Electronics > Projects, Designs, and Technical Stuff
SMPS for vacuum tube power amplifiers.(status: back at it)
T3sl4co1l:
How is a device intrinsically unsafe?
Energized, stick it up your bum? Not very safe, no, wouldn't recommend that. ;D
Energized, under a cover, or inside an insulated box, connected with insulated terminals, connectors, whatever -- not a problem.
We handle hundreds of volts on a daily basis -- to varying degrees of safety mind, but mains outlets are hardly mass murders. YMMV by country -- US plugs being notorious (you can easily touch the prongs when partially inserted), but 120V also arguably not being very dangerous by itself. UK and AUS plugs being safer, with the metal bit on the end, atop an insulated shank, and preferably with the outlets having shutters that retract when a ground prong is inserted. And arguably being more justified in the increased cost, at the higher voltage.
All a matter of safe practice. And where possible, safe hardware and tools. You don't have to get obnoxious with rubber gloves and face shields and finger guards all over -- after all, the most unsafe protocol is the one that doesn't get followed! -- but there are some very reasonable and affordable steps that can be taken to improve confidence in things.
Tim
SK_Caterpilar_SK:
--- Quote from: TimNJ on March 29, 2019, 09:57:20 pm ---I work on offline AC-DC SMPSs all day. Shocked myself many times, but haven't been seriously hurt. Classic electrician's rule is to "keep one hand in your pocket". That's a good rule of thumb here too. Try to work with just one hand, especially when the circuit is powered up.
Of course, there are many other preventative measures to prevent yourself from getting cooked, but that's a good start.
--- End quote ---
I know that rule very well. I did get bit quite a bit of times and usually it was because of my stupidity. I did not expect the inductor to zap me but the voltage was so hight it penetrated the isolation. Something that is so obvious, but for some reason im still an idiot sometimes. Nothing to major tho. Since that day I use speacial isolated gloves if I really want to look at stuff and handle electronics while turned on, I use covered probes right to the tip. And no the gloves wont be penetrated by the sharp leads sticking out the bottom of the PCB. And me having dry hands as the sands of sahara is also a bonus.
Learned my lesson lol. But the question still remains. I see a lot of feedback circuits, but Im afraid I dont get their function(how does it work exactly). I mainly look at the TL431 feedback loop with an opto. So far doing research about the regulation.
SK_Caterpilar_SK:
--- Quote from: T3sl4co1l on March 29, 2019, 10:07:00 pm ---How is a device intrinsically unsafe?
Energized, stick it up your bum? Not very safe, no, wouldn't recommend that. ;D
Energized, under a cover, or inside an insulated box, connected with insulated terminals, connectors, whatever -- not a problem.
We handle hundreds of volts on a daily basis -- to varying degrees of safety mind, but mains outlets are hardly mass murders. YMMV by country -- US plugs being notorious (you can easily touch the prongs when partially inserted), but 120V also arguably not being very dangerous by itself. UK and AUS plugs being safer, with the metal bit on the end, atop an insulated shank, and preferably with the outlets having shutters that retract when a ground prong is inserted. And arguably being more justified in the increased cost, at the higher voltage.
All a matter of safe practice. And where possible, safe hardware and tools. You don't have to get obnoxious with rubber gloves and face shields and finger guards all over -- after all, the most unsafe protocol is the one that doesn't get followed! -- but there are some very reasonable and affordable steps that can be taken to improve confidence in things.
Tim
--- End quote ---
Unsafe..well there aint nothing safe on 450V of DC with abou 60W of power backing it, no matter if its generated from 12V or 240V. The thing is I dont like working arround mains because ITS UNFORGIVING. You do a mistake you pay for it. Doesnt have to be about touching live stuff. Even simple mistakes can turn into disasters. The deal is I simply never was comfortable working arround those voltages. Maybe fixing powersupplies, its not a problem, but powering my own circuit with mains? Something I havent done yet and also I dont really "have the balls" to just turn it on. Sometimes shit can go haywire and I simply hate to risk anything.
Zero999:
Do away with the power transformer altogether and go with good old school hot chassis. This sounds dangerous, but it needn't be: the inputs and outputs can be coupled with transformers, with sufficient isolation for mains use.
SK_Caterpilar_SK:
--- Quote from: Zero999 on March 29, 2019, 10:50:35 pm ---Do away with the power transformer altogether and go with good old school hot chassis. This sounds dangerous, but it needn't be: the inputs and outputs can be coupled with transformers, with sufficient isolation for mains use.
--- End quote ---
Now that is what engineers were thinking of when they were designing all american 5 and 6 radios. Make the chassis hot or not- aint a good idea if you want the thing to be showed of not just working. And if you want a metal enclosure for the thing to make it premium looking.
Now I would use a 3 wire plug anyways. But ground loops are still gona persist as an issue, and isolating the output from the input mains seems to logical since you dont want to spend tons of money for tranformers that will put your sound into the amplifier, afterall the catch of a tube amp is its high input impedance. Your solution, is not what Im after.
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