Telecine Posted January 8, 2021 Share Posted January 8, 2021 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. Link to comment Share on other sites More sharing options...
andyr Posted January 8, 2021 Share Posted January 8, 2021 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 1 Link to comment Share on other sites More sharing options...
Telecine Posted January 8, 2021 Author Share Posted January 8, 2021 (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 January 8, 2021 by Telecine Link to comment Share on other sites More sharing options...
Snoopy8 Posted January 8, 2021 Share Posted January 8, 2021 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... Link to comment Share on other sites More sharing options...
Telecine Posted January 8, 2021 Author Share Posted January 8, 2021 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. Link to comment Share on other sites More sharing options...
stereo coffee Posted January 9, 2021 Share Posted January 9, 2021 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. 2 Link to comment Share on other sites More sharing options...
muon* Posted January 9, 2021 Share Posted January 9, 2021 Sure it doesn't have a symbol with the 15v? Link to comment Share on other sites More sharing options...
andyr Posted January 9, 2021 Share Posted January 9, 2021 (edited) 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 January 9, 2021 by andyr 1 Link to comment Share on other sites More sharing options...
Telecine Posted January 9, 2021 Author Share Posted January 9, 2021 43 minutes ago, muon* said: Sure it doesn't have a symbol with the 15v? It has this: - - - - - ______ Dashed line on top, undashed line underneath, whatever that means. Link to comment Share on other sites More sharing options...
muon* Posted January 9, 2021 Share Posted January 9, 2021 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. 1 Link to comment Share on other sites More sharing options...
Telecine Posted January 9, 2021 Author Share Posted January 9, 2021 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. Link to comment Share on other sites More sharing options...
muon* Posted January 9, 2021 Share Posted January 9, 2021 18vdc 1 Link to comment Share on other sites More sharing options...
Telecine Posted January 9, 2021 Author Share Posted January 9, 2021 1 minute ago, muon* said: 18vdc Regulated DC I think, so less common to find a replacement for. Link to comment Share on other sites More sharing options...
stereo coffee Posted January 9, 2021 Share Posted January 9, 2021 23 minutes ago, Telecine 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. Link to comment Share on other sites More sharing options...
stereo coffee Posted January 9, 2021 Share Posted January 9, 2021 5 minutes ago, Telecine said: Regulated DC I think, so less common to find a replacement for. But easy to build 1 Link to comment Share on other sites More sharing options...
Telecine Posted January 9, 2021 Author Share Posted January 9, 2021 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: Link to comment Share on other sites More sharing options...
rockeater Posted January 9, 2021 Share Posted January 9, 2021 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... 1 Link to comment Share on other sites More sharing options...
Telecine Posted January 9, 2021 Author Share Posted January 9, 2021 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. Link to comment Share on other sites More sharing options...
stereo coffee Posted January 9, 2021 Share Posted January 9, 2021 1 hour ago, Telecine said: Bit hard to know because it is captively connected to the device: 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. Link to comment Share on other sites More sharing options...
Telecine Posted January 9, 2021 Author Share Posted January 9, 2021 (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 January 9, 2021 by Telecine Link to comment Share on other sites More sharing options...
Snoopy8 Posted January 9, 2021 Share Posted January 9, 2021 I may have missed it, but curious to know what this device is 1 Link to comment Share on other sites More sharing options...
Telecine Posted January 9, 2021 Author Share Posted January 9, 2021 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. 1 Link to comment Share on other sites More sharing options...
Telecine Posted January 9, 2021 Author Share Posted January 9, 2021 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. Link to comment Share on other sites More sharing options...
stereo coffee Posted January 9, 2021 Share Posted January 9, 2021 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. 1 Link to comment Share on other sites More sharing options...
Rich1949 Posted January 11, 2021 Share Posted January 11, 2021 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. 1 Link to comment Share on other sites More sharing options...
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