Using 866A Mercury Vapour Rectifiers?

[fdegrove]

Ola hombre,

On this particular occasion I advised this type of filtering.
On any rectifier tube you will have the recommend value of input cap given by the manufacturer.

Generally,nothing against CLC filtering.
You should try a choke with your preamp for a sonic blast away experience.

Brett,

Send some "poulet roti" my way please!
Not polluted by mercury if possible?

Buenas noches,

Paco

[Brett]

Originally posted by fdegrove
Ok Brett ,if you know what you're doing,then fine.

I seldom know what I'm doing. The more I learn the less I know, and the more I accept.

The info I shared is from sleeping whith the RCA secretaries.
You can call that anecdotal for sure.

Whatever you want to call it, it sounds like a lot more fun than reading the manuals.
I also have a lot of jokes about, special tube handling proceedures, red hot anodes and appropriate mountings, but I won't mention them here or the fuddy-duddy's will have apoplexy.

The Freddy M. tubes' low internal impedance is something of little importance to me.Not necessarily a blessing.
I always try to depend on very good PSU regulation where called for so that I do not depend on the capabilties of transformer and rectifiers to respond immediately to current demands.

Agree, adding a good shunt reg is always beneficial

Seriously,I see a lot of people toying with tubes having read page one of the books and then complaining afterwards that things don't seem to turn out what they expected.

What, you mean I have to read a <i>whole</i> page of the manual?

As a general rule of thumb a tube is designed for a certain job and logic has it that when it can do more it can do less,right?
Well,with tubes this just doesn't hold up:there are working points that need to be respected or results can be unpredictable.
Sometimes you can get away with it,other times you face Mr.Murphy
Pretty soon you'll have someone using thyratrons to fire up their B+.....

Yes generally, but I was referring to the 6D22S, 6CJ3/6CH3, EY/PY500A type tubes, which for a typical tube pre or power are fine.

It was meant as a cautionary note.

Always wise.

Ciao

[fdegrove]

Hi Brett,

And you wonder why Grey is complaining about USA levels of education?
I could go on about that problem ad infinitum.Frustaaating!

Whatever you want to call it, it sounds like a lot more fun than reading the manuals.

Actually,I may surprise you here:I found the manuals far more interesting than these secretaries although we were all interested in tubes.

Now I should really hit the sack,5.49 AM here...

Ciao too,

[richt]

THANKS

PACO !

[jackinnj]

With mercury vapor rectifiers you should wait a minimum of 4 minutes warmup time before applying the high voltage. Hallicrafters actually says in the HT45 manual that 15 minutes is preferable (this is a solid kilowatt linear amp from the 1960's.)

The ARRL handbooks of the 1950s and 1960s often discussed the noise with mercury rectifieres.

[almarcy]

I have used 866A with good results.

Let the tubes stand upright for a week or so before applying filament power.

And KEEP them upright or start over!

Run the tubes on filaments only for a couple days before applying B+ for the first time.

Check the filament voltage and adjust as needed before applying B+.

Noise? I got no stinking noise

L-C-L-C filters work well.

Happy Ears!
Al

[martinab2]

I had always assumed that designers put mercury rectifiers in farady cages to limit the effects of the rf noise they produced, but if the following is true then maybe it was the other way round:

(RCA data sheet for 872 rectifier)

"Shields and rf filter circuits shuld be provided for the 872-A if it is subjected to extraneous high-frequency fields during operation. These fields tend to produce breakdown effects in mercury vapour and are detrimental to tube life and performance"

"Rf filters are employed to prevent damage caused by rf currents which might otherwise be fed back into the rectifier tubes"

[EC8010]

Thanks for the tip on the RCA 827-A data sheet, very informative. My understanding is that mercury vapour rectifiers have a negative resistance at part of their IV characteristic and that this can combine with the leakage inductance and stray capacitance of the mains transformer to produce a circuit that can oscillate if excited. Since the system is excited at a 50Hz (or 60Hz) rate, this can lead to squegging at a 50Hz rate. Ferrite beads are usually touted as the cure. The RSGB and ARRL manuals are good places to look for information on using these rectifiers.

[rcavictim]

Originally posted by Brett

Great,

I have some huge trannys that are specifically for the 866A, so I've thought about powering up the dozen 866As I have in front of a rotisserie, and cookin' me some audiophile grade chickens.
Hmmmm, so sweet in the middle.

Brett,

If you want serious DC for a transmitting tube power amp and ALSO want to cook chickens, forget Hg recifier tubes and just use microwave oven magnetrons as the rectifier diodes!