Rudimentary help: voltage drop & watts

[mrr3000gt]

I am working on my Marshall JCM2000 and I have replaced a 1/4 resistors with another of the same spec & rating (1/4 watt, metal film).

Volts in is about 55, volts across is 45 (voltage drop of about 10.1). With the resistor at 10K (10,000 ohms) is the power dissapated at 0.01 watts (P=E^2/R)?

I feel like a nimrod forgetting such a fundamental 

What threw me off is people replace this resistor with a 1/2 watt routinly and if the dissapation is so low, it does not make sense (so I thought I was calculating something wrong)..

[sluckey]

(voltage drop of about 10.1). With the resistor at 10K (10,000 ohms) is the power dissapated at 0.01 watts (P=E^2/R)?

That's correct.

What threw me off is people replace this resistor with a 1/2 watt routinly and if the dissapation is so low, it does not make sense (so I thought I was calculating something wrong)..

Maybe they just have a stash of 1/2 watters but no 1/4 watters.

[Iannone]

And some of us old farts have enough trouble reading the color codes on a 1/2W resistor without having to put a 1/4W under a microscope!

[stingray_65]

And some of us old farts have enough trouble reading the color codes on a 1/2W resistor without having to put a 1/4W under a microscope!

+1

I only buy 1/2W or bigger just so I can see and handle them.

Ray

[HotBluePlates]

I don't remember, but I thought I saw somewhere that 1/4w CC resistors were once more expensive than 1/2w resistors, because 1/2w was a more commonly-used rating.

If I'm not making that up (cause I could be remembering wrong), the same thing applies today, but in reverse; given solid-state and miniaturization, 1/4w and sometimes smaller is the norm.

Most people don't calculate anything, they just slap the same part in an amp they see used in a vintage amp (or clone). However, modern-day Marshall will use most likely the cheapest part that does the job, as it will shave production cost. And the wave-solder machine doesn't need to read the color code... 

[mrr3000gt]

I ended up leaving the 1/4 watt on because it did not make sense to replace it with a 1/2 watt (as I had 1/4 watters and I would have to order 1/2 watt).

What threw me off was the scale of how little the wattage was - I thought I was doing something wrong.

And I cant read metal film resistor colors on 1/4 either - its a measurement-with-the-fluke deal only!