Hello I build in last years lots of tubes amps. and always use 5u4, 5y3, az41, etc for rectifier.
Never use mercury rectifier because i´read out there in the web, "mercury rectifier is very dangerous"
Today I´find NOS Philips AX50 mercury rectifier; and my question is:
_Why is more dangerous than 5u4g? (i´now mercury, but why?)
_what I need for safe use mercury tube?
thanks.
Alejo
Never use mercury rectifier because i´read out there in the web, "mercury rectifier is very dangerous"
Today I´find NOS Philips AX50 mercury rectifier; and my question is:
_Why is more dangerous than 5u4g? (i´now mercury, but why?)
_what I need for safe use mercury tube?
thanks.
Alejo
You don't want to use Mercury vapor rectifiers, even if you think you do. Using them for audio is dumb. They are in my view the hallmark and signature of inexperience.
True, they emit a pretty blue glow, but they are really, Really, *REALLY* noisy rectifiers. They make enough noise that back in the day you could literally hear in your AM broadcast radio receiver if the radio amateur next door keyed his Morse code transmitter. The Mercury vapor rectifiers acts as wide band audio and RF noise generators when they are conducting. This is not switching noise, it happens even if they only conduct DC.
That said, if you insist, then:
*) Mercury vapor rectifier tubes cannot really take high peak currents when used as AC rectifiers. So you usually use them in choke input filters. Any input capacitor in cap input filters needs to be really small, on the order of a few uF. The data sheet will tell you more. If it doesn't say anything, then it is assumed you will only use choke input.
*) They need a pre-heating time. Meaning you apply heater power to the rectifiers for several minutes before you apply the high AC voltage. This is to allow the Mercury inside the rectifiers time to fully evaporate before switching on. Doubly important if the tubes has been moved or shaken since last time they had power applied.
*) When hot the tubes contains a fair amount of Mercury vapor. As opposed to ordinary, liquid Mercury at room temperature this stuff is fairly nasty. If you accidentally break a rectifier while power is applied, the vapor will immediately disperse in your living room. It will be impossible to avoid inhaling some of it, or prevent getting Mercury all over the place. So condemn your house, and build a new one. Much safer for your family that way. Check symptoms for Mercury poisoning, they are quite entertaining.
*) When Silicon rectifiers of reasonable voltage rating was introduced, there was a stampede of radio amateurs away from Mercury rectifiers. With good reason I'd say.
Sorry to be the bringer of bad news. However I'd rather say this now before you build anything with them, and then post photos, asking for comments.
True, they emit a pretty blue glow, but they are really, Really, *REALLY* noisy rectifiers. They make enough noise that back in the day you could literally hear in your AM broadcast radio receiver if the radio amateur next door keyed his Morse code transmitter. The Mercury vapor rectifiers acts as wide band audio and RF noise generators when they are conducting. This is not switching noise, it happens even if they only conduct DC.
That said, if you insist, then:
*) Mercury vapor rectifier tubes cannot really take high peak currents when used as AC rectifiers. So you usually use them in choke input filters. Any input capacitor in cap input filters needs to be really small, on the order of a few uF. The data sheet will tell you more. If it doesn't say anything, then it is assumed you will only use choke input.
*) They need a pre-heating time. Meaning you apply heater power to the rectifiers for several minutes before you apply the high AC voltage. This is to allow the Mercury inside the rectifiers time to fully evaporate before switching on. Doubly important if the tubes has been moved or shaken since last time they had power applied.
*) When hot the tubes contains a fair amount of Mercury vapor. As opposed to ordinary, liquid Mercury at room temperature this stuff is fairly nasty. If you accidentally break a rectifier while power is applied, the vapor will immediately disperse in your living room. It will be impossible to avoid inhaling some of it, or prevent getting Mercury all over the place. So condemn your house, and build a new one. Much safer for your family that way. Check symptoms for Mercury poisoning, they are quite entertaining.
*) When Silicon rectifiers of reasonable voltage rating was introduced, there was a stampede of radio amateurs away from Mercury rectifiers. With good reason I'd say.
Sorry to be the bringer of bad news. However I'd rather say this now before you build anything with them, and then post photos, asking for comments.
The biggest problems of all are when one inadvertently gets broken, there is sufficient elemental mercury in a cold tube to constitute a significant environmental and hence health hazard. Clean up depending on the surface it spills on can be problematic, in any event it is usually recommended that a local hazzmat specialist do the clean up. There are recommended clean up procedures for fluorescent lamps which generally contain a lot less mercury afaik.
The worst case scenario might be if an operating tube got broken and the vapor escaped because it will quickly condense leaving micro-droplets of mercury on everything it touches.
I was given a bunch of 866 rectifiers, I don't plan to use them, in fact I will return them at some point to the original owner.
The two things I try to avoid having in my house are MV rectifiers and PCB filled oil caps..
The worst case scenario might be if an operating tube got broken and the vapor escaped because it will quickly condense leaving micro-droplets of mercury on everything it touches.
I was given a bunch of 866 rectifiers, I don't plan to use them, in fact I will return them at some point to the original owner.
The two things I try to avoid having in my house are MV rectifiers and PCB filled oil caps..
I was thinking of using Mercury rectifiers when I came accross with this thread.There is no safe use with MVRs
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The only thing that Hg diodes have going for them is glowey bottle kewelness. Back in "the day", they were used for applications requiring high PRV, high currents, and superior voltage regulation. These days, all of this is available with silicon that does not require another hole in the chassis, a special, low voltage, high current, and insulated to stand up to 10KV filament xfmr.
Like the OP explained, Hg diodes are liable to RF parasitics (since it's a glow discharge, it has negative resistance) require preheating (~30 secs if the Hg hasn't been disturbed since last power down, ~30mins if it has -- otherwise poofage due to having Hg droplets bridging the anode and cathode is a distinct possibility). Too much bother.
One thing that you don't have to worry about is UV, since glass is opaque to UV (only fused quartz is transparent to UV, and is standard for UV sources).
If you just have to have that glowey bottle goodness, look into substituting xenon diodes for the Hg vapor variety. You will still have to deal with that RF parasitic problem, however.
Personally, I'd say t'hellwiddit. If you can't do it with vacuum diode(s) you're better off going Si instead.
Like the OP explained, Hg diodes are liable to RF parasitics (since it's a glow discharge, it has negative resistance) require preheating (~30 secs if the Hg hasn't been disturbed since last power down, ~30mins if it has -- otherwise poofage due to having Hg droplets bridging the anode and cathode is a distinct possibility). Too much bother.
One thing that you don't have to worry about is UV, since glass is opaque to UV (only fused quartz is transparent to UV, and is standard for UV sources).
If you just have to have that glowey bottle goodness, look into substituting xenon diodes for the Hg vapor variety. You will still have to deal with that RF parasitic problem, however.
Personally, I'd say t'hellwiddit. If you can't do it with vacuum diode(s) you're better off going Si instead.
Hi!
Reports of the danger and RF hash of MV rectifiers are exagerating. Of course one should be extremely careful not to break the glass as mercury is hazardous. I remember the times when mercury was common in thermometers. I remeber these things also falling on the floor and the mercury beeing spilled. I even saw this happen in a hospital once. No clean up team had to come to remove the spill. And the people vitnessing this are still alive
Also many people claim MV tubes provide much better sound than vacuum rectifiers.
I used 866As a lot. RF is not really an issue in a well laid out PSU.
I wrote about a 866A PSU here:
VinylSavor: Single Ended Amplifier Concept, Part 5
Best regards
Thomas
Reports of the danger and RF hash of MV rectifiers are exagerating. Of course one should be extremely careful not to break the glass as mercury is hazardous. I remember the times when mercury was common in thermometers. I remeber these things also falling on the floor and the mercury beeing spilled. I even saw this happen in a hospital once. No clean up team had to come to remove the spill. And the people vitnessing this are still alive
Also many people claim MV tubes provide much better sound than vacuum rectifiers.
I used 866As a lot. RF is not really an issue in a well laid out PSU.
I wrote about a 866A PSU here:
VinylSavor: Single Ended Amplifier Concept, Part 5
Best regards
Thomas
Hi,
there's an important difference between breaking an MV rectifier or a Hg thermometer... In the former case, the Hg is vaporized! It would spread around the room in litterally seconds. People would need to hold their breath and clear the house immediately and then wait outside for hours or days until all the vapor has deposited on surfaces (which then need to be cleaned ). In the latter case, the droplets can just be collected on a piece of paper and discarded. Liquid mercury would only release some vapor when left lying on the floor for weeks. Remember you could drink a thermometer and not get poisoned; the vapour reaching the lungs is where poisoning takes place.
Tip: a rather cool looking high-vacuum diode with high PIV, cheap too, is the U19/CV187...
Kenneth
there's an important difference between breaking an MV rectifier or a Hg thermometer... In the former case, the Hg is vaporized! It would spread around the room in litterally seconds. People would need to hold their breath and clear the house immediately and then wait outside for hours or days until all the vapor has deposited on surfaces (which then need to be cleaned
). In the latter case, the droplets can just be collected on a piece of paper and discarded. Liquid mercury would only release some vapor when left lying on the floor for weeks. Remember you could drink a thermometer and not get poisoned; the vapour reaching the lungs is where poisoning takes place.Tip: a rather cool looking high-vacuum diode with high PIV, cheap too, is the U19/CV187...
Kenneth
Hi Kenneth,
that would be the case when the glass breaks in operation, which is much more inlikely than a breakage while handling the tubes outside of the amp.
I fully agree: MV tubes are dangerous and need to be handled with very special care. But tube amps in general are dengerous. If you fall on a tube amp with exposed tubes (which is very common) and the amp is switched on, you will most likely get a shock.
Life is dangerous. What is inportant is to know and understand the dangers and take the necessary precautions. MV rectifiers are not evil.
Best regards
Thomas
that would be the case when the glass breaks in operation, which is much more inlikely than a breakage while handling the tubes outside of the amp.
I fully agree: MV tubes are dangerous and need to be handled with very special care. But tube amps in general are dengerous. If you fall on a tube amp with exposed tubes (which is very common) and the amp is switched on, you will most likely get a shock.
Life is dangerous. What is inportant is to know and understand the dangers and take the necessary precautions. MV rectifiers are not evil.
Best regards
Thomas
I'm sorry, but I have to disagree with this, at least for the benefit of other readers.
The problem with MV rectifiers is that if one accidentally breaks while hot, no matter how rarely that may happen, the consequences are much greater than if I broke just any old tube in my collection (external anode ceramic tubes might be an exception, if not nearly as problematic...)
The issue is long term exposure to Mercury vapors, particularly for young children. In practice there would be no way to clean up after a MV rectifier breaks. You would literally have to discard all the loose items in the room, and physically remove the outhermost layer of walls, ceilings and floor. The microscopic droplets of condensed Mercury from a leak of Mercury vapor will not be cleaned off by any means, short of physical removal of the substrate (floorboards, furniture, paint, wallpaper, etc.)
In reality the contamination may spread to the whole house, which pretty much means it could be easier to just crush the whole thing, contents included, and start anew. Hardly the issue if you broke the odd EL34 in operation...
The first time you break a hot MVR, you are screwed. Simple as that, and people need to be made aware of this. Pardon my French.
The reference to the haphazard treatment of Mercury spills in the past is not a valid excuse. I can point to an incident with another hazardous chemical, which took place in a stairwell at the Institute for Physics and Astronomy, at the University of Aarhus, Denmark, in the late sixties. Already then the scientists knew they had a long term problem, even if the acute danger was virtually zero. Eventually they realized the only reasonable thing to do was to break out the hammers and chisels, and physically remove the outermost layer of brickwork, ceramic floor tiles and replace the steel railings. So they did.
For those, who may not be aware: Long term exposure to Mercury vapors in the environment plus young children equals dumb teenagers with poor motor skills.
The real issue here are all the superfluous warnings we find on just about any item we can buy or acquire. They make it difficult for people to differentiate the real dangers among the noise from the Nanny state.
Finally, why don't you just use 3B28s instead? Same electric properties if you like the sonics of MV rectifiers, with none of the potential problems. There is just no excuse for recommending the use of MV rectifiers.
They need to go extinct.
Hi Knarf,
As I mentioned I will not argue about the dangers of mercury and I fully agree, mercury is hazardous.
What I feel is much more problematic in terms of mercury content are CFL lamps. Here the problem is that almost nobody who uses them is even aware of their mercury content. Albeit they contain much less than a MV tube, they are out there in billions in the housholds and even in the hands of children.
And who knows which other products are out there which contain mercury or other hazardous materials which we are not even aware of. In the case of MV tubes it is obvous and the name of the tube even clearly says it.
Best regards ... Thomas
As I mentioned I will not argue about the dangers of mercury and I fully agree, mercury is hazardous.
What I feel is much more problematic in terms of mercury content are CFL lamps. Here the problem is that almost nobody who uses them is even aware of their mercury content. Albeit they contain much less than a MV tube, they are out there in billions in the housholds and even in the hands of children.
And who knows which other products are out there which contain mercury or other hazardous materials which we are not even aware of. In the case of MV tubes it is obvous and the name of the tube even clearly says it.
Best regards ... Thomas
There is an interesting blog entry on the clarisonus blog that seems to be fairly well reasoned and documented.
Personally I find CFL's a much more dangerous threat than mercury tubes and I can categorically state that 3B28's are inferior sounding to mercury I'd easily choose sand over the Xenon tubes.
dave
Personally I find CFL's a much more dangerous threat than mercury tubes and I can categorically state that 3B28's are inferior sounding to mercury I'd easily choose sand over the Xenon tubes.
dave
Interesting reference, thanks. Basically repeats all the info from this thread. The follow-up is also worth a read, except none of the articles really deal with the issue of breaking a hot MVR in operation.
Would you mind expanding on your comments re. the CFLs, please? Are you referring to numbers in operation versus the much rarer MVRs, or relative danger of a CFL versus a MVR?
One of the linked articles provides a reference for the Mercury content in a 816 rectifier, 0.5g. That tube has a quarter of the power handling capacity of an 866, but even then we can assume for argument's sake that the figure holds also for those. Since even a 'dirty' CFL contains only about 0.004g, 4mg, of Mercury, one would have to break 125 CFLs to release as much Mercury as is found in a single 816 (866?).
Newer CFLs are down to 1mg (0.001g) of Mercury per, making the relative breakage trouble of MVRs versus CFLs 500 to 1.
Home exercise for all: Find a dead power tube about the size of an EL34 or so, vacuum needs to be intact. Break the tube somewhere easy to clean up, after you have deposited a small pile of talc or similar fine powder on top of it. Notice spread of talc in air after tube breakage.
Explosive decompression of a hot MVR *will* spread microscopic drops of Mercury for a fair distance, and unfortunately it doesn't take much. This is one of those cases, where intuition breaks down a bit. Yes, the hot Mercury vapors will condense pretty quickly when meeting the much colder air, but by the formed droplets are microscopic and can still float quite far on the air currents in a room.
TL;DR: "Drunk driving is fine, I have been doing it for years without consequences."
- Frank.
Mercury...
Still use Mercury in dental-fillings here in UK....
My first dentist, when I was a kid, mixed the amalgam in the palm of his ungloved hand....
(Mind you--He was a little strange....)
Whilst I agree the mercury is dangerous, we mustn't forget that its been used for many years in all sorts of industries--Including medical....
I used to play with the stuff when I was a kid, --still got a bottle of about 5Kgs in the garage somewhere....
Its like everything else, Know the risks, and take appropriate safeguards....
As to MVR being noisy, I dont know, not used one in an amp--but I used a large 100A 50V mercury rectifier as part of a cinema arc supply.
--HUGE it was, like a hideously de-formed baby that glowed bright purple, like summit from Frankensteins lab!
--This was within 2 feet of the soundhead and pre-amp of the projector, and used all tube technology, EF37A as the first gain-stage...
No apparent 'noise' pick-up from rec was ever noticed....
I know of a cinema still using the original 1930's mercury arc rec, modified to run a Xenon bulb, still going strong, its set into what looks like a safe in the rear projection-room wall, made by 'Hewittic' as I recall....
Still use Mercury in dental-fillings here in UK....
My first dentist, when I was a kid, mixed the amalgam in the palm of his ungloved hand....
(Mind you--He was a little strange....)
Whilst I agree the mercury is dangerous, we mustn't forget that its been used for many years in all sorts of industries--Including medical....
I used to play with the stuff when I was a kid, --still got a bottle of about 5Kgs in the garage somewhere....
Its like everything else, Know the risks, and take appropriate safeguards....
As to MVR being noisy, I dont know, not used one in an amp--but I used a large 100A 50V mercury rectifier as part of a cinema arc supply.
--HUGE it was, like a hideously de-formed baby that glowed bright purple, like summit from Frankensteins lab!
--This was within 2 feet of the soundhead and pre-amp of the projector, and used all tube technology, EF37A as the first gain-stage...
No apparent 'noise' pick-up from rec was ever noticed....
I know of a cinema still using the original 1930's mercury arc rec, modified to run a Xenon bulb, still going strong, its set into what looks like a safe in the rear projection-room wall, made by 'Hewittic' as I recall....
You reminded me of an amalgum filling I have. A quick google suggests it is still in widespread use.
If I remember correctly, the practical difference with the mercury rectifier is its impedance. Once it strikes it conducts very well and is susceptible to the circuit trying to draw too much current.
In a general sense, this makes them more suited to class B amps with their variable current draw, and less to class A amps where the source resistance is exploited in reducing ripple.
If I remember correctly, the practical difference with the mercury rectifier is its impedance. Once it strikes it conducts very well and is susceptible to the circuit trying to draw too much current.
In a general sense, this makes them more suited to class B amps with their variable current draw, and less to class A amps where the source resistance is exploited in reducing ripple.
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