[Amps] one more time - Ameritron fuse question

[Will Matney]

Dan,

Slow blow would be best in my opinion using 8 ampere fuses which in my 
opinion is still a little to small. I dont think running 10 or 12 ampere 
ones would hurt. When a short occurs, there's a huge amount of current 
drawn and each of the three sizes would blow quickly. Matter of fact, 
just the transformers surge current is whats blowing the 8 ampere fast 
blows. You can figure that 8 amperes at 120 Vac is 960 watts input which 
is not very much. At 50% efficiency let's say, would only be 480 watts 
output, and about 576 watts at 60%, this being only the amplifier class 
efficiency. There are other losses too which will add to this number 
(more torwards 400 watts output for 960 watts input, or power supply and 
transformer losses).

Will


Well you guys are batting 100% so far i now have one more Ameritron 811H 
question.  I have replaced the grid resitor and replaced all four tubes 
(one was shorted causing the resitor to blow). All is well works great 
never better...switched to 240 from 120 and even better. Great output 
and amp seems happy sounds and works very well.....

now the problem. To keep the fuses to spec Ameritron states a 8 amp fuse 
on both sides at 240 volt versus 12 amp at 120 volts. It was running 
fine with the original 12 amp ceramiic 3ag 250 volt fuses but thought i 
better get them down to the rated 8 amp. Put in a set of C3ag 8 amp 250 
v ceramic fast blo fuses and switched on the amp.. nothing. a little 
jump of the needles bit nothing. checked the fuses both blown.. tried 
again same thing. replace with 10 amp fuses all ok.... voltage on the 
240 voly line is near 240 so it is where it should be

should I try/use slow-blow fuses at 8 amps. would that be better then 
the 10 or 12 amp fast blo fuses?

I do have a step start (slow start) device coming.. This might correct 
the problem with fast blo at 8 amps.. BUT you guys are the experts..
thanks for any and all opinions... 

Dan