hmm...
they shouldn't really be used as a fuse in that situation.
i mean i guess all you'd need is for the resistor to blow open instead of shorting.
but it wouldn't really protect anything since it wouldn't shut down your b+ and your plates would still be connected.
Source for 100 Ohm carbon comp 5%?
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diagrammatiks
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Re: Source for 100 Ohm carbon comp 5%?
Marshall used that same "flying" screen resistor scheme on some early JTM45 & 50's as well. However, the 18W amps used only a single board mounted 100 ohm 1W Piher CF that fed both screen grids. I say nothing wrong with restoring it back to RK specs as long as it's reliable.gktamps wrote: Interesting thing is Retro-King put the socket-mounted 100 Ohm resistors in series with board-mounted resistors (forget the value at the moment).
I'm guessing they use CC resistors not just for perceived/real tonal characteristics, but also to act as a sort of fuse, but are the carbon film resistors able to serve that same purpose?
Here's my take on the usage of CC; many Marshall style builders because they can't find the original CF(Piher or Iskra) resistors will use the Allen-Bradley or sometimes the Stackpole CC in their place because there's some perceived positive affect over new production CC or CF.
FWIW, in my 18W build each power tube has it's own board mounted 1K smaller wattage WW screen resistor and I also fused the HT center tap.
TM
Re: Source for 100 Ohm carbon comp 5%?
TM - what size fuse did you use for the HT center tap?
Re: Source for 100 Ohm carbon comp 5%?
1/4Agktamps wrote:TM - what size fuse did you use for the HT center tap?
TM
Re: Source for 100 Ohm carbon comp 5%?
For our 100w Dumble amps would a 500ma fuse on the CT be a good thing to have?
And is 500ma the right value?
And is 500ma the right value?
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: Source for 100 Ohm carbon comp 5%?
In the bigger two tube Marshalls I've installed either .375 or .500mA slow blow type and I double that rating for 4 tubes. I believe in being a bit conservative with the fuse rating. Also, the HT fuse should be a slow blow as well.Structo wrote:For our 100w Dumble amps would a 500ma fuse on the CT be a good thing to have?
And is 500ma the right value?
TM
Re: Source for 100 Ohm carbon comp 5%?
UR right. I just today replaced a 2.7k CC screen resistor on a Boogie MK III that read 990.John_P_WI wrote:I can guarantee that the carbon comps on the tube sockets drift way out of range with the heat.... just sayin.
Re: Source for 100 Ohm carbon comp 5%?
Yep... I've got about 4000 in stockgktamps wrote:Thank you - Steve has them at $1.85 each.
Steve