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[BillD 239]

 

 

I measured the voltage across the existing LED in the C-1 and it was 1.9 volts.

 

It appears that the specs for the LED specified is 4 volts.  I assume that the replacement resistor increases the voltage to the LED?

 

Also the company that lists the LED only shows a 470 ohm 1/2 watt resistor. I also assume that the 470 ohm resistor will work in place of a 480 ohm resistor? 

 

Sorry for all of the questions, but this will be my first mod to any stereo equipment and I want to get it right.  A couple of times previously I have successfully repaired cold solder joints in audio/video gear.  This project looks like it is something I can attempt.

 

Thanks again.

 

 

You need to measure the voltage with the LED and resistor out of circuit.  That will give you the input voltage.  I assumed it was 12Vdc, which is the same for the op-amps that are powered by the same supply.  Anyway, the LED drops 4V (V_f ) @ 20ma, so you can use Ohms law to figure out R to drop it the remaining 8V, which comes out to 400Ω.  I meant to type 470Ω rather than 480Ω, sorry.  You can probably get away with a ¼W resistor to dissipate the extra power, but I used a ½W for safety (and it fits OK).  Anyway, mine works fine with a 470Ω resistor in place.

 

 

[sanford lindstrom 35]

Thanks.

 

I will order the parts tomorrow.