Isolation Transformer Purpose?
 

I'm not a ham operator! But I figure you guys can explain what an
Isolation Transformer does.

I came up with one at an estate sale this weekend of a former TV
repairman. Among the 1970s vintage test equipment and color bar
generators was this xfmr. This unit says "Isolation Transformer 5
Amps, 600 Watts" on one side and "Isolation: Primary 120 VAC,
Secondary 120 VAC" on the other. It's about 8" square and as you can
imagine, quite heavy.

I was guessing it keeps voltage spikes out of the equipment that's
plugged into it, but then I saw some old posts in this group which
mentions grounded chassis.

Do people who have fairly modern ham equipment still use these things?

Isolation Transformer Purpose?
 

wrote in message
...
I'm not a ham operator! But I figure you guys can explain what an
Isolation Transformer does.

I came up with one at an estate sale this weekend of a former TV
repairman. Among the 1970s vintage test equipment and color bar
generators was this xfmr. This unit says "Isolation Transformer 5
Amps, 600 Watts" on one side and "Isolation: Primary 120 VAC,
Secondary 120 VAC" on the other. It's about 8" square and as you can
imagine, quite heavy.

I was guessing it keeps voltage spikes out of the equipment that's
plugged into it, but then I saw some old posts in this group which
mentions grounded chassis.

Do people who have fairly modern ham equipment still use these things?

They are useful for older equipment where it is convenient to have the 120V
supply "floating" above ground. In other words, there is 120VAC potential
across the transformer, but neither leg has potential from that leg to
ground. They are used on the bench where "hot" chassis poses a shock
risk/hazard. They are also handy where "leaky" bypass capacitors across the
AC line cause GFIs to trip (as in radios such as R390A). I have a 1KVA unit
and used it quite often. It does little for shielding against spikes or
other line noise.

Good find.

Barry - N4BUQ

Isolation Transformer Purpose?
 

wrote in message
...
I'm not a ham operator! But I figure you guys can explain what an
Isolation Transformer does.

I came up with one at an estate sale this weekend of a former TV
repairman. Among the 1970s vintage test equipment and color bar
generators was this xfmr. This unit says "Isolation Transformer 5
Amps, 600 Watts" on one side and "Isolation: Primary 120 VAC,
Secondary 120 VAC" on the other. It's about 8" square and as you can
imagine, quite heavy.

I was guessing it keeps voltage spikes out of the equipment that's
plugged into it, but then I saw some old posts in this group which
mentions grounded chassis.

Do people who have fairly modern ham equipment still use these things?

The transformer is not to keep out the spikes. Some of the older equipment
(vacuum tubes) did not have transfromers in them and one side of the chassie
was connected to the neutral side of the power plug. If the house
receptical was not wired correctly or if the plug was put in backwards then
the chassie of the equipment would be connected to the hot wire and if you
touched it and were grounded you would get shocked or worse and could die.

Sometimes when testing equipment without a transformer in it the isolation
transformer was used to make sure the grounded chassie would not be
connected to the hot side of the incomming AC power.
Many times the test equipment would have its chassie connected to the ground
and the chassie of the two pieces of equipment would be connected together.

Modern equipment with transistors seldom have this problem.

Isolation Transformer Purpose?
 

In article , "Ralph Mowery" wrote:

wrote in message
...
I'm not a ham operator! But I figure you guys can explain what an
Isolation Transformer does.

I came up with one at an estate sale this weekend of a former TV
repairman. Among the 1970s vintage test equipment and color bar
generators was this xfmr. This unit says "Isolation Transformer 5
Amps, 600 Watts" on one side and "Isolation: Primary 120 VAC,
Secondary 120 VAC" on the other. It's about 8" square and as you can
imagine, quite heavy.

I was guessing it keeps voltage spikes out of the equipment that's
plugged into it, but then I saw some old posts in this group which
mentions grounded chassis.

Do people who have fairly modern ham equipment still use these things?

The transformer is not to keep out the spikes. Some of the older equipment
(vacuum tubes) did not have transfromers in them and one side of the chassie
was connected to the neutral side of the power plug. If the house
receptical was not wired correctly or if the plug was put in backwards then
the chassie of the equipment would be connected to the hot wire and if you
touched it and were grounded you would get shocked or worse and could die.

Sometimes when testing equipment without a transformer in it the isolation
transformer was used to make sure the grounded chassie would not be
connected to the hot side of the incomming AC power.
Many times the test equipment would have its chassie connected to the ground
and the chassie of the two pieces of equipment would be connected together.

Modern equipment with transistors seldom have this problem.


Isolation transformers such as the ones Tripplite sells, do filter well.
They also eliminate the ground to line spike issue. One leg of the secondaries
is tied to ground, eliminating any differential noise.

greg

Isolation Transformer Purpose?
 

In article , (GregS) wrote:
In article , "Ralph Mowery"
wrote:

wrote in message
...
I'm not a ham operator! But I figure you guys can explain what an
Isolation Transformer does.

I came up with one at an estate sale this weekend of a former TV
repairman. Among the 1970s vintage test equipment and color bar
generators was this xfmr. This unit says "Isolation Transformer 5
Amps, 600 Watts" on one side and "Isolation: Primary 120 VAC,
Secondary 120 VAC" on the other. It's about 8" square and as you can
imagine, quite heavy.

I was guessing it keeps voltage spikes out of the equipment that's
plugged into it, but then I saw some old posts in this group which
mentions grounded chassis.

Do people who have fairly modern ham equipment still use these things?

The transformer is not to keep out the spikes. Some of the older equipment
(vacuum tubes) did not have transfromers in them and one side of the chassie
was connected to the neutral side of the power plug. If the house
receptical was not wired correctly or if the plug was put in backwards then
the chassie of the equipment would be connected to the hot wire and if you
touched it and were grounded you would get shocked or worse and could die.

Sometimes when testing equipment without a transformer in it the isolation
transformer was used to make sure the grounded chassie would not be
connected to the hot side of the incomming AC power.
Many times the test equipment would have its chassie connected to the ground
and the chassie of the two pieces of equipment would be connected together.

Modern equipment with transistors seldom have this problem.


Isolation transformers such as the ones Tripplite sells, do filter well.
They also eliminate the ground to line spike issue. One leg of the secondaries
is tied to ground, eliminating any differential noise.

greg

As Trip Lite says...

* Superior line noise reduction and spike suppression
* Faraday Shield offers 100% isolation from the input AC line
* Secondary neutral to ground bonding eliminates common mode noise
* Removes EMI/RFI noise, utility switching transients and background spikes
* Select models feature hospital-grade plug and receptacles

Isolation Transformer Purpose?
 

In article , (GregS) wrote:
In article ,
(GregS) wrote:
In article , "Ralph Mowery"
wrote:

wrote in message
...
I'm not a ham operator! But I figure you guys can explain what an
Isolation Transformer does.

I came up with one at an estate sale this weekend of a former TV
repairman. Among the 1970s vintage test equipment and color bar
generators was this xfmr. This unit says "Isolation Transformer 5
Amps, 600 Watts" on one side and "Isolation: Primary 120 VAC,
Secondary 120 VAC" on the other. It's about 8" square and as you can
imagine, quite heavy.

I was guessing it keeps voltage spikes out of the equipment that's
plugged into it, but then I saw some old posts in this group which
mentions grounded chassis.

Do people who have fairly modern ham equipment still use these things?

The transformer is not to keep out the spikes. Some of the older equipment
(vacuum tubes) did not have transfromers in them and one side of the chassie
was connected to the neutral side of the power plug. If the house
receptical was not wired correctly or if the plug was put in backwards then
the chassie of the equipment would be connected to the hot wire and if you
touched it and were grounded you would get shocked or worse and could die.

Sometimes when testing equipment without a transformer in it the isolation
transformer was used to make sure the grounded chassie would not be
connected to the hot side of the incomming AC power.
Many times the test equipment would have its chassie connected to the ground
and the chassie of the two pieces of equipment would be connected together.

Modern equipment with transistors seldom have this problem.


Isolation transformers such as the ones Tripplite sells, do filter well.
They also eliminate the ground to line spike issue. One leg of the secondaries
is tied to ground, eliminating any differential noise.

greg

As Trip Lite says...

* Superior line noise reduction and spike suppression
* Faraday Shield offers 100% isolation from the input AC line
* Secondary neutral to ground bonding eliminates common mode noise
* Removes EMI/RFI noise, utility switching transients and background spikes
* Select models feature hospital-grade plug and receptacles

But, there are transformers without the bonding, as most service shops would use.
It would be easy to add a switch to bond either leg to ground. Might be handy.

greg

Isolation Transformer Purpose?
 

"GregS" wrote in message
...
In article , "Ralph
Mowery" wrote:

wrote in message
...
I'm not a ham operator! But I figure you guys can explain what an
Isolation Transformer does.

I came up with one at an estate sale this weekend of a former TV
repairman. Among the 1970s vintage test equipment and color bar
generators was this xfmr. This unit says "Isolation Transformer 5
Amps, 600 Watts" on one side and "Isolation: Primary 120 VAC,
Secondary 120 VAC" on the other. It's about 8" square and as you can
imagine, quite heavy.



Isolation transformers such as the ones Tripplite sells, do filter well.
They also eliminate the ground to line spike issue. One leg of the
secondaries
is tied to ground, eliminating any differential noise.

greg


While there are transformers designed to keep out spikes and filter the
line, you have to look at the question.
The transformer was mentioned was with test equipment. Usually it is to
isolate the hot chassies, not to eliminate spikes and noise.

Isolation Transformer Purpose?
 

"Ralph Mowery" wrote in
m:

"GregS" wrote in message
...
In article , "Ralph
Mowery" wrote:

wrote in message
news:abba9e19-931b-4c77-b1e9-38218c607f78@
34g2000hsf.googlegroups.com...
I'm not a ham operator! But I figure you guys can explain what an
Isolation Transformer does.

I came up with one at an estate sale this weekend of a former TV
repairman. Among the 1970s vintage test equipment and color bar
generators was this xfmr. This unit says "Isolation Transformer 5
Amps, 600 Watts" on one side and "Isolation: Primary 120 VAC,
Secondary 120 VAC" on the other. It's about 8" square and as you can
imagine, quite heavy.



Isolation transformers such as the ones Tripplite sells, do filter
well. They also eliminate the ground to line spike issue. One leg of
the secondaries
is tied to ground, eliminating any differential noise.

greg


While there are transformers designed to keep out spikes and filter the
line, you have to look at the question.
The transformer was mentioned was with test equipment. Usually it is
to
isolate the hot chassies, not to eliminate spikes and noise.




And I might add was not identified ad being a Tripplite transformer. Since
it came from a TV reapir man's gear it was as you say to isolate the hot
chassis of some of the old time consumer electronics.

--
Panzer

Isolation Transformer Purpose?
 

In article , "Ralph Mowery" wrote:

"GregS" wrote in message
...
In article , "Ralph
Mowery" wrote:

wrote in message
...
I'm not a ham operator! But I figure you guys can explain what an
Isolation Transformer does.

I came up with one at an estate sale this weekend of a former TV
repairman. Among the 1970s vintage test equipment and color bar
generators was this xfmr. This unit says "Isolation Transformer 5
Amps, 600 Watts" on one side and "Isolation: Primary 120 VAC,
Secondary 120 VAC" on the other. It's about 8" square and as you can
imagine, quite heavy.



Isolation transformers such as the ones Tripplite sells, do filter well.
They also eliminate the ground to line spike issue. One leg of the
secondaries
is tied to ground, eliminating any differential noise.

greg


While there are transformers designed to keep out spikes and filter the
line, you have to look at the question.
The transformer was mentioned was with test equipment. Usually it is to
isolate the hot chassies, not to eliminate spikes and noise.

I was responding to someone who said it did not provide filtering. Regardless,
an isolation transformer should have an electrostatic shield between
the line and output, cutting down electrostatic conduction. Any standard isolation transformer
sold in the US must have the secondary tied to ground by NEC code.
In all cases, you are isolating the mains from the equipment. Even if one leg of the output
is grounded, its still isolated from the mains. The problem is if you put your body within the
chassis somewhere.

greg

Isolation Transformer Purpose?
 

In article , (GregS) wrote:
In article , "Ralph Mowery"
wrote:

"GregS" wrote in message
...
In article , "Ralph
Mowery" wrote:

wrote in message
...
I'm not a ham operator! But I figure you guys can explain what an
Isolation Transformer does.

I came up with one at an estate sale this weekend of a former TV
repairman. Among the 1970s vintage test equipment and color bar
generators was this xfmr. This unit says "Isolation Transformer 5
Amps, 600 Watts" on one side and "Isolation: Primary 120 VAC,
Secondary 120 VAC" on the other. It's about 8" square and as you can
imagine, quite heavy.



Isolation transformers such as the ones Tripplite sells, do filter well.
They also eliminate the ground to line spike issue. One leg of the
secondaries
is tied to ground, eliminating any differential noise.

greg


While there are transformers designed to keep out spikes and filter the
line, you have to look at the question.
The transformer was mentioned was with test equipment. Usually it is to
isolate the hot chassies, not to eliminate spikes and noise.

I was responding to someone who said it did not provide filtering. Regardless,
an isolation transformer should have an electrostatic shield between
the line and output, cutting down electrostatic conduction. Any standard
isolation transformer
sold in the US must have the secondary tied to ground by NEC code.
In all cases, you are isolating the mains from the equipment. Even if one leg
of the output
is grounded, its still isolated from the mains. The problem is if you put your
body within the
chassis somewhere.

I also would have to say a TEST equipment isolation transformer is
really needed for GROUND isolation perhaps more so that mains
isolation.

greg