Bottlehead Kits > Eros Phono
Eros-2: I built it my way
pechelman:
--- Quote from: georgeged on March 02, 2021, 09:52:12 AM ---I thought military grade RN60 or its industrial grade equivalent CMF60 is 1W@70°. 47K used is RN70/CMF70, which, as far as I know, is 1.75W. Am I wrong?
--- End quote ---
quick look at the datasheets shows RN60 at .25W @ 70°C and an RN70 and .75W @ 70°C. The RN70 apparently used to be rated at 1W but was downgraded sometime in the past.
Reference: https://www.vishay.com/docs/31027/cmfmil.pdf
Paul Birkeland:
--- Quote from: georgeged on March 02, 2021, 09:52:12 AM ---I bought Takman REY 1W, but they didn't fit - leads are too thick. I will search for something which will fit.
--- End quote ---
When I run into that problem I will use my side cutters to cut the resistor leads to a point so they will poke into the boards.
--- Quote from: georgeged on March 02, 2021, 09:52:12 AM ---I'm confused as to the correct power ratings for the Dale resistor ranges. I thought military grade RN60 or its industrial grade equivalent CMF60 is 1W@70°. 47K used is RN70/CMF70, which, as far as I know, is 1.75W. Am I wrong?
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CMF/RN60 resistors are 1/4W rated.
CMF/RN70 resistors are 3/4W rated.
That is the maximum power rating assuming the ambient temp around the resistor isn't over 70C. The datasheet can be a bit confusing because it's so comprehensive. If we consider the 47K resistor with ~150V across it, that's just under 0.5W of dissipation. For a CMF-70, that will give you +50C of temp rise, and we recommend staying under 100C total. On a toasty PC board, you may go well over that. Based on what's in the datasheet, they are rating the resistors to run up around 130C max, which would likely discolor the PC board and possibly burn up other components close by.
The 27K RN60 dissipates less power, but it's smaller size means it will experience a similar temperature rise. That part is in a pretty tight space, and I also noticed that you have the 100uF caps sitting right next to that part instead of bent over and hanging off the side, so heat will continue to be an issue there.
We tend to suggest going with approximately triple the wattage that would be the bare minimum.
Another trick you can use is to just buy a couple resistors of a higher value and parallel them together before sticking them on the board.
georgeged:
Thank you Paul. I will order replacements.
Deke609:
Beautiful build! Nicely done.
cheers, Derek
Natural Sound:
How does it sound compared to the stock build?
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