Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jeff on April 01, 2012, 07:45:29 pm
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I'm trying to rebuild something and I noticed something I thought was unusual. The 2 prong AC power cord's white goes to the fuse. The black goes to the switch and a 100K ohm resistor to the chassis. Does this make any sense? I don't know if someone was in here before me and rewired it incorrectly but is there any situation where you'd have your chassis connected to your 120 AC with a 100K resistor?
I thought this was wierd because I've never seen anything like that before.
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Please remove that resistor immediately!
The two-prong wiring is only half-wrong, because you could insert the plug either way, so half the time it'd be right...
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OK thanks that's what I thought. What would the purpose be let's say if you did have it in right? Knowing that this is wrong would help me to know that the wires have been played with. Is there any reason this would ever be done back in the 2 prong days? I've heard of caps(death caps) but not 100K resistors.
You know what I mean? Was this ever old practise or is it completlely wrong under any circumstance and therefore everything else is suspect.
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I meant the white neutral going to the fuse. You'd like to fuse to break the connection to the black hot, so you didn't have a blown fuse and still have a possible shock hazard.
The "half-right" comment was if you had the plug flipped so the white wire was actually in the hot contact of the socket, then the fuse would interrupt the hot connection.
I can't think of a good reason to intentionally add leakage from line to chassis by using that 100k resistor. That's like removing a good cap and adding a known failing cap in its place.
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or is it completely wrong under any circumstance and therefore everything else is suspect.
I would say yes it's wrong. That wont fix the Hot chassis problem with a 2 prong cord and a ground (flip) switch.
As far as _ everything else _ being suspect? What do you mean?
Just because one part was modded it doesn't mean anything else was also tampered with.
Brad :icon_biggrin:
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I just mean if this is dangerous as I thought and if this would have never left any factory in this condition then, I conclued , that someone has been in here before and they didn't know what they're doing.
Just trying to do some Sherlock Holmesin' Cuz I can't find schematics anywhere ...and I looked...and looked...and looked.
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Gotch ya Plate. thanks. I am going to add a 3 prong. So black>fuse>switch>transmormer White>transformer Green>chassis.
Eliminate the 100K.
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I'm trying to rebuild something
What are you working on?
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Someone gave me a whole bag of tubes(55) to fix their Cordovox CL 20. Basically same guts as a Fender Vibrotone or Leslie 16, but marketed for accordion. I'm in the dark cuz I don't have a schematic but the guy is going to use it for guitar anyway. The only thing I'm not too sure about is the inductor. It's not marked so I don't know if it's the right mH. The hi pass cap's the same so I'm guessing the inductor is the same too since they work together. If the cap was higher or lower I'd imagine the inductor would be different to compensate. I'm guessing the cap mates with it's corresponding inductor. I'll let you know how it turns out.