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!

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

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/

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/

""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/

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/

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/

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

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
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