Westinghouse H-104 power supply
 

Looking for help on this one. Am I reading the schematic correctly - 265V
across the 5U4 filament, and 268V across the plate? I also notice that the
tap to the pilot lamps is not labeled, although I know from the parts list
that they are 6.3V.

I'm looking to replace the fried transformer, but I'm a bit in over my head
with regard to what to replace it with or whether to have it rewound.

Jeff

Westinghouse H-104 power supply
 

"Unrevealed Source" wrote in message
...
Looking for help on this one. Am I reading the schematic correctly - 265V
across the 5U4 filament, and 268V across the plate? I also notice that
the tap to the pilot lamps is not labeled, although I know from the parts
list that they are 6.3V.

I'm looking to replace the fried transformer, but I'm a bit in over my
head with regard to what to replace it with or whether to have it rewound.



No. The 268 volts is to each plate and chassis ground, and is AC. The 265
volts is available on either side of the filament, and is the B+ line going
into the first filter.

Westinghouse H-104 power supply
 

"Brenda Ann" wrote in message
...



No. The 268 volts is to each plate and chassis ground, and is AC. The 265
volts is available on either side of the filament, and is the B+ line
going into the first filter.



The filament voltage on your 5U4 is 5 volts (DC is pulled directly off the
filament (directly heated cathode))

Westinghouse H-104 power supply
 

The 268V to each plate I understand. What do you mean when you say 265V
"available" on either side of the filament? There is definitely output
from the transformer wired across the filament, but shouldn't that be 5V,
not 265V?

Unfortunately I don't have a working transformer to measure what's going on
with this.

Jeff


"Brenda Ann" wrote in message
...

"Unrevealed Source" wrote in message
...
Looking for help on this one. Am I reading the schematic correctly -
265V across the 5U4 filament, and 268V across the plate? I also notice
that the tap to the pilot lamps is not labeled, although I know from the
parts list that they are 6.3V.

I'm looking to replace the fried transformer, but I'm a bit in over my
head with regard to what to replace it with or whether to have it
rewound.



No. The 268 volts is to each plate and chassis ground, and is AC. The 265
volts is available on either side of the filament, and is the B+ line
going into the first filter.

Westinghouse H-104 power supply
 

Unrevealed Source wrote:
Looking for help on this one. Am I reading the schematic correctly -
265V across the 5U4 filament, and 268V across the plate?

You are interpreting it incorrectly.

The 268 volts you are seeing on each plate is 268 volts -AC- to ground; to
put it another way, you are looking at a transformer with a 268-0-268
volt secondary (or a transformer with a 536 volt *center-tapped* secondary).

The 265 volts you refer to is +265 volts -DC-, measured from the
filament (cathode) to ground. The voltage -across- the 5U4 filament is 5
volts AC, the filament voltage of a 5U4.

I also notice that the tap to the pilot lamps is not labeled,
although I know from the parts list that they are 6.3V.

Yes, this feeds 6.3 volts AC to the pilot lights and the filaments of
the other tubes.

Assuming that this radio is intended for use at (nominally) 115 VAC, you
will need a transformer with a 110-120 v primary, and the following
three secondaries: 500 volts center tapped (250-0-250), 6.3v and 5 v.

I'm looking to replace the fried transformer, but I'm a bit in over
my head with regard to what to replace it with or whether to have it
rewound.

Jeff

This is a fairly typical receiver transformer. Check the web site of
Antique Electronics Supply and Hammond Transformers. Look for one with
these approximate electrical characteristics and physical
characteristics that most closely match the existing one. Rewinding will
probably cost more than a new one.

By the very nature of your question, it indicates that you are a
beginner -- which is OK; we were all beginners at one time. Just be
careful; these voltages, if not fatal, can at least be harmful.

Needless to say, check the radio for other faults so as not to toast the
replacement transformer.

Merry Christmas and good luck!

Westinghouse H-104 power supply
 

"Carter-k8vt" wrote in message
t...

The 268 volts you are seeing on each plate is 268 volts -AC- to ground; to
put it another way, you are looking at a transformer with a 268-0-268
volt secondary (or a transformer with a 536 volt *center-tapped*
secondary).

I've got that part - thanks for confirming.

The 265 volts you refer to is +265 volts -DC-, measured from the filament
(cathode) to ground. The voltage -across- the 5U4 filament is 5 volts AC,
the filament voltage of a 5U4.

So I need to apply 5V AC across the filament (pins 2 and 8). That's
consistent with what my understanding would have been. And the 265V is
generated by the tube, correct? This would be a pulsed DC, would it not,
coming directly off the tube? In circuit, it is constant DC due to the
filter capacitors? Do I understand this correctly?

By the very nature of your question, it indicates that you are a
beginner -- which is OK; we were all beginners at one time. Just be
careful; these voltages, if not fatal, can at least be harmful.

Yes, relative to almost all of you, I am indeed a relative beginner. And
this is my first experience with a transformer/rectifier-based radio, so I
apologize if my questions are somewhat stupid.

Jeff

Westinghouse H-104 power supply
 

Unrevealed Source wrote:
"Carter-k8vt" wrote in message
t...

The 268 volts you are seeing on each plate is 268 volts -AC- to
ground; to put it another way, you are looking at a transformer
with a 268-0-268 volt secondary (or a transformer with a 536 volt
*center-tapped* secondary).

I've got that part - thanks for confirming.

Let me toss you a minor curve ball: If you were repairing this radio in
its era, you would indeed be looking for a replacement transformer with
approximately a 270-0-270 high voltage secondary winding; this is
because it was designed for 110 volts AC coming out of the socket on
your wall. Today, that voltage is 115 to 120 volts or even a bit higher
and using -today's- line voltage with a 270-0-270 winding would give you
a bit more than the 265 volts DC B+ that you are looking for. So, what I
am saying is that you could (should?) look for a transformer with a
220-0-220 or 250-0-250 high voltage winding; i.e. less (than 270-0-270)
is better.

The 265 volts you refer to is +265 volts -DC-, measured from the
filament (cathode) to ground. The voltage -across- the 5U4 filament
is 5 volts AC, the filament voltage of a 5U4.

So I need to apply 5V AC across the filament (pins 2 and 8). That's
consistent with what my understanding would have been.

Yes. That is why your replacement transformer needs a 5 volt secondary
winding (with enough current for a 5U4 filament).

And the 265V is generated by the tube, correct?

Yes, the tube changes (or 'rectifies') the 268 volts AC to 265 volts DC.

This would be a pulsed DC, would it not, coming directly off the
tube?

Yes.

In circuit, it is constant DC due to the filter capacitors?

Yes (and also due to a filter choke if one is present (rest of the
schematic is cut off).

Do I understand this correctly?

Yes.

By the very nature of your question, it indicates that you are a
beginner -- which is OK; we were all beginners at one time. Just be
careful; these voltages, if not fatal, can at least be harmful.

Yes, relative to almost all of you, I am indeed a relative beginner.
And this is my first experience with a transformer/rectifier-based
radio, so I apologize if my questions are somewhat stupid.

Jeff

Nope, not stupid. Again, we were ALL beginners at one time. Asking
questions is how you learn...

Westinghouse H-104 power supply
 

In article ,
Carter-k8vt wrote:

Let me toss you a minor curve ball: If you were repairing this radio in
its era, you would indeed be looking for a replacement transformer with
approximately a 270-0-270 high voltage secondary winding; this is
because it was designed for 110 volts AC coming out of the socket on
your wall.

How can we be sure it was designed for 110 volts AC coming out of the
socket on the wall? But that is really irrelevant because the schematic
says the voltages were measured with 117 volts AC coming out of the
socket on the wall, not 110 volts AC.

Today, that voltage is 115 to 120 volts or even a bit higher
and using -today's- line voltage with a 270-0-270 winding would give you
a bit more than the 265 volts DC B+ that you are looking for. So, what I
am saying is that you could (should?) look for a transformer with a
220-0-220 or 250-0-250 high voltage winding; i.e. less (than 270-0-270)
is better.

The specifications listed with the schematic say the radio is designed
to operate with voltages coming out of the socket on the wall of 105-120
volts AC, which would seem to cover "today's" voltage of 120 volts.
Unless the OP has a voltage greater than 120 volts AC coming out of the
socket on his wall I would think he should go for a transformer to the
original spec. Also if his line voltage is high, going for a
transformer with a lower voltage high voltage winding is going to do
nothing to bring down the heater voltage to normal. If this is really
an an important issue, what he should do is look for a transformer with
a tapped primary, unfortunately these don't seem to be as common as they
once were when the transformers in some equipment had taps for low and
high line voltage as well as the nominal line voltage.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

Westinghouse H-104 power supply
 

In article ,
Carter-k8vt wrote:

Let me toss you a minor curve ball: If you were repairing this
radio in its era, you would indeed be looking for a replacement
transformer with approximately a 270-0-270 high voltage secondary
winding; this is because it was designed for 110 volts AC coming
out of the socket on your wall.

John Byrns wrote:

How can we be sure it was designed for 110 volts AC coming out of the
socket on the wall?

Well, I can't "be sure". See below.

But that is really irrelevant because the schematic says the voltages
were measured with 117 volts AC coming out of the socket on the wall,
not 110 volts AC.

I would humbly offer in my defense that I do NOT have the schematic for
this radio, nor did I try and find it on line. I just went by the
partial schematic sent by the original poster which
made NO mention of 117 volts.

Today, that voltage is 115 to 120 volts or even a bit higher and
using -today's- line voltage with a 270-0-270 winding would give
you a bit more than the 265 volts DC B+ that you are looking for.
So, what I am saying is that you could (should?) look for a
transformer with a 220-0-220 or 250-0-250 high voltage winding;
i.e. less (than 270-0-270) is better.

The specifications listed with the schematic say the radio is
designed to operate with voltages coming out of the socket on the
wall of 105-120 volts AC, which would seem to cover "today's" voltage
of 120 volts.

Again, I do not have the schematic so I cannot read what you are
quoting. However, I would respectfully suggest that the 117 volt figure
they quote is a NOMINAL number. Although I was probably either not yet
born (or was very young) when this radio was new, it is my best
understanding that, GENERALLY SPEAKING, line voltages were
(significantly?) lower back then and higher today, no matter what was
printed on the schematic. Also, please note that I stated "could
(should?) look for a transformer with a 220-0-220 or 250-0-250 high
voltage winding". So I -did- try and leave a little "wiggle room". :-)


Unless the OP has a voltage greater than 120 volts AC coming out of
the socket on his wall I would think he should go for a transformer
to the original spec. Also if his line voltage is high, going for a
transformer with a lower voltage high voltage winding is going to do
nothing to bring down the heater voltage to normal.

But isn't "half a loaf better than none"? Instead of having the B+ AND
filament voltage be high, you would at least be making the B+ lower.

Going from 110 volts primary to 120 volts will raise the B+ from 265 to
290 volts, while raising the filament voltage from 6.3 to 6.8+ volts.
Neither is a desirable situation, but I personally would rather have the
lower B+. Your mileage may vary.

If this is really an an important issue, what he should do is look
for a transformer with a tapped primary, unfortunately these don't
seem to be as common as they once were when the transformers in some
equipment had taps for low and high line voltage as well as the
nominal line voltage.

Agreed! Theoretically, a tapped primary would be the perfect solution;
-realistically-, that ain't gonna happen. Realistically, the choice is
between both high B+ AND high filament voltage versus just high filament
voltage. You pays yer money and you takes yer pick...

Regards and Happy New Year,
Carter K8VT

Westinghouse H-104 power supply
 

Carter wrote:
The 268 volts you are seeing on each plate is 268 volts -AC- to ground; to
put it another way, you are looking at a transformer with a 268-0-268
volt secondary (or a transformer with a 536 volt *center-tapped*
secondary).

Carter,
lets get in the habit of saying "to CHASSIS" rather than "to GROUND". I
mentioned this before in this group... its really the correct term to be
using, especially since sometimes we are working on "hot chassis" sets too.

Good response, otherwise!

Mark Oppat


"Carter-k8vt" wrote in message
t...
Unrevealed Source wrote:
Looking for help on this one. Am I reading the schematic correctly -
265V across the 5U4 filament, and 268V across the plate?

You are interpreting it incorrectly.

The 268 volts you are seeing on each plate is 268 volts -AC- to ground; to
put it another way, you are looking at a transformer with a 268-0-268
volt secondary (or a transformer with a 536 volt *center-tapped*
secondary).

The 265 volts you refer to is +265 volts -DC-, measured from the filament
(cathode) to ground. The voltage -across- the 5U4 filament is 5 volts AC,
the filament voltage of a 5U4.

I also notice that the tap to the pilot lamps is not labeled,
although I know from the parts list that they are 6.3V.

Yes, this feeds 6.3 volts AC to the pilot lights and the filaments of the
other tubes.

Assuming that this radio is intended for use at (nominally) 115 VAC, you
will need a transformer with a 110-120 v primary, and the following three
secondaries: 500 volts center tapped (250-0-250), 6.3v and 5 v.

I'm looking to replace the fried transformer, but I'm a bit in over my
head with regard to what to replace it with or whether to have it
rewound.

Jeff

This is a fairly typical receiver transformer. Check the web site of
Antique Electronics Supply and Hammond Transformers. Look for one with
these approximate electrical characteristics and physical characteristics
that most closely match the existing one. Rewinding will probably cost
more than a new one.

By the very nature of your question, it indicates that you are a
beginner -- which is OK; we were all beginners at one time. Just be
careful; these voltages, if not fatal, can at least be harmful.

Needless to say, check the radio for other faults so as not to toast the
replacement transformer.

Merry Christmas and good luck!

Westinghouse H-104 power supply
 

The part of the schematic that I didn't post does indeed show 117 volts as
the expected input.

So one final question, and then I think I've got it. I've gone online and
found a few sources for what should be a compatible transformer. 270-0-270,
plus 5V and a 6.3V. I also looked up the current draw of a 5U4 and found
that I need at least 3A across the filmanent, so I'll be sure to buy one
that is appropriate. But about that 270V - do I need to take into account
any kind of voltage drop across the plate? Obviously the schematic is
showing resulting voltages, not transformer output voltages as I originally
though. So is 270 the right spec? The 5U4 has about a 50V drop across the
plate.

Jeff



"Carter-k8vt" wrote in message
. net...
Unrevealed Source wrote:
"Carter-k8vt" wrote in message
t...

The 268 volts you are seeing on each plate is 268 volts -AC- to ground;
to put it another way, you are looking at a transformer with a 268-0-268
volt secondary (or a transformer with a 536 volt *center-tapped*
secondary).

I've got that part - thanks for confirming.

Let me toss you a minor curve ball: If you were repairing this radio in
its era, you would indeed be looking for a replacement transformer with
approximately a 270-0-270 high voltage secondary winding; this is
because it was designed for 110 volts AC coming out of the socket on
your wall. Today, that voltage is 115 to 120 volts or even a bit higher
and using -today's- line voltage with a 270-0-270 winding would give you
a bit more than the 265 volts DC B+ that you are looking for. So, what I
am saying is that you could (should?) look for a transformer with a
220-0-220 or 250-0-250 high voltage winding; i.e. less (than 270-0-270)
is better.

The 265 volts you refer to is +265 volts -DC-, measured from the
filament (cathode) to ground. The voltage -across- the 5U4 filament
is 5 volts AC, the filament voltage of a 5U4.

So I need to apply 5V AC across the filament (pins 2 and 8). That's
consistent with what my understanding would have been.

Yes. That is why your replacement transformer needs a 5 volt secondary
winding (with enough current for a 5U4 filament).

And the 265V is generated by the tube, correct?

Yes, the tube changes (or 'rectifies') the 268 volts AC to 265 volts DC.

This would be a pulsed DC, would it not, coming directly off the tube?

Yes.

In circuit, it is constant DC due to the filter capacitors?

Yes (and also due to a filter choke if one is present (rest of the
schematic is cut off).

Do I understand this correctly?

Yes.

By the very nature of your question, it indicates that you are a
beginner -- which is OK; we were all beginners at one time. Just be
careful; these voltages, if not fatal, can at least be harmful.

Yes, relative to almost all of you, I am indeed a relative beginner. And
this is my first experience with a transformer/rectifier-based radio, so
I apologize if my questions are somewhat stupid.

Jeff

Nope, not stupid. Again, we were ALL beginners at one time. Asking
questions is how you learn...

Westinghouse H-104 power supply
 

Again, I do not have the schematic so I cannot read what you are
quoting.

http://www.nostalgiaair.org/Resources/451/T0000451.htm

Look here. There are several to choose from. Perhaps there is a run or
version number to be had. Start with the first H104.

http://www.nostalgiaair.org/PagesByM...3/M0024073.pdf This page
identifies the different suffixed chassis. A tube change.



Paul P.

Westinghouse H-104 power supply
 

And perhaps some of these links may be helpful.
http://www.ppinyot.com/HomePage.htm

I put this together to help out other hobbiest. Nothing for sale on this
web site.

Paul
www.ppinyot.com

Westinghouse H-104 power supply
 

Mark Oppat wrote:
Carter wrote:
The 268 volts you are seeing on each plate is 268 volts -AC- to ground; to
put it another way, you are looking at a transformer with a 268-0-268
volt secondary (or a transformer with a 536 volt *center-tapped*
secondary).

Carter,
lets get in the habit of saying "to CHASSIS" rather than "to GROUND". I
mentioned this before in this group... its really the correct term to be
using, especially since sometimes we are working on "hot chassis" sets too.

Good response, otherwise!

Mark Oppat

Mark, you are absolutely correct! As I stand at the Gateway to
Geezerdom, old (bad) habits die hard. ;-) To CHASSIS is indeed the
proper way to state it...

HNY,
Carter K8VT

Westinghouse H-104 power supply
 

In article ,
"Mark Oppat" wrote:

Carter wrote:
The 268 volts you are seeing on each plate is 268 volts -AC- to ground; to
put it another way, you are looking at a transformer with a 268-0-268
volt secondary (or a transformer with a 536 volt *center-tapped*
secondary).

Carter,
lets get in the habit of saying "to CHASSIS" rather than "to GROUND". I
mentioned this before in this group... its really the correct term to be
using,

"CHASSIS" sounds good for AC sets like the one being discussed here.

especially since sometimes we are working on "hot chassis" sets too.

How many "hot chassis" sets actually have a hot chassis? "GROUND" seems
more correct for "AC/DC" sets where the power line neutral is not
connected to the chassis, in the case of "AC/DC" sets "NEUTRAL" would
seem to be most accurate, except for those sets using full wave voltage
doublers, which calls for yet another word.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

Westinghouse H-104 power supply
 

"Unrevealed Source" wrote in message
...
The part of the schematic that I didn't post does indeed show 117 volts as
the expected input.

So one final question, and then I think I've got it. I've gone online and
found a few sources for what should be a compatible transformer.
270-0-270, plus 5V and a 6.3V. I also looked up the current draw of a 5U4
and found that I need at least 3A across the filmanent, so I'll be sure to
buy one that is appropriate. But about that 270V - do I need to take into
account any kind of voltage drop across the plate? Obviously the
schematic is showing resulting voltages, not transformer output voltages
as I originally though. So is 270 the right spec? The 5U4 has about a
50V drop across the plate.

That 50V drop is figured into the resulting DC output voltage, once
filtered. (DC filtered voltage = AC voltage (of one half of the transformer
at any peak) x 1.414)

Westinghouse H-104 power supply
 

How about COMMON? This would take care of the AC/DC sets with a floating
"ground", any set using the chassis as the power return connection, sets
with back bias, sets with printed circuit boards and no chassis, and battery
portables with nothing like an earth ground connection.
--
Jim Mueller

To get my real email address, replace wrongname with eportiz. Then replace
nospam with sacbeemail.

"John Byrns" wrote in message
...
In article ,
"Mark Oppat" wrote:


snip


Carter,
lets get in the habit of saying "to CHASSIS" rather than "to GROUND".
I
mentioned this before in this group... its really the correct term to be
using,

"CHASSIS" sounds good for AC sets like the one being discussed here.

especially since sometimes we are working on "hot chassis" sets too.

How many "hot chassis" sets actually have a hot chassis? "GROUND" seems
more correct for "AC/DC" sets where the power line neutral is not
connected to the chassis, in the case of "AC/DC" sets "NEUTRAL" would
seem to be most accurate, except for those sets using full wave voltage
doublers, which calls for yet another word.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

Westinghouse H-104 power supply
 

""to common B-" is fine if thats what you are tying to on a return side, but
"to chassis" is the correct term in the case we were dealing with here.

I just want to break the habit many servicers have of saying "to GROUND" as
its definitely NOT "GROUND" unless you bond the chassis to ground...and, 90%
of the time its just not... and a goodly portion of the sets being restored
are indeed what can be called "hot chassis" or AC-DC sets... which, unless
converted to have a polarized plug with ground can not be referred to ever
as being grounded.

Mark Oppat

"Jim Mueller" wrote in message
...
How about COMMON? This would take care of the AC/DC sets with a floating
"ground", any set using the chassis as the power return connection, sets
with back bias, sets with printed circuit boards and no chassis, and
battery portables with nothing like an earth ground connection.
--
Jim Mueller

To get my real email address, replace wrongname with eportiz. Then
replace nospam with sacbeemail.

"John Byrns" wrote in message
...
In article ,
"Mark Oppat" wrote:


snip


Carter,
lets get in the habit of saying "to CHASSIS" rather than "to GROUND". I
mentioned this before in this group... its really the correct term to be
using,

"CHASSIS" sounds good for AC sets like the one being discussed here.

especially since sometimes we are working on "hot chassis" sets too.

How many "hot chassis" sets actually have a hot chassis? "GROUND" seems
more correct for "AC/DC" sets where the power line neutral is not
connected to the chassis, in the case of "AC/DC" sets "NEUTRAL" would
seem to be most accurate, except for those sets using full wave voltage
doublers, which calls for yet another word.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

Westinghouse H-104 power supply
 

Mark, it is worth noting that some modern high tech IC based equipment
is built on multilayer PC boards, and one of the layers is commonly
referred to as the "ground plane", and even in lesser equipment using
simple two sided boards, there are often large areas of foil referred to
as a "ground plane".

I think your condemnation of the term "ground" is misplaced given its
common usage even in the most modern technologically advanced equipment.
I think the problem is that you are confusing "ground" with "earth" and
they are not always the same thing.


Regards,

john Byrns


In article ,
"Mark Oppat" wrote:

""to common B-" is fine if thats what you are tying to on a return side, but
"to chassis" is the correct term in the case we were dealing with here.

I just want to break the habit many servicers have of saying "to GROUND" as
its definitely NOT "GROUND" unless you bond the chassis to ground...and, 90%
of the time its just not... and a goodly portion of the sets being restored
are indeed what can be called "hot chassis" or AC-DC sets... which, unless
converted to have a polarized plug with ground can not be referred to ever
as being grounded.

Mark Oppat

--
Surf my web pages at, http://fmamradios.com/

Westinghouse H-104 power supply
 

John,
I stand my "ground" here. "Ground" IS INDEED "earth", one is the USA term,
one is used in the UK and elsewhere most often. However, in antique
radios we should use the term "CHASSIS" if that is what you are tying onto,
or "B-", also called "Common Negative, or Common neg" when you are tying to
that.

Mark Oppat


"John Byrns" wrote in message
...
Mark, it is worth noting that some modern high tech IC based equipment
is built on multilayer PC boards, and one of the layers is commonly
referred to as the "ground plane", and even in lesser equipment using
simple two sided boards, there are often large areas of foil referred to
as a "ground plane".

I think your condemnation of the term "ground" is misplaced given its
common usage even in the most modern technologically advanced equipment.
I think the problem is that you are confusing "ground" with "earth" and
they are not always the same thing.


Regards,

john Byrns


In article ,
"Mark Oppat" wrote:

""to common B-" is fine if thats what you are tying to on a return side,
but
"to chassis" is the correct term in the case we were dealing with here.

I just want to break the habit many servicers have of saying "to GROUND"
as
its definitely NOT "GROUND" unless you bond the chassis to ground...and,
90%
of the time its just not... and a goodly portion of the sets being
restored
are indeed what can be called "hot chassis" or AC-DC sets... which,
unless
converted to have a polarized plug with ground can not be referred to
ever
as being grounded.

Mark Oppat

--
Surf my web pages at, http://fmamradios.com/

Westinghouse H-104 power supply
 

Mark Oppat wrote:

John,
I stand my "ground" here. "Ground" IS INDEED "earth", one is the USA term,
one is used in the UK and elsewhere most often. However, in antique
radios we should use the term "CHASSIS" if that is what you are tying onto,
or "B-", also called "Common Negative, or Common neg" when you are tying to
that.

I'd be careful with "B-" as that's sometimes not circuit common
(return) -esp. with output tubes needing a negative bias. Chassis is
also dangerous because most AA5s use an isolated circuit common - with
the only (active) parts tied to chassis being the tuning cap (and
sometimes associated trimmers) - which are RF coupled to circuit common
through a cap. Though line AC can couple "backwards" through those caps
- (if they aren't leaking) - their small value should limit any shock
current to "tingle" level. The last thing you'd want someone to do is
tie a typical AA5 common to the chassis... Yes I know - some are anyway
- but they *should* be isolated from the user by design - where a
floating AA5 isn't.

Just my .02
--
randy guttery

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so vital to the United States Silent Service:
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Westinghouse H-104 power supply
 

My post was intentionally mentioning that "B-" or "common neg" are NOT
necessarily "Chassis"... they are separate terms... sorry if that wasn't
clear.

Mark Oppat



"Randy or Sherry Guttery" wrote in message
. ..
Mark Oppat wrote:

John,
I stand my "ground" here. "Ground" IS INDEED "earth", one is the USA
term, one is used in the UK and elsewhere most often. However, in
antique radios we should use the term "CHASSIS" if that is what you are
tying onto, or "B-", also called "Common Negative, or Common neg" when
you are tying to that.

I'd be careful with "B-" as that's sometimes not circuit common
(return) -esp. with output tubes needing a negative bias. Chassis is also
dangerous because most AA5s use an isolated circuit common - with the only
(active) parts tied to chassis being the tuning cap (and sometimes
associated trimmers) - which are RF coupled to circuit common through a
cap. Though line AC can couple "backwards" through those caps - (if they
aren't leaking) - their small value should limit any shock current to
"tingle" level. The last thing you'd want someone to do is tie a typical
AA5 common to the chassis... Yes I know - some are anyway - but they
*should* be isolated from the user by design - where a floating AA5 isn't.

Just my .02
--
randy guttery

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