mercury vapor... i love it!!!

[HollowState]

The real risk involving using MV rectifier would be breaking the tube while operating (hot) which would cause contamination of the room with mercury vapors -nasty perspective .One would have to abandon the listening room for a couple -few years .

While this is an extreme case, and easily preventable, I'd be more concerned about starting a fire were this to actually happen.

The amount of mercury in a small tube rectifier like an 866 or 816 is relatively small. Since mercury loves to amalgamate with other metals, proper clean up would involve pouring powdered tin, or zinc over the spill. (copper, lead or silver would also work) The mercury will immediately become a solid and is easier to pick up as it is locked up in an amalgam and poses no threat.

We all know that mercury evaporates at room temperature. If no clean up were attempted, this small amount would dissipate in a matter of days or weeks. Not years. It would be necessary to ventilate the room for at least that long. And I've been told that mercury vapor can be detected with an ultra-violet light to cast it's shadow. I also believe there are inexpensive "sniffer" type testing devices available.

Never attempt to vacuum up raw mercury as this would only spread it around more making clean up much worse. And for a tiny spill as mentioned here, never get any government agency involved. They will exaggerate the situation way beyond reality making it your worst nightmare. Or so I've been told.

Victor

[limono]

Cool,
I'll keep agencies and authorities out of my tube affairs .I have a few types of MV rectifiers waiting to be used (Big WE M, 872, 866 , 83 , 82 ). One of old WE (forgot the type and don't want to dive into shelfs to check ) is a little foggy/gassy inside .Do you think its a problem ? Regards, L

[Jeb-D.]

Besides bling factor, why are some tubes charged with types of gasses? what are the performance benefits vs. regular vacuum?

[6f6]

If you want to have a pretty light display on your amplifier, you can resort to VR tubes (0A2, 0C3, 0D3). They serve a useful purpose and they look nice too.

[HollowState]

Besides bling factor, why are some tubes charged with types of gasses? what are the performance benefits vs. regular vacuum?

Two main reasons. Heaver current capability and lower voltage drop.

[kevinkr]

Originally posted by Jeb-D.
Besides bling factor, why are some tubes charged with types of gasses? what are the performance benefits vs. regular vacuum?

Hi Jeb,
If you are talking about mercury vapor rectifiers the mercury vapor lowers the voltage drop across the tube to typically 15V or less and at quite high currents in some cases.

They also exhibit a relatively constant drop over large swings in load current resulting in much better voltage regulation with variable loads. (Like big class B amplifiers.)

Some damper tubes are nearly as good at currents below roughly 1A, 5AR4 will manage 25 - 30V at 250mA..

Mercury rectifiers are right perty to look as long as you don't get one made with quartz glass which does not block UV. (Rare)

[7N7]

Originally posted by limono
Cool,
I'll keep agencies and authorities out of my tube affairs .I have a few types of MV rectifiers waiting to be used (Big WE M, 872, 866 , 83 , 82 ). One of old WE (forgot the type and don't want to dive into shelfs to check ) is a little foggy/gassy inside .Do you think its a problem ? Regards, L

Mercury vapour rectifiers must be warmed up before HT is applied.

When they have not been used for a long time, the standard recommendation is that they be warmed up for about 30 minutes. Once this has been done and provided they are used regularly a few minutes is enough.


7N7

[Jeb-D.]

So, Kevin and HollowState. Do you know if a tube has to be designed from the ground up for gas or can conventional tubes be charged with it? Also, does it only apply to diodes?

In otherwords can I take some of my favorite triodes and have them charged with Xenon (obviously MV is wouldn't be do-able). And have the behave like on Steroids?

Like say, a 6c33c that can pass 1A+ continuous with a lower Rp. If you know what I'm getting at.

If it may be a worthwhile experiment, I may have the resources to try it, and the amp to try it in

[HollowState]

One of old WE (forgot the type and don't want to dive into shelfs to check ) is a little foggy/gassy inside .Do you think its a problem ? Regards, L

Difficult to say without knowing more. Some rectifiers that contain mercury, and are old, may have some amount of air due to a compromised vacuum. In others, the mercury may not condense totally when cool. One way to help judge is to light the filament and watch what happens inside. Normally the mercury will vaporize and slowly coat the inside making it more opaque. If the filament seems to light very dim it may have air inside. If it smokes it definitely has air.

I've seen tubes, mostly transmitting types, that were air bottles and the filament had smoked giving the inside an ugly yellowish color.

Something to be very cautious of when using NOS American 866's (RCA, Sylvania, etc) from the 60's and 70's is they can short out when first powered up. These tubes had a coating on the plate and body surrounding the cathode that would peel off and flake when first heated up. This applies mainly when they haven't been used in a long time and mostly to the fatter bulb style, as compaired to the slim types of later production. These flakes would find their way between the plate and cathode structure and the tube would short, often with dramatic results.

If anyone has these old rectifiers, look for an orange peel texture to the coating on the elements. This is a dead giveaway. But I've seen perfectly smooth coatings wrinkle and peel too. With these old dogs, it's always best to heat them up and test with low voltage before using them. This also applies to old 872's as well. Voice of experience here.

Victor

[HollowState]

Do you know if a tube has to be designed from the ground up for gas

Yes.

In otherwords can I take some of my favorite triodes and have them charged with Xenon (obviously MV is wouldn't be do-able). And have the behave like on Steroids?

Absolutely not. You would ruin the tube and turn it into fast acting switch, like a thyratron.