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Is this arcing?

I just rebuilt a National 183d Shortwave receiver I bought from my friend, he said he plugged it in and turned it on, and was treated to a fireworks show in the 5U4 rectifier.
It turned out the filter cap was shorted, the 5U4 was open (lit up, bur passed no voltage out), and had a 15 amp fuse in the fuse holder, instead of the 2 amp that was supposed to be there. Luckily the power transformer was not damaged.
 
I once had a McIntosh MA-6100 that came equipped with roll pins installed in the fuse holders, the circuit breaker was damaged by arcing during many reset attempts, it was a wreck, the glass faceplate was damaged as well. I pulled the outputs which were shorted, installed fuses, and used it as a preamp for many years, before I got the C-22
 
s-petersen said:
I once had a McIntosh MA-6100 that came equipped with roll pins installed in the fuse holders, the circuit breaker was damaged by arcing during many reset attempts, it was a wreck, the glass faceplate was damaged as well. I pulled the outputs which were shorted, installed fuses, and used it as a preamp for many years, before I got the C-22
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Visions of a dead horse whipping neme for the PO.
 
A cousin was into playing music with a band, and was into that crowd, he got it from someone that was using it as an amp for a band, so it saw much abuse
 
now I wonder how hot it would need to be in order for the powder to light off. I expect fairly toasty, which would mean quite a lot of current flow through the shell, quite possibly more than the wiring was actually capable of delivering.
 
ok I had to look it up
looks like about 330F to light smokeless powder according to the internet. Black powder is like 800F. 330F is still pretty damn hot though.
 
The story I heard was it was a fuse for the headlights, and there was a short there, the case on a 22 is fairly thin, and hot spots are possible.
I'll bet Mythbusters has a segment on it. I'll have to look it up
Edit: Mythbusters did it, but there wasn't enough velocity to hurt you.
it also needed higher current wiring to ignite the cartridge
https://mythbusters.fandom.com/wiki/Frog_Giggin'_(Myth)
 
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tuberadios69 said:
Did you receive your 280's and is the amp functioning properly, now?
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Thanks for asking! I purchased three 280's, so I have a couple spares for the future. They all await my return to my studio in a few weeks... it's an exercise in patience for me :0.
 
cademan said:
You might be overthinking this. :D just replace the rectifier tube and watch it for the first few minutes. It should start to produce music between 25 to 45 seconds after power on.
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You're probably overthinking this.
Tubes fail, that's why they're in sockets.

gadget73 said:
from the first post





just my 2 cents, I wouldn't read too much into why it may have failed based purely on the fact it was just shipped. Bang these things around and bad stuff can happen.
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A couple years back I convinced myself to list and sell an amp from my collection.
A Guy called & it was going to be his first tube amp, I was excited and I lit it up prior to his arrival. The amp was a HH Scott model 208 that's completely restored and has worked perfectly up to this point.
Dude arrives and I show him to my room and the moment his foot steps through the door, the rectifier begins to arc, amp begins to hum at max volume, and I begin trying to figure out how to explain myself...
The guy didn't understand that the amp had failed I had to explain to him what just happened that he would not be buying my amp today, but I'd call once I got it fixed.
Because my guest was curious I managed to hook up some MC30s and show him some tube sound.
The next day I called my mentor.
I told him what I saw, and he said "why don't you put a rectifier in it?"
"Because I don't know what caused the failure"
"Probably just an arcing rectifier, put a new rectifier in it & dont overthink it"


When I called the young man back to let him know I'd fixed it, he informed me that he went ahead and ordered a brand new tube amplifier from the internet because apparently he liked something about what he heard. He was no longer in the market.
The fix:
I ordered a rectifier and decided it's ok if the cause of the failure is unknown. The fix is known...
Another wise mentor of mine said "theres things in life you cant know. Dont waste a whole lot of time trying to know the unknowable."
 
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