Power Adapter ISSUES

Hughesie

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hi guys i really need your help on this one

i have a phonic mm1002a (my first mixing desk)

and dug it out a few days to discover that the power adapter is faulty and doesn't work at all. i would use a universal adapter except it has a unique powe input (circular pin design) not the standard kettle plug design

please help me it has become an item that i tresure


and don't suggest phonic i have already tried them
 

Chris15

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Are you sure that the power supply is in fact faulty? Try checking it with a meter. If it is dead, perhaps try sending it to a service dept. If it is not dead, perhaps it is the power connector. More details might help us with with more ideas. Voltage, connector images, etc. A service type establishment may be able to get a service manual which would enable them to troubleshoot more effectively.
 

Hughesie

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Melbourne, Australia
pictures are coming here is what it says

input 240v-50hz
output 16.8v x2 ac 0.5a

i think it might be a loose wire not being an electrics expert i can fix it
 
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Chris15

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Hughesie89 said:
pictures are coming here is what it says

input 240v-50hz
output 16.8v x2 ac 0.5a

i think it might be a loose wire not being an electrics expert i can fix it
A couple of questions:
Do you have a multimeter?
I am guessing that this is a heavy, transformer based supply?
If so, you should find that between pins you should be able to find the transformer windings. I would be guessing a number in the tens of ohms.
How many pins are there in the connector and any indications of how they are wired?

The thought of a loose wire would seem logical.
 

Hughesie

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Melbourne, Australia
ok i have taken some pictures and will upload them now

i have treated the adapter very well

i took the cover to have a look and i don't even know what am looking at
 

Chris15

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Pity about the multimeter. One of those 3 pins will be a common and the other two will each be 16.8 volts AC. At least that would be my guess. Can you take the cover off?
 

Chris15

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The left hand side in the first picture is the mains input. It is at this point that I MUST warn you not to plug this in and turn it on without the cover properly attached.

Picture 3, can you pull the heat shrunk connections off? I am thinking that they are removable terminals.

Also could you open the connector up? There might be a disconnection there.
 

Chris15

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It may be worth your while trying to get your self a multimeter after the ANZAC Day holiday. A basic one will only set you back about $10. If you can get one, then it should be an easy matter to diagnose the fault. I am sure that you will find other uses for it also, things like checking if a cable is broken spring to mind. Let me know if / when you get one and we'll see about diagnosing the fault.
 

Mayhem

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Ok guys – first off it is good to see the thought process here and so far so good. One thing to keep in mind is that the first thing to look for in any electronic problem is a mechanical fault. Such things as broken wires (as you noted), dry solder joints, blown fuses and worn connections are often the most common faults.

I agree with Chris that a multimeter would be very helpful here, as currently you are looking only at the power pack as the fault. Could also be the desk (fuse, switch, wire etc inside).

Looking at the pictures, I wonder if the connector is making good contact? There connectors can loosen up, so that the pins no longer actually touch the sockets. One thing to try is closing the sockets up a little using a small screwdriver. Or, open up the pins a little.

However, you do need to first off isolate the power supply as the fault. If you can get your hands on a multimeter, test the power at the 3 pin socket. Before you do this, put the power pack together to make sure you don’t get a zap. Given that this power pack has no diode rectification, your will need to have your meter set to AC volts.

You could probably take it into your school and ask one of the manual arts teachers to check it for you. If the power pack works, then you will need to look at the desk.
 

Chris15

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I am guessing that Victoria is currently on school holidays as NSW are. The fact that the plugpack has a marked output of 16.8V AC, it is going to have an AC output. From the looks of it, the three output wires are connected to the two ends and the centre tap of the transformer. Therefore, inside the mixer there will be rectification diodes and other power supply circuitry as well as (hopefully) a fuse. With a multimeter, it should be a one minute process to check the transformer is working. In reality, you only need an AC voltmeter, so when you get back to school, your science dept. might be able to help you out there. In all likelihood, it is probably only a simple fault like a blown fuse or a dry joint or a disconnected wire, but a multimeter is really going to make diagnosing that fault much easier.
 

Mayhem

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Ok – was just shutting down my PC and noticed that I still had your pictures open. I had another look at the pic of the back of your desk and noticed two things that I missed earlier (was watching the Simpsons at the time!).

1. When compared to the other pins, the lower left pin has been squashed – note the gap on the others. This could be a problem. There is also some discolouration adjacent to this pin but that could also be camera flash.

2. I noticed also that the power switch shows signs of arcing (or heat damage), with an obvious burn mark on the bottom.

I have a sneaking suspicion that there is some damage to the power input stage of this desk and that your best bet would be to have someone service it for you.

It is possible that the power connector has been wiggled a bit too much when connecting/disconnecting the power supply and this has squashed the pin and resulted in a high resistance connection. This could then result in heat damage that could be seen in the switch. Although, I wouldn’t like to state exactly what has happened to the switch. It is difficult to see if that is an arc or overheating. Then again, it could be a switch fault or something else in the vicinity of the switch and the squashed pin could be pure coincidence and not affecting the power at all. However, if it were mine I would certainly spread that pin to ensure that it makes good contact.

You could do that first and then see if the board works. I would do so with the switch off and just see if anything trips the RCD that you are sure to be testing it on. If nothing untoward happens, I would switch the power off at the wall and then switch the desk on before switching the unit on at the wall.

In saying this however, I still recommend that you get someone qualified to take a look at it for you, as that switch will certainly need replacing.
 

Chris15

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It is starting to look less like this is a problem with the power pack and more like a problem with the power supply inside the mixer. Taking Mayhem's advice and getting it looked at by a professional would seem to be an appropriate thing to do. We will continue to provide advice if you would like it, but I think there will be a point where we draw a line and recommend that you have it professionally serviced, not necessarily because we are questioning your ability, but because if you were to follow our instructions and something were to go wrong, then you could hold us liable and I for one do not need that.
 

Hughesie

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ok i have sent it to a friend who is an electronics expert

hopefully he will fix the problem

just in case i have sent an email t the place i purchaced the item from also some good news is i was looking at new phonic desks and they all seem to have that adapter input style (screw 3 pin design
 

Chris15

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Hughesie89 said:
just in case i have sent an email t the place i purchaced the item from also some good news is i was looking at new phonic desks and they all seem to have that adapter input style (screw 3 pin design
You would want to check VERY Carefully that the voltages and pinouts are the same before you even thought about substituting the power supplies. Failure to do so could mean that you destroy another power supply. Consider what we have said in that it might not actually be the external power supply but rather something internal in the mixer.
 

Hughesie

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Melbourne, Australia
i have just recived a message from a person i emailed about the adapter

Electronic stores like Dick Smith carry a variety of power adaptors. As
long as the voltage and currents (amps) is the same as , or very close
to what you require it should work. Also, the pin connection needs to be
the same. (obviously)

Also, CMC are the Australian distributors of Phonic. See
www.cmcmusic.com.au

Regards,


Greg Goris
Store Manager
 

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