Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Jul Sun 22, 2018 7:37 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 7 posts ] 
Author Message
 Post subject: ACME T-8394M, what is it?
PostPosted: Mar Wed 14, 2018 11:20 pm 
Member

Joined: Oct Wed 04, 2017 12:27 am
Posts: 31
I picked up an ACME T-8394M thinking it was an isolation transformer, but that doesn't appear to be what was intended. It has multiple voltage inputs and a gauge to show output voltage. Does anybody know anything about these little transformers?


Top
 Profile  
 
 Post subject: Re: ACME T-8394M, what is it?
PostPosted: Mar Thu 15, 2018 2:47 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 11643
Location: North of Mpls, Minnesota
It is a 300 watt isolation transformer, tapped to adjust the output voltage.

Dave


Top
 Profile  
 
 Post subject: Re: ACME T-8394M, what is it?
PostPosted: Mar Thu 15, 2018 4:11 am 
Member

Joined: Oct Wed 04, 2017 12:27 am
Posts: 31
That was the impression I was under when I got it. However, I was testing it with a multimeter and it seems to have continuity from plug to socket. I guess I need to take the plates off and see what's different.


Top
 Profile  
 
 Post subject: Re: ACME T-8394M, what is it?
PostPosted: Mar Thu 15, 2018 4:32 am 
Member
User avatar

Joined: Nov Mon 02, 2009 7:01 am
Posts: 2824
Location: Lincoln City, OR
Greetings to the Forum:

Be careful with those things. They never seem to do quite what you expect. Just ask Wile E. Coyote.

Regards,

_________________
Jim T.
KB6GM


Top
 Profile  
 
 Post subject: Re: ACME T-8394M, what is it?
PostPosted: Mar Sat 17, 2018 12:57 am 
Member

Joined: Jun Fri 19, 2009 6:34 pm
Posts: 7748
Location: Long Island
It does not appear to be an isolation transformer, despite what many seem to think. It is almost certainly an adjustable autotransformer. They were common television accessories back in the 1950s and '60s. The old series string tube black and white sets were very susceptible to high and low line voltages; too low and the picture would be shrunken and dark, too high and the repairman would be there replacing tubes every few weeks. It presumably has only one winding and if so, it cannot be used for ground isolation purposes.

But all is not lost. Line voltages tend to be a few volts higher in many locales nowadays and antique radios tend to run cooler and better on lower line voltages. So this transformer still could be helpful and useful for powering radios after you have fixed them.

_________________
"Hell, there are no rules here--we're trying to accomplish something!"

Thomas A. Edison


Top
 Profile  
 
 Post subject: Re: ACME T-8394M, what is it?
PostPosted: Mar Sun 18, 2018 5:10 am 
Member

Joined: Oct Wed 04, 2017 12:27 am
Posts: 31
Hi Chris, I've seen some of your other posts on isolation transformers. I think you hit the nail on the head with this ACME transformer's intended purpose. When I looked inside it even had a "May 53" stamp which would be the right stretch of time. The only thing that puzzles me is I tried the test you suggested on another post of wiring a small incandescent in series with the outlet connections and ground and it didn't illuminate at all. Nor does my volt meter show anything when I put it in the bulb's place.

Even if I still need to build/ acquire an isolation transformer the T-8394 is pretty interesting. It looks good paired with my old Crosley 628 which doesn't need modern rural line voltage anyway. As all ways, thanks for all the input!


Top
 Profile  
 
 Post subject: Re: ACME T-8394M, what is it?
PostPosted: Mar Sun 18, 2018 1:36 pm 
Member

Joined: Jun Fri 19, 2009 6:34 pm
Posts: 7748
Location: Long Island
It is always better to assume a transformer is not a ground isolation type until proven otherwise, than it is to think it might be and then find out it's isn't. That goes for your bona fide isolation transformer once you get one. Test it once in a while to be sure nothing has gone wrong since you last looked.

The fact that your ohmmeter shows continuity from input to output on this Acme is sufficient to say that it is not a true isolation transformer. Why the incandescent bulb did not light on either side of the outlet should be investigated further. It may mean that whatever you used as ground for the test is not really grounded. It's more common than you think in this era of plastic plumbing, conduit, and outlet boxes! You do not need the transformer present to check this; simply take the test lamp from hot to neutral at the outlet to see if it works, then from hot to ground. If it lit from hot to neutral, it should light again to the same brightness assuming you've got a good ground. If you find out that ground is missing from somewhere it should exist, get an electrician to look into it.

One should also note that these "television accessory" live voltage transformers came in different shapes and sizes. Some of them really do provide true ground isolation and were used to eliminate ground loop hum, as well as step the voltage up or down as needed. Others are standard 12-volt power transformers that can be set in "buck" or "boost" configurations by reversing a plug or throwing a switch. Since the windings are series subtracting or series adding in a buck or boost transformer, there is no isolation possible with them. And there were two-winding isolation transformers with grounded secondary neutrals, same as medical and data center isolation transformers made today. Those almost invariably have three wire cords and outlets, and in most cases it is possible to break the internal connection between the secondary and ground, turning them into ground isolation transformers.

_________________
"Hell, there are no rules here--we're trying to accomplish something!"

Thomas A. Edison


Top
 Profile  
 
Post New Topic Post Reply  [ 7 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: fpliuzzi, Willitwork and 8 guests



Search for:
Jump to:  
























Privacy Policy :: Powered by phpBB