1. Could I parallel the plates of a full-wave rectifier to make a half-wave
rectifier with double the current capacity?

2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a single
rectifier tube?

3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?

4. What are the restrictions and caveats?

Thanks in advance,

Jon

"Jon Yaeger" wrote in message
...
1. Could I parallel the plates of a full-wave rectifier to make a
half-wave
rectifier with double the current capacity?

2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a single
rectifier tube?

3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?

4. What are the restrictions and caveats?

Thanks in advance,

Jon

Hi Jon,
I would like to attempt to answer one of those questions. There are many
more Rodents who are better able to answer the rest. No matter how many tube
rectifiers you use, it is primarily the wire size in the transformer that
will ultimately determine the current capability.
Cordially,
west

On Sat, 17 Sep 2005 15:51:53 -0400, Jon Yaeger
wrote:

1. Could I parallel the plates of a full-wave rectifier to make a half-wave
rectifier with double the current capacity?

Sure. It's good practice to include small series
resistors to equalize plate currents.

2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a single
rectifier tube?

Perzactly.

3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?

Somewhat less, but more than half. For typical devices,
maybe 15 volts, but somewhere in that range.

4. What are the restrictions and caveats?

For common oxide cathode bottles with 10 or 15 watt
heaters/ filaments equalizing resistors might be
in the 20 to 50 ohm range, something like that.

Good fortune,

Chris Hornbeck

"Jon Yaeger" wrote in message
...

Jon scribbled;

1. Could I parallel the plates of a full-wave rectifier to make a
half-wave
rectifier with double the current capacity?

2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a single
rectifier tube?

3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?

4. What are the restrictions and caveats?

Thanks in advance,

Jon

Using two rectifier tubes was very comon in A lot of theatre amps, The
Altec 256 A
used a pair of 5R4s in this 75 W amp. My Dear old dad used A pair of WE
421 ??
in his 75 W amp......if you are concerned about voltage drop , why not
use SS ??
...............GC

"Jon Yaeger"

1. Could I parallel the plates of a full-wave rectifier to make a
half-wave
rectifier with double the current capacity?


** Yep.

2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a single
rectifier tube?

** Yep.


3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?


** Situation #2 is not described adequately.


4. What are the restrictions and caveats?


** If one tube stops working, or goes missing - trouble.

The remaining tube cops a big overload and may fail.

Since the supply is then half wave, the PT's iron core will saturate and
cause a high primary current flow.

Too much heat in the primary will make the smoke come out.




.......... Phil

Phil Allison wrote:
"Jon Yaeger"

1. Could I parallel the plates of a full-wave rectifier to make a
half-wave
rectifier with double the current capacity?


** Yep.

2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a single
rectifier tube?

** Yep.


3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?


** Situation #2 is not described adequately.


4. What are the restrictions and caveats?


** If one tube stops working, or goes missing - trouble.

The remaining tube cops a big overload and may fail.

Since the supply is then half wave, the PT's iron core will saturate and
cause a high primary current flow.

Too much heat in the primary will make the smoke come out.


For perhaps this reason it was common practice to parallel rectifier
tubes by using one plate on each tube for one winding and the other for
the other.

But it's simpler today to avoid use of rectifier tubes unless you are
building for nuclear war. Rectifier tubes DO NOT constitute a delayed
warm up system. And theories of better sound due to lack of transient
pulses have been largely disproved, at least in competently designed
equipment. Proper layout and bypassing of electrolytics combined with
judicious use of RF chokes are radically superior.

in article , west at
wrote on 9/17/05 6:54 PM:

"Jon Yaeger" wrote in message
...
1. Could I parallel the plates of a full-wave rectifier to make a
half-wave
rectifier with double the current capacity?

2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a single
rectifier tube?

3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?

4. What are the restrictions and caveats?

Thanks in advance,

Jon

Hi Jon,
I would like to attempt to answer one of those questions. There are many
more Rodents who are better able to answer the rest. No matter how many tube
rectifiers you use, it is primarily the wire size in the transformer that
will ultimately determine the current capability.
Cordially,
west


Thanks, West.

Yes and no. Everything "downstream" from the rectifier depends upon its
current rating. If your tranny windings are rated at 200 ma and you have a
100 ma rectifier, but your circuit draws 150 ma, you've got a problem.

in article , Chris Hornbeck at
wrote on 9/17/05 7:19 PM:

On Sat, 17 Sep 2005 15:51:53 -0400, Jon Yaeger
wrote:

1. Could I parallel the plates of a full-wave rectifier to make a half-wave
rectifier with double the current capacity?

Sure. It's good practice to include small series
resistors to equalize plate currents.

2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a single
rectifier tube?

Perzactly.

3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?

Somewhat less, but more than half. For typical devices,
maybe 15 volts, but somewhere in that range.

4. What are the restrictions and caveats?

For common oxide cathode bottles with 10 or 15 watt
heaters/ filaments equalizing resistors might be
in the 20 to 50 ohm range, something like that.

Good fortune,

Chris Hornbeck


Chris,

Thanks for your reply. I plan to use indirectly heated cathodes (e.g.
6AX5GT). Would that change the resistor requirements?

Jon

"Accessory Section 8"
Phil Allison wrote:


** If one tube stops working, or goes missing - trouble.

The remaining tube cops a big overload and may fail.

Since the supply is then half wave, the PT's iron core will saturate and
cause a high primary current flow.

Too much heat in the primary will make the smoke come out.


For perhaps this reason it was common practice to parallel rectifier
tubes by using one plate on each tube for one winding and the other for
the other.


** It would seem to be the safer option.


But it's simpler today to avoid use of rectifier tubes unless you are
building for nuclear war. Rectifier tubes DO NOT constitute a delayed
warm up system.


** Huh ????

If SS diodes are used, then electros can be overvoltaged at switch on - no
so with a tube rectifier.

Plus, the internals can be at dangerously high voltages even with all tubes
pulled out - something that might bother some home constructors and
novices.




............ Phil

"Jon Yaeger" wrote in message
...
in article , west at
wrote on 9/17/05 6:54 PM:

"Jon Yaeger" wrote in message
...
1. Could I parallel the plates of a full-wave rectifier to make a
half-wave
rectifier with double the current capacity?

2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a
single
rectifier tube?

3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?

4. What are the restrictions and caveats?

Thanks in advance,

Jon

Hi Jon,
I would like to attempt to answer one of those questions. There are many
more Rodents who are better able to answer the rest. No matter how many
tube
rectifiers you use, it is primarily the wire size in the transformer
that
will ultimately determine the current capability.
Cordially,
west


Thanks, West.

Yes and no. Everything "downstream" from the rectifier depends upon its
current rating. If your tranny windings are rated at 200 ma and you have
a
100 ma rectifier, but your circuit draws 150 ma, you've got a problem.

Of course Jon. That's why I didn't want to get into the load because of the
many issues to consider there and I simply do not have that much expertise
with tube loads. I didn't see at the time any answers to your query so I
thought, lets give it a crack.
west

On Sat, 17 Sep 2005 22:27:09 -0400, Jon Yaeger
wrote:

I plan to use indirectly heated cathodes (e.g.
6AX5GT). Would that change the resistor requirements?

Well, it's just a matter of conservative engineering,
and is independent of the devices. You'd want to
make the same provisions paralleling *any* devices,
and in any application.

My only (poorly) expressed exception might be for
exotic valve rectifiers, like thoriated-tungsten
filaments and such. The trouble with Usenet is the
inability to properly weight "footnote" comments.

Anyhoo, fear not. 'S all good.

And, FWIW, in conservative useage, the equalizing
resistors are often skipped. Not that big a biggie.
IIRC, the cost-more-than-my-house Ongaku didn't
bother.

Good fortune,

Chris Hornbeck

Jon Yaeger wrote:

1. Could I parallel the plates of a full-wave rectifier to make a half-wave
rectifier with double the current capacity?

Yes.



2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a single
rectifier tube?

Yes you may.



3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?

Less voltage drop.



4. What are the restrictions and caveats?

Cheaper to use some silicon,
and some series R to limit charge currents into the C1 of the PS.



Patrick Turner.



Thanks in advance,

Jon

Phil Allison wrote:

"Accessory Section 8"
Phil Allison wrote:


** If one tube stops working, or goes missing - trouble.

The remaining tube cops a big overload and may fail.

Since the supply is then half wave, the PT's iron core will saturate and
cause a high primary current flow.

Too much heat in the primary will make the smoke come out.


For perhaps this reason it was common practice to parallel rectifier
tubes by using one plate on each tube for one winding and the other for
the other.

** It would seem to be the safer option.

But it's simpler today to avoid use of rectifier tubes unless you are
building for nuclear war. Rectifier tubes DO NOT constitute a delayed
warm up system.

** Huh ????

If SS diodes are used, then electros can be overvoltaged at switch on - no
so with a tube rectifier.

Nearly all well made tube radios and amplifiers are made using
capacitors able to take a high surge voltage or a voltage equal to the
unloaded B+ for some considerable time because they don't want
the elcaps to blow if an output tube or two go open
thus allowing the B+ to soar to a higher than usual value.

In a recent rebuild of a pair of Quad II I used silicon rectifiers each with
current limiting R in series, then 100uFx 450VW rated, then 100 ohms, then the
GZ32 was used as
a slow turn on diode-resistor equal to about 80 ohms with both halves in
parallel,
then a 470uF cap also rated for 450VW and to anchor the CT.
The usual ripple voltage at the CT in the original rubbishy PS that
QuadII had was about 17Vrms, but with my arrangement
there is around 100mV, so the PS caused IMD is far less than the THD from the
tubes
at all levels to clipping.
( The original amps have about as much IMD in the N&D character as the THD
even in class A.)
There is actually no need to retain the use of the tube rectifier at all
and a simple resistor in place of what i did will work just as well since
the slow turn on really conveys no real useful delay, especially
when the KT66 age and they take longer to come on.
But for appearances i retained the GZ32 this time,
but where people don't mind the missing tube, then the rectifier socket can be
removed and the
470uF cap can be placed on the chassis top to replace the tube
and there is more room under the chassis for the rest of the mods.
The amp will run cooler this way.

In practice, at turn on, even indirectly heated rectifiers come on faster than
output tubes, so some voltage
soaring occurs anyway.
In many amps the tube rectifiers are directly heated and the B+
soars to the same voltage as with SS rectifiers in about 4 seconds, before
sagging back due to the combined effects of the power tranny
winding resistances, diode resistances, and choke/resistor drops.

Plus, the internals can be at dangerously high voltages even with all tubes
pulled out - something that might bother some home constructors and
novices.

Traps do exist for the unwary who never assume there will
be issues which will trip them up due to an incomplete knowledge of their
activities......

Patrick Turner.



........... Phil

Jon Yaeger wrote:

1. Could I parallel the plates of a full-wave rectifier to make a half-wave
rectifier with double the current capacity?

No. Not unless it also has _two cathodes_ to put in parallel.

2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a single
rectifier tube?

No but you could put the two full-wave devices in parallel. Small
resistors in the anodes to equalise current are advisable.

3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?

Same.


best

Andy

in article , Andy Cowley at wrote
on 9/21/05 11:32 AM:

Jon Yaeger wrote:

1. Could I parallel the plates of a full-wave rectifier to make a half-wave
rectifier with double the current capacity?

No. Not unless it also has _two cathodes_ to put in parallel.

2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a single
rectifier tube?

No but you could put the two full-wave devices in parallel. Small
resistors in the anodes to equalise current are advisable.

3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?

Same.


best

Andy


Andy,

Thanks for your reply.

I've received about 3 yes answers to your no.

Why couldn't I parallel the anodes in a single tube??

Would would be a typical value (including wattage) of an equalizing
resistor, say, for a 5AR4?

Thanks in advance,

Jon

"flipper"

Why couldn't I parallel the anodes in a single tube??

I imagine he's thinking of the peak cathode current that would need to
double with the anodes in parallel and, so, then being on the same
phase


** Which popular rectifier tube has two anodes and only one common)
cathode ?




............ Phil

On Wed, 21 Sep 2005 15:32:15 GMT, Andy Cowley
wrote:

1. Could I parallel the plates of a full-wave rectifier to make a half-wave
rectifier with double the current capacity?

No. Not unless it also has _two cathodes_ to put in parallel.

It would be difficult and very inefficient to make
one *without* two cathodes.

2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a single
rectifier tube?

No but you could put the two full-wave devices in parallel. Small
resistors in the anodes to equalise current are advisable.

BZZT.

3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?

Same.

BZZT.

Thanks for playing,

Chris Hornbeck

"flipper"


It would be difficult and very inefficient to make
one *without* two cathodes.

GE 6X5-GT



** Each plate structure of a 6X5 "sees" only half the cathode.

So it *effectively* has two.

Paralleling the plates will double the current capacity - peak and
average.



.............. Phil

"flipper"
"Phil Allison"



** Which popular rectifier tube has two anodes and only one common)
cathode ?

What the heck does 'popularity' have to do with it?



** Obscure types are simply not relevant to the the issue here.




............. Phil

"flipper"
"Phil Allison"


It would be difficult and very inefficient to make
one *without* two cathodes.

GE 6X5-GT


** Each plate structure of a 6X5 "sees" only half the cathode.

If you say so.


** It does, whether I say it or not.


So it *effectively* has two.

Perhaps, but that wasn't the question.


** It is completely germane to the *issue*.



Paralleling the plates will double the current capacity - peak and
average.


......... Phil

"flipper"
"Phil Allison"


** Which popular rectifier tube has two anodes and only one common)
cathode ?

What the heck does 'popularity' have to do with it?



** Obscure types are simply not relevant to the the issue here.

Nonsense.

** Go **** yourself - **** brain.




............. Phil

Jon Yaeger wrote:

in article , Andy Cowley at wrote
on 9/21/05 11:32 AM:


Jon Yaeger wrote:


1. Could I parallel the plates of a full-wave rectifier to make a half-wave
rectifier with double the current capacity?


No. Not unless it also has _two cathodes_ to put in parallel.


2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a single
rectifier tube?

No but you could put the two full-wave devices in parallel. Small
resistors in the anodes to equalise current are advisable.

3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?


Same.


best

Andy



Andy,

Thanks for your reply.

I've received about 3 yes answers to your no.

Why couldn't I parallel the anodes in a single tube??

Would would be a typical value (including wattage) of an equalizing
resistor, say, for a 5AR4?

Thanks in advance,


There is a single cathode in most full-wave rectifiers (there
are a few exceptions - e.g. 5690) so if you parallel the anodes
you will double the current in the cathode. In normal full wave
operation the current is flowing alternately to the anodes and
the cathode current is usually pretty close to the real limit.
You will be exceeding the cathode max current rating in most
cases even though on average there will be no excess current
through the tube as it gets a half cycle rest during each cycle.
In the case of a 5AR4 you will still be within the absolute max.
cathode current but I would expect the tube to wear out and
loose emision _much_ more quickly.

You can parallel the tubes by using each as a full wave rectifier,
both tubes will be conducting on every half cycle and the peak
cathode current will be halved compared to using each tube as a
half wave rectifier.

The resistor value you need will depend on the dynamic impedance
of the tube at the operating point. That is the slope of the
current vs. tube voltage drop curve. I'd guess around 100 ohms
(the recommended protective resistance at 400 V RMS in) would
be good. Dissipation will be close to a watt so 2W components
should be fine.


best

Andy

"Andy Cowley"

There is a single cathode in most full-wave rectifiers...


** What mind bending drugs are you on - ****wit ??

The direct, bloody opposite is true.


( snip mucho absolute crap)



In the case of a 5AR4 you will still be within the absolute max.


** The 5AR4 has TWO CATHODES !!!!!!!!!!!!!

What drugs are you on - ****wit ???



You can parallel the tubes by using each as a full wave rectifier,
both tubes will be conducting on every half cycle and the peak
cathode current will be halved compared to using each tube as a
half wave rectifier.


** Based on this same pommy idiot's previous whacko assertions.

( snip even worse verbal diarrhoea. )


**** off - you PITA limey bloody idiot !!!!





........... Phil

"flipper" wrote in message
...
: On Thu, 22 Sep 2005 15:47:39 +1000, "Phil Allison"
: wrote:
:
:
: "flipper"
: "Phil Allison"
:
:
: ** Which popular rectifier tube has two anodes and only one common)
: cathode ?
:
: What the heck does 'popularity' have to do with it?
:
:
:
: ** Obscure types are simply not relevant to the the issue here.
:
: Nonsense.
:
: ** Go **** yourself - **** brain.
:
:
: My, my, my, but you do fall all to pieces when your little 'gotcha'
: games don't work.
:
Ok, *here* i can agree with you
R.

Jon Yaeger wrote:

1. Could I parallel the plates of a full-wave rectifier to make a half-wave
rectifier with double the current capacity?

2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a single
rectifier tube?

3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?

Will not be 1/2 of 25 volts since the conduction depends on the '3/2' power law.
Probably something like 18 volts. Where is my HP67 when I need it?

4. What are the restrictions and caveats?

Thanks in advance,

Jon

Here is what Terman has to say.

"Parallel Operation of Rectifiers- High Vacuum Rectifiers may be operated in
parallel without any particular precautions other then ensuring that the units
in parallel are reasonably similar in characteristics"

For a bit of a margin of safety I would derate to perhaps 80% of rated capacity
in order to account for dis-similarity in the tubes used.

Cheers, John Stewart

John Stewart wrote:

Jon Yaeger wrote:

1. Could I parallel the plates of a full-wave rectifier to make a half-wave
rectifier with double the current capacity?

2. Could I then not put two such half-wave devices in a full-wave
configuration, and thus double the original current capacity of a single
rectifier tube?

3. If the nominal voltage drop was 25V through a single full-wave
rectifier, what would be the voltage drop across situation #2 above?

Will not be 1/2 of 25 volts since the conduction depends on the '3/2' power law.
Probably something like 18 volts. Where is my HP67 when I need it?

Found it. The HP67, that is. If the rectifiers are identical the drop will be 15.7
volts when connected as in your example. JLS

BTW, there is a large set of rectifier static drops given on page 1171 of RDH4.
Unfortunately, the 6AX5 is not included.

4. What are the restrictions and caveats?

Thanks in advance,

Jon

Here is what Terman has to say.

"Parallel Operation of Rectifiers- High Vacuum Rectifiers may be operated in
parallel without any particular precautions other then ensuring that the units
in parallel are reasonably similar in characteristics"

For a bit of a margin of safety I would derate to perhaps 80% of rated capacity
in order to account for dis-similarity in the tubes used.

Cheers, John Stewart