[Mike Rivers[_2_]]

On 10/26/2015 3:38 PM, Angus Kerr wrote:
I can't believe that a product like that could be sold where there is
no protection for the transformer which is never switched off! Just
humming away until..... The incoming AC line looks like it's
insulated with electrical tape and is soldered to the transformer
wires. I don't know if there is an earth connection from the
transformer core to the case.

Well, remember, this was an inexpensive reverb from the days when a
studio reverb was an EMT plate for about $5,000. MicMix didn't stay in
the reverb business for very long once affordable digital reverbs came
along.



--
For a good time, visit http://mikeriversaudio.wordpress.com

[david gourley[_2_]]

said...news:1be5c756-5ea8-417b-a293-1864ec141c28
@googlegroups.com:

On Sunday, October 25, 2015 at 9:37:22 AM UTC-7, wrote:
I have a Master Room XL-121 Spring Reverb which I bought used
years ago and haven't powered it on in several years. When I recently
powered it up I received a shock from the case. It has a 2 prong
AC receptacle so it is not a grounded device. I measured about 40
volts AC from the case to ground.

So my question is what might be the cause? This unit is probably
over 30 years old so I might expect the filter capacitors to be
going bad, but I also suspect the power transformer.

Gary V

As a follow up, I followed John Williamson's advice and left it on
overnight which alleviated the problem. For now I will not do any
invasive surgery because when I put it to use, it sounded pretty
darn nice. This reverb unit has enough gain so you can directly insert
a guitar and use the output into a guitar amplifier - in this case
a 1970's Fender Champ. In spite of the transformer's close
proximity to the reverb tank (as Phil Allison pointed out), it
is remarkably quiet and lacking any noticeable hum.

Again, thanks to the group for the excellent advice. My order
list for DigiKey is growing...

Also, glad you could see the photo's; I'm not much into social
media web sites so I stumbled a bit figuring out how to
make it work.

Gary V

Does that Fender Champ have a 2-conductor plug? Were you using that when
you got that shock?

I don't remember when they changed those to a grounded plug, but they
eventually did. My '68 Champ has a 2-conductor, which I'm changing over to
a grounded one just for that reason. As is, it hums more if the plug is in
one position as opposed to the other position. I've been 'bit' by it
before.

david

[mcp6453[_2_]]

On 10/26/2015 4:58 PM, david gourley wrote:
said...news:1be5c756-5ea8-417b-a293-1864ec141c28
@googlegroups.com:

On Sunday, October 25, 2015 at 9:37:22 AM UTC-7, wrote:
I have a Master Room XL-121 Spring Reverb which I bought used
years ago and haven't powered it on in several years. When I recently
powered it up I received a shock from the case. It has a 2 prong
AC receptacle so it is not a grounded device. I measured about 40
volts AC from the case to ground.

So my question is what might be the cause? This unit is probably
over 30 years old so I might expect the filter capacitors to be
going bad, but I also suspect the power transformer.

Gary V

As a follow up, I followed John Williamson's advice and left it on
overnight which alleviated the problem. For now I will not do any
invasive surgery because when I put it to use, it sounded pretty
darn nice. This reverb unit has enough gain so you can directly insert
a guitar and use the output into a guitar amplifier - in this case
a 1970's Fender Champ. In spite of the transformer's close
proximity to the reverb tank (as Phil Allison pointed out), it
is remarkably quiet and lacking any noticeable hum.

Again, thanks to the group for the excellent advice. My order
list for DigiKey is growing...

Also, glad you could see the photo's; I'm not much into social
media web sites so I stumbled a bit figuring out how to
make it work.

Gary V

Does that Fender Champ have a 2-conductor plug? Were you using that when
you got that shock?

I don't remember when they changed those to a grounded plug, but they
eventually did. My '68 Champ has a 2-conductor, which I'm changing over to
a grounded one just for that reason. As is, it hums more if the plug is in
one position as opposed to the other position. I've been 'bit' by it
before.

david


If your equipment has a "death cap" you want to get rid of it. The shock could be a leaking death cap. If it shorts, you
get 120 volts on the chassis.

[John Williamson]

On 26/10/2015 21:12, mcp6453 wrote:
If your equipment has a "death cap" you want to get rid of it. The shock could be a leaking death cap. If it shorts, you
get 120 volts on the chassis.

Just to confirm. The unit in question has a total of zero, none, zip
capacitors connected between the power line and the rest of the circuit,
so a failing capacitor cannot give the user a shock. I would estimate
the internal DC supply voltage does not exceed about 24 volts. The worst
that any of the visible capacitors failing can do is to give an
incredible amount of hum on the output and possible chemical damage to
the PCB.

However, as one of them does seem to be bulging somewhat, it might be a
good idea to replace all the electrolytics as a matter of course, but
not as a safety concern.

--
Tciao for Now!

John.

[david gourley[_2_]]

mcp6453 said...news:gYudnYnrg-GnCrPLnZ2dnUU7-
:

On 10/26/2015 4:58 PM, david gourley wrote:
said...news:1be5c756-5ea8-417b-a293-1864ec141c28
@googlegroups.com:

On Sunday, October 25, 2015 at 9:37:22 AM UTC-7,
wrote:
I have a Master Room XL-121 Spring Reverb which I bought used
years ago and haven't powered it on in several years. When I recently
powered it up I received a shock from the case. It has a 2 prong
AC receptacle so it is not a grounded device. I measured about 40
volts AC from the case to ground.

So my question is what might be the cause? This unit is probably
over 30 years old so I might expect the filter capacitors to be
going bad, but I also suspect the power transformer.

Gary V

As a follow up, I followed John Williamson's advice and left it on
overnight which alleviated the problem. For now I will not do any
invasive surgery because when I put it to use, it sounded pretty
darn nice. This reverb unit has enough gain so you can directly insert
a guitar and use the output into a guitar amplifier - in this case
a 1970's Fender Champ. In spite of the transformer's close
proximity to the reverb tank (as Phil Allison pointed out), it
is remarkably quiet and lacking any noticeable hum.

Again, thanks to the group for the excellent advice. My order
list for DigiKey is growing...

Also, glad you could see the photo's; I'm not much into social
media web sites so I stumbled a bit figuring out how to
make it work.

Gary V

Does that Fender Champ have a 2-conductor plug? Were you using that
when
you got that shock?

I don't remember when they changed those to a grounded plug, but they
eventually did. My '68 Champ has a 2-conductor, which I'm changing over
to
a grounded one just for that reason. As is, it hums more if the plug is
in
one position as opposed to the other position. I've been 'bit' by it
before.

david


If your equipment has a "death cap" you want to get rid of it. The shock
could be a leaking death cap. If it shorts, you
get 120 volts on the chassis.

I will as I install the grounded power cable on the amp. It hasn't changed
though, as it's been like that since I got the amp in '68.

david

[[email protected]]

On Monday, October 26, 2015 at 2:01:10 PM UTC-7, david gourley wrote:
said...news:1be5c756-5ea8-417b-a293-1864ec141c28
@googlegroups.com:

On Sunday, October 25, 2015 at 9:37:22 AM UTC-7, wrote:
I have a Master Room XL-121 Spring Reverb which I bought used
years ago and haven't powered it on in several years. When I recently
powered it up I received a shock from the case. It has a 2 prong
AC receptacle so it is not a grounded device. I measured about 40
volts AC from the case to ground.

So my question is what might be the cause? This unit is probably
over 30 years old so I might expect the filter capacitors to be
going bad, but I also suspect the power transformer.

Gary V

As a follow up, I followed John Williamson's advice and left it on
overnight which alleviated the problem. For now I will not do any
invasive surgery because when I put it to use, it sounded pretty
darn nice. This reverb unit has enough gain so you can directly insert
a guitar and use the output into a guitar amplifier - in this case
a 1970's Fender Champ. In spite of the transformer's close
proximity to the reverb tank (as Phil Allison pointed out), it
is remarkably quiet and lacking any noticeable hum.

Again, thanks to the group for the excellent advice. My order
list for DigiKey is growing...

Also, glad you could see the photo's; I'm not much into social
media web sites so I stumbled a bit figuring out how to
make it work.

Gary V

Does that Fender Champ have a 2-conductor plug? Were you using that when
you got that shock?

I don't remember when they changed those to a grounded plug, but they
eventually did. My '68 Champ has a 2-conductor, which I'm changing over to
a grounded one just for that reason. As is, it hums more if the plug is in
one position as opposed to the other position. I've been 'bit' by it
before.

david

Yes, it's a 2 prong ac plug. Some years ago I put a little piece of tape
on one side for the reason you mentioned. Seems at the time I may
have had a similar problem getting shocked. I know I should upgrade
it to a grounded plug but it's served me well for years and I must say,
it sounds really good as is, particularly with single coil pickups. My
favorite is a Fender Mustang - and with a spring reverb in front of it,
simply amazing.

Gary V

[Scott Dorsey]

John Williamson wrote:
On 26/10/2015 21:12, mcp6453 wrote:
If your equipment has a "death cap" you want to get rid of it. The shock could be a leaking death cap. If it shorts, you
get 120 volts on the chassis.

Just to confirm. The unit in question has a total of zero, none, zip
capacitors connected between the power line and the rest of the circuit,
so a failing capacitor cannot give the user a shock. I would estimate
the internal DC supply voltage does not exceed about 24 volts. The worst
that any of the visible capacitors failing can do is to give an
incredible amount of hum on the output and possible chemical damage to
the PCB.

No, no, he is referring to a line filter cap on the Fender Champ, which
is in fact likely to be the original poster's actual problem.
Adding cords with safety grounds to both devices is probably a good plan
although it may be nontrivial with the Champ.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[John Williamson]

On 26/10/2015 22:05, Scott Dorsey wrote:
John Williamson wrote:
On 26/10/2015 21:12, mcp6453 wrote:
If your equipment has a "death cap" you want to get rid of it. The shock could be a leaking death cap. If it shorts, you
get 120 volts on the chassis.

Just to confirm. The unit in question has a total of zero, none, zip
capacitors connected between the power line and the rest of the circuit,
so a failing capacitor cannot give the user a shock. I would estimate
the internal DC supply voltage does not exceed about 24 volts. The worst
that any of the visible capacitors failing can do is to give an
incredible amount of hum on the output and possible chemical damage to
the PCB.

No, no, he is referring to a line filter cap on the Fender Champ, which
is in fact likely to be the original poster's actual problem.
Adding cords with safety grounds to both devices is probably a good plan
although it may be nontrivial with the Champ.

In that case, I slouch corrected. I thought we were still talking about
the OP's problem.


--
Tciao for Now!

John.

[Scott Dorsey]

John Williamson wrote:
On 26/10/2015 22:05, Scott Dorsey wrote:
John Williamson wrote:
On 26/10/2015 21:12, mcp6453 wrote:
If your equipment has a "death cap" you want to get rid of it. The shock could be a leaking death cap. If it shorts, you
get 120 volts on the chassis.

Just to confirm. The unit in question has a total of zero, none, zip
capacitors connected between the power line and the rest of the circuit,
so a failing capacitor cannot give the user a shock. I would estimate
the internal DC supply voltage does not exceed about 24 volts. The worst
that any of the visible capacitors failing can do is to give an
incredible amount of hum on the output and possible chemical damage to
the PCB.

No, no, he is referring to a line filter cap on the Fender Champ, which
is in fact likely to be the original poster's actual problem.
Adding cords with safety grounds to both devices is probably a good plan
although it may be nontrivial with the Champ.

In that case, I slouch corrected. I thought we were still talking about
the OP's problem.

The OP had the reverb unit plugged into a Champ, it seems. And something
was leaking. Given that the Champ is famous for that, I suspect it was
not the reverb unit leaking at all.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[[email protected]]

On Monday, October 26, 2015 at 3:31:21 PM UTC-7, Scott Dorsey wrote:
John Williamson wrote:
On 26/10/2015 22:05, Scott Dorsey wrote:
John Williamson wrote:
On 26/10/2015 21:12, mcp6453 wrote:
If your equipment has a "death cap" you want to get rid of it. The shock could be a leaking death cap. If it shorts, you
get 120 volts on the chassis.

Just to confirm. The unit in question has a total of zero, none, zip
capacitors connected between the power line and the rest of the circuit,
so a failing capacitor cannot give the user a shock. I would estimate
the internal DC supply voltage does not exceed about 24 volts. The worst
that any of the visible capacitors failing can do is to give an
incredible amount of hum on the output and possible chemical damage to
the PCB.

No, no, he is referring to a line filter cap on the Fender Champ, which
is in fact likely to be the original poster's actual problem.
Adding cords with safety grounds to both devices is probably a good plan
although it may be nontrivial with the Champ.

In that case, I slouch corrected. I thought we were still talking about
the OP's problem.

The OP had the reverb unit plugged into a Champ, it seems. And something
was leaking. Given that the Champ is famous for that, I suspect it was
not the reverb unit leaking at all.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Sorry for the confusion. The original amp where I was shocked was a
modern amp with a 3 prong ground plug. I was only using the Champ
to make point about the combined Champ/Spring Reverb sound I appreciate.

Gary V

[Phil Allison[_4_]]

JackA wrote:


** Then he took a voltage measurement that was completely normal.

Completely normal? Not sure how you came to that conclusion.



** Transformers with the secondary wound over the primary have capacitance between the two. Ones similar to the OP's example have about 100 to 150pF.

At 60Hz, the impedance is about 20Mohms and a standard DMM with 10Mohms input resistance reads about 30% of the AC voltage present on the primary if connected from secondary to ground.

A similar amount of stray capacitance exists between the primary and the frame of the same transformer, adding to the above when the transformer is bolted to a metal case which itself is electrically connected to the secondary.

So a reading between 40VAC and 60VAC is to be expected using a DMM connected between the case and supply ground with units like the OP's.

The steady current available is a only 4 to 6 microamps, however the peak current is much higher under certain conditions.

With no external connection to the case, it constantly floats at a voltage close to 120VAC. If the OP was holding a grounded jack plug in one hand and touched the case with other, the stray capacitance charges instantly via body resistance with a spike of current of many milliamps. If he brushed his fingertips over the case, the current spikes are rapidly repeated and cause very noticeable tingles.



..... Phil

[John Williamson]

On 27/10/2015 03:57, Phil Allison wrote:
JackA wrote:


** Then he took a voltage measurement that was completely normal.

Completely normal? Not sure how you came to that conclusion.



** Transformers with the secondary wound over the primary have capacitance between the two. Ones similar to the OP's example have about 100 to 150pF.

At 60Hz, the impedance is about 20Mohms and a standard DMM with 10Mohms input resistance reads about 30% of the AC voltage present on the primary if connected from secondary to ground.

A similar amount of stray capacitance exists between the primary and the frame of the same transformer, adding to the above when the transformer is bolted to a metal case which itself is electrically connected to the secondary.

So a reading between 40VAC and 60VAC is to be expected using a DMM connected between the case and supply ground with units like the OP's.

The steady current available is a only 4 to 6 microamps, however the peak current is much higher under certain conditions.

With no external connection to the case, it constantly floats at a voltage close to 120VAC. If the OP was holding a grounded jack plug in one hand and touched the case with other, the stray capacitance charges instantly via body resistance with a spike of current of many milliamps. If he brushed his fingertips over the case, the current spikes are rapidly repeated and cause very noticeable tingles.

Quite. I frequently feel a "sticky" feeling when I lightly brush my
fingers along the exposed metalwork of any portable device that's on
charge. Repeated checks of the wall wart power supplies show no defects
in the insulation. I even feel it when I'm wearing rubber soled shoes
standing on a dry wooden floor, so am insulated from the ground myself.
My capacitance and the frequency of the charge current ripple lets a
small but feelable current flow between me and the device in question.


--
Tciao for Now!

John.

[Phil Allison[_4_]]

John Williamson wrote:



** Transformers with the secondary wound over the primary have capacitance between the two. Ones similar to the OP's example have about 100 to 150pF.

At 60Hz, the impedance is about 20Mohms and a standard DMM with 10Mohms input resistance reads about 30% of the AC voltage present on the primary if connected from secondary to ground.

A similar amount of stray capacitance exists between the primary and the frame of the same transformer, adding to the above when the transformer is bolted to a metal case which itself is electrically connected to the secondary.

So a reading between 40VAC and 60VAC is to be expected using a DMM connected between the case and supply ground with units like the OP's.

The steady current available is a only 4 to 6 microamps, however the peak current is much higher under certain conditions.

With no external connection to the case, it constantly floats at a voltage close to 120VAC. If the OP was holding a grounded jack plug in one hand and touched the case with other, the stray capacitance charges instantly via body resistance with a spike of current of many milliamps. If he brushed his fingertips over the case, the current spikes are rapidly repeated and cause very noticeable tingles.



Quite. I frequently feel a "sticky" feeling when I lightly brush my
fingers along the exposed metalwork of any portable device that's on
charge. Repeated checks of the wall wart power supplies show no defects
in the insulation. I even feel it when I'm wearing rubber soled shoes
standing on a dry wooden floor, so am insulated from the ground myself.
My capacitance and the frequency of the charge current ripple lets a
small but feelable current flow between me and the device in question.



** Switch mode PSUs and chargers normally have EMI suppression caps wired from the "hot" side to the load side that makes the problem much worse than with transformers.

The caps used are typically 1000 to 2200pF, class Y types.

The possible peak surge currents have enough energy to damage semiconductors at the inputs and outputs of many audio/video devices.


.... Phil

[JackA]

On Monday, October 26, 2015 at 6:48:23 PM UTC-4, wrote:
On Monday, October 26, 2015 at 3:31:21 PM UTC-7, Scott Dorsey wrote:
John Williamson wrote:
On 26/10/2015 22:05, Scott Dorsey wrote:
John Williamson wrote:
On 26/10/2015 21:12, mcp6453 wrote:
If your equipment has a "death cap" you want to get rid of it. The shock could be a leaking death cap. If it shorts, you
get 120 volts on the chassis.

Just to confirm. The unit in question has a total of zero, none, zip
capacitors connected between the power line and the rest of the circuit,
so a failing capacitor cannot give the user a shock. I would estimate
the internal DC supply voltage does not exceed about 24 volts. The worst
that any of the visible capacitors failing can do is to give an
incredible amount of hum on the output and possible chemical damage to
the PCB.

No, no, he is referring to a line filter cap on the Fender Champ, which
is in fact likely to be the original poster's actual problem.
Adding cords with safety grounds to both devices is probably a good plan
although it may be nontrivial with the Champ.

In that case, I slouch corrected. I thought we were still talking about
the OP's problem.

The OP had the reverb unit plugged into a Champ, it seems. And something
was leaking. Given that the Champ is famous for that, I suspect it was
not the reverb unit leaking at all.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Sorry for the confusion. The original amp where I was shocked was a
modern amp with a 3 prong ground plug. I was only using the Champ
to make point about the combined Champ/Spring Reverb sound I appreciate.

I ALL make sense to me!!

Thanks

Jack

Gary V

[JackA]

On Monday, October 26, 2015 at 11:57:11 PM UTC-4, Phil Allison wrote:
JackA wrote:


** Then he took a voltage measurement that was completely normal.

Completely normal? Not sure how you came to that conclusion.



** Transformers with the secondary wound over the primary have capacitance between the two. Ones similar to the OP's example have about 100 to 150pF..

At 60Hz, the impedance is about 20Mohms and a standard DMM with 10Mohms input resistance reads about 30% of the AC voltage present on the primary if connected from secondary to ground.

A similar amount of stray capacitance exists between the primary and the frame of the same transformer, adding to the above when the transformer is bolted to a metal case which itself is electrically connected to the secondary.

So a reading between 40VAC and 60VAC is to be expected using a DMM connected between the case and supply ground with units like the OP's.

The steady current available is a only 4 to 6 microamps, however the peak current is much higher under certain conditions.

With no external connection to the case, it constantly floats at a voltage close to 120VAC. If the OP was holding a grounded jack plug in one hand and touched the case with other, the stray capacitance charges instantly via body resistance with a spike of current of many milliamps. If he brushed his fingertips over the case, the current spikes are rapidly repeated and cause very noticeable tingles.



.... Phil

First: OP? Original Poster? Maybe I've been away from usenet too long!

So much for leakage capacitance, inductance and stray magnetic flux heating the ferrous frame, the device (reverb) is faulty. I THINK we agree on that?

Jack

[Scott Dorsey]

wrote:
Sorry for the confusion. The original amp where I was shocked was a
modern amp with a 3 prong ground plug. I was only using the Champ
to make point about the combined Champ/Spring Reverb sound I appreciate.

Now I am even more confused.

Yes.... it's correct that you can't use a high-Z voltmeter to measure chassis
leakage, so you don't really know how much leakage you have or where it is
coming from.

But you know that if it _is_ coming from the reverb unit, which to be honest
is kind of unlikely, that it's coming from the transformer because there is
nothing else for it to be coming from.

So I would be inclined to put a three-prong cord on the reverb unit and
if the transformer is leaking resistively, it will fail, and if it's just
leaking capacitively, it'll be fine.

But I'd also check that guitar amp and I'd check the outlet with an outlet
tester.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[JackA]

On Tuesday, October 27, 2015 at 4:24:57 AM UTC-4, John Williamson wrote:
On 27/10/2015 03:57, Phil Allison wrote:
JackA wrote:


** Then he took a voltage measurement that was completely normal.

Completely normal? Not sure how you came to that conclusion.



** Transformers with the secondary wound over the primary have capacitance between the two. Ones similar to the OP's example have about 100 to 150pF.

At 60Hz, the impedance is about 20Mohms and a standard DMM with 10Mohms input resistance reads about 30% of the AC voltage present on the primary if connected from secondary to ground.

A similar amount of stray capacitance exists between the primary and the frame of the same transformer, adding to the above when the transformer is bolted to a metal case which itself is electrically connected to the secondary.

So a reading between 40VAC and 60VAC is to be expected using a DMM connected between the case and supply ground with units like the OP's.

The steady current available is a only 4 to 6 microamps, however the peak current is much higher under certain conditions.

With no external connection to the case, it constantly floats at a voltage close to 120VAC. If the OP was holding a grounded jack plug in one hand and touched the case with other, the stray capacitance charges instantly via body resistance with a spike of current of many milliamps. If he brushed his fingertips over the case, the current spikes are rapidly repeated and cause very noticeable tingles.

Quite. I frequently feel a "sticky" feeling when I lightly brush my
fingers along the exposed metalwork of any portable device that's on
charge. Repeated checks of the wall wart power supplies show no defects
in the insulation. I even feel it when I'm wearing rubber soled shoes
standing on a dry wooden floor, so am insulated from the ground myself.
My capacitance and the frequency of the charge current ripple lets a
small but feelable current flow between me and the device in question.

Forgive me, but my fist time for, "wall wart"; though you misspelled Wall Mart!!
I see they call AC adapter, Power Bricks, too!!
Go to run, the sun is out and my Cloud is screwed up!! :-)

Jack


--
Tciao for Now!

John.

[JackA]

On Monday, October 26, 2015 at 11:57:11 PM UTC-4, Phil Allison wrote:
JackA wrote:


** Then he took a voltage measurement that was completely normal.

Completely normal? Not sure how you came to that conclusion.



** Transformers with the secondary wound over the primary have capacitance between the two. Ones similar to the OP's example have about 100 to 150pF..

At 60Hz, the impedance is about 20Mohms and a standard DMM with 10Mohms input resistance reads about 30% of the AC voltage present on the primary if connected from secondary to ground.

A similar amount of stray capacitance exists between the primary and the frame of the same transformer, adding to the above when the transformer is bolted to a metal case which itself is electrically connected to the secondary.

So a reading between 40VAC and 60VAC is to be expected using a DMM connected between the case and supply ground with units like the OP's.

The steady current available is a only 4 to 6 microamps, however the peak current is much higher under certain conditions.

With no external connection to the case, it constantly floats at a voltage close to 120VAC. If the OP was holding a grounded jack plug in one hand and touched the case with other, the stray capacitance charges instantly via body resistance with a spike of current of many milliamps. If he brushed his fingertips over the case, the current spikes are rapidly repeated and cause very noticeable tingles.



.... Phil

Phil, if you REALLY want to impress me, you can tell me why transformers are typically designed with insulation NOT EXCEEDING 40 volts/mil, REGARDLESS of the type insulation?

Jack

[Phil Allison[_4_]]

JackA wrote:



** Transformers with the secondary wound over the primary have capacitance between the two. Ones similar to the OP's example have about 100 to 150pF.

At 60Hz, the impedance is about 20Mohms and a standard DMM with 10Mohms input resistance reads about 30% of the AC voltage present on the primary if connected from secondary to ground.

A similar amount of stray capacitance exists between the primary and the frame of the same transformer, adding to the above when the transformer is bolted to a metal case which itself is electrically connected to the secondary.

So a reading between 40VAC and 60VAC is to be expected using a DMM connected between the case and supply ground with units like the OP's.

The steady current available is a only 4 to 6 microamps, however the peak current is much higher under certain conditions.

With no external connection to the case, it constantly floats at a voltage close to 120VAC. If the OP was holding a grounded jack plug in one hand and touched the case with other, the stray capacitance charges instantly via body resistance with a spike of current of many milliamps. If he brushed his fingertips over the case, the current spikes are rapidly repeated and cause very noticeable tingles.



First: OP? Original Poster?


** Yes, Gary Y.


So much for leakage capacitance, inductance and stray magnetic flux heating the ferrous frame, the device (reverb) is faulty. I THINK we agree on that?


** No, IMO the reverb is being falsely accused.



.... Phil

[JackA]

On Wednesday, October 28, 2015 at 2:11:56 AM UTC-4, Phil Allison wrote:
JackA wrote:



** Transformers with the secondary wound over the primary have capacitance between the two. Ones similar to the OP's example have about 100 to 150pF.

At 60Hz, the impedance is about 20Mohms and a standard DMM with 10Mohms input resistance reads about 30% of the AC voltage present on the primary if connected from secondary to ground.

A similar amount of stray capacitance exists between the primary and the frame of the same transformer, adding to the above when the transformer is bolted to a metal case which itself is electrically connected to the secondary.

So a reading between 40VAC and 60VAC is to be expected using a DMM connected between the case and supply ground with units like the OP's.

The steady current available is a only 4 to 6 microamps, however the peak current is much higher under certain conditions.

With no external connection to the case, it constantly floats at a voltage close to 120VAC. If the OP was holding a grounded jack plug in one hand and touched the case with other, the stray capacitance charges instantly via body resistance with a spike of current of many milliamps. If he brushed his fingertips over the case, the current spikes are rapidly repeated and cause very noticeable tingles.



First: OP? Original Poster?


** Yes, Gary Y.


So much for leakage capacitance, inductance and stray magnetic flux heating the ferrous frame, the device (reverb) is faulty. I THINK we agree on that?


** No, IMO the reverb is being falsely accused.

Hopefully, you're not employed by Underwriters Laboratories!! :-)

Jack



... Phil

[Phil Allison[_4_]]

JackA wrote:



** No, IMO the reverb is being falsely accused.

Hopefully, you're not employed by Underwriters Laboratories!! :-)


** You need to get a DMM, switch it to AC volts a test few items that have no supply ground connection.


..... Phil

[JackA]

On Wednesday, October 28, 2015 at 7:47:16 PM UTC-4, Phil Allison wrote:
JackA wrote:



** No, IMO the reverb is being falsely accused.

Hopefully, you're not employed by Underwriters Laboratories!! :-)


** You need to get a DMM, switch it to AC volts a test few items that have no supply ground connection.

I'll do that after creating my will!! :-)

Jack


.... Phil

[[email protected]]

Maybe not so relevent, but since the era of non-polarized plugs,
I always have handy a simple 10 cent neon lamp.

Holding one wire and touching the other to a chassis shows me
leakage. I use that indication to mark the plug for next time.