[John Frake]

I am designing and building a px25 class A amp, given the simplicity of the circuitry design may be an overstatement however I would like to use the 83 Mercury Vapour Rectifier. I am unsure about the need to heat the filament before applying 350V AC to the rectifier's anodes. Data sheets on the 866A are quite specific "no HT before a warm-up period" howver I can find no such warnings in any of my info on the 83. Does anyone have any information or experience of using this rectifier that they could pass on?

Regards

john

[Peter Wieck]

John wrote:
I am designing and building a px25 class A amp, given the simplicity of the circuitry design may be an overstatement however I would like to use the 83 Mercury Vapour Rectifier. I am unsure about the need to heat the filament before applying 350V AC to the rectifier's anodes. Data sheets on the 866A are quite specific "no HT before a warm-up period" howver I can find no such warnings in any of my info on the 83. Does anyone have any information or experience of using this rectifier that they could pass on?

Regards

john

The 83 is a low-loss mercury rectifier with no worries as to the
rectifier itself when AC hits it. The 866A is a half-wave rectifier,
the 83 a full wave, so apart from their construction differences, they
are functionally different beasts as well.

Apart from all that, _why_ would you use an 83? Looks? Two diodes and
two resistors (if installed in a 4-pin socket) will do the trick at a
much lower load on your transformer. Two diodes alone if directly
in-circuit. The only application I have seen for them commonly are in
(mostly Hickok) tube testers, and of those, most I have seen have the
SS replacement as noted. Hickok wanted the low loss and stability of
the 83 in the days before reliable silicon came along, and the dangers
of mercury were not well known. Add to this, it is a troublesome tube
given to slow failure. Today there is no earthly reason for such a
tube.

Peter Wieck
Wyncote, PA

[Alan Douglas]

Hi,
The 83 was originally designed for radios with class-B output
stages in 1932. It was not pre-heated in that application, and
presumably they got away with it. However class B had a very short
vogue and the 83 went out of use within a year. If it hadn't been for
Hickok rediscovering it, 83s would be as rare now as 82s are.

The 83 would be a poor choice of rectifier, because it produces RF
hash that needs to be filtered out of the B+, and also because it is
very prone to arcover from line transients. If you do use it, a line
fuse is absolutely necessary. Hickok can get away with using the 83
since the the B+ is only 150V in a tube tester. Likewise the lack of
preheat, since no current flows until the Test button is pushed.

Alan

[GerryE123]

John Frake wrote in message ...
I am designing and building a px25 class A amp, given the simplicity of the
circuitry design may be an overstatement however I would like to use the 83
Mercury Vapour Rectifier. I am unsure about the need to heat the filament
before applying 350V AC to the rectifier's anodes. Data sheets on the 866A
are quite specific "no HT before a warm-up period" howver I can find no
such warnings in any of my info on the 83. Does anyone have any
information or experience of using this rectifier that they could pass on?

Hi John:

Peter and Alan gave you all the technical reasons not to use the 83. All I
can tell you is that my amp uses the 83 and it's easily one of the best amps
I have heard. It's a single-ended 45 amp that I purchased from a friend.
He had it custom built with top quality parts. A number of years back, my
friend brought the amp to one of the NY Noise shows and he thought it was
one of the best amps at the show. Below are two links to photos of the amp.
In the second photo, you will see two toggle switches on the back of the
amp. One is for AC and the other is for B+. After turning on the AC
switch, I wait a minimum of 5 minutes (usually longer), before I turn on the
B+.

http://i27.photobucket.com/albums/c1...123/set45a.jpg

http://i27.photobucket.com/albums/c1...123/set45b.jpg

Gerry

[Bob H.]

Hi Gerry

Nice amp. What kind of 45's are those? They seem pretty big.

Bob H.

[Ned Carlson]

Peter Wieck wrote:

John wrote:

I am designing and building a px25 class A amp, given the simplicity of the circuitry design may be an overstatement however I would like to use the 83 Mercury Vapour Rectifier. I am unsure about the need to heat the filament before applying 350V AC to the rectifier's anodes. Data sheets on the 866A are quite specific "no HT before a warm-up period" howver I can find no such warnings in any of my info on the 83. Does anyone have any information or experience of using this rectifier that they could pass on?

Regards

john


The 83 is a low-loss mercury rectifier with no worries as to the
rectifier itself when AC hits it. The 866A is a half-wave rectifier,
the 83 a full wave, so apart from their construction differences, they
are functionally different beasts as well.

Apart from all that, _why_ would you use an 83? Looks? Two diodes and
two resistors (if installed in a 4-pin socket)

Using a resistor defeats the idea of the 83, 83's, like other
gas tubes, have a (relatively) constant voltage drop.



--
Ned Carlson
SW side of Chicago, USA
www.tubezone.net

[Johnystardust]

Fristly thank you to all of you for the replies. My reason for using the 83 is basically low voltage drop, looks, novelty value and that I have 4 of them. I will use Rf chokes to filter out the hash. I know my reasons are not all very objective but then neither are PX25 Se amps. I have a 350- 320-0-320-350 volts MT and can use a seperate 5.3v 3A transformer for the 83 heater if necessary. If 83s are as unreliable as suggested I may decide to switch to a 5U4G or 5AR4 or GZ32.

Thanks again for the comments


john



On 10/07/2006 00:19:45 Alan Douglas adouglasatgis.net wrote:

Hi, The 83 was originally designed for radios with class-B output stages
in 1932. It was not pre-heated in that application, and presumably they
got away with it. However class B had a very short vogue and the 83 went
out of use within a year. If it hadn't been for Hickok rediscovering it,
83s would be as rare now as 82s are.

The 83 would be a poor choice of rectifier, because it produces RF hash
that needs to be filtered out of the B+, and also because it is very prone
to arcover from line transients. If you do use it, a line fuse is
absolutely necessary. Hickok can get away with using the 83 since the the
B+ is only 150V in a tube tester. Likewise the lack of preheat, since no
current flows until the Test button is pushed.

Alan

[Johnystardust]

Thats a very pretty amp with avery unusual layout. Much impressed. I have a few 45s I am try them later. have some VT52s but they are going to fund this amp. Some decisions are hard!

regards

john

On 10/07/2006 03:40:35 "GerryE123" wrote:

I am designing and building a px25 class A amp, given the simplicity of

the circuitry design may be an overstatement however I would like to use
the 83 Mercury Vapour Rectifier. I am unsure about the need to heat the
filament before applying 350V AC to the rectifier's anodes. Data sheets
on the 866A are quite specific "no HT before a warm-up period" howver I
can find no such warnings in any of my info on the 83. Does anyone have
any information or experience of using this rectifier that they could
pass on?

Hi John:

Peter and Alan gave you all the technical reasons not to use the 83. All
I can tell you is that my amp uses the 83 and it's easily one of the best
amps I have heard. It's a single-ended 45 amp that I purchased from a
friend. He had it custom built with top quality parts. A number of years
back, my friend brought the amp to one of the NY Noise shows and he
thought it was one of the best amps at the show. Below are two links to
photos of the amp. In the second photo, you will see two toggle switches
on the back of the amp. One is for AC and the other is for B+. After
turning on the AC switch, I wait a minimum of 5 minutes (usually longer),
before I turn on the B+.

http://i27.photobucket.com/albums/c1...123/set45a.jpg

http://i27.photobucket.com/albums/c1...123/set45b.jpg

Gerry

[Peter Wieck]

GerryE123 wrote:

http://i27.photobucket.com/albums/c1...123/set45a.jpg

http://i27.photobucket.com/albums/c1...123/set45b.jpg

NICE Eye-Candy in an industrial no-nonsense sort of way.

"Looks" are a perfectly acceptable reason for choosing a tube. But as
Alan stated, be sure to use a line fuse _AND_ when the 83 begins to
crap out, expect all sorts of strange behavior. At the end of its life,
it will start off perfectly nicely, but an hour or two start to
degrade, finally to nothing at all. As it gets closer and closer to
final death (and assuming no spectacular failures), that delay will
become shorter and shorter. Of course, this will not show up on a tube
tester, because one is unlikely to leave it under test for the
necessary time.

Peter Wieck
Wyncote, PA

[Johnystardust]

Thanks for the advice, if the HT drain is about 120Ma I will start with a 250ma quick blow fuse and adjust if necessary

regaatds

John

On 10/07/2006 14:51:04 "Peter Wieck" wrote:

GerryE123 wrote:

http://i27.photobucket.com/albums/c1...123/set45a.jpg

http://i27.photobucket.com/albums/c1...123/set45b.jpg

NICE Eye-Candy in an industrial no-nonsense sort of way.

"Looks" are a perfectly acceptable reason for choosing a tube. But as
Alan stated, be sure to use a line fuse _AND_ when the 83 begins to crap
out, expect all sorts of strange behavior. At the end of its life, it
will start off perfectly nicely, but an hour or two start to degrade,
finally to nothing at all. As it gets closer and closer to final death
(and assuming no spectacular failures), that delay will become shorter and
shorter. Of course, this will not show up on a tube tester, because one
is unlikely to leave it under test for the necessary time.

Peter Wieck Wyncote, PA

[GerryE123]

"Bob H." wrote in message
ps.com...

Hi Gerry

Nice amp. What kind of 45's are those? They seem pretty big.

Bob H.

Thanks Bob and John.

Bob - those are EML solid-plate 45s. They are currently the "hot" 45 in the
market. People seem to prefer them to the EML mesh-plate 45s. Some people
also like the TJ pseudo "mesh-plate" 45s. A few of us have compared the
EMLs to old stock 45s and depending on which brand of old-stock 45s were
used, the EMLs were either a little or much better.

I recently did get to do a brief comparison of my amp to a 2 -3 times more
expensive Tucker/Exemplar SE 45 and my amp was at least as good in every
parameter except where it blew away the T/E in the low frequencies. Below
is one more link to my amp showing the underside. As you can see, clean and
simple. Also, the built in attenuators allow for direct source connection.

http://i27.photobucket.com/albums/c1...123/set45c.jpg

Gerry

[Bob H.]

It's nice to see 45's being made. I think I'll convert my test amp to
45's after sampling 2a3's. I've used 45's as a line driver in a
ultrapath line amp (ala Jack Elliano), I ran a 27, a 26, a 6sn7. All
were nice tubes, but the 45 was easily the best one by far. It was
lightning fast, had great depth, great bass, and great highs.
Luckily I stocked up on them years ago, so no worries there.

Enjoy
Bob H.