[Dave89]

Hi I've constructed a velleman amp, 2x30watt output, model K4003.

Now to power this you need a 50Va transformer. I bought one and the pins along the input side are labelled

0 120 0 120

and the output

0 12 0 12

Now for the input I connected the live to the outer pin and the neutral to the outer pin (being AC it doesn't matter which) I then bridged the middle two pins.

Now for the output I connected the middle two pins the ground on my PCB and the outer pins, one to AA and one to AB on my PCB

http://www.velleman.be/Downloads/0/Manual_K4003.pdf
If you take a look their on page 6 you can see.

Well I plugged it in and it didn't bang or explode which was relieving, but after about 10 seconds I could smell something and it was burning, a small output of smoke seemed to be emitted too. I instantly unplugged it and haven't touched it since, but can someone who knows more about electronics than me tell me if I have wired this up incorrectly, and ifi have how I should correct it.

Many thanks for any help you can offer.

[labman]

It looks to me like the transformer you bought is meant to have 2 separate inputs. You have the 2 primary windings wired up in series, not parallel, giving you 6 volts output instead of 12. Wire it up with hot to both the 120 inputs, and neutral to both 0 inputs, and try it.

[Dave89]

It looks to me like the transformer you bought is meant to have 2 separate inputs. You have the 2 primary windings wired up in series, not parallel, giving you 6 volts output instead of 12. Wire it up with hot to both the 120 inputs, and neutral to both 0 inputs, and try it.

Right thanks for your reply.

So on the input side I should connect the Live wire to the two pins labelled 120V and the neutral to the two pins labelled 0V

You say the output is only delivering 6V not 12?

The transformer I have is:
http://www.rapidelectronics.co.uk/rk...0994&XPAGENO=1

The 0-12 0-12 Model.

Thanks for your help

[labman]

As far as I can tell, that is how it should work in the USA. Now, if your hot wire is 220 volts, the way you have it wired up should work. Either 120 wired in parallel, or 220 wired in series should work. Check the rest of the circuit and see if you could be drawing too much power.

[Dave89]

Well the national grid is delivering 230V so I currently have the following:

0 120 0 120
Live bridged neutral

But I should have the input side as:

0 120 0 120
Neutral live neutral live (by splitting each wire into two)

Is that correct?

Thanks for your help

[labman]

No, the way you had it should be correct for incoming 230.

[Dave89]

Right thanks very much for your help. I cannot understand why it wouldn't work. The amp specifically requires 50Va transformer so its not as though its pulling to hard on the transformer, especially for it to smoke. I shall get it tested and see if that reveals anything.

Thanks again

[jr32bask]

Its sounds to me like u have wired something else wrong away from your amp check and make sure u didn't wire something up backwards

[Stratmando]

Sounds? Like the transformer may be wired for 120 or 240 volts in and 12 or 24 volts out.
If 240 volts, line may be to 0, then the 120 to the other zero, then the 120 to the other 120. So the primary are in series, if 120 volts, connect the 2 0's to neutral and the 2 120 volts to line(120).
Output may be 12 volts in series, 0 to a 12, and the 0 and 12 left over is the 12 volts out, this gives 24 volts out, for 12 volts out, it may be in parallel, 0 to 0 and 12 to 12.

[Stratmando]

After seeing this:
Velleman Inc.
And this:

http://www.vellemanusa.com/downloads...k4003_rev1.pdf
I would say on the 12 volt side It may need a 0 and 0 tied together and the 2 12's will be the 2 12's needed. If Phasing is a problem, you may need to have a 12 and a 0 for the common and the 0 and 12 be the 2 12 needed to be rectified(ran through the diodes) to convert to DC voltage.

[tkrussell]

Jr, this extremely detailed revelation of an answer :

its sounds to me like u have wired something else wrong away from your amp check and make sure u didnt wire something up backwards

Came 4 years too late.

This thread is closed.