Converting a 14VDC plug adapter to 14VAC, maybe one for Crossy?

[Kenny202]

Got a vintage 80's 90's piece of Electronic Musical equipment (guitar foot pedal) from Japan, 100 volt. It came with its original 14VAC power supply and a 220/100 piggy back voltage adapter. No problems at all but the power supply is quiet heavy and bulky and so is the piggy back 220/100v adaptor, and always a chance of plugging the 100V power supply straight into 220 as they are the same plug.

 

So I thought easy. I would just buy a little 220 / 14v power supply plug adaptor (same photo attached) off Lazada. I saw quite a lot then noticed the supply I need is 14VAC, not DC. All the ones available DC. There is an AC one available but the price about 1500 baht vs 100 baht. My units rated at 500ma. The little plug adapter power supply rated at 1amp. Now I figure there is more circuitry to make a DC power supply than an AC one as you have to convert the AC primary to DC (add a bridge rectifier or whatever they use these days) So I thought I would buy the 14VDC adapter and simply take the rectifier out. As it turns out not as simple as that as the input voltage is variable 100-220 and I guess they must have extra componentry to sort this out. So I took it to my electronics tech today and he sorted it for 100 baht. Haven't picked it up yet but he says it AC now and works perfectly.

 

What I am mainly interested in is how can the original bulky heavy one, which obviously has some sort of iron core trans inside and rated at 0.8 amps, be so much bigger and heavier than this little tiny light plug pack which puts out the same voltage at 1 amp? I am actually an electrician in another life and remember sometime around the 80s / 90s transformers all changed, as did ballasts in fluorescent lights. lighting transformers etc and became very light. It nearly felt wrong to replace them with these little toy things.

How they get the same result these days using such a light little unit as compared to the old heavy ones....and should this new little plug pack be ok?   

[SomchaiDIY]

1 hour ago, Kenny202 said:

What I am mainly interested in is how can the original bulky heavy one, which obviously has some sort of iron core trans inside and rated at 0.8 amps, be so much bigger and heavier than this little tiny light plug pack which puts out the same voltage at 1 amp? I am actually an electrician in another life and remember sometime around the 80s / 90s transformers all changed, as did ballasts in fluorescent lights. lighting transformers etc and became very light. It nearly felt wrong to replace them with these little toy things.

How they get the same result these days using such a light little unit as compared to the old heavy ones....and should this new little plug pack be ok?   

One reasons for smaller transformer is higher frequency

 

If frequency is increased transformer conductor size can reduce for same current output

 

Small power supply can have many kHz at the transformers

 

AC to AC adapter can use same method

 

 

[Crossy]

I've hidden a link to a "transformerless" power supply.

• Bloody lethal
• Provides DC anyway

Anyway, our OP is going to hit many issues.

 

It's correct that the existing unit has a nice, heavy, iron cored transformer. You should be able to get a 220V => 500mA 12V transformer (conventional type) which would reduce the weight that needs moving around.

 

The lightweight AC units (usually intended to drive halogen lamps) produce high-frequency AC. Now of course the works inside the pedal are optimised for 50/60Hz AC and may or may not work on the several kHz that comes from these adaptors. The pedal may in fact work OK on a DC supply. The only way to be sure is the examine the circuit.

 

I'd be tempted to try it on 12V DC, if it works, great.

 

 

 

[Kenny202]

3 hours ago, Crossy said:

I've hidden a link to a "transformerless" power supply.

• Bloody lethal
• Provides DC anyway

Anyway, our OP is going to hit many issues.

 

It's correct that the existing unit has a nice, heavy, iron cored transformer. You should be able to get a 220V => 500mA 12V transformer (conventional type) which would reduce the weight that needs moving around.

 

The lightweight AC units (usually intended to drive halogen lamps) produce high-frequency AC. Now of course the works inside the pedal are optimised for 50/60Hz AC and may or may not work on the several kHz that comes from these adaptors. The pedal may in fact work OK on a DC supply. The only way to be sure is the examine the circuit.

 

I'd be tempted to try it on 12V DC, if it works, great.

 

 

 

This is the sort of adaptor I'm talking about Crossy, not an LED power supply. It actually has like a tiny power supply inside, as well as a lot of other circuitry. I notice it doesn't give a value for Freq on the secondary side. So are you saying the Frequency on the secondary could be anything or too high? I do see these sort of adapters in use all the time for various things but mainly charging batteries in phones or appliances. Is that the deal? Frequency not important charging a battery but using as a power supply no good?

 

And if using a similar DC charger / adapter would the freq still not be all over the place or does the DC side of it correct the frequency. The kind of modern guitar pedal I am talking about does use these light little weight adapters but they are DC in and maybe they have some circuitry inside to correct all these issues? 

[sometimewoodworker]

2 minutes ago, Kenny202 said:

This is the sort of adaptor I'm talking about Crossy, not an LED power supply. It actually has like a tiny power supply inside, as well as a lot of other circuitry. I notice it doesn't give a value for Freq on the secondary side. So are you saying the Frequency on the secondary could be anything or too high? I do see these sort of adapters in use all the time for various things but mainly charging batteries in phones or appliances. Is that the deal? Frequency not important charging a battery but using as a power supply no good?

 

And if using a similar DC charger / adapter would the freq still not be all over the place or does the DC side of it correct the frequency. The kind of modern guitar pedal I am talking about does use these light little weight adapters but they are DC in and maybe they have some circuitry inside to correct all these issues? 

 

The problem with answering your questions is that size is virtually irrelevant to the circuitry inside and there are so many ways to construct a power supply that without the supply in question and a verity of bench test equipment any one of those designs might be in use.

 

The simplest answer is to buy a supply sold for your equipment, then it should be designed so that it’s output is perfectly suited to the input you need.
 

However given that a) such a supply isn’t available, b) you don’t have the equipment to test a random supply, & c) you don’t have an unlimited number of supplies to test. Then 1st go by price, in general the higher the price the better the design and components (Apple power supplies are criticised for being expensive but they almost never fail) . Of course price doesn’t tell you anything about the output apart from cheaper supplies are less likely to produce a smooth 12V as that increases the components so the price.

 

TLDR try the one you’ve got it may work, if not try to buy an expensive/more expensive one that you can return if it’s no good.

[Crossy]

50 minutes ago, Kenny202 said:

This is the sort of adaptor I'm talking about Crossy, not an LED power supply. It actually has like a tiny power supply inside, as well as a lot of other circuitry. I notice it doesn't give a value for Freq on the secondary side. So are you saying the Frequency on the secondary could be anything or too high? I do see these sort of adapters in use all the time for various things but mainly charging batteries in phones or appliances. Is that the deal? Frequency not important charging a battery but using as a power supply no good?

 

And if using a similar DC charger / adapter would the freq still not be all over the place or does the DC side of it correct the frequency. The kind of modern guitar pedal I am talking about does use these light little weight adapters but they are DC in and maybe they have some circuitry inside to correct all these issues? 

 

 

99% of the adaptors like this are DC output (like the one in your image), DC does not have a "frequency".

 

The lumpy units like you have for your pedal are a simple iron transformer (hence the weight) frequency out = frequency in (50Hz here).

 

The reason that the modern units are so light is that they have high frequency transformers (and the associated electronics to allow their use) which are much lighter than the lumps of iron. They are invariably DC output. The light ones that are actually AC output are not 50Hz (and as I said are usually intended to drive halogen lamps [not LEDs]).

 

You are not going to find a 14V AC power supply which is both light and 50Hz output. You will likely be able to find a 50Hz one that is heavy, but at least you won't need to lug the 100V converter around too.

 

Just get the right transformer for your pedal from the manufacturer, far easier and safer.

[Kenny202]

20 minutes ago, Crossy said:

 

99% of the adaptors like this are DC output (like the one in your image), DC does not have a "frequency".

 

The lumpy units like you have for your pedal are a simple iron transformer (hence the weight) frequency out = frequency in (50Hz here).

 

The reason that the modern units are so light is that they have high frequency transformers (and the associated electronics to allow their use) which are much lighter than the lumps of iron. They are invariably DC output. The light ones that are actually AC output are not 50Hz (and I said are intended to drive halogen lamps [not LEDs]).

 

You are not going to find a 14V AC power supply which is both light and 50Hz output. You will likely be able to find a 50Hz one that is heavy, but at least you won't need to lug the 100V converter around too.

 

Just get the right transformer for your pedal from the manufacturer, far easier and safer.

Ahhh no I got you. Of course DC doesn't have a frequency. Unfortunately as so old the manufacturer, or any other manufacturer doesn't make these anymore. They really were a one off back in the day. I do have the original power supply albeit 100V, and a step up transformer but it is a bulky set up and more avenue for fault and noise as this is a musical device. I can live with it of course if I have to but a smaller one connection set up of course would be better. I have had the tech adapt the 220 / 14V plug adapter to AC already and he says its working fine although I doubt he would have tested the frequency. Probably an impossible question to answer but would it likely do any harm to try it at least? Could the higher frequency if present do any damage? If you think there is any chance of damaging the unit I'll just chuck it and use the 100V one. There is one I see advertised on Lazada or Ali but its 1500 baht, a generic Chinese one so not a lot of trust there. Looks like a similar type of light weight adapter. Whether they have put frequency correction in their or not (if such a thing possible) I am not sure.    

 

Are you saying a DC one may work because it's possible there is DC circuitry inside the unit? Maybe a bridge rectifier circuit after the power supply goes in, which if using a DC supply would simply by pass the AC/DC converter and run the unit normally? Again would there be any danger in connecting a 14V DC power supply quickly to see if it worked? As there are lots of them cheap and readily available

[Crossy]

I doubt trying a DC adaptor would do any harm, the internals are almost certainly DC anyway and there's an internal rectifier etc. I had an old router that used an AC output adaptor, this did NOT work with a DC supply, but no damage was caused.

 

If you have a modified unit that's producing 14V AC at some indeterminate frequency give it a try, I doubt any actual harm will come to the beast.

 

[Kenny202]

47 minutes ago, Crossy said:

I doubt trying a DC adaptor would do any harm, the internals are almost certainly DC anyway and there's an internal rectifier etc. I had an old router that used an AC output adaptor, this did NOT work with a DC supply, but no damage was caused.

 

If you have a modified unit that's producing 14V AC at some indeterminate frequency give it a try, I doubt any actual harm will come to the beast.

 

I actually managed to find the proper AC/AC Transformer type adapter on Lazada for 500 baht. And its 220v as well. Before I was only finding DC and 110 volt primary. I don't know how their search engines work but often type in an exact match to a products description and it doesn't come up. But search in Google or something and comes up there for lazada. Thanks for all the help certainly learnt a few things anyway