A good source for an inexpensive Isolated Variable AC Power Supply

[vortalexfan]

Hello everyone, I've been trying to look up an inexpensive (under $50) Isolated Variable AC Power Supply (like the one that Shango066 uses in his Videos or like the Heathkit one that Radiotvphononut uses in his videos) and I've not found anything so far, and what ones I have found they wanted over $300 or more for them and some ridiculuous amount for shipping costs that brings the cost to almost $800.

The reason why I ask is that I have a 1947 vintage Westinghouse AM/FM Bakelite Tabletop radio thats an AA6 set that is receiving absolutely no signal whatsoever on either AM or FM and I want to try and hook my signal generator up to it to check the front end out on the radio but since I don't have an isolated power supply to hook the radio up to, I dare not try and work on that radio right now otherwise I might fry my test gear and I don't want to fry my signal generator.

Anyone on here have any suggestions for a good isolated variable AC power supply that I could use to plug my series string radios into for troubleshooting purposes?

Thanks for your help.

[init4fun]

Originally Posted by vortalexfan

Hello everyone, I've been trying to look up an inexpensive (under $50) Isolated Variable AC Power Supply (like the one that Shango066 uses in his Videos or like the Heathkit one that Radiotvphononut uses in his videos) and I've not found anything so far, and what ones I have found they wanted over $300 or more for them and some ridiculuous amount for shipping costs that brings the cost to almost $800.

The reason why I ask is that I have a 1947 vintage Westinghouse AM/FM Bakelite Tabletop radio thats an AA6 set that is receiving absolutely no signal whatsoever on either AM or FM and I want to try and hook my signal generator up to it to check the front end out on the radio but since I don't have an isolated power supply to hook the radio up to, I dare not try and work on that radio right now otherwise I might fry my test gear and I don't want to fry my signal generator.

Anyone on here have any suggestions for a good isolated variable AC power supply that I could use to plug my series string radios into for troubleshooting purposes?

Thanks for your help.

like everything else in our hobby , if ya gotta have it now your gonna pay a premium , but if you can bide your time till the swap meets start back up , I'll bet you can find what you want for your target price (and not end up with cheaply made junk in the process) . For the meantime , you could rig up your own home made isolation transformer if you have a couple of old radio or TV power transformers kicking around in your parts stash . You'd connect the 6 volt secondaries of both transformers to each other , the primary of one would connect to your 110V AC power source and the primary of the other will become your isolated 110V AC supply to power the radio from . This , while not as elegant as a fancy pre built unit , will certainly isolate and protect your test equipment till you can get something within your price target .

[vortalexfan]

Originally Posted by init4fun

like everything else in our hobby , if ya gotta have it now your gonna pay a premium , but if you can bide your time till the swap meets start back up , I'll bet you can find what you want for your target price (and not end up with cheaply made junk in the process) . For the meantime , you could rig up your own home made isolation transformer if you have a couple of old radio or TV power transformers kicking around in your parts stash . You'd connect the 6 volt secondaries of both transformers to each other , the primary of one would connect to your 110V AC power source and the primary of the other will become your isolated 110V AC supply to power the radio from . This , while not as elegant as a fancy pre built unit , will certainly isolate and protect your test equipment till you can get something within your price target .

Ok, so I did find this on ebay, what do you think?

https://www.ebay.com/c/1020961952

With that I could just hook a Powerstat variac up to the 115 or 125 volt power outlet (one of those older ungrounded ones) and then I'd have my isolated Variable power supply. It would be less than $50 (for the transformer anyways), and then getting the variac would be another $75 on top of that (buying at a different time).

[init4fun]

Originally Posted by vortalexfan

Ok, so I did find this on ebay, what do you think?

https://www.ebay.com/c/1020961952

With that I could just hook a Powerstat variac up to the 115 or 125 volt power outlet (one of those older ungrounded ones) and then I'd have my isolated Variable power supply. It would be less than $50 (for the transformer anyways), and then getting the variac would be another $75 on top of that (buying at a different time).

That isolation transformer is PERFECT ! If you have the cash by all means grab that , it's identical to the one I use and I have no complaints with mine (Isolates perfectly , what more could ya ask ) .

[vortalexfan]

Originally Posted by init4fun

That isolation transformer is PERFECT ! If you have the cash by all means grab that , it's identical to the one I use and I have no complaints with mine (Isolates perfectly , what more could ya ask ) .

I just bought it, it cost me a little more than what I would of liked to of paid for one but not much, it came out to around $66 and some change after tax and shipping costs factored in, which is much more reasonable that the $200-$300 that some sellers were asking for them.

[init4fun]

Awesome !!!! post up some pics when it arrives

[mr_fixer]

That transformer is only rated for 15 watts, it would be undersized with a AA6 radio, i think a AA5 is around 50-ish watts.

[init4fun]

Originally Posted by mr_fixer

That transformer is only rated for 15 watts, it would be undersized with a AA6 radio, i think a AA5 is around 50-ish watts.

That is not the same transformer as vortalexfan showed the other day . Perhaps the seller used the same ad and listed a different transformer after vortalexfan bought the one he bought ? When he posts pics of the one that was originally listed you'll see that it's much beefier than the one the listing is now showing .

This one is not the exact one that was listed in that link earlier , but it looks very similar to the one that vortalexfan bought (except that vortalexfan's one has three power outlets VS the single one seen on this transformer)

[dieseljeep]

Originally Posted by init4fun

That is not the same transformer as vortalexfan showed the other day . Perhaps the seller used the same ad and listed a different transformer after vortalexfan bought the one he bought ? When he posts pics of the one that was originally listed you'll see that it's much beefier than the one the listing is now showing .

This one is not the exact one that was listed in that link earlier , but it looks very similar to the one that vortalexfan bought (except that vortalexfan's one has three power outlets VS the single one seen on this transformer)

The one shown is the same as the few I have. A 100watt with a primary selector switch.
I read a voltage from the secondary to ground with a digital meter. I thought, maybe it was overheated and damaged. Checked with a Megger, primary to secondary, primary to core, secondary to core. All OK.
I thought, using a digital meter was not the right decision, too sensitive!

[DavGoodlin]

That old Stancor looks fantastic for almost any radio, for a TV you need about 300 watts and color TV 400 watts minimum.

I found this Halldorson 500 VA with tap switches. I still use an oversized powerstat that was liberated from a theatrical lighting dimmer, in line before it rather than risk a mechanical failure of the switches, which are buried inside. The meter is pretty worthless accuracy wise.
Halldorson-variable-Transformer-.jpg

[Electronic M]

Originally Posted by DavGoodlin

That old Stancor looks fantastic for almost any radio, for a TV you need about 300 watts and color TV 400 watts minimum.

I found this Halldorson 500 VA with tap switches. I still use an oversized powerstat that was liberated from a theatrical lighting dimmer, in line before it rather than risk a mechanical failure of the switches, which are buried inside. The meter is pretty worthless accuracy wise.
Attachment 201469

If you have a variac(with voltage step up at the top of it's range) in series you can use an isolation transformer in overload mode for short stints say under 10min. Before I had decent sized isolation I would set my 120V in variacs output close to 140V and drive my isolation transformer off of it for small monochrome TVs and it would be sufficient for quick diagnostic power ups... gotta watch the temp when doing that though. That transformer developed a primary to secondary short after a couple years in service.

[vortalexfan]

The one I got is a 350 Watt unit, (350 VA) with 3 different voltage tapped outlets, one for 105 VAC, one for 115 VAC and one for 125 VAC, the one you saw in the "link" was a different one because I already bought the unit that that link originally went to.

I have pictures of the unit I bought posted below because I just got it today in the mail.

[DavGoodlin]

Those 3-tap units are not easy to find, congratulations.

[vortalexfan]

Originally Posted by DavGoodlin

Those 3-tap units are not easy to find, congratulations.

Thanks, it is a beast, weighs probably a good 40 lbs. or so.

And it does work!