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Advice sought for a 240V TO 18V 50mA power adaptor replacement


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I have a device with a captive 240V TO 18V 50mA power adaptor. The power adaptor has some mechanical noise, so looking for options to replace it.

 

Any recommendation would be gratefully received.

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13 minutes ago, Telecine said:

 

I have a device with a captive 240V TO 18V 50mA power adaptor. The power adaptor has some mechanical noise, so looking for options to replace it.

 

 

Can't quite figure out what you're looking for, John!  :(

 

Is it a mains 240v AC to 18v/50ma AC step down transformer?

 

Or a mains 240v AC to 18v/50ma DC converter?

 

If the former - Jaycar or Altronics should sell them.

 

If the latter - Sbooster or Gieseler will be able to supply you.

 

Andy

 

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Posted (edited)
20 minutes ago, andyr said:

 

Can't quite figure out what you're looking for, John!  :(

 

Is it a mains 240v AC to 18v/50ma AC step down transformer?

 

Or a mains 240v AC to 18v/50ma DC converter?

 

If the former - Jaycar or Altronics should sell them.

 

If the latter - Sbooster or Gieseler will be able to supply you.

 

Andy

 

 

Neither can I, LOL.

 

It is labelled an MEP (brand) Adaptor. The label says Input ~240V, Output +/- 18V, Current 50mA.

 

It is a small power supply brick with an AC cord to the wall on one end and a thinnish cable on the other. That cable is captively wired to the device.

 

Nothing on it says that it is DC output and the specs for the device don't say. It is of a 1989 vintage if that helps. Someone with some knowledge of it says it is a DC adaptor.

 

I can't find a suitable replacement, the 50mA output being the problem. Giessler doesn't have anything suitable and I can't find the current output spec of the Sbooster.

 

 

Edited by Telecine
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I am using a Gieseler 18V power supply. It does not matter if the DC output is more than 500 mA; your device will only draw what it needs.

 

Please check your device on its back panel, and when the plug goes in.  It may say whether it is DC or AC.  Also manual.  

 

Alternately, take it to Jaycar and they should be able to measure and suggest a replacement...

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10 minutes ago, Snoopy8 said:

I am using a Gieseler 18V power supply. It does not matter if the DC output is more than 500 mA; your device will only draw what it needs.

 

Please check your device on its back panel, and when the plug goes in.  It may say whether it is DC or AC.  Also manual.  

 

Alternately, take it to Jaycar and they should be able to measure and suggest a replacement...

 

Thanks, I wasn't aware of that.

 

Nothing on the device or in the manual says whether or not it is DC. I suspect it is. I will take it to Jaycar as you suggest.

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This will read a bit like a see-saw, but all make sense.  It is the meaning of regulated vs unregulated voltage....   Something to be aware of is that unregulated power adapters usually rate their output voltage at their maximum stated output current. Therefore if obtaining an adapter with higher current and the voltage is unregulated , then the unregulated voltage to match to 50ma will be needed to be lower, approximately 15v DC.  

as the 15V DC adapter will be measuring approximately 18 volts DC,up until its current rating approaches, it will then in most cases drop back to 15 V DC

 

Better than being on the see-saw, is to jump off, & stop seeing big retailers as one stop shops.  and  choose or indeed DIY build a 18v DC regulated supply, which should maintain 18 volts at the rated current.  There are many ways of precisely regulating voltage at 50ma, most of which easily surpass what is obtained off the shelf in shops.      https://refsnregs.waltjung.org/

 

I will post up a few schematics in the next few days to get the ball rolling. 

 

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Sure it doesn't have a symbol with the 15v?

 

2-19.jpg.db585c28f6741dac715af9b14a16ead5.jpg

 

 

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2 hours ago, Telecine said:

 

It is labelled an MEP (brand) Adaptor. The label says Input ~240V, Output +/- 18V, Current 50mA.

 

 

Aah, OK - then it is a DC regulated supply!  Also, it produces +18v DC and -18v DC - so an Sbooster or Clay's 'normal' PSes won't do - as they merely produce +ve DC.

 

Clay might have a power supply that produces + and -18v ... you need to ask him.

 

Alternatively, Rod Elliott's Project 'P05-Mini' will certainly do the trick for you.

 

Andy

 

Edited by andyr
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43 minutes ago, muon* said:

Sure it doesn't have a symbol with the 15v?

 

2-19.jpg.db585c28f6741dac715af9b14a16ead5.jpg

 

 

 

It has this:

- - - - -

______

 

Dashed line on top, undashed line underneath, whatever that means.

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1 minute ago, Telecine said:

 

It has this:

- - - - -

______

 

Dashed line on top, undashed line underneath, whatever that means.

in reference to the 15v? maybe that's DC and they have the symbol printed wrong.

 

Can you post a pic, John.

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2 minutes ago, muon* said:

in reference to the 15v? maybe that's DC and they have the symbol printed wrong.

 

Can you post a pic, John.

 

image.thumb.png.bff2fdba05e281c3cfa22c3173b6d3f4.png

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1 minute ago, muon* said:

18vdc

 

Regulated DC I think, so less common to find a replacement for. 

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23 minutes ago, Telecine said:

 

image.thumb.png.bff2fdba05e281c3cfa22c3173b6d3f4.png

Whilst that indeed is 18v DC the + and - markings infers it could have both positive and negative voltage - if it has both polarities and earth , you would expect a 3 pin connector at the DC output voltage end.

 

Or it could also be the manufacturer being complete and expressing ground with the negative symbol, in which case the output connector will just be 2 pin, typified by the barrel type connector usually 2.1 or 2.5mm.  an image of the connector will help to confirm in which case its far more likely to be 18v + positive and earth.   

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5 minutes ago, Telecine said:

 

Regulated DC I think, so less common to find a replacement for. 

But easy to build 🙂🥮

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2 minutes ago, stereo coffee said:

Whilst that indeed is 18v DC the + and - markings infers it could have both positive and negative voltage - if it has both polarities and earth , you would expect a 3 pin connector at the DC output voltage end.

 

Or it could also be the manufacturer being complete and expressing ground with the negative symbol, in which case the output connector will just be 2 pin, typified by the barrel type connector usually 2.1 or 2.5mm.  an image of the connector will help to confirm in which case its far more likely to be 18v + positive and earth.   

 

Bit hard to know because it is captively connected to the device:

 

image.thumb.png.a40d43ac23294d74bdb9b2fa7d9aa96e.png

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I have 18V DC supply for the old Nitsuko phone.

Could you also post a picture of the plug that goes into equipment?

Someone also has to measure polarity of it...

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5 minutes ago, rockeater said:

I have 18V DC supply for the old Nitsuko phone.

Could you also post a picture of the plug that goes into equipment?

Someone also has to measure polarity of it...

 

It is captively connected Roman, no plug. It appears to have three wires, a green, a blue and a brown.

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1 hour ago, Telecine said:

 

Bit hard to know because it is captively connected to the device:

 

image.thumb.png.a40d43ac23294d74bdb9b2fa7d9aa96e.png

But the internal parts show, as well as the three wires, that it is dual polarity, the give-away is the dual capacitors at the end. 

 

If the mechanical noise is the relays, then replacing with solid state relay types, should not be too difficult. If you can slide the board out and take an image of top and bottom of the board, I can have a go at drawing its schematic, also if you can use a magnifying glass, identify part numbers. 

 

 

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Posted (edited)
6 minutes ago, stereo coffee said:

But the internal parts show, as well as the three wires, that it is dual polarity, the give-away is the dual capacitors at the end. 

 

If the mechanical noise is the relays, then replacing with solid state relay types, should not be too difficult. If you can slide the board out and take an image of top and bottom of the board, I can have a go at drawing its schematic, also if you can use a magnifying glass, identify part numbers. 

 

 

 

Very kind of you, thanks.

 

I will have to do some further disassembly to get those shots. The circuit board is attached to that portion of the case that you can see in the photos and has a top cover that prevents obtaining a photo from above. 

Edited by Telecine
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I may have missed it, but curious to know what this device is ⁉️ 

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5 minutes ago, Snoopy8 said:

I may have missed it, but curious to know what this device is ⁉️ 

 

B&W High Pass Alignment Filter. It is an active filtering device to turn a 4th Order Bessel Alignment into a 6th Order Butterworth alignment for B&W 800 series speakers.

 

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1 hour ago, stereo coffee said:

But the internal parts show, as well as the three wires, that it is dual polarity, the give-away is the dual capacitors at the end. 

 

If the mechanical noise is the relays, then replacing with solid state relay types, should not be too difficult. If you can slide the board out and take an image of top and bottom of the board, I can have a go at drawing its schematic, also if you can use a magnifying glass, identify part numbers. 

 

 

 

The buzz that it has is coming from the power supply.

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21 minutes ago, Telecine said:

 

The buzz that it has is coming from the power supply.

 

Likely then a transformer winding, but may also be parts of the rectifier, namely diodes and capacitors. 

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Hi

If your device is still working , although the PSU is noisy , it shouldn't be to difficult to measure the DC input with a multimeter and then once you establish the voltages where the power comes into the device you will have a basis for getting a new 240 AC to DC plugpack.

 

From the pictures you posted the device looks quite basic although the function is still unclear to me.

Seems like it's a switchable Audio filter with two separate Op-Amps and some filtering . The components that I see suggests it's two separate audio channels which are changed over by  a Relay ?

 

B&W High Pass Alignment Filter. ?   ...I'm lost when it comes to Speaker Crossover stuff. sorry!

 

The two Op-amps are type AD 711 AQ which operate on a maximum voltage of +18 / -18 volts power rail.

So the transformer in the wall adaptor may well have a centre tapped secondary feeding into rectifiers to give the split rail plus and minus DC output.

 

You could cut the cable between the supply and device and measure the voltages !

Eventually you will need to connect a new supply in anyway! assuming you're good with a soldering iron or know someone who is !

 

Hope I can help further and look forward to hearing from you.

 

 

 

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@Telecine

 

the product has a tested date of 1989,  that’s 30 + years....

if it’s a DC supply out 18+/- VDC,  I’d suggest you replaced the electrolytic capacitors in it.... it looks like they are basic small cheap caps especially the values on it,  Prob no more than $10 total however that’s assuming as I haven’t seen the rest of the circuit 

 

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4 minutes ago, Addicted to music said:

@Telecine

 

the product has a tested date of 1989,  that’s 30 + years....

if it’s a DC supply out 18+/- VDC,  I’d suggest you replaced the electrolytic capacitors in it.... it looks like they are basic small cheap caps especially the values on it,  Prob no more than $10 total however that’s assuming as I haven’t seen the rest of the circuit 

 

 

Good advice and I agree. Just need to locate a suitable regulated 18v DC power supply.

 

Great to see you back here.

Edited by Telecine
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1 hour ago, Telecine said:

 

Just need to locate a suitable regulated 18v DC power supply.

 

 

Not just a "suitable regulated 18v DC power supply ", John!  A "suitable regulated +/-18v DC power supply."

 

@Gieseler Audio may well be able to supply one.

 

Andy

 

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18 minutes ago, andyr said:

 

Not just a "suitable regulated 18v DC power supply ", John!  A "suitable regulated +/-18v DC power supply."

 

@Gieseler Audio may well be able to supply one.

 

Andy

 

 

Thanks Andy.

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I could probably make up a custom PSU to suit but it would way less expensive just to get your current one repaired.

As previously mentioned it probably just needs a new transformer & maybe the filter capacitors replaced.

I'm sure Andy at HiFi Repair Services could handle it.

https://www.hifirepairservices.com.au

 

 

 

 

Edited by Gieseler Audio
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