Another post about floating grounds etc. I decided to look into this isolation transformer. My isolation so far has been don't touch anything if power plugged in. I have seen it mentioned many times in post about isolation transformers. For grins I measured to ground on my 10A1 Admiral chassis. 36 volts. I reversed the plug and got 45 volts. Now that isn't real serious unless one is well grounded, but why risk it. It would appear there are no complete setup isolation transformers I can find. Do you buy a transformer and make your own? Doesn't seem to difficult. But how do they provide more safety than the transformer in my set already? Any web site with details and how to build? And it would seem best that it could be combined with a variac. Also why not a volt meter and ammeter included in the deluxe set so I could see what voltage my variac is putting out along with the current draw. Any thoughts?

:Another post about floating grounds etc. I decided to look into this isolation transformer. My isolation so far has been don't touch anything if power plugged in. I have seen it mentioned many times in post about isolation transformers. For grins I measured to ground on my 10A1 Admiral chassis. 36 volts. I reversed the plug and got 45 volts. Now that isn't real serious unless one is well grounded, but why risk it. It would appear there are no complete setup isolation transformers I can find. Do you buy a transformer and make your own? Doesn't seem to difficult. But how do they provide more safety than the transformer in my set already? Any web site with details and how to build? And it would seem best that it could be combined with a variac. Also why not a volt meter and ammeter included in the deluxe set so I could see what voltage my variac is putting out along with the current draw. Any thoughts?
:

:Another post about floating grounds etc. I decided to look into this isolation transformer. My isolation so far has been don't touch anything if power plugged in. I have seen it mentioned many times in post about isolation transformers. For grins I measured to ground on my 10A1 Admiral chassis. 36 volts. I reversed the plug and got 45 volts. Now that isn't real serious unless one is well grounded, but why risk it. It would appear there are no complete setup isolation transformers I can find. Do you buy a transformer and make your own? Doesn't seem to difficult. But how do they provide more safety than the transformer in my set already? Any web site with details and how to build? And it would seem best that it could be combined with a variac. Also why not a volt meter and ammeter included in the deluxe set so I could see what voltage my variac is putting out along with the current draw. Any thoughts?
:
Rich,
I think that the main problem is with equipment without transformers, where the line cord is connected to the chassis and then the B+ is established through the filter. A close look at a unit with a transformer will identify if the power is isolated.
On my work bench i have a Variac plugged into line power then a isolation transformer plugged into the Variac output. I modified the cord on the Variac to install a volt meter and use an amp clamp to make measurements as i increase voltage. My radios plug into the isolation transformer.
I feel safer working this way as i do forget to unplug the radio when i am working on it.
You did give me a thought, i am going to install a pilot lamp on the Variac so i know when i left power on.
Thanks,
Mitch

Thanks for your reply Mitch. This morning I did a little test with my 1953 Arvin AA5. Back in about 2001 I replaced its bad power cord with a new one with a polarized two prong plug. I don't remember how I determined what on hookup. As a curiosity I checked its chassis to ground. With the radio off I measured 121 vac. With the radio on I measured zero. I guess this proves these old radio's need to be kept playing. Meanwhile my research for an isolation transformer setup goes on. And I need to understand why these measurement occur. But right now I am waiting for UPS today with parts for my signal generator. Rich

Hello Rich. Here is a link showing the hot chassis problem and what can be done about it. This is for the Hallicrafters S-38, but does apply to any AA5 radio.

http://www.the-s38-guy.com/Page_2.html

Hello Rich. Here is a link showing the hot chassis problem and what can be done about it. This is for the Hallicrafters S-38, but does apply to any AA5 radio.

http://www.the-s38-guy.com/Page_2.html

:Thanks for your reply Mitch. This morning I did a little test with my 1953 Arvin AA5. Back in about 2001 I replaced its bad power cord with a new one with a polarized two prong plug. I don't remember how I determined what on hookup. As a curiosity I checked its chassis to ground. With the radio off I measured 121 vac. With the radio on I measured zero. I guess this proves these old radio's need to be kept playing. Meanwhile my research for an isolation transformer setup goes on. And I need to understand why these measurement occur. But right now I am waiting for UPS today with parts for my signal generator. Rich
:
For some reason, this question always generates a LOT of opinions. I've seen posts on ARF go on for page after page. Some, as you might have noticed, get quite contentious.
Any way, I have my isolation transformer plugged in first, then my variac, (actually a really nice Eico with both volt and amp meters). I've also made ABSOLUTELY sure that the outlets are wired correctly, and ground goes to the building service ground.
I think it's cool that you've actually made some tests. Why didn't I think of that? (Rhetorical question, as I said, I'm sure my bench is totally safe.)
Terry

::Thanks for your reply Mitch. This morning I did a little test with my 1953 Arvin AA5. Back in about 2001 I replaced its bad power cord with a new one with a polarized two prong plug. I don't remember how I determined what on hookup. As a curiosity I checked its chassis to ground. With the radio off I measured 121 vac. With the radio on I measured zero. I guess this proves these old radio's need to be kept playing. Meanwhile my research for an isolation transformer setup goes on. And I need to understand why these measurement occur. But right now I am waiting for UPS today with parts for my signal generator. Rich
::
:For some reason, this question always generates a LOT of opinions. I've seen posts on ARF go on for page after page. Some, as you might have noticed, get quite contentious.
:Any way, I have my isolation transformer plugged in first, then my variac, (actually a really nice Eico with both volt and amp meters). I've also made ABSOLUTELY sure that the outlets are wired correctly, and ground goes to the building service ground.
:I think it's cool that you've actually made some tests. Why didn't I think of that? (Rhetorical question, as I said, I'm sure my bench is totally safe.)
:Terry
:

Terry:
Funny you should remind me of:

"I've also made ABSOLUTELY sure that the outlets are wired correctly, and ground goes to the building service ground."

Back in my Delta days, I had an assignment to calibrate a new piece of test equipment using a frequency counter on a bench I usually didn't use. I turned off power to the whole bench using the master switch whenever I was working around "hot" parts of the counter. All of a sudden, there was a sound like an arc welder and a great big ball of fire and smoke came out of a very expensive frequency counter. It later turned out that the idiot (who later made management, of course) that wired the bench put the power switch in the neutral side of the power line, instead of the hot. The bench and all the test equipment was grounded to the ground wire of the power line, so we had a nice little booby trap waiting for some boob (me) to walk into it, which I promptly did. After that, I also made ABSOLUTELY sure that the outlets are wired correctly, and ground goes to the building service ground.
Lewis

:::Thanks for your reply Mitch. This morning I did a little test with my 1953 Arvin AA5. Back in about 2001 I replaced its bad power cord with a new one with a polarized two prong plug. I don't remember how I determined what on hookup. As a curiosity I checked its chassis to ground. With the radio off I measured 121 vac. With the radio on I measured zero. I guess this proves these old radio's need to be kept playing. Meanwhile my research for an isolation transformer setup goes on. And I need to understand why these measurement occur. But right now I am waiting for UPS today with parts for my signal generator. Rich
:::
::For some reason, this question always generates a LOT of opinions. I've seen posts on ARF go on for page after page. Some, as you might have noticed, get quite contentious.
::Any way, I have my isolation transformer plugged in first, then my variac, (actually a really nice Eico with both volt and amp meters). I've also made ABSOLUTELY sure that the outlets are wired correctly, and ground goes to the building service ground.
::I think it's cool that you've actually made some tests. Why didn't I think of that? (Rhetorical question, as I said, I'm sure my bench is totally safe.)
::Terry
::
:
:
:
:Terry:
:Funny you should remind me of:
:
:"I've also made ABSOLUTELY sure that the outlets are wired correctly, and ground goes to the building service ground."
:
:Back in my Delta days, I had an assignment to calibrate a new piece of test equipment using a frequency counter on a bench I usually didn't use. I turned off power to the whole bench using the master switch whenever I was working around "hot" parts of the counter. All of a sudden, there was a sound like an arc welder and a great big ball of fire and smoke came out of a very expensive frequency counter. It later turned out that the idiot (who later made management, of course) that wired the bench put the power switch in the neutral side of the power line, instead of the hot. The bench and all the test equipment was grounded to the ground wire of the power line, so we had a nice little booby trap waiting for some boob (me) to walk into it, which I promptly did. After that, I also made ABSOLUTELY sure that the outlets are wired correctly, and ground goes to the building service ground.
:Lewis
:
Terry