127Vac 60Hz to 24Vac 50Hz

Dear sirs,

Here in the country that I live the outlet voltage is 127V and frequency 60Hz but I need 24V 50Hz (precise) 100mA how do I build a converter?

I have a REGA turntable bought in England and I'll install here in my house in Brazil.

Please, take a look at the attached photo.

Regards,

Fernando - Call sign PU2PLL - Brazil

Hi this is an AC adaptor it means AC to DC converter, 24V @100mA is DC. For your application you can use a transformer 115V to 24 V if you do not need more precise voltage or frequency.
Go head with custom inverter 24V@50Hz if you need precise voltage and frequency

Hi,

it means AC to DC converter

Click to expand...

I can´t confirm this.
@smijesh: Why do you think it is DC output?

****
Turntable often use synchnron motors. If this is the case here: you need a frequency converter with very stable and accurate frequency.
I have no idea if there is a ready to buy converter with the quality you need.
My idea: [AC --> DC] --> [DC --> AC].
[AC --> DC] is not critical.
But for [DC --> AC] you need to read through the specifications in the datasheets.

Klaus

you can do this with a class AB (audio) amplifier - assuming you mean 24V AC 50Hz and not 240Vac, 50 Hz, you can do the latter with a step up transformer from the audio amp ....

Riga Research turntables use synchronous 24V motors so it isn't possible to change to a similar 127V/60Hz adapter.

My first thought is that Riga export to many countries so contact them and ask for a 60Hz belt pulley. Different motor to platter speeds is achieved by fitting different diameter pulley wheels to the motor so the gearing ratio adapts to give the correct playback speed. It would be a two minute job to swap one wheel for another and the cost would be very low.

The adapter is AC output but if Riga can't supply one, any similarly rated adapter should work equally well.

Brian.

Simplified schematic of 60 Hz frequency conversion to 50 Hz, while dropping 120V mains to 24 VAC.



The 3uF capacitor drops a large portion of the incoming AC, by reactance (not resistance). Thus it does not generate so much heat. However there are voltage drops across other components, and they generate heat.

The 50 Hz bias signal generator isn't shown. It's another project in itself, and there is more than one topology to provide it.

Please, take a look at the attached photo.

Click to expand...

The output is 24V AC; inside there is a little transformer.

You do not need 50Hz or 24VAC precisely; there are circuits within the gadgets that will do the needful.

Perhaps you have a strobe adjustment on the platter; if not read the manual on how to adjust the rpm...

solution:

From the local market, just get an wall adapter that gives 24VAC output (100mA is the typical current output and you need not worry much about the current rating)

In the worst case, you may have to take two 12VAC adapters and and combine the input in parallel and the output in series (you need to take care of the phase).

- - - Updated - - -

Turntable often use synchnron motors.

Click to expand...

Certainly correct; but using the power line frequency (via the adapter) to run the synchronous motor in a turntable is bad engineering.

However, I had a table clock that run on the power line frequency (but that was in the US) and it ran fine for years without losing a second (figuratively; I had no reference).

I expect a decent company to synthesize the frequency and even then I expect that there will be somewhere a pot to fine tune (the final speed of the turntable).

Most of the turntables are belt driven and the ratio is large (close to an hundred) and slippage is possible...

Hi,

Certainly correct; but using the power line frequency (via the adapter) to run the synchronous motor in a turntable is bad engineering.

However, I had a table clock that run on the power line frequency (but that was in the US) and it ran fine for years without losing a second (figuratively; I had no reference).

Click to expand...

Here in Europe the mains frequency is very stable. You can rely on the frequency and run a synchronous clock on that frequency.
The frequency is continously kept close to 50Hz. There are power platns just to maintain frequency (short time) within tight limits and long time it is adjusted to an atomic clock.
Read this: https://www.mainsfrequency.com

There are several power plants. Maybe a year ago there really was an issue as one of these power plants failed to operate.
Mains frequency operated clocks were off about 5 minutes within some months...

Klaus

There are power platns just to maintain frequency (short time) within tight limits and long time it is adjusted to an atomic clock. Read this: https://www.mainsfrequency.com

Click to expand...

Many thanks for the interesting link; here in India the mains frequency is 50+/-3 Hz and it is not guaranteed to stay in this range.

When you connect several generators in parallel, they must be frequency sync'd. Here we do not have a national grid and that results in a huge waste of energy.

However, I did not understand one thing in the link you sent: why the phase angle (shown near the bottom of main page) fluctuates rapidly even though the frequency does not?