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Voltage reducer? - samsdad - 12-19-2016

Hello,

Maybe I am lacking in the search-skills department but I was wondering what you guys use for a voltage reducer to match the voltages on what these radios were designed for. I understand that the Philco 38-116 was meant for more like 110-115v rather than today's 120v. I'm also getting a Radiola 60 if that changes the analysis.

Thanks and regards.

RE: Voltage reducer? - morzh - 12-19-2016

The single most effective way for large radios is the bucking transformer. If you want it inside the radio.
Basically it is simply a transformer that converts 120V to say 12V, and then the 120V AC is put through the secondary in counterphase so the 12V gets subtracted from 120V. Then it gets to the actual radio's transformer's primary.
The secondary has to be for the same current as the radio's primary.

http://dynacotubeaudio.forumotion.com/t3063-built-a-bucking-transformer

RE: Voltage reducer? - samsdad - 12-19-2016

(12-19-2016, 02:16 PM)morzh Wrote:  The single most effective way for large radios is the bucking transformer. If you want it inside the radio.
Basically it is simply a transformer that converts 120V to say 12V, and then the 120V AC is put through the secondary in counterphase so the 12V gets subtracted from 120V. Then it gets to the actual radio's transformer's primary.
The secondary has to be for the same current as the radio's primary.

http://dynacotubeaudio.forumotion.com/t3063-built-a-bucking-transformer

Read the thread. One of the folks pointed to Circuit Specialists who carry this: VARIAC-Auto Transformer 20 AMP
In the description it states, in part:

Rated at 110V input with an output voltage of 0-130V. Maximum output current is 20A or 2KVA. This auto transformer is VERY popular for home coffee roasting machines. It allows much greater control of the temperature of the roasting of coffee beans. They can also be used in science labs, audiophile (Great for old Tube Amplifiers), Science lab, hobby, film & video lighting applications. The auto transformer or Variac (both terms apply to the same item) is used to adjust the AC power either up or down. For instance if the AC power from the power company was 125 VAC and your application required 90 VAC, then this Auto transformer could be plugged in and the AC voltage could be adjusted to the desired level.

I'll admit that I'm greener than grass and definitely not an electrician. What does the 110v input rating refer to, since later it states that if the AC power is 125VAC you can adjust it down to 90, etc. Is this the right thing for what I'm looking for?

RE: Voltage reducer? - David - 12-19-2016

Her is a link to all about circuits. David   http://www.allaboutcircuits.com/textbook/alternating-current/chpt-9/winding-configurations/

RE: Voltage reducer? - Radioroslyn - 12-19-2016

(12-19-2016, 02:39 PM)samsdad Wrote:  
(12-19-2016, 02:16 PM)morzh Wrote:  The single most effective way for large radios is the bucking transformer. If you want it inside the radio.
Basically it is simply a transformer that converts 120V to say 12V, and then the 120V AC is put through the secondary in counterphase so the 12V gets subtracted from 120V. Then it gets to the actual radio's transformer's primary.
The secondary has to be for the same current as the radio's primary.

http://dynacotubeaudio.forumotion.com/t3063-built-a-bucking-transformer

Read the thread. One of the folks pointed to Circuit Specialists who carry this: VARIAC-Auto Transformer 20 AMP
In the description it states, in part:

Rated at 110V input with an output voltage of 0-130V. Maximum output current is 20A or 2KVA. This auto transformer is VERY popular for home coffee roasting machines. It allows much greater control of the temperature of the roasting of coffee beans. They can also be used in science labs, audiophile (Great for old Tube Amplifiers), Science lab, hobby, film & video lighting applications. The auto transformer or Variac (both terms apply to the same item) is used to adjust the AC power either up or down. For instance if the AC power from the power company was 125 VAC and your application required 90 VAC, then this Auto transformer could be plugged in and the AC voltage could be adjusted to the desired level.

I'll admit that I'm greener than grass and definitely not an electrician. What does the 110v input rating refer to, since later it states that if the AC power is 125VAC you can adjust it down to 90, etc. Is this the right thing for what I'm looking for?

Using a variac is a bit overkill if your just want to drop the line voltage. As Mike mention a low voltage transformer wired to buck against the input work great and is pretty inexpensive. Found the transformer on epay.
http://www.ebay.com/itm/Basler-24vct-40va-control-transformer-120v-input-new-free-shipping-/322352787188?hash=item4b0db92ef4:g:ZmEAAOSwpLNX9--D
It's good for about 2.5A @24vac. When wired properly if your line voltage is 125v the output would be 101vac. You could use a 120v to 12v transformer which would give you 113vac.

RE: Voltage reducer? - samsdad - 12-19-2016

Honestly I have no business trying to put in a transformer. Even though the variac would be overkill (except, apparently, when one is trying to get the perfect roast) I'm gonna have to go that route absent any objections in terms of whether it is sufficient electronically.

RE: Voltage reducer? - morzh - 12-19-2016

Either way will work. Variac is huge and weighs about 30lbs. You can wire it to power bunch of stuff. Like a power strip to power several radios. And you don't need a large one as it will likely be a radio at a time, so even 250 VA would do, let alone 500VA (that I have). Unless you want to do home roasting, espresso and listen to radio at the same time.

RE: Voltage reducer? - Mondial - 12-19-2016

This one would be more than adequate, and its a much more manageable size and weight:

https://www.circuitspecialists.com/variac-variable-ac-ps05kva.html

RE: Voltage reducer? - morzh - 12-20-2016

This is exactly what I have. 500VA. Same model. Quite enough for everything i do.


I do in fact have a 2kVA variac but it is a boost variac, it can go to 240V. Not for the regular repair things.

RE: Voltage reducer? - samsdad - 12-20-2016

Thanks for everyone's input, I appreciate it.

RE: Voltage reducer? - Arran - 12-24-2016

 I can't speak about the 38-116 (consult manual) but with regards to a Radiola 60 it already has a 125 volt setting on the power supply chassis via a bat switch.
Regards
Arran

RE: Voltage reducer? - AI2V - 02-06-2017

My house has 128-130 volts and has for decades. I've never done anything to my many radios involving the high line voltage. Tubes don't burn out any faster and neither did the old light bulbs.

My suggestion is to simply to ignore it and relax.

RE: Voltage reducer? - morzh - 02-06-2017

I probably would agree with this for the radios that are for the exhibition mostly and are played for demo or every once in a while to keep it alive.

For a daily player I would still recommend some form of voltage reduction as it will shorten tubes' service life some.

RE: Voltage reducer? - Steve Davis - 02-06-2017

When the line voltage is on the high side, I would be more concerned about the power transformer than the tubes. Philco radios, for the most part, have pretty robust transformers, therefore, not so much of a problem. Not so with some of the other brands. High line voltages can cause the power transformer to saturate, leading to very high operating temperature.

Steve