Hi! So first things first, I understand everything about the dangers of these tubes and how to properly heat them and all that other jazz. I also have worked on guitar amplifiers for a few year. So, I’m green but not green green. With that said, I’ve always wanted to build a MV display of sorts, flip switch ohhhh ahhhh kinda thing. I have two NL866a and their filament transformer that came out of a Kepco power supply. I’d like to somehow not use a second transformer for the plates and just stick to the two tubes and the FT. I crudely made a sketch. Laugh away 😂. Am I in the ballpark? Do I need resistors on the leads going to the plates? Again, Just trying to get em to glow for a display. Thank you!
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That circuit can't work as-is, but regardless, a line operated, non-isolated circuit is a big no-no.
So bedsides the non-isolated part, care to share what else I’m missing or anything to get me to where I’m looking to go? Thanks ! Will I end up needing another transformer then?
You'll need a 120VAC primary power transformer, with the right secondary voltage and current capability for the HV.
Maybe someone has used these tubes and can recommend one.
Mercury vapor tubes are also extremely dangerous because of the mercury inside.
We've been through this before. This tube should be considered as toxic waste.
https://www.diyaudio.com/community/threads/what-i-need-for-safe-use-mercury-rectifier.183782/
Maybe someone has used these tubes and can recommend one.
Mercury vapor tubes are also extremely dangerous because of the mercury inside.
We've been through this before. This tube should be considered as toxic waste.
https://www.diyaudio.com/community/threads/what-i-need-for-safe-use-mercury-rectifier.183782/
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The person I got the set up from was able to get them to ionize by applying 12vdc to the plates using a Eico 20v transformer and two 39 ohm resistors with the negative attached to one side of the filament.
I appreciate your concern and opinion. As I stated in the original post, I’m fully aware of the dangers but that’s not what I’m looking for on this post. Thank you
You might also want to consider the possible UV hazard these tubes can present depending on the type of glass used in the envelope. Yeah I know you don't want to hear that, but many of us share a common concern for the well being of inexperienced hobbyists just getting started here.
I've never really understood the visual allure, but have some friends who still use them both for technical and aesthetic reasons.
Sounds like you have a possible solution with a relatively low voltage transformer (24V ought to be sufficient) with series resistors to limit the current. I recommend adding a fuse in the secondary of the transformer you use to drive the plates, and select resistor values that limit the current through the rectifier to a few hundred mA at most.
I've never really understood the visual allure, but have some friends who still use them both for technical and aesthetic reasons.
Sounds like you have a possible solution with a relatively low voltage transformer (24V ought to be sufficient) with series resistors to limit the current. I recommend adding a fuse in the secondary of the transformer you use to drive the plates, and select resistor values that limit the current through the rectifier to a few hundred mA at most.
Circuit-wise, it wouldn't work as there's no circuit where the current can flow.
The circuit from the top of the primary you drew isn't closed. Where would the current return to?
Jan
The circuit from the top of the primary you drew isn't closed. Where would the current return to?
Jan
The NC transformer center tap to the lower 120V line wire , the plates each with big series resistor to limit the current to the standby switch . And a fuse for the whole circuit ...
I don't like the ideea of using rectifiers just for light ... but .
I don't like the ideea of using rectifiers just for light ... but .
If you want to make them glow, just run DC through them with a current limiting resistor calculated for the rectifier rating. Although some can glow at 12V, I would use 20V. Some MV rectifiers have higher strike voltages than others.
Would this work? I’m still curious what to do with the red/yellow ct wire. On my fender amps is grounded.
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I use a pair on 2 monoblocks mostly for looks but they are functional. IIRC, the size of the glow is directly related to the current draw so unless you are powering something you may be disappointed.
My opinion? Don't mess with them. This is like PCB oil capacitors - it's not just a health hazard. When one of these suckers gets popped, it's a hazmat issue. Even relatively small amounts, when scattered significantly, get very, very expensive to clean up. An 866 might be a few thousand dollars to clean up if it were to break. Something big like an ignitron could be $50,000 or more.
Yep, 666A's glow brighter with a heavier load, nice set up Mr WM.
The amount of mercury in these things is small, having mucked about with valves for about a decade I've had no big OP sized valves break, plenty of B9a types yes, but no G, BG etc bottles. At school in the 70's we used to muck about with mercury, poke it with our hands and generally play with it, still alive & mostly sane.
Valves running at high voltage are dangerous but so is travelling in a car, riding a motorbike or living in a big city in the USA with loads of nutcases running around with firearms. It's all about perspective. these are fascinating devices, I'm quite happy to muck about with them. Still, if you live in the USA where litigation is a national passtime it might be an issue. Fortunately I live in England. Nuff said.
The amount of mercury in these things is small, having mucked about with valves for about a decade I've had no big OP sized valves break, plenty of B9a types yes, but no G, BG etc bottles. At school in the 70's we used to muck about with mercury, poke it with our hands and generally play with it, still alive & mostly sane.
Valves running at high voltage are dangerous but so is travelling in a car, riding a motorbike or living in a big city in the USA with loads of nutcases running around with firearms. It's all about perspective. these are fascinating devices, I'm quite happy to muck about with them. Still, if you live in the USA where litigation is a national passtime it might be an issue. Fortunately I live in England. Nuff said.