Hi
New here and this is my first post. I'm also quite new to electronics although I'm learning.
I have a pair of m-audio monitors that I have had for quite a few years. I have replaced the power caps in them last year as the old ones were starting to bulge and I figured I should replace them before they go. That all went well and had no problems, until a month ago when one monitor would no longer power up.
I checked the transformer for voltage on the secondary winding and there is no voltage. I also checked the secondary resistance with my meter and did get readings of .9 ohms left side to centre and .9 ohms right side to centre and finally 1.8 ohms on right side to left side. The primary side is all coated with goo so I have not checked the resistance yet until I get all the goo off.
I also checked the main line fuse.
Since there is no voltage coming out the secondary winding should I just order another transformer?
I am a bit lost in finding a new transformer this is a centre tap 18-0-18 v transformer with no VA markings on it.
I was on the Antek web site looking at transformers but noticed that none of them are center tap.
I have taken a couple of pic of the old transformer and the specs on the back of the monitor.
I also checked the voltage on the working monitor which with no load is outputting 19v on the secondary windings center to side and 38v across
Ones on the antec site that I'm thinging might work are
AN-0220 - 25VA 20V Transformer - AnTek Products Corp
or
AS-0518 - 50VA 18V Transformer - AnTek Products Corp
but I need some guidance on this as I'm not sure what the original transformers VA is. The dimensions of the orginal are 2.95" diameter and 1.5" high if that helps.
New here and this is my first post. I'm also quite new to electronics although I'm learning.
I have a pair of m-audio monitors that I have had for quite a few years. I have replaced the power caps in them last year as the old ones were starting to bulge and I figured I should replace them before they go. That all went well and had no problems, until a month ago when one monitor would no longer power up.
I checked the transformer for voltage on the secondary winding and there is no voltage. I also checked the secondary resistance with my meter and did get readings of .9 ohms left side to centre and .9 ohms right side to centre and finally 1.8 ohms on right side to left side. The primary side is all coated with goo so I have not checked the resistance yet until I get all the goo off.
I also checked the main line fuse.
Since there is no voltage coming out the secondary winding should I just order another transformer?
I am a bit lost in finding a new transformer this is a centre tap 18-0-18 v transformer with no VA markings on it.
I was on the Antek web site looking at transformers but noticed that none of them are center tap.
I have taken a couple of pic of the old transformer and the specs on the back of the monitor.
I also checked the voltage on the working monitor which with no load is outputting 19v on the secondary windings center to side and 38v across
Ones on the antec site that I'm thinging might work are
AN-0220 - 25VA 20V Transformer - AnTek Products Corp
or
AS-0518 - 50VA 18V Transformer - AnTek Products Corp
but I need some guidance on this as I'm not sure what the original transformers VA is. The dimensions of the orginal are 2.95" diameter and 1.5" high if that helps.
Attachments
Match the physical size or weight.
The audio ratings suggest you may be closer to 100VA.
> none of them are center tap.
They are often dual-winding, which can be connected CT.
The audio ratings suggest you may be closer to 100VA.
> none of them are center tap.
They are often dual-winding, which can be connected CT.
Those ratings on the back panel look wildly optimistic given the transformer's dimensions. I have a 15VA toroid here, its 70mm across, a 30VA is 85mm across so I'd say you're spot on with a 20-25VA.
Find the biggest transformer which will still fit inside the cabinet, 20VA is woeful for an active speaker.
Incidentally if all the windings show low resistance then the fault's not with the trafo, must be something else.
Find the biggest transformer which will still fit inside the cabinet, 20VA is woeful for an active speaker.
Incidentally if all the windings show low resistance then the fault's not with the trafo, must be something else.
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if the fuse is not blown the transformer should be ok... the fuse protects the transformer... you can measure the transformer resistance from the line cord.. it should be a few ohms... if its open,, meaning it reads nothing....... Problem...?? (off and on switch )... (bad fuse holder ) (check fuse again ).... end of power cord sometimes gets damaged... at the power cord at the plug end.... check both side of the cord to the amp to make sure one side of the cord is not open.... also.. the secondary usually does not open its the primary.. hope that helps....... am thinking... I think you put the cart before the horse.....sounds like something more simple..........................
Ok.. I looked it up on ebay just like any good electronic teck would..lol... it has a 110/ 220 switch.... and a power switch... and either one could be at fault..... check the 110/220 switch to make sure its not stuck in the middle...... and you can measure both switches to see if they are ok.... a good switch will read... .2. or .1 ohms..... and that's just the resistance in the test wires.....
Ok.. I looked it up on ebay just like any good electronic teck would..lol... it has a 110/ 220 switch.... and a power switch... and either one could be at fault..... check the 110/220 switch to make sure its not stuck in the middle...... and you can measure both switches to see if they are ok.... a good switch will read... .2. or .1 ohms..... and that's just the resistance in the test wires.....
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It's not that a transformer can't go bad, but it's more likely that something else is wrong, so please diagnose it properly.
Transformer
As PRR says if you don't know the VA rating all you can do is is match the volume of the transformers. On this basis the AS-0518 is going to be about right. Just connect one blue wire to one green to make the centre tap on the secondary and parallel the reds and blacks if you are running on 115v mains.
But before buying anything make absolutely sure that you have mains going into the primary of the transformer, i.e. measure the ac voltage on the actual transformer's primary wires.
Have you got separate transformers for the LF and HF amplifiers? There seems to be a mismatch between transformer rating, which seems to be no more than 50VA, and the quoted power consumption of the unit at 100W.
As PRR says if you don't know the VA rating all you can do is is match the volume of the transformers. On this basis the AS-0518 is going to be about right. Just connect one blue wire to one green to make the centre tap on the secondary and parallel the reds and blacks if you are running on 115v mains.
But before buying anything make absolutely sure that you have mains going into the primary of the transformer, i.e. measure the ac voltage on the actual transformer's primary wires.
Have you got separate transformers for the LF and HF amplifiers? There seems to be a mismatch between transformer rating, which seems to be no more than 50VA, and the quoted power consumption of the unit at 100W.
Thanks everyone for the reply's.
I'm going to get all the goop off the switch and line voltage selector and check them out, also the fuse again. The monitor uses a computer power cord so I have lots of them that I can switch out.
To Goulton no there is only one transformer.
I will get everything checked again and update later.
Thanks
I'm going to get all the goop off the switch and line voltage selector and check them out, also the fuse again. The monitor uses a computer power cord so I have lots of them that I can switch out.
To Goulton no there is only one transformer.
I will get everything checked again and update later.
Thanks
Read the label on the transformer in the picture which says 'built in thermal fuse'.
If that has failed then it is also quite likely that there is another underlying cause such as something shorted on the secondary side which is possible if the secondaries are not fused.
If that has failed then it is also quite likely that there is another underlying cause such as something shorted on the secondary side which is possible if the secondaries are not fused.
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