« Reply #2 on: August 28, 2011, 10:39:40 AM »
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!
Why does it happen? Because it happens - Roll the bones...

JohnRoberts

Re: Resistor ID
« Reply #3 on: August 28, 2011, 11:11:06 AM »
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
Quote
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.
Quote
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
Cancel the "cancel culture", do not participate in mob hatred.

Walrus

Re: Resistor ID
« Reply #4 on: August 28, 2011, 12:01:38 PM »
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
Kevin.

riggler

Re: Resistor ID
« Reply #5 on: August 28, 2011, 12:33:00 PM »
Geesh, I am still newbie enough. Thanks guys. Will try replacing this resistor first and see what happens.
Why does it happen? Because it happens - Roll the bones...

riggler

Re: Resistor ID
« Reply #6 on: August 28, 2011, 02:08:26 PM »
That did the trick!

I got lucky, and Radio Shack had a two-pack of 10R 1/2 watt resistors. Got phantom now, works great!

Thanks guys!
Why does it happen? Because it happens - Roll the bones...


 

Related Topics

  Subject / Started by Replies Last post
8 Replies
2512 Views
Last post June 29, 2004, 01:13:41 PM
by b3groover
9 Replies
2522 Views
Last post February 21, 2005, 10:01:44 AM
by jensenmann
5 Replies
2712 Views
Last post May 25, 2005, 02:44:00 PM
by matta
28 Replies
11443 Views
Last post February 21, 2009, 05:11:13 AM
by tongenerator