Hi

Really basic question but please don't laugh. Best way to power this? Would it be simply wire the brown and blue to a normal 3 pin plug without ground (have done this and it causes hum) it's a 25w rig.

Any other suggestions or should this be the way to go?

You MUST connect ground to this box. Add some screw somewhere on the box and connect ground.


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Ok just run the ground wire from plug to the box somewhere? Is that why it's buzzing then?

I think someone else on here a while back said they had humming issues with that particular rig, can't remember who it was now.

The box should be earthed as it has 230v wires running through it and a 230v transformer. If any of these items failed.. e.g the insulation wore down and the conductor touched the metal box, it would become live to touch and be a shock hazard. The fuse in the plug wouldn't blow as currently there is no earth attached etc..

It is always a good idea to use the star grounding method that you often see in high quality audio amplifiers for rigs. That way all the items in the rig have the same ground potential, eliminating ground loop problems that can often occur. The safety earth connection can also be made to this star point too.

Hard to see what they have done from the pic.

When you say hum, is that happening with nothing else plugged into the rig? e.g audio source... or are you getting it when you plug in the audio to the phono socket?

Also where is your antenna? Is it near the rig or your audio source?

No the hum is there without anything plugged in. More of a buzz really quite faint but there. It happens with an antenna or dummy load plugged in.

Here's more pics for clarification

Well it sounds like it could be rf getting into the audio or possibly a faulty power supply. Or maybe a ground loop hum.

You could eliminate the power supply if you have a battery that could power the rig temporary, I have solved a few problems with stuff I built. Had a humming noise, so powered the rig off a powertool battery for a few seconds. As soon as I done that, humming went away so I knew it was the psu. In the end I found the supply needed more microfarads to bring down the ripple.

If you do try this, make sure you dont connect the power the wrong way round though! as mosfet and transisitors don't really like that

I see you just sent some more pics, looks fairly well built. I see that the builder has kinda put a star ground by connecting a tag onto the capacitors minus terminal onto the ground of the box. From there the other items e.g the pll and stereo coder pick up their ground through the box.

I notice from your previous posts you had problems before and sent it back to the builder, it looks like he has upgraded the stereo coder inputs to be sheilded. What did he say?

The rig fan has its own regulator so that will stop the electrical noise made by the fan coming out on the dial.

How many microfarads does the capacitor have? If the ripple is too high it will cause a humming noise coming out on the carrier.

Personally, if I was to try and get rid of the hum/buzz I would simplify the rig. Disconnect the stereo coder from the pll and also disconnect its power supply from the regulator. If that doesn't solve the issue, I would then try bypassing the power supply with a battery... If still no good, would have to disconnect the pll from the pa and test that on its own.

Usually you can sort problems out by a process of elimination but sometimes the problem can be a combination of two things connected together causing the problem too...

The big capacitor is 10000uF. I sent it back and he said it seemed OK to him and did a few amends as you can see. Once he sent it back it was better but still buzzed a bit. Also it's never on frequency totally (it never shows up tuned on the radio) including the car radio when driving around so it's not overload. That made me think it must be something I've done which is connect to a plug and maybe done it wrong haha.

Enigma has been building for decades, I used to get my stuff from him in the 90s and he knows his stuff. I'd be very surprised if you were supplied with a faulty transmitter (twice!).
Have you tried testing the transmitter into a dummy load without audio cable connected?
Also try disconnecting the Stereo module.

....Using that transmitter around most DJ equipment will cause RF feedback problems.
If it's still humming without audio connected that suggests a problem within the unit.
I see the bias control is at the maximum level, has it been correctly set or did you re-adjust it? Setting it too high can cause problems like humming etc with the overloading.

Thanks teck. Yeah I think it's probably something I can sort but it does hum even without audio and into a dummy load.
Because I'm an idiot can you tell me which pot is the bias one and I can try and reduce a little bit in sure that's not the issue as I haven't messed with any of the circuitry once since I received.

I made that box
"More of a buzz really quite faint but there"
most of the non regulated rigs will hum a little
I have tested the box before sending and yes when you put your amplifier to max power you will have a little hum but you will not notice it when you put audio trough it

If it is the power supply that is causing the buzzing/humming, what you are hearing is the dc ripple. You will never be able to get rid of the ripple entirely but you can do things to minimize the fluctuation. More microfarads may help.

Can you hear the humming noise when you have the amplifier you are listening to on a relatively low volume setting?

https://vimeo.com/165908234

Not sure if the attached helps. It's the noise I get, I then move the video to the rig. It sounds like it's in time with the fan but not sure. This was without anything plugged into the audio and running into a dummy load. I know the rig was near the radio but it makes no difference being further away.

Ok not the fan, I just manually stopped it for a minute and the buzz was still there

Ok well that is an annoying buzz lol, but is that with the volume on your hifi turned up to max or at a low setting? What I am trying to find out is how severe the buzz is. A normal healthy unregulated rig will sound similar to that if you turn the volume up to full on your hifi but it doesn't mean anything is neccesarily wrong... If you are hearing the buzz and the volume on the hifi is at low setting and the buzz is impeding the audio (if you connected it) then something is not quite right.

I think if you want to eliminate the fan, you would need to electrically disconnect it rather than stop the fan manually. It has its own regulator which is a handy trick to get rid of fan noise so is unlikely to do anything but you can try..

That was at full volume but it's audible when low and if you had music playing it would be there although low. I've never heard this kind of low hum on any pirate rigs round these parts before and it sounds quite unprofessional in my opinion.

Even at a low volume it's quite audible.

Any electricians near Yorkshire fancy having a look one evening lol

Yes I appreciate you turned up the volume so could hear noise better on video. You will always have some noise on the carrier from an unregulated psu rig, the alternative would be to change it for a good quality switch mode power supply (if the psu is def the cause of the problem).

What you need really is an electronics engineer friend, someone with an oscillscope etc... I used to know a guy out that way in Leeds but unfortunately he decided to travel the world lol

Is there any chance that some of it could be RF breakthrough on your receiving equipment ? This can still happen on a dummy load; especially if it's mains powered, close by, and on the same ring as the Tx power.
If it's definitely the rig, then I would think the most likely cause would be RF breakthrough in the stereo coder; either directly, or via the input wiring. If you want to tackle it yourself, you could disconnect the audio going into the driver board (from the coder), to see whether it disappears or significantly reduces.